Original:Traditional Field Crops 12

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Cover

Contents

[edit] Traditional Field Crops (Peace Corps, 1981, 283 p.)

[edit] Appendices

[edit] Appendix A - Measurements and conversions

Area

1 HECTARE(ha) = 10,000 sq. meters = 2.47 acres = 1.43 manzanas (Central America)

1 ACRE = 4000 sq. meters = 4840 sq. yards = 43,560 sq. ft. = 0.4 hectares = 0.58 manzanas (Central America)

1 MANZANA (Central America) = 10,000 sq. varas = 7000 sq. meters = 8370 sq. yards = 1.73 acres = 0.7 hectares

Length

1 METER (m) = 100 cm = 1000 mm = 39.37 inches (in.) = 3.28 feet(ft.)

1 CENTIMETER (cm) = 10 mm = 0.4 in.

1 INCH (in.) = 2.54 cm = 25.4 mm

1 VARA (Latin America) = 32.8 in. = 83.7 cm

1 KILOMETER (km) = 1000 m = 0.625 miles

1 MILE = 1.6 km = 1600 m = 5280 ft.

Weight

1 KILOGRAM (kg) = 1000 grams (g) = 2.2 pounds (1bs.) = 35.2 ounces (oz)

1 POUND (lb.) = 16 oz. = 454 g = 0.45 kg

1 OUNCE (oz) = 28.4 g

1 METRIC TON = 1000 kg = 2202 1bs.

1 LONG TON = 2240 1bs; 1 SHORT TON = 2000 1bs.

1 QUINTAL = 100 1bs. (Latin America); 112 1bs. (British); 100 kg (metric)

Volume

1 LITER (1) = 1000 cubic centimeters (cc) = 1000 milliliters (ml) = 1.06 U.S. quarts

1 GALLON (U.S.) = 3.78 liters = 3780 cc (ml)

1 FLUID OUNCE = 30 cc (ml) = 2 level tablespoons (measuring type)

Miscellaneous Conversions

Lbs./acre X 1.12 = kg/ha; lbs/acre X 1.73 = lbs/manzana

Kg/ha X 0.89 = lbs./acre; kg/ha X 1.54 = lbs./manzana

Lbs./manzana X 0.58 = lbs./acre; lbs./manzana X 0165 = kg/ha

Temperature:

C° = (F° - 32) X 0.55
F° = (C° X 1.8) + 32


[edit] Appendix B - How to conduct a result test

When is Result Testing Needed?

  • To test responses to an improved practice under actual farming conditions: Research station conditions are often more ideal or at least different from actual on-farm conditions. What works well under the more controlled situation of the station may be less than satisfactory in farmers' fields where soil and management are likely to be much less than optimal.
  • To test responses in different geographic regions
  • To measure the profitability of a new practice
  • To measure the variability of results: Farmers are just as interested in the variability of benefits from a new practice as they are in the average benefit. A practice that produces large benefits on some farms but little or none on others is unlikely to gain wide acceptance.

The Procedure

  • Clearly describe the practice to be tested
  • Divide the test region into zones: The work area may have significant variations in soils, rainfall, elevation, farming systems, etc. It is important to divide the testing region into separate zones if they differ enough from each other to warrant separate recommendations. The number of zones will depend on your area's diversity, the complexity of the practice you are testing, and time and budget limitations. In most cases you will be dealing with no more than two to three test zones within a municipality.
  • Decide on the number of farms to be included per test zone: Naturally, the more tests and farms that are included per test zone, the more representative the results will be and the more specific will be the recommendation that follows. However, costs will be higher and so will time requirements.

Two factors determine the number of farms that should be included in a test area:

  • If high average benefit is expected from the new practice as opposed to the traditional one, fewer farms need to be included than if the average benefit is lower.
  • If a large variation is expected in farm to farm results, more farms need to be included than if a smaller variation is expected,


NUMBER OF FARMS TO INCLUDE IN A RESULT TEST

If you expect an average increase over normal yields of:

And if you expect yield variation between farms within the region to be:

Then you should include this number of farms in your test: (10 maximum)

100 percent

Quite variable

6


Fairly consistent

4

50 percent

Quite variable

9


Fairly consistent

5

25 percent

Quite variable

10


Fairly consistent

6

Extension workers ideally should consult an experienced researcher or extension officer in deciding how many farms to include in a result test. If professional advice is not available it may be better to proceed with result tests using less precise sampling methods. The table below is based on a 5001000 farm work area.

  • Decide on how long to run a result test: If the expected benefits of the new practice are likely to be significantly related to weather conditions during the growing period, the test should be repeated over several years. This is often the case with tests involving fertilizer use and changes in plant density and tends to be true with most other practices, at least to some extent. Repeat testing is especially indicated if the first trial takes place during an unusual weather year. Long-term weather records can help determine this, but if not available, local extensionists and farmers can be of help.
  • Select individual farms: It is important that selected farms be representative rather than "typical". The participating farms should reflect a cross-section of those in the test area so that trial results can be converted into recommendations generally suitable for the entire area. Remember also that you should be just as interested in determining the variation of response among farms as in the average overall response. Farmers do not harvest averages'
Ideally, the farms should be chosed at random, but this is never completely practical due to the limitations imposed by accessibility and farmer cooperation. However, the less the choice of farms is confined to a particular class of farms and the more you choose farms on an "as they come" basis, the closer you will be to achieving a valid representation. This principle is much easier to violate than one might expect. For instance, it is easier to work with farms close to a road, with familiar farmers or with farms where good results can be expected. Such biases can totally discredit the results.
  • Decide what kind of control plot is needed: If the result test is to compare an old practice with a new one, a control or check plot will be necessary. However, if a totally new crop is being introduced rather than a new practice or new variety, no control plot is needed.
  • Choose the location and size of the plots: Plot location will depend a lot on the feelings of the cooperating farmer. This is no problem, as long as he or she does not purposely select the best piece of ground on the farm. Random choice is the best method here unless parts of the farm have been subjected to very unusual management practices such as ultrahigh fertilizer applications. Both the test plot and the control plot should be in the same field and preferably adjoining each other. This helps ensure that both plots are subjected to the same variables. In fact, it may be best to avoid using farms where the two plots cannot be located in the same field.
The plots should be large enough so that the usual farming methods can be followed, yet small enough so that the results are clearly visible. The test and the control plot do not have to be the same size. The test plot can be a portion of it serving as the control plot.
  • Conducting and supervising the test: The farmer and his or her usual extra workers should handle all the land preparation, planting, weeding, and other operations normally associated with the crop. They-should also apply the new practice themselves under the guidance of the extension worker(s). This assures that the result test is fully representative of actual farming conditions.
Make sure that all variables other than the practice or input being tested are held constant. One common error of both farmers and extensionists is to take better care of the test plot than the control plot. Such preferential treatment can completely invalidate the results. Documentation is vital. All inputs used should be measured and recorded to the extent possible. Weather data such as rainfall, hail, and unusual temperature extremes should also be recorded if possible along with any visual differences between the test and control plot during growth.
  • Collecting Data: No conclusions can be drawn from the result tests until yields have been measured. The goal is to weigh the harvest from the test plot and an equal area of control plot. The extensionists and the farmer should decide on a harvest date and arrangements should be made to obtain an accurate scale. Gross yields from both plots can be measured at the same time and then converted to a kg/ha, 1bs./ acre or other locally used yield standard.
However, you should always obtain a Yield sample prior to the actual harvest date just in case the plots are inadvertently harvested without measuring yields before the agreed upon date. A properly collected random yield sample is usually accurate within 5 percent of the actual yield and is a cheap insurance policy.
  • Analysis of the results: Good records are essential to any valid analysis of the results. By far the best way of interpeting the results is to run a standard-statistical analysis of the yield data. You do not need formal training in statistics to do this. Appendix F gives easy to follow instructions for carrying out a statistical analysis which will enable you to determine the standard deviation (a measure of the variability of responses from the average).
Calculate the standard deviation, since it serves as basis for giving realistic yield expectations when making recommendations to farmers.

Reducing the Risk To Participating Fanners

  • Subsidizing inputs:
Result tests: There are two schools of thought here. Some extension specialists feel that all new inputs for the test plots should be provided free to the farmer. They feel this makes it easier to find collaborators and also helps assure control over the plots. Others feel that no compensation should be given unless a completely new or unknown input is involved, Much of the choice depends on the economic condition and receptiveness of the local farmers. Result demonstrations: Inputs should ordinarily not be subsidized unless there is still some uncertainty about the profitability of the new practice, in which case it probably should not be at the demonstration phase anyway.
NOTE: If subsidies are provided, be sure to include the true costs of the inputs when doing a cost/benefit study.
  • Reducing the number of farm tests :
Result tests: Reducing the number of tests may make the test results unrepresentative for the area. Result demos: Reducing their number will not affect the demonstration principle, but may slow the rate of mass acceptance by farmers.
  • Reducing plot size:
Result tests: Plot size should be large enough to allow normal growing practices to be followed. Rather than cut plot size below this limit, subsidies should be offered. Result demos: Let the farmers choose their own plot sizes as long as normal growing practices can be followed.
  • Guaranteeing the price or the yield: The extension agency may guarantee a certain yield or market price to a cooperating farmer, perhaps in the form of a purchase contract. This should only be done with result tests. Demonstrations should stand on their own.


[edit] Appendix C - How to conduct a result demonstration

Examine the Recommendation that Will be Demonstrated

Make sure that the recommendation is:

  • Adapted to local growing conditions.
  • Within the economic means of most of the local farmers.
  • Adequately tested under local farming conditions
Select Demonstration Sites Since the goal of a result demonstration is to promote acceptance Since the goal of a result demonstration is to promote acceptance of a new practice on a mass scale, the main concern is maximum effective exposure when selecting sites. However, if the recommendation involved is suited to several types of soils or other variations commonly found in the local area, be sure to include some farms in each category. Here are some selection guidelines:
  • Choose Key Farmers These are not necessarily the best or the most progressive farmers, since these may be regarded as being too exceptional by other farmers. Do not turn down a "progressive" farmer, but concentrate on seeking out influential farmers.
  • Chose Conspicuous Sites Sites should be near roads, trails or public gathering places.
  • Group Demonstrations on Rented or Donated Land These can be very effective, but the group should be a pre-existing one, rather than being specially organized on-the-spot to conduct the demonstration.
  • Special Factors in Fertilizer Demonstrations Do not use a field that has received unusually heavy rates of fertilizer in the past. Fertilizer demonstrations give the most spectacular visual responses and yield differences on low fertility land, but do not purposely seek out unusually poor land for the demonstration,
  • The "Spontaneous" Demonstration: Another approach which can be very effective in certain cases is to look for a farmer's field that already demonstrates the value of what you are trying to promote. One disadvantage is that there is usually no control plot for comparison.

Preparing for The Demonstration

After selecting the sites, the extension worker should discuss the demonstration with the farmer, including the approximate dates of important operations such as planting, fertilizer application, etc. Make sure the necessary inputs are on hand. The extensionist should thoroughly understand the what, ho´: and why of the procedures involved in preparing and growing the demonstration plot.

Supervision and Management

The extensionist should be present during the application of any new procedure(s) involved with the demonstration plot to assure that the farmer does them correctly. To make the demonstration realistic, the farmer and his or her usual help should do most of the work.

Avoid the strong tendency to favor the "new practice" plot through overly careful tending or protecting it from limiting factors without regard to cost. Visiting farmers can often easily spot these atypical factors, which may seriously affect the demonstration promotional value.

Observation And Records

The main objective of demonstration plots is to promote improved practices, but they can also provide some very useful information in return for the small amount of extra work required to keep records and accurately measure yields. Here are some suggestions:

  • Maintain some kind of chronological record of each demonstration, noting such things as date and amount of input application, weather conditions, visual observations, etc.
  • Make a yield estimate using the random sample technique explained in Appendix L.
  • Check these estimates with what the participating farmers claim for their yields.

Promotion and Followup

Demonstrations are supposed to serve as "living" examples of the benefits of an improved practice (or "package of practices"). Neighboring farmers should be invited to see the demonstration during the crop's growth at any time when the desired results can be clearly seen (such as larger, greener plants resulting from fertilizer use). Final yield results should be discounted conservatively.

Organized sessions for visiting farmers should be arranged if the new practice requires explanation or new skills, both of which are very likely. This is known as a method-result demonstration and such a session should be conducted by a qualified and locally-experienced extension worker fluent in the local language.

The real test of a demonstration is how rapidly farmers begin to adopt the new practice. SOME CAUTIONS:

  • Do not use a result demonstration to test the outcome of a recommendation. That is what a result test is designed to do. Result demonstrations are for promoting practices that have already been largely locally proven. Never undertake a result demonstration unless you are reasonably sure the practice is beneficial.
  • Do not promise too much in the way of results. Be conservative.
  • Do not run a demonstration on your own land.
  • Do not sacrifice quality of work for quantity of work.
  • Do not favor one demonstration over another.


[edit] Appendix D - How to conduct an elementary statistical analysis

A result test consists of a number of individual trials on representative farms within a local area in order to compare a new practice with an old one. The results of these trials provide the final basis for making specific, locally adapted recommendations to farmers. In order to correctly interpret a result test, the yield results must be given at least an elementary statistical analysis to determine the two most important measures of the new practice's actual benefits:

  • The average benefit: This is the average yield increase of the new practice over the old practice.
  • The standard deviation: This indicates how much the individual results vary from the overall averages. It is the indicator of the variability of responses around their average. Remember that farmers seldom harvest "averages" and are very interested in knowing the likely variation in benefits.

The calculations are not difficult if you follow these standard procedures:

1. Arrange the data in column form, as in the table on the next page. 2. Calculate the following averages by adding up the appropriate columns and dividing by the number of individual trials involved. (Refer to table on the next page.)
a. Average (mean) yield for the old (control) practice.
b. Average (mean) yield for the new practice
c. Average benefit: the average yield increase of the new practice compared to the old one.
3. The Square of the Benefit: This is a standard statistical procedure used to calculate the standard deviation. However, the differences between the squares of the individual benefits have no significance. What is important is the sum of the squares, since it is from this that the standard deviation is determined. 4. Calculate the standard deviation: It is the most important statistic you will derive from the results since it shows the variability of responses from the average. The procedure for calculating the standard deviation is best shown by the following example. 5. Summarize the Data
a. Average yield of the new practice: 23.6 but/acre
b. Average yield of old practice (control or check plot): 17.2 but/acre
c. Average benefit (new over old practice): 6.5 but/acre
d. Standard deviation 2.8 but/acre or 16%
6. Interpret the Data: Once the average benefit and the standard deviation has been calculated, you can answer four key questions which are used to come up with a recommendation based on the test results:
a. What was the average increase in yield from the new practice? Solution using the data ill Step 5: [6.5 / 17.2] x 100 38% b. What is the minimum increase in yield that farmers can expect three out of four times? Solution: Multiply the standard deviation as a percentage (16%) by 0.7, a mathematical constant used in statistics. Then subtract the result from the average increase in yield expressed as a percentage (38%). Solution using above data: 16% x 1.0 = 16% 38% - 16% = 22% increase

File:P313.GIF
Data from a Maize Variety Test on 25 Farms

How to Calculate the Standard Deviation
a. Sum of the squares of the benefit = 1236 bushels b. (Sum of the benefits)² / number of farms = (162)² / 25 = 1050 bushels c. Subract (b) from (a): 1236 - 1050 = 186 bushels d. The difference (c) / Number of farms - 1 = 186 / 24 = 7.75 bushels e. Standard deviation = square root of (d) or (7.75)½ = 2.8 bushels f. [Standard deviation (e) x 100] / Average yield of the control = [2.8 x 100] / 17.2 = 16% Therefore: 16% = the standard deviation (variation) as a percentage of the average yield under the old practice (control).
c. What is the minimum increase in yield that farmers can expect three out of four times? Solution: Multiply the standard deviation as a percentage (16%) by 0.7, a mathematical constant used in statistics. Then subtract the result from the average increase in yield expressed as a percentage (38%). Solution using above data: 16% x 1.0 = 16%
38% - 16% = 22% increase d. What percent of the farmers are likely to get no increase in yield from the new practice? Solution: Divide the average benefit by the standard deviation to obtain a ratio. Then look up the answer according to this ratio in the following table, interpolating if needed. Solution using above data: 6.5 but / 2.8 but = 2.3 (ratio) Answer = 1% of farmers

Answer (percent)

2.6

Fewer than 0.5%

2.3

1%

2.0

2%

1.6

5%

1.3

10%

1.0

15%

0.8

20%

0.7

25%

7. Interpreting the Results on an Economic Basis

Since most new practices involve increased costs, the real test of their benefits is the increase in net returns over the increase in costs. The same statistical procedures used above can also be applied to the net economic benefit and the cost/benefit ratio tests.


[edit] Appendix E - How to convert small plot yields

When dealing with yields from field trials, demonstration plots, and farmers' fields, you will usually want to convert them to a kg/ha, lbs./acre or other standard basis. There are several easy ways to do this, and they are best shown by example.

PROBLEM 1: Pora harvests 300 kg of shelled maize off a field measuring 30 X 40 meters. What is her yield on a kg/ha basis?

SOLUTION

Method 1:

10000 sq. m (1 hectare) / plot area in sq. m × plot yield in kg = yield in kg/ha
10000 sq. m × 1200 sq. m × 300 kg = 2500 kg/ha of maize from Pora's field

Method 2: Make a proportion

File:Field crops IMG000.GIF

10000 sq. m / 1200 sq. m = Y1 / 300 kg

To solve the proportion for Y1, cross multiply like this:

1200 Y1 = 300 kg X 10000.

Then solve for Y1:

Y1 = [300 kg × 10000] / 1200

Y1 = 2500 kg/ha of maize from Pora's field

PROBLEM 2: Lam harvests 150 lbs. of dried cowpea seed off a field measuring 45 X 75 feet. What is his yield in terms of lbs. per acre?

SOLUTION

Method 1: 43560 sq. ft. (1 acre) / plot area in sq. ft. × plot yield in lbs. = yield in lbs./acre

43560 sq. ft / 3375 sq. ft. × 150 lbs. = 1936 lbs./acre of cowpeas from Lam's plot

Method 2: Make a proportion

Area1 Yield1
-------- = --------
Area2 Yield2

43560 sq. ft. / 3375 sq. ft. = Y1 / 150 lbs.

Then cross multiply and solve for

Y1 like this:

3375 Y1 = 150 lbs. × 43560

Y1 = [150 X 43560 ] / 3375

Y1 = 1936 lbs./acre of cowpeas from Lam's plot

NOTE: You can "mix" units of measure from different systems if you know the conversions. Examples:
1 Acre = 400 sq. m
1 Manzana (Central America) = 1.73 acres = 0.7 ha = 7000 sq. m


[edit] Appendix F - How to take soil samples

1. Divide the Farm into Sampling Units: Each sample sent to the lab is really a composite sample made up of 10-20 sub-samples taken from an area that is uniform in color, texture, topography, past management, and other characteristics that may influence soil fertility. A farm may have several of these distinct areas which are referred to as sampling units.

Begin by drawing a map of the farm land to be sampled, and then divide it into separate sampling units according to the above criteria. Each sampling unit should contain only one type of soil (that is, do not combine red soil with black soil, hill soil with level soil, fertilized soil with unfertilized soil, etc.). It is important to have a good idea of the land's fertilizer and liming history to avoid variations within one sampling unit.

File:P317.GIF
Map

The final map with numbered sampling units might look like this:

Size of sampling units: A sampling unit should usually not exceed 4-6 ha. Of course, small farms will have much smaller sampling units.

2. For each sampling unit, collect sub-samples for making a composite sample representing that unit.

  • If the farm has three sampling units, the farmer will send in three soil samples to the lab. Each sample will consist of 10-20 sub-samples taken at random within the sampling unit.
  • Depth of sampling: Most labs want topsoil samples only about 15-20 cm deep. When sampling fields to be used for pasture, a 5 cm depth is sometimes requested by the lab. Avoid including any subsoil in a topsoil sample unless the topsoil layer is very thin because of erosion.
  • To take a sub-sample: A shovel and a machete can be used, although a soil auger is better when the ground is very hard.
If using a shovel, make a hole with 45° sides to the right depth and then carefully dig out a slice about 3-5 cm thick. The slice should extend to the appropriate vertical sampling depth and be uniform in thickness. Holding the face of the soil slice with your hand will keep it from crumbling apart. Scrape off any surface litter before sampling. Trim down the width of the soil sample on the shovel with the machete until it is about 4-5 cm wide and then dump it in a pail. Sampling guidelines: Do not take sub-samples from fertilizer bands, under animal droppings or along a fence line or extreme end of a field. Use a thoroughly clean pail that has not been used to hold fertilizer. Galvanized pails will make zinc tests inaccurate.
  • Preparing a composite sample: After collecting the 10-20 random sub-samples within one sampling unit, thoroughly mix them in the pail and then take out enough soil to fill up the soil sample box.
Guidelines: Never mix soil from different sampling units. Do not oven dry wet samples, because this will cause a falsely high potassium reading in the test. Air dry them instead. Clean out the pail completely before moving to another sampling unit.
  • Fill out the informal sheet: The form from the soil laboratory will request information about the soils' slope, drainage, cropping history and yields, past applications of fertilizers and lime, crops to be grown and desired yields.

When to take soil samples: Send them in at least two months before you need the results. In areas with a concentrated planting season, farmers tend to wait until the last minute to send in samples, and the lab is unable to process all of them on time.

How often is testing needed? Under low to moderate rates of fertilizer use, a field should be sampled about once every three to five years, since the soil's fertility level is unlikely to change significantly on a year-toyear basis. This is fine, since farmers with limited capital should concentrate on feeding the present crop rather than building up the soil's general fertility level.


[edit] Appendix G - Hunger signs in the reference crops

[edit] Nitrogen

Maize, Sorghum, Millet

Young plants are stunted and spindly with yellowish-green leaves. In older plants, the tips of the lower leaves first show yellowing which progresses up the mid-rib in a "V" shaped pattern, while the leaf margins remain green. In some cases, a general yellowing of the lower leaves occurs. In severe cases, the lower leaves soon turn brown and die from the tips down. (This "firing" can also be caused by drought which prevents N uptake.) Maize ears are mall and pinched at the tips.

Legumes

The lower leaves begin to turn light green and then yellow with the symptoms progressing gradually upward. Plant growth is stunted.


[edit] Phosphorus

Maize, Sorghum, Millet

Hunger signs are most likely during early growth. Mild shortages usually cause stunting without clear leaf symptoms. More severe shortages cause a purplish color starting at the tips of the lower (older) leaves which may begin to turn brown and die. Some varieties of maize and sorghum do not show a purplish color but rather a bronze coloration of the same pattern. Disregard purple stems.

In maize and sorghum, symptoms usually disappear once the plants reach 40-45 cm, but yields will be severely lowered. Maize ears from Pdeficient plants are somewhat twisted, have irregular seed rows, and seedless tips.

Legumes

Phosphorus hunger signs often are not well defined. Plants lack vigor and have few side branches. Upper leaves become dark green, but remain small. Flowering and maturation are retarded.


[edit] Potassium

Maize, Sorghum, Millet

The three crops rarely show symptoms the first several weeks of growth. The margins of the lower leaves turn yellow and die, starting at the tip. Potassium-deficient plants have short internodes and weak stalks. Maize stalks sliced lengthwise often reveal nodes that are a darkish brown. Maize ears from potassium-deficient plants are often small and may have pointed, poorly seeded tips.

Legumes

Potassium deficiency is seldom seen in beans, but can occur in highly infertile soils or those high in calcium and magnesium. Symptoms are yellowing and death of leaf tips and margins, beginning on the lower leaves and gradually moving upwards.


[edit] Calcium

Beans

Calcium deficiency in beans is uncommon, but most likely to occur in combination with aluminum toxicity in very acid soils. Leaves stay green with a slight yellowing at the margins and tips. Leaves may pucker and curl downwards. Peanuts

Light green plants with a high percentage of "pops" (unfilled pods) show symptoms of calcium deficiency.


[edit] Magnesium

Maize, Sorghum, Millet

A general yellowing of the lower leaves is the first sign. Eventually, the area between the veins turns light yellow to almost white while the veins remain fairly green. As the deficiency progresses, the leaves turn reddish-purple along their edges and tips, starting at the lower leaves and working upward. Beans

Most likely in acid soils or those high in Ca and K. Yellowing between the veins appears first on older leaves and then moves upward. Leaf tips show the first effects.


[edit] Sulfur

Where to suspect: Sulfur deficiencies may be suspected where there are volcanic or acid, sandy soils, and where low S fertilizers have been used for several years.

Maize, Sorghum, Millet

These crops have relatively low S needs. Stunted growth, delayed maturity, and a general yellowing of the leaves (as distinguished from N deficiency) are the main signs. Sometimes, the veins may stay green which may be mistaken for zinc or iron deficiency. However, iron and zinc hunger are more likely in basic or only slightly acid soils. Beans

Upper leaves become uniformly yellow.


[edit] Zinc

Zinc deficiencies occur where soil pH is above 6.8 and high rates of P are used, especially if placed in a band or hole near the seeds.

Maize

Maize shows the most clear-cut zinc hunger signs of all crops. If severe, symptoms appear within two weeks of emergence. A broad band of bleached tissue on each side of the midribs of the upper leaves, mainly on the lower part of the leaves, is typical. The mid-rib and leaf margin stay green, and the plants are stunted. Mild shortages may cause a striping between the veins similar to manganese or iron deficiency. However, in Fe and Mn shortages, this interveinal striping runs the full length of the leaf.

Sorghum

Similar to maize, but less interveinal striping, and the white band is more defined.

Legumes

Interveinal yellowing of the upper leaves.


[edit] Iron

Iron deficiencies can be suspected where soil pH is above 6.8.

Maize, Sorghum, Millet

Sorghum is much more prone to iron deficiency than maize. All three crops show an interveinal yellowing that extends the full length of the leaves and occurs mainly on the upper leaves.

Legumes

Interveinal yellowing of the upper leaves occurs. They eventually may turn uniformly yellow.


[edit] Manganese

Where to suspect: Manganese deficiencies are uncommon in maize, millet, or sorghum. It occurs in soils which have a pH of 6.8 or above and in sandy or heavily leached soils.

Peanuts

Yellowing between the veins of the upper leaves which eventually turn uniformly yellow and then bronze is a symptom.

Beans

Plants are stunted. Upper leaves become yellow between the small veins and eventually take on a bronzed appearance.

Manganese toxicity occurs on very acid soils and is accentuated by poor drainage. Beans are very susceptible. The upper leaves show an interveinal yellowing. Easily confused with Zn or Mg deficiency, but Zn deficiency is very uncommon in highly acid soils.


[edit] Boron

Where to suspect: Boron deficiencies can be suspected in acid, sandy soils or high pH soils. Beans and peanuts are the most susceptible of the reference crops.

Peanuts

Foliage may be normal, but kernels often have a hollowed out, brownish area in the meat. This is usually referred to as "internal damage".

Beans

Thick stems and leaves with yellow and dead spots. If less severe, leaves are puckered and curl downward. Easily confused with leafhopper or virus attack. In very severe cases, plants stay stunted and may die shortly after emergence. Boron toxicity can be caused by applying a fertilizer containing boron too close to the seed row or by applying B non-uniformly. Symptoms are yellowing and dying along the leaf margins of the plants shortly after emergence.


[edit] Appendix H - Miscellaneous pulses

[edit] Chickpeas

Other names: Garbanzo, gram pea Scientific name: Cicer arietum

Main areas of production: 90% of the world's production occurs in India and Pakistan, but chickpeas are also an important crop in Lebanon, Turkey, Syria, Iran, Bangladesh, Burma, Nepal, Colombia, Argentina, and Chile. Adaptation, Characteristics

Chickpeas prefer cool, semiarid conditions. The seeds have a very permeable coat and lose their viability (germination ability) quickly under high humidity. The crop has a very deep root system and is a very efficient extractor of soil phosphorus. It has good nitrogen fixing ability.

Uses and Nutritive Value

Chickpeas are consumed as immature seeds (and pods) or as mature seeds. Also used as a coffee substitute after roasting. The seeds contain about 70 percent protein.

World chickpea production averaged around 7 million tons/year during the 1975-1977 period and was largely concentrated in India and Pakistan.


[edit] Pigeonpeas

Other names: Gandul
Scientific name: Cajanus cajan

Main areas of production: India, the Caribbean (especially the Dominican Republic and Puerto Rico). Colombia, Panama, Venezuela, the Middle East, and parts of Africa.

Adaptation, Characteristics

This is a woody, erect, shortlived perennial which can reach a height of three to four meters. Pods are pea like and flair, with three to seven seeds. Seed color varies from white to red or almost black. Plants can be used as a windbreak. Pigeonpeas are very drought resistant and tolerate a wide variety of soils and rainfall conditions. They are usually treated as an annual or biennial and prunted to encourage branching after each crop. They are often interplanted with maize, sorghum, millet, beans, and squash. Early varieties take 12-14 weeks until pod initiation and a total of five to six months to maturity.

Late varieties take about 9-12 months. Although the plants will grow for three to four years, yields tend to decline. It is often best to treat it as an annual or to slash it back and take ratoon crops using the cut branches and leaves as livestock feed.

Regional figures are not available for pigeonpea production, but worldwide production probably totals about hall that of chickpeas.

Green pod yields range from about 1000-4000 kg/ha with up to 8000 kg/ha possible. Yields of dry seeds average about 600-1100 kg/ha, but up to 2000 kg/ha is possible. The plants are very efficient nitrogen fixers.

Nutritive Value and Uses

Both the dry seeds and the young green ones (sometimes with the pods) are eaten. Mature dry seeds contain about 20 percent. The dried stalks and branches are used for firewood, thatching, and baskets. The crop is also valuable as a forage, windbreak and green manure (organic fertilizer) crop, and for soil erosion control on slopes.


[edit] Lima beans

Scientific name:

Main areas of production: One of the most widely grown pulses in both temperate and tropical areas. Lima beans are the main pulse crop in the wet rainforest regions of tropical Africa and Latin America. Extensively grown in Liberia, Burma, and Nigeria.

Types

Most breeding research has focused on the erect, non-vining bushy types with strong stems and a self-standing ability. However, these bush varieties are not well adapted to hot, humid conditions like the vining types of limes.

Adaptation, Characteristics

The vining varieties require a support crop or other form of staking. They tolerate wetter weather during growth than cowpeas or common beans but need dry weather during the late stages when harvested in the mature form. Limas are less drought-tolerant than many other legumes and are very sensitive co soil acidity (the optimum pH is about 6-7). Varieties are either day neutral or short-day in their response to day length. Vining types have been grown up to elevations of 2400 m in the topics.

Nutritive Value and Uses

Lima beans are grown mainly for the dry, shelled beans, but the immature seeds are sometimes cooked as a vegetable along with the pods and leaves. Some varieties have a dangerous level of hydrocyanic acid (HCN) in the leaves, pods, and seeds, but this can be dissipated by boiling and changing the cooking water. Colored seed varieties are higher in HCN than white ones.

The plants also are used as a green manure crop and as a cover crop (to protect the soil from erosion). The seeds contain about 20 percent protein in the mature, dry form.


[edit] Mung beans

Other names: Golden gram, green gram

Scientific names: Phaseolus aureus

Mung beans are an important crop in India, China, and the Philippines and have been introduced into other areas. They are fairly drought tolerant but susceptible to poor drainage. They are eaten as boiled mature seeds, green pods or sprouts. The crop is also used for forage, green manure or as a cover crop. Mung beans are efficient nitrogen fixers.


[edit] Soybeans

Scientific name: Glycine max

The most extensive areas of soybean production are in the U.S., Brazil, Argentina, China. and other parts of Southeast Asia, although the crop is grown in many other areas worldwide. Its reputation as a high protein crop (35-40 percent protein) has tempted many Volunteers to introduce the soybean to their work areas. However, one should be aware of the following potential problems:

  • Local pulses may be better adapted to the area. Soybeans do not tolerate soil acidity well and prefer a pH between 6.0 and 7.0. High rainfall and humidity encourages diseases and insects.
The crop is largely grown for export and for making soybean oil and meal, the latter used in livestock feed.
  • Cooked soybeans often have an unpleasant off-flavor or odor which can make them unpalatable to many people. However, the University of Illinois has developed an inexpensive cooking method that solves this problem. Peanuts have the advantage over soybeans of being both a cash crop and a food crop and are also more droughttolerant.
  • As with some sorghums and millets, soybeans are highly photosensitive to daylength, and varieties have a very narrow range of adaptation north and south of their origins. U.S. Corn Belt varieties are normal;´ grown under very long summer daylengths and if moved to short day tropical areas, they become dwarfed and reach maturity much too quickly. However, varieties are available for tropics.
  • While soybeans are an extremely efficient nitrogen fixer, they require a unique type of Rhizobia bacteria unlikely to be present in soils not previously cropped to soybeans. In such cases, the seed needs to be innoculated with a commercial stain of Rhizobium japonicum. Soybean Rhizobia are adversely affected by soil pH's much below 6.0.


[edit] Winged beans

Scientific name: Phophocarpus tetragonalobus

Winged beans are not a row crop, but have received much publicity as a possible "wonder crop." In the interest of clarification, some basic facts are presented here.

The plants are twining vines that grow to over three meters when supported and produce pods with four longitudinal jagged "wings" that contain up to 20 seeds. Winged beans are adapted to the wet tropics and have some valuable characteristics:

  • The dry seeds contain about 34 percent protein and 18 percent oil which makes them about equal to soybeans. The young leaves and pods can be eaten too.
  • Some varieties produce edible tubers with a reputed protein content of 20 percent, although some investigators feel that this is considerably overestimated.
  • They are a very efficient nitrogenfixing legume and produce good yields. Yields of up to 2500 kg/ha of mature dry seed have been reported.

Now for some of the disadvantages of winged beans:

  • The plants must be staked or they will not flower well, although they can be grown prostrate for their tubers.
  • The seeds must be cooked using a special technique and soften slowly in water. The cooked, mature seeds have a strong flavor which is disliked by some. However, they do not have potential for the making of curds and tofu as with soybeans. The seeds have some likely metabolic (digestive) inhibitors that have not been adequately investigated.

Introducing a new crop into an area is usually a task hefter left to professionals associated with a research station that has the money, time, skills, and discipline for such an undertaking. The extension workers' job is to provide the tested recommendations for the crops grown in an area.


[edit] Appendix I - Troubleshooting common crop problems

It takes a lot of practice and detective work to accurately troubleshoot crop problems. Some abnormalities like wilting or leaf yellowing can have numerous causes.

First, learn to distinguish normal from abnormal growth when you walk through a farmer's field. Keep a close watch for telltale trouble signs such as abnormal color, stunting, wilting, leaf spots, and signs of insect feeding. Make a thorough examination of affected plants, including the root system and the inside of the stem, unless the problem is obvious. Obtain deyailed information from the farmer concerning all management practices that might have a bearing on the problem (i.e. fertilizer and pesticide applications, name of crop variety, etc.). Note whether the problem occurs uniformly over the field or in patches. This can provide valuable clues, since some problems like nematodes and poor drainage seldom affect the entire field.

Troubleshooting tools

  • A pocketknife for digging up seeds or slicing plant stems to check for root and stem rots or insect borers.
  • A shovel or trowel for examining plant roots or checking for soil insects or adequate moisture.
  • A pocket magnifying glass to facilitate identification of insects and diseases.
  • A reliable soil pH test kit for checking both topsoil and subsoil pH. Especially useful in areas of high soil acidity. Beware of cheap kits, especially those using litmus paper. The HelligeTruog kit is one of the best and costs about U.S.


Troubleshooting Guide


CROP APPEARANCE

PROBABLE CAUSES

POOR SEEDLING EMERGENCE (Carefully dig up a section of row and look for the seeds)

Low-germination seed


Planting too deep or too shallow


Soil crusting or overly cloddy soil


Lack of moisture


Clogged planter


Seeds washed out by heavy rain


Fertilizer burn


Pre-emergence damping-off disease


Birds, rodents


Seed-eating insects (wireworms, seed corn maggots, seed corn beetle)

WILTING(Pull up a few plants carefully using a shovel or trowel and examine the roots. Check stem for borers or rotted or discolored tissue.)

Actual lack of moisture due to drought or poor irrigation management (watering toc lightly or too infrequently)


Diseases (bacterial or fungal wilts, certain types of rot and stem rots)


Very high temperatures, especially if combined with dry, windy conditions


Root pruning by hoe or cultivator


Nematodes (especially if confined to patches and when plants wilt despite having sufficent water)


Stem breakage or kinking

LEAF ROLLING OR CURLING

Lack of moisture (maize, sorghum, millet)


Virus


Sucking insects feeding on stem or leaves


Boron, calcium deficiency (beans only)


Verticillium wilt (peanuts)

LEAF CRINKLING, PUCKERING LEAF "BURNING" OR BROWNING

Aphids, leafhoppers feeding on leaves or stems


Drought


Excessive heat


Fertilizer burn


Insecticide overdose


Dipterex, Azodrin (Nuvacron), or methyl parathion injury on sorghum


Herbicide damage


Nutrient deficiency


Aluminum, iron, or manganese toxicity due to excessive acidity (below pH 5.5)


Salinity or sodium problems (confined largely to low ainfall areas, especially if irrigated)


Boron toxicity from irrigation water (low rainfall areas) of improper placement of fertilizer boron

LEGGY, SPINDLY PLANTS HOLES IN LEAVES

Lack of sunlight caused by overcrowding or long periods of heavy cloudiness


Caterpillars


Beetles


Earwigs


Crickets


Snails, slugs, especially on beans (check for slime trails)


Breakdown of dead tissue due to fungal or bacterial leaf spots

SPOTS ON LEAVES

Fungal or bacterial leaf spots


Virus


Sucking insects


Spilling of fertilizer on leaves


Herbicide spray drift, especially paraquat (Gramoxone)


Sunscald (beans)

LEAF MALFORMATION WITH STEM CURVING & TWISTING (Broadleaf plants only) LEAF MOTTLING, LEAF MALFORMATION, PLANT

2,4-D type herbicide damage due to spray


drift or a contaminated sprayer (broadleaf


crops only)


Virus

MALFORMATION LEAF STRIPING



Nutrient deficiency


Virus


Genetic

YELLOWING, STUNTING

Nutrient deficiency


Poor drainage


Nematodes


Low pH (excessive acidity)


Root rot, stem rot

OVERNIGHT DEFOLIATION OF PLANTS

Leaf cutter ants, grazing animals

PLANTS CUT OFF AT OR NEAR GROUND LEVEL TWISTING TUNNELS IN LEAVES YOUNG SEEDLINGS COLLAPSE NEAR GROUND LEVEL AND DIE POOR GROWTH, LACK OF VIGOR

Cutworms


Mole Crickets


Leaf miners


Fungal seedling blights


Heat girdling of stem (beans)


Too dry or too wet


Too hot or too cold


Insects, diseases


Weeds


Unadapted variety


Low pH


Salinity-alkalinity problems


Overcrowding


Shallow soil


Soil compaction, hardpan


Poor drainage


Nutrient deficiency


Faulty fertilizer practices


Nematodes


Excessive cloudiness


Herbicide carryover


Overall poor management


Damaged seed (beans)

LODGING OR STALK BREAKAGE (Maize, Sorghum, Millet)

Overcrowding


Stalk rots


Rootworms


High wind


K deficiency

POOR NODULATION ON PEANUTS, COWPEAS, SOYBEANS; OTHER LEGUMES THAT ARE EFFICIENT N FIXERS (Carefully dig up the root system and check for nodulation; clusters of fleshy nodules, especially on the taproot, and with reddish interiors are signs of good nodulation. Don't confuse nodules with nematode galls')

Soil lacks the correct type of Rhizobia-seed innoculation is needed


Improper innoculation: wrong strain, innoculant too old or improperly stored


Exposure of innoculated seed to excessive sunlight or contact with fertilizer or certain seed treatment fungicides


Excessive acidity (soybeans are especially sensitive to soil pH's below 6.0)


Molybdenum deficiency


Plants are too young (it takes 2-3 weeks after plant emergence for the nodules to become visible)


[edit] Appendix J - Guidelines for using pesticides

Pesticides are poisons and are used to kill particular plants and animals that reduce the productivity of a farmer's crop. Fortunately, however, many pesticides have unwanted side effects and may be hazardous to nonpest plants and animals, including man.

Pesticide toxicity to animals may be acute, i.e., having effects resulting in illness or death, or it may be chronic, i.e., having effects that may not be apparent for many years. Chronic toxicity may take the following forms:

oncogenicity - cancercausing
teratogenity - causing deformities in offspring
mutagenicity - causing genetic mutations
reproductive effects effecting an individual's capacity to bear young

It is important that the farmer and extension worker be aware of the level of toxicity of the chemicals with which they are working and the following table lists the relative acute toxicity of some commonly used pesticides. The toxicity classes presented are based upon oral and dermal acute toxicity to rats.

class 1 = most dangerous; requiring a label reading "danger"
class 2 = less dangerous; requiring a label reading "warning"
class 3 = less dangerous; requiring a label reading "caution"

Please note that the toxicity classes only refer to acute toxic effects and the chemical may be a Class 3, least dangerous, and still have serious potential long-term toxicity.

The acute toxicity is rated accordingly to the dose of pesticide that is lethal to 50 percent of the test animals that ingest it (oral LD50) or absorbed through their skin (dermal LD50). The LD50 of a pesticide is measured in milligrams of pure chemical per kiligrams of test animal body weight (mg/kg). The lower the LD50 the less chemical required to kill 50 percent of the test animals and thus, the higher is the pesticide's toxicity. There are several important considerations in using the LD50 ratings.

1. The LD50 ratings are based on the amounts of 100 percent strength from one percent up to 95 percent. After dilution with water for spraying, actual strength may only be about 0.1-0.2 percent. As a general rule a pesticide which is highly toxic as a concentrate (Class 1) will still be dangerous when diluted to the concentration at which it is useful. 2. The LD50 ratings give little information on the cumulative effect of repeated exposure. 3. If spilled on the skin, liquid insecticides are more readily absorbed than wettable powders or dusts. 4. Note that some insecticides like TEPP and Phosdrin are about as toxic dermally as they are orally. 5. Even Class 3 (least dangerous) insecticides like Malathion can cause severe poisoning if enough is ingested or spilled on the skin, especially in the concentrated form.

Pesticides include insecticides, fungicides, herbicides, nematicides and rodenticides. In general the herlucides and fungicides are not in the highly toxic categories (1 and 2) whereas a fair number of the insecticides and nematicides are very dangerous to use.

Table J-1 gives a partial listing of insecticides, their dermal and oral LD50s and the chemical group to which each insecticide belongs as follows:

CH = chlorinated hydrocarbon,
OP = organic phosphate,
C = carbamate,
M = miscellaneous

The antidote for poisoning varies with the chemical group. Aside from this difference, it's hard to make meaningful distinctions between these chemical groups. For example, Aldrin, DDT, Endrin, Heptachlor, Lindane. and Kelthane (dicofol) have long residual lives and are all CH's. However, in terms of their immediate toxicity, they vary greatly - DDT is a Class 4 (least dangerous), while Endrin is a Class 1 (most dangerous). Other CH's like Methoxychlor have relatively short residual lives. The OP's and C's break down fairly quickly, but, also vary greatly in toxicity.

Insecticide Names: Note that each insecticide may be marketed under several different trade names. Many extension bulletins refer to insecticides by their non-commercial chemical names (i.e. Sevin is a trade name for carbaryl). This can create much confusion in indentifying insecticides.

The following pesticides have been suspended, canceled or withdrawn United States and their use should not be encouraged in international agriculature projects:

DDT

Mirex

DBCP

Aldrin

Chlordane

2,4,5-T

Dieldrin

Heptachlor BHC

(benzene hexochloride)

Endrin

TOK

Amitroz


Kepone

Pirimicosb



gardona



dimethoate(dusts only)



galecron*

*Only can be applied under specialized handling conditions on non-food (cathon) crops where mixer/loads exposure can be carefully controlled.

File:P340.GIF
Table J-1 Toxicity of Selected Insecticides

File:P341.GIF
Table J-1 Toxicity of Selected Insecticides - continue 1

File:P342.GIF
Table J-1 Toxicity of Selected Insecticides - continue 2

Table J-1 Toxicity of Selected Insecticides


Category I

Common Name

Other Trade or Chemical Names

LD50 Oral

Rating Dermal

Chemical Group

Dasanit 6

Terracur, fensulfothion

2-10

3-30

OP

Disyston 6

Disulfoton, Fruminal, oxydisulfoton

7

15

OP

Dyfonate 6

Fonofos

8

25

OP

Endrin 2,5,6

Hexadrin

1

18

CH

Parathion 6

Ethyl parathion, Bladan, Niran, E-605, Polidol E-605, Phoskil, Orthophos, Ekatox, Parathene, Panthion, Thiophos, Alkron

13

21

OP

Phosdrin 6

mevinphos, Phosphene, Menite

6

5

OP

Systox 6

demeton, Solvirex, Systemox, Demox

6

14

OP

Telodrin

isobenzan

5-30

5-30

CH

TEPP 6

Tetron, Vapotone, Kilmite 40

1

2

OP

Thimet 6

phorate, Rampart

2

6

OP

Temik 6

aldicarb

1

below5

C

Aldrin 2,5

Aldrite, Aldrosol, Drinox, Seedrin, Octalene

39

98

CH

Azodrin 6

Nuvacron, Monocron, monocrotophos

17

126

OP

Bidrin 6

Ekafos, Carbicron

21

43

OP

Birlane 6

chlorfenvinphos, Supona, Sapecron

10-155

108

OP

Dieldrin 2,5

Alvit, Octalax, Dieldrite

46

90

CH

Furadan 4

carbofuran, Curaterr (See below for granules)

11

10,000

C

Gusathion 6

Guthion, Carfene, azinphosmethyl

12

220

OP

Methyl Parathion 6

Folidol M, Parathion M, Nitrox, Metron, Parapest, Dalf, Partron, Phospherno

14

67

OP

Lannate 6

Methomyl, Nudrin

17-24

1000

C

Monitor 6

Tamaron, methamidophos

21

118

OP

Mocap 6

Jolt, Prophos, ethoprop

61

26

OP

Thiodan

endosulfan; Cyclodan, Malix, Thimul, Thiodex

43

130

CH

Trithion

carbophenothion, Carrathion

30

54

OP

Nemacur 6

phenamiphos, fenamiphos

8

72


Category II

BHC 2,5

benzene hexachloride, Hexachlor, Benzahex, Benzel, Soprocide, Dol, Dolmix, Hazafor, HCH

600

---

CH

Bux

Bufenkarb, metalkamate

87

400

C

Chlordane

Chlorkill, Orthochlor, Belt, Ascrotoxyphos pon

335

840

CH

Ciodrin

Basudin, Spectracide, Diazol,

125

385

OP

Diazinon

Gardentox, Sarolex

180

900

OP

Dibrom

naled, Bromex

250

800

OP

Dimethoate

Cygon, Rogor, Perfekthion, Roxon, De-Feud

215

400

OP

Dursban

chlorpyrifos, Lorsban

97-276

---

OP

Dipterex

Dylox, Klorfon, Danex, Trichiorfon, Neguvon, Anthon, Bovinox, Proxol, Tugon, Trinex

180

2000

OP

Folimat

methoate

50

700

OP

Folithion

Nuval, Agrothion, fenitrothion

500

1300

OP

Hostathion

triazaphos

80

1100

OP

Heptachlor 2,5

Drinox H-34, Heptamul

100

195

CH

Lebaycid

Fenthion

200

1300

OP

Lindane 2

Gamma BHC, Gammexane, Isotox, OKO, Benesan, Lindagam, Lintox, Novigam, Silvanol

88

1000

CH

Metasystox

oxydemetonmethyl

47

173

OP

Mirex 5

dechlorane

300

800

CH

Toxaphene 3,7

Motox, Strobane T, Toxakil, Magnum 44

50

1075

CH

Unden

Baygon, Suncide, Senoran, Blattanex, PHC, porpoxur

100

1000

C

Vapona

DDVP, dichlorvos, Nuvah, Phosvit

90

107

OP

Category III

DDT 2,5

Anofex, Genitox, Gesarol, Neocid, etc.

113

2510

CH

Galecron

chlordimeform, Fundal 127-

372

3000

OP

Gardona 5

Appex, Rabon

4000

5000

OP

Kelthane 3

dicofol, Acarin, Mitigan

1100

1230

CH

Malathion

Cythion, Unithion, Emmatos, Fy- fanon, Malaspray, Malamar, Zithiol

1375

4444

OP

Methoxychlor

Marlate

5000

6000

OP

Morestan

Forstan

1800

2000+


Orthene

Acephate, Ortran

866

---

OP

Sevin

carbaryl, Vetox, Ravyon, Tricarnam

850

4000

C

Tedion

Tetradifon

14,700

10,000

CH

Volaton

phoxim, Valexon

1845

1000+

OP

Actellic

pirimiphos-methyl, Blex, Silosan

2080

2000+

OP

The following pesticides have been restricted for use in the United States, based on human hazard, and their use should not be encouraged in international small farmers' agricultural projects:

methyl paralthion

methamidophos

ethyl paralthion

methomyl (lannote) tamaron (monitor)

parathion

carbofubon (except granular formulations) dyfonate trithion

The following pesticides are being investigated by the U.S. Environmental Protection Agency under the Rebuttable Presumption Against Registration (RPAR) Program. These pesticides have possible risks in the following five areas, but the risks have not been proven and they are therefore still permitted for use:

1. Acute toxicity;
2. Chronic toxicity including oncogenic and mutagenic effects;
3. Other chronic effects;
4. Effects on wildlife; and
5. Lack of emergency treatment.

Pesticides presently under RPAR review include the following:

Beronyl

EBDC's, including Maneb, mancozeb, metiram, nodam, zireb, amobam

Cadmium

Ethylene dibromide

Captan

Ethylene oxide

Diallate

Inosyohk Arsenicals


Lindane Maleic


Hydrozide


Sulfate


Toxaphene


Trifnralin

General Information on Common Insecticides

I Bacillus Thuringiensis

A biological insecticide made from a natural bacteria that kills only certain types of caterpillars; most effective against cabbage loopers but also against hornworms (Protoparce) and earworms (Heliothis). Non-toxic to humans and animals. Insects don't die immediately but stop feeding within a few hours - it may take a few days for them to die. Apply before the caterpillars are large for best results. Needs no stickerspreader for most formulations. Compatible with most other pesticides. Don't store the diluted spray for more than 12 hours. Dosage varies widely with the particular formulation, II Diazinon (Basudin, Diazol, etc.)

Fairly broad-spectrum including control of many soil insects but not as effective on beetles (except for the Mexican bean beetle). Highly toxic to bees. Aboveground insect control: 4cc/ liter of Diazinon 25 percent EC or Basudin 40 percent WP. Dimethoate (PerfekthionR CygonR RogorR etc.)

A systemic insecticide of moderate toxicity to humans (Class 2). Specifically for sucking insects (aphids, leafhoppers, thrips, stinkbugs, mites, etc.) and leaf miners. Should provide control for 10-14 days. Don't apply within 1421 days of harvest. Highly toxic to bees with a one- to two-day residual effect. General dosages for the three most common formulations (all emulsifiable concentrates are given below):

Formulation of dimethoate

Dosage-cc/100 liters

200 grams active ingred./liter

100-200

400 grams a.i./liter

50-100

500 grams a.i./liter

50-75

Dipterex (trichlorfon, DyloxR,DanexR, KlorfonR etc.)

Provides fairly broad spectrum insect control but not as effective on aphids, mites and thrips. Dipterex causes severe injury when applied to sorghum. Low to high toxicity for humans.

General above-ground insect control: 125-250 cc (100-200 grams) of Dipterex per 100 liters of water or 5-10 cc .

Armyworms or earworms feeding in the leaf whorl or maize: Dipterex 2.5 percent granules give longer control than sprays; apply a pinch in each whorl which works out to about 10-15 kg/ha (lbs./acre) of granules. 100 cc of the granules weigh about 60 g. Furadan (Carbofuran)

A systemic insecticidenematocide available in 3 granular formulations (3 percent, 5 percent, 10 percent) and as a wettable powder. The wettable powder formulation is considered too toxic for normal use, however; the pure strength chemical has an extremely high oral but very low dermal toxicity. Furadan granules are usually applied to the soil either in the seed furrow or in a band centered over the crop row; furadan kills soil nematodes and soil insects but is also absorbed by the roots and translocated throughout the plant where it controls sucking insects, stem borers, and leaf feeding beetles and caterpillars for up to 30-40 days. Band treatments are recommended for root feeding soil insects, while seed furrow applications can be used for foliar insects. Furadan can also be band applied during the growing season if it is cultivated into the soil or can be applied to the leaf whorl of maize. May cause minor foliar injury to peanuts; do not place in contact with sorghum or bean seed.

Kelthane (dicofol, Acarin, Mitigan, Carbax)

Kills mites only; not harmful to beneficial insects. Gives good initial control of mites and has good residual activity against them; non-systemic. Spray undersides of leaves. Don't feed crop residues to dairy or slaughter anitreatment is effective approximately four months.

Sevin (carbaryl, Vetox, Ravyon, etc.)

Broad-spectrum insect control except for aphids and mites. Very low toxicity for humans (Class 3). Very toxic to bees with a 7-12 day residual effect. General dosage for Sevin: Use the 50 percent WP at 8-16 cc per/1. Use 80 percent WP at 5-10 cc/1 or 1.252.5 tablespoons/gallon. Can be applied right up to harvest time on the reference crops.

Household dosages: For cockroaches and ants, use as a 2.5 percent strength spray (active ingredient basis); this equals about 100 cc of Sevin 80 WP per liter of water; don't use more than twice a week.

Ticks, lice, fleas, horn flies on beef cattle, horses, swine: Use 20 cc Sevin 80 percent WP per liter of water. Don't apply within five days of slaughter.

Mites, lice, fleas on poultry: Use at same rate as for beef cattle and apply about 4 liters per 100 birds; don't apply within seven days of slaughter.

Volaton (Valexon, phoxim)

A less toxic and persistent replacement for Aldrin for soil insect control. Low toxicity for humans. Also available as a liquid formulation for leaf insects. General dosage for Volaton: Use the 2.5 percent granules at 60 kg/ha for furrow application and 120 kg/ha for broadcast application. Work into the top 5-7.5 cm of soil. Fungicides: Except for mercury based fungicides used for seed treatment like Agallol, Semesan, and Ceresan, fungicides pose little hazard to health. Their oral toxicity is comparatively low, and there is little danger of dermal absorption. Some may cause allergies in sensitive people through skin contact and can be eye irritants as well.

Low toxicity (Class 3). General dosage: Use the 35 percent WP formulation at four to five cc per liter of water. Use the 18.5 percent EC at 1.5cc per liter of water.

Lebaycid (Fenthion, Baytex, Baycid)

A relatively low toxicity (Class 2) organic phosphate for chewing and sucking insects, including mites. Don't spray plants when temperatures exceed 32°C. Very toxic to bees with two to three days' residual activity. General dosage for Lebaycid: Use Lebaycid 40 percent WP at 1.5-2 g per liter of water; use Lebaycid 50 percent EC at 1-1.5 cc/liter of water.

Malathion (Cythion, Unithion, Mala spray)

A broad-spectrum insecticide of low human toxicity (Class 3). Not as effective on armyworms, earworms, and flea beetles. Its residual activity is decreased if mixed with water above pH 8.0.

Can be mixed with other pesticides except Bordeau and lime sulfur. Liquid formulations are moderately toxic to bees with less than two hours' residual effect; wettable powder formulations are highly toxic but have less than one day's residual effect on bees. General dosage for Malathion: Four to five cc of Malathion 50 percent or 57 percent EC per liter of water. Use Malathion 25 pecent WP at 12 cc/liter.

Using Malathion for Control of Stored Grain Insects

Grain which is to be held in storage should be protected from stored grain insects. An approved grain protectant applied to the grain at time of storage will help prevent an early infestation. Premium grade Malathion is the only protectant available. Malathion can be applied as a dust or spray at the following rates:

1. One percent dust on wheat flour at the rate of 60 lbs. per 1000 bushels of grain.
2. One pint of 57 percent (five pounds/gallon) EC in three to five gallons of water per 1000 bushels of grain.


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Table J-2: Some insecticide recommendations for specific insects attacking the reference crops

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Table J-2: Some insecticide recommendations for specific insects attacking the reference crops - continue 1

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Table J-2: Some insecticide recommendations for specific insects attacking the reference crops - continue 2

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Table J-2: Some insecticide recommendations for specific insects attacking the reference crops - continue 3

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Table J-2: Some insecticide recommendations for specific insects attacking the reference crops - continue 4

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Table J-2: Some insecticide recommendations for specific insects attacking the reference crops - continue 5

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Table J-2: Some insecticide recommendations for specific insects attacking the reference crops - continue 6

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Table J-2: Some insecticide recommendations for specific insects attacking the reference crops - continue 7

Bee Poisoning Hazard of Pesticides

Most bee poisoning occurs when insecticides are applied during the crop's flowering period. Spray drift is another hazard. To avoid bee kill:

  • Do not apply insecticides toxic to bees when crops are flowering. Insecticides applied as a dust are the most harmful to bees.
  • Do not dump unused quantities of dusts or sprays where they might become a bee hazard. Bees will sometimes collect any type of fine dust when pollen is scarce.
  • Use insecticides of relatively low toxicity and residual effect for bees.
  • Plug up or cover the hive entrances the night before spraying and then reopen them once the residual effect is over.

None of the fungicides is toxic to bees. The same is true with most herbicides, although Gesaprim (AAtrex, Atrazine) and the 2,4-D herbicides are low to moderate in toxicity.

Here is a partial guide to the relative toxicity of various insecticides for bees. Note the differences in residual effect.

WHEN APPLIED AS A SPRAY

Insecticide

Toxicity to Bees

Residual Effect

Aldrin

Very high

Several days

Diazinon

High

One day

Dipterex

Low to High

2-5 hours

Lebaycid

Very high

2-3 days

Kelthane (dicofol)

Low


Methyl parathion

High

Less than one day

Malathion

Moderate (liquid)

Less than 2 hours


High (wettable powder)

Less than one day

Metasystox

Moderate

None

Dimethoate

Very High

1-2 days

Sevin

Moderate to High

7-12 days

Insecticide Safety Guidelines

1. Read and follow label instructions: If the label is vague, try and obtain a descriptive pamphlet. Not all insecticides can be applied to all crops. Inappropriate use can damage plants or result in undesirable residues. The label should state the minimum allowable interval between application and harvest. 2. Never buy insecticides that come in unlabeled bottles or bags; you may not be buying what you think. This is a serious problem in developing countries where small farmers often purchase insecticides in Coke bottles, etc. 3. When working with farmers, especially those using backpack sprayers instead of tractor sprayers, NEVER use or recommend those insecticides in toxicity Class 1. Their safe use requires extraordinary precautions and safety devices (gloves, special respirators, protective clothing, etc.). Whenever possible, avoid using Class 2 products. Unfortunately, extension pamphlets in many developing countries commonly recommend Class 1 and Class 2 products. 4. If using Class 2 insecticides, wear rubber gloves and a suitable respirator (good ones cost ), as well as long pants and a long-sleeve shirt; wear rubber boots if using a backpack sprayer. This clothing should be washed separately from other garments. 5. Do not handle plants within five days after treatment with a Class 1 insecticide or with Gusathion (Guthion). Do not handle plants within one day of using methyl parathion. 6. Class 1 and 2 insecticides are likely to be especially common in tobacco and cotton growing areas. 7. Do not smoke or eat while applying pesticides. Wash up well afterwards. 8. Repair all leaking hoses and connections before using a sprayer. 9. Prepare insecticide solutions in a wellventilated place, preferably outdoors. 10. Never spray or dust on very windy days or against a breeze. 11. Notify beekeepers the day before spraying. 12. Insecticide poisoning hazards increase in hot weather. 13. Store insecticides out of reach of children and away from food and living quarters. Store them in their original labeled containers which should be tightly sealed. 14. Leftover spray mixtures should be poured into a hole dug in the ground well away from streams and wells. 15. Do not contaminate steams or other water sources with insecticides either during application or when cleaning equipment. 16. Make sure insecticide containers are never put to any other use. Burn sacks and plastic containers (don't breath the smoke). Punch holes in metal ones and bury them. 17. Make sure that farmers are well aware of safety precautions. It is important that they understand that insecticides vary greatly in their toxicity. 18. Make sure that you and your client farmers are familiar with the symptoms of insecticide poisoning and the first aid procedures given below.

Symptoms of Insecticide Poisoning

Organic Phosphates & Carbamates (Parathion, Malathion, Sevin, etc.)

Both groups affect mammals by inhibiting the body's production of the enzyme cholinesterase which regulates the involuntary nervous system (breathing, urinary and bowel control, and muscle movements).

Initial Symptoms:

Dizziness, headache, nausea, vomiting, tightness of the chest, excessive sweat-ing. These are followed or accompanied by blurring of vision, diarrhea, watering of the eyes, excessive salivation, muscle twitching, and mental confusion. Tiny (pinpoint) pupils are another sign.

Late Symptoms:

Fluid in chest, convulsion, coma, loss or urinary or bowel control, loss of breathing.


Note: Repeated exposure to these organic phosphate and carbamate insecticides may increase susceptibility to poisoning by gradually lowering the body's cholinesterase level without producing symptoms. This is a temporary condition. Commerical insecticide applicators in the U.S. usually have their cholinesterase levels routinely monitored.

Symptoms of Chlorinated Hydrocarbon Poisoning (Aldrin, Endrin, Chlor cane, Dieldrin, etc.)

Apprehension, dizziness, hyper-excitability, headache, fatigue, and convulsions. Oral ingestion may cause convulsions and tremors as the first symptoms.

First Aid Measures

1. In severe poisoning, breathing may stop, which makes mouth to mouth resuscitation the first priority. Use full CPR if the heart has stopped. 2. If the insecticide has been swallowed and the patient has not vomited, induce vomiting by giving a tablespoon of salt dissolved in half a glass of warm water. An emetic like Emesis (syrup of Ipecac) may be more effective, This should be followed by 30 grams (1 oz.) of activated charcoal* dissolved in water to help absorb the remaining insecticide from the intestines. 3. Get the patient to a doctor as soon as possible. Bring along the insecticide label. 4. In the meantime, make the patient lie down and keep warm. 5. If excessive amounts are spilled on the skin (especially in the concentrate form), immediately remove clothing and bathe the skin in generous amounts of water and soap. 6. If the eyes have been contaminated by dusts or sprays, flush them immediately for at least five minutes with copious amounts of water. Insecticide absorption through the eyes is very rapid.

Antidotes

Whenever possible, antidotes should be given only under medical supervision. Too much or too little


[edit] Appendix K - Guidelines for applying herbicides with sprayers

The farmer should calibrate his/ her sprayer when a pesticide needs to be applied at an accurate dosage in order to avoid applying too much, which wastes money and might make the product ineffective. When working with small fields, farmers can usually use generalized recommendations given in cc/liter or tablespoons/gallon for insecticides and most fungicides. However, most herbicides require more accurate application, which means that sprayer calibration is usually needed.

The Principles Involved

When a pesticide recommendation is given in terms of kg/ha or lbs./ acre of active ingredient or actual product, the farm needs to know two things before he/she can apply the correct dosage:

  • The amount of pesticide needed for his/her particular field.
  • The amount of water needed to convey the pesticide to the plants or soil and give adequate coverage.

Once these are know, it is a simple matter of mixing the correct amounts of water and pesticide together, then spraying.


[edit] Calibration of backpack sprayers

NOTE: Only backpack sprayers with continous pumping action should be used when calibration is needed; compression type sprayers (the garden variety that needs to be set down to be pumped up) are not suitable because of their uneven pressure.

Step 1: Fill the sprayer with three to four liters of water and begin spraying the soil or crop using the same speed, coverage and pressure that will be used in applying the pesiticide Measure the area covered by this amount water. Repeat this procedure several times to determine the average area sprayed. You can measure the area in terms of squre feet or in terms of row length.

Step 2: Based on the area covered, you can calculate the amount of water needed to cover the field. For example, if three liters covered 60 square feet, and the field measures 20 x 30 feet, it would take 30 liters of water to cover the field.

Step 3: Determine the number of sprayer tankfuls of water needed to cover the field. For example, if the backpack sprayer holds 15 1, it will take two tankfuls to cover the field.

Step 4: Determine how much actual pesticide is needed for the field. If 4 kg of Sevin 50 percent wettable powder are needed per hectare and the farmer's field is 600 square feet, this would mean that 240 l of insecticide are required. Here's how we worked it out:

600 sq. m / 10,000 sq. m = X / 4000

X = 240

Step 5: Divide the amount of pesticide needed for the field by the number of sprayer tankfuls of water to determine how much pesticide is needed per tankful:

240 g Sevin 50% WP / 2 tankfuls = 120 g Sevin/ tankful

NOTE: A sprayer should be recalibrated each time it is used on a different crop, different of stage of crop growth or when another pesticide is used.

Alternate Method Using Row Length

When a pesticide is to be applied to a crop grown in rows, you can use row length instead of area as the basis for calibration. PROBLEM: Label instructions advise Juan to apply Malathion 50 percent strength liquid at the rate of 4 1/ha. His field measures 40 x 50 m and the bean rows are spaced 50 cm apart. His backpack sprayer hold 15 1, and he needs to know how much Malathion should be added to each tankful.

SOLUTION

1. Follow the same procedure as with Step 1 of the 'first method but measure the amount of row length covered by the 34 1 instead of area. Suppose that Juan was able to cover 150 m of row length with 3 1. 2. Find out how many meters of row length his field has. Let's say the crop rows are running the long way (i.e. 50 m). Number of rows x 50 m = field's total row length Number of rows = 40 m / 0.8 m (i.e. the field's width) (80 cm) 50 rows x 50 m = 2500 m of row length in Juan's field 3. Find out how much water will be needed to cover the 2500 m of row length based on 3 1 per each 150 m 150 m / 2500 m = 3 1 / X 1 150 X = 7500 X = 50 l of water needed to cover the field 4. Find out how much Malathion 50 percent liquid will be needed for the field based on 4 1 of the pesticide per hectare (10,000 sq. m). Since Juan's field measures 40 x 50m, its area is 2000 sq. m. 2000 sq. m / 10,000 sq. m = X 1 Malathion / 4 1 Malathion X = 0.8 1 or 800 cc of Malathion needed 5. Find out how much Malathion is needed per sprayer tankful based on a capacity of 15 1. 50 1 of water needed / 15 1 tank capacity = 3.33 tankfuls needed 800 cc Malathion / 3.33 tankfuls = 240 cc of Malathion 50% liquid needed per sprayer tankful


[edit] Calibration of tractor sprayers

Things To Do Before Calibrating a Sprayer

  • Rinse out the tank and refill it with clean water.
  • Remove and clean all nozzles and screens. Use an old toothbrush.
  • Start the sprayer and flush the hoses and boom with plenty of clean water.
  • Replace screens and nozzles and make sure that they are of the correct spray pattern type and size.
  • Check all connections for leaks.
  • Adjust the pressure regulator to the correct pressure with the tractor engine running at field operating speed and with the nozzles running.
  • Check the water output of each nozzle and replace any that are 15 percent above or below the average. Remember to:
  • Calibrate the sprayer using the same tractor speed and spray pressure that will be used to apply the pesticide.

When using water to calibrate, the spray rate of the water may differ somewhat from that of the actual pesticide-water solution due to differences in density and viscosity,

Calibration Method

1. Drive the tractor at field operating speed in the appropriate gear and measure the distance covered in terms of meters per minute (1 k.p.h. = 16.7 m per minute)

2. Operate the sprayer at the correct pressure with the tractor stationary, and measure the total output of the spray boom in liters per minute. To do this, use a jar to measure the individual output of several nozzles, calculate the average, and then multiply this by the number of nozzles to get the total output.

3. Measure the width of coverage of the spray boom in meters. Do this by multiplying the number of nozzles on the boom by their spacing in centimeters and then divide by 100 to obtain the total width in meters.

4. Use this formula to determine how many liters of water are needed per hectare:

Liter/hectare = 10,000 x output of spray boom in l/m / tractor speed in m/mint x boom width in m

Once you know the volume of water needed per acre or hectare, you can determine how much pesticide needs to be added per tankful of water by using the same procedure as given for backpack sprayers.

Adjusting Sprayer Output

If the water output is too low or too high per hectare, change nozzle sizes or tractor speed. Changing the spraying pressure is relatively ineffective and may distort the spray pattern or cause excessive drift. Pressure must be increased four-fold in order to double output.


[edit] How to clean sprayers

In most cases, herbicide residues can be removed from sprayers by rinsing them out thoroughly with soap and water. However, the phenoxy herbicides (2,4-D, 24-5-%, MCPA, Tordon, etc.) cannot be removed with normal cleaning procedures, and contaminated sprayers may cause damage when used to apply pesticides to broadleaf crops. In fact, farmers should preferably use a separate sprayer for applying phenoxy herbicides, but reasonably good cleaning can be achieved as follows:

For backpack (knapsack sprayers: Fill the sprayer with water and add household ammonia at the rate of about 20 cc (ml) per liter of tank capacity. Spray part of the mixture out through the nozzle, and then let the sprayer sit for a day. Spray out the rest of the solution and then rinse with detergent and water. To test the sprayer, refill it with water and spray a few sensitive plants (tomatoes, beans, cotton, etc.). If injury signs are not noticed within a day or two, the sprayer is probably safe to use on broadleaf crops.
NOTE: Household ammonia or lye may damage the inner pressure cylinder if it is made of brass; in this case, use activated charcoal as below.

For tractor sprayers: Use two pounds of washing soda or soda ash (a 50-50 mix of washing soda and lye) 250 grams per 100 liters in the same way as for backpack sprayers. Activated charcoal, if available, will do a very quick job in just two to three minutes when used at 1 kg per 100 liters. Rinse out the sprayer with soap and water afterwards.

Symptoms of phenoxy herbicide damage: Only broadleaf plants are affected. In minor cases, the leaves show a slight downward curvature. If injury is severe, leaves and stems become very curved and twisted with considerable leaf distortion.

All washing should be done at a site away from drinking water sources for people or livestock or water bodies that might be polluted by the washwater.


[edit] Appendix L - Important planting skill for extension workers

Most extension workers need five basic planting skills:

1. How to calibrate a planter. 2. How to calculate the probable final stand, given seed spacing and row width. 3. How to calculate the inrow seed spacing needed to provide a given population at various row widths. 4. How to determine the amount of seed needed for a given field size. 5. How to determine a farmer's actual plant population in the field Using a measuring tape.


[edit] Calculation of final stand

The calculation of the final stand is accomplished by the following formula:

Plant population/ha = [100,000,000 cm² /ha ] / [seed spacing in the row in cm × row width in cm]

For example, if the row width is 40 cm and seeds are spaced 10 cm apart. the final stand, assuming 100 percent germination and no plant mortality, would have:

100,000,000 / 40 x 10 = 50,000 plants

Likewise if the crop is planted in hills the calculation made is:

Plant population/ha = [100,000,000 (cm²/ha) x number of seeds/hill] / row width (cm) x hill spacing (cm)

Thus planting in 50 cm width with 50 cm between hills and two seeds planted per hill yields:

100,000,000 x 2 / 50 x 50 = 80,000 plants/ha

The same formula can be used to calculate the in-row seed spacing needed to provide a given population at various row widths. For example, if an optimal population of 100,000 plants/ha is desired, then:

100,000 plants/ha = 100,000,000 / [row seed width × seed spacing (cm)

or:

row width x seed spacing = 1000 cm²

This spacing can be achieved using:

10 cm seed-spacing in 100 cm row width,
20 cm seed-spacing in 50 cm row width,
15 cm seed-spacing in approx. 70 cm rows, etc.

Note again that the calculation does not account for losses due to poor germination or plant mortality. You may want to plant 15 or 20 percent more than the amount you wish to harvest in order to account for these probable losses.


[edit] How to determine amount of seed needed to plant a given field size

You first need to know how many seeds of each crop are contained in a kilogram. The most accurate way of calculating this is to weigh out a 60 g sample of the seed and count it if you can find a reliable scale (i.e. at the post office or at a pharmacy). Multiplying the number by 10 will give the number of seeds per kilogram. Ot wise, you can use the table below as a rough guide:

Table 15 Number of Seeds per Kilogram

Maize

1760-2860

Sorghum

26,400-44,000

Peanuts

1100-1540

Beans

3000-3960

Cowpeas

3960-4040


To find the kilograms of seed needed per hectare, simply divide the number of seeds needed by the number of seeds/kg. Multiplying this times the size of the field in hectares will give the total amount of seed required.


[edit] How to determine a farmer's actual plant population

When troubleshooting a farmer's field, it is usually valuable to check out his plant population, since this has an important influence on yield potential and response to fertilizer. This can be easily done by counting the plants in 510 randomly selected strips of row each equal to 1/1000th of a hectare.

Step 1: First determine the field's average row width by measuring the distance across 10 complete rows and then dividing by 10. Do this at several random locations to get a representative average.

Step 2: Refer to the 1/1000th hectare row length chart for the proper random selection procedure.

Step 3: Select at random five to ten row strips of the appropriate length and count the number of plants in each and record it.

Step 4: Multiply the average number of plants in the row strips by 1000 to yield the plant population per hectare.

How to Make A Pre-Harvest Yield Estimate

A pre-harvest yield estimate can be accurate to within 5 percent of the actual harvested yield if the correct procedure is used. When working with trial and demonstration plots, you should always take such a pre-harvest yield sample of both the test plot and the control plot. There is always the chance that the plots might be inadvertently harvested before the agreed-upon time without the yields being measured. Pre-harvest yield sampling is also a quick way of estimating crop yields in farmers' fields.

General Principles Of Yield Sampling

1. Samples should be collected at random for various portions of the field or plot. Do not purposely select samples from higher- or lower-producing areas within the plot or your estimate may be very inaccurate A random sampling pattern should be determined before you enter the field so you will not be tempted to choose them by visual appearance.
2. Don't collect yield samples more than one week before the actual harvest.
3. When taking each sample, the area (or row length) to be harvested must be precisely measured. Do not estimate' Remember that any error in the sample area size will be magnified hundreds of times when converting the yield to a larger land unit basis.
4. You must adjust the sample weights to account for factors like excess moisture, damage, and foreign matter.

How to Take Samples and Estimate Yields

1. The Sampling Procedure

a. Number of samples: For plots less than 0.5 ha, take a minimum of five samples. For plots of over 0.5 ha, take between five and ten. If crop growth is not very uniform, take ten samples. b. Size of each sample: Take each sample from the samesized area or same amount of row length. Individual sample size should be between 2.5 and 5.0 square meters. For row crops, the area of a sample is determined by multiplying row length by row width. (Harvesting three meters of corn row planted in rows one meter wide will give you a sampling area of three square meters.) Alternatively, use a section of row length equal to 1/1000th of a hectare. This will make later math calculations simpler, and the 1/1000 ha row length can be taken from the following table.

Row Width

1/1000th hectare Row Length

50 cm

20.00 m

60 cm

16.67 m

70 cm

14.28 m

75 cm

13.33 m

80 cm

12.50 m

90 cm

11.11 m

100 cm

10.00 m

110 cm

9.10 m

c. Taking a random sample: Decide on the sampling pattern before entering the field, and do not deviate from it. To randomize, the field can be divided up into sections and each section given a number drawn from a hat. Or you can pick randomized starting points at the side of the field and then enter random distances from the starting point. A good system for row crops is to number the rows and select them at random, then select the distance into the row (field) at random. NOTE: Exclude three meters or four rows of perimeter from your sampling area along all four sides of the plot to ensure sampling from the heart of the plot.

2. Accuracy: Use a tape to measure each sampling area or row length. Use an accurate scale to record the total weight of the samples within one plot.

3. Handling the Samples: The samples should be harvested and processed according to local prevailing methods. If drying is required before shelling or threshing, be sure the location is secure and free from rodents or birds.

4. Weighing the Sample: Use an accurate portable scale. You do not need to weigh individual samples separately, but only the fatal collective sample from the plot. If you cannot find a good portable scale, have the grain weighed in town.

5. Checking Grade: Take a random sample of the collective sample and have it checked for moisture content and any other graded qualities if necessary. (Refer to the storage section in Chapter 7 for how to determine grain moisture content.)

6. Yield Calculations:

Size of total sample area = No of samples × size of individual sample areas

IMG001.GIF

7. Correcting for Moisture: Yields are usually based on grain that is dry enough to store in shelled form (usually 13-14 percent moisture content). If you base your estimates on the weight of a high moisture sample, you should revise the yield downward using this simple formula (otherwise, dry the grain first).

Grain weight after drying = [% dry matter before drying / % dry matter after drying] x original grain weight

Example: Suppose you weigh a collective sample of "wet" grain and then estimate the plot yield to be equal to 3500 kg/ha. A moisture test shows the sample has 22 percent moisture; what is the actual yield based on 13 percent moisture?

22% moisture = 78% dry matter,
13% moisture = 87% dry matter

78% / 87% x 3500 kg/ha = 3138 kg/ha yield based on 13% moisture

A Yield Estimate Example

Suppose you are taking a yield estimate on a farmer's maize plot which is slightly less than 0.5 hectare. The rows are planted 90cm apart, and you decide to take six samples, each consisting of 1/1000th hectare of row length. The collective weight of the shelled, dried maize is 18 kg. What is the estimated yield on a per hectare basis?

Solution:

area of collected sample = 6/1000ths of a hectare = 60 sq. meters

18 kg x [10000 sq.m (1 hectare) / 60 sq. meters] = 3000 kg/ha estimated yield