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Maintenance liming: slight limings to supplement the lime store is best done in early spring after plowing and then well mixed.
Maintenance liming: slight limings to supplement the lime store is best done in early spring after plowing and then well mixed.


[[Category:Agriculture_manual]]
[[Category:Agriculture manual]]
[[Category:Soil]]
[[Category:Soil]]
[[Category:Fertilizer]]

Revision as of 12:19, 26 September 2010

Part 2: Soil improvement and fertilisation

Plant nutrition

Previously it was believed that for their nutrition, plants consumed organic matter from the soil (humus theory). Through research at the end of the 18th century, a different view was attained regarding their nutrition. Plant did not absorb organic matter from the ground but produced it themselves. This required:

  • carbon dioxide (CO2)
  • water
  • salts

With these simple inorganic substances, plants build a wide variety of organic compounds as carbohydrates (sugars, starches, cellulose), fats, oils, proteins, ... This requires:

  • the absorption of CO2 by diffusion from the air entered through the plant's stomata
  • the absorption of water trough the roots by osmosis from the soil (water is transported via the half-permeable wall from the weakest to the strongest salt solution)
  • the absorption of salts: only possible if they are dissolved in soil water. Salts split apart in water into charged particles (ions). NaCl (table salt) splits apart into Na+ and Cl-. The absorption of salts can only be done trough the form of ions. The uptake of ions occurs trough ion exchange. If the plant absorbs a positive ion, it will have to give up a positive ion. Conversely, he must give off a negative ion if it absorbs a negative ion. The absorption of a positive ion done by giving up an H+, the absorption of a negative ion is done by giving off a negative HCO3-.
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Nutrition constituents

Carbon dioxide (CO2) and water (H2O) are the main fertilisers; they supply the elements C, H and O, essential building blocks of all organic parts of the plant. In addition, the plant has a number of necessary elements required for several organic compounds.

  • Main elements of macro-elements: N, P, K, S, Ca, Mg of which the plant needs relatively large quantities.
  • Trace elements or micro-elements: Mn, Cu, B, Mo, Zn, Fe of which the plant needs only very small quantities in comparison to the main elements (up to 1000 times less)
  • Non-essential elements: of which the plants can be develop themselves even in their absence: Na, Cl, Al, Si

In practice, the fertilision is mostly done using N, P, K. The soil in Belgium contains sufficient amounts of S, so that adding this is not necessary. Ca is supplied together with different N- and P-fertilizers. Lime fertilizers are not supplied because of Ca-needs but to improve the pH and the soil structure. Trace elements are often found in small amounts in the administered fertilizers.

All nutrients except for CO2, are generally absorbed by the plant from the soil. Plant nutrition comes in several forms:

  • dissolved in soil water as ions: directly absorbable by the plant
  • Adsorbed unto the clay-humus complex: clay and humus particles are electrically negatively charged. Thus they attract positively charged particles (H+, K+, Na+, NH4+, Ca2+, Mg2+, ...) and hold these. Trough exchange with positive ions from the soil water, these are released again and can be absorbed through the plant.
  • Mineral reserve: solid constituents of the soil consist of minerals (carbonates, phosphates, silicates, quartz). These include Na, K, Ca, Mg, Fe which are gradually released by the weathering of the rocks.
  • Organic reserves: the remains of dead plants and animals that are not directly absorbable. They are gradually made available to the plant by mineralization. The total reserve on plant nutrition is often enormous, only a small portion of this is absorbable by the plant.
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Soil analysis

A soil analysis includes the determination of:

  • the soil type
  • the level of acidity in PH-KCl
  • the level of humus in carbon %
  • the absorbable level of P, K, Mg, Ca and Na for the plant

On request, additional determinations can be implemented, such as the determination of specific trace elements. The levels of nutrients are expressed in mg pure element per 100g air-dry soil. The analysis results can be compared with a target result. The target result is specific for each lot and takes into account the soil type, the level of carbon and probing depth. The level of fertilisation is categorised into 7 rating classes.

Example 1 of a soil analysis (Soil analysis service of Belgium):

Plot details B.D. Serial: T0007111 Nr. of the probing: JR21 (4) lot name: Garden

Analysis results and assessment:

Determination Determination result Target figure* Assessment
Soil type 10 -- Coarse sand
Acidity: pH-KCl 7,3 5,4 High. Do not lime.
Humus: carbon 2,2 2,3 Normal.
Phosphorus (P) 65 21 Very High. Do not administer phosphorus for the next years.
Potassium (potash) (K) 42 27 High. At most, only administer provisional light potash manures
Magnesium (Mg) 28 8 High. Magnesium fertilisation is unnecessary for the moment.
Calcium (Ca) 535 103 High
  • Target figures are individual per plot. They are dependant on the texture (soil) and the humus content (volume/weight) for a given soil. With numbers off the target figures, the ratio can be more important than the level itself.

Fertilisation advise: in kg/are (1 are = 100m²) for a vegetable garden

Liming: 0.0 kg acid binding value per 100m² Nitrogen: Following nitrogen fertilization is to be considered as an average for this plot with the user-specified crop (all per 100m²).

For coal, leek, tomatoes, celery, spinach, etc: approx. 1.5 kg of nitrogen. This corresponds (in commercial fertilizer) to:

  • Approximately 5.6 kg ammonia nitrate 27% N
  • Approximately 15.0 kg of nitrogen fertilizer and 10% N
  • Approximately 7.3 kg ammonium sulphate 20.5% N

For potatoes, onions, endive, cucumbers, salsify, lettuce: approximately 1.2 kg of nitrogen. This corresponds (in commercial fertilizer) to:

  • Approximately 4.4 kg ammonia nitrate 27% N
  • Approximately 12.0 kg of nitrogen fertilizer and 10% N
  • Approximately 5.9 kg ammonium sulphate 20.5% N

For strawberries, shallots, sprouts, lettuce, carrots, approximately 0.8 kg of nitrogen. This corresponds (in commercial fertilizer) to:

  • Approximately 3.0 kg ammonia nitrate 27% N
  • Approximately 8.0 kg of nitrogen fertilizer and 10% N
  • Approximately 3.9 kg ammonium sulphate 20.5% N

Additional determinations:

Analysis results (in mg/kg dry soil = ppm)

Copper (Cu) 10.42 ppm normal levels
Lead (Pb) 37.52 ppm normal levels
Zinc (Zn) 64.43 ppm normal levels
Cadmium (Cd) 0.33 ppm normal levels
Cobalt (Co) upto 2.56 ppm normal levels
Boron (B) 0.90 ppm relatively high levels

Conclusion: The boron level is fairly high, we recommend to not give any boron fertilizer. All other levels are favorable normal levels. As far as the analyses allow to determine, the cultivation of vegetables can be done without any health risk.

PH (KCl) Humus (%C) P, K, Mg, Ca, Na, B, Cu, Co
1: strong acid 1: very low 1: very low
2: Low 2: Low 2: Low
3: rather low 3: rather low 3: relatively low
4: favorable 4: normal 4: normal
5: fairly high 5: fairly high 5: quite high
6: High 6: High 6: High
7: very high 7: boggy 7: very high

Example 2 of a soil analysis (Soil Service of Belgium):

Plot Details Serial B.D.: SO206010 Nr. of the probing: 133 (4) Lot name: Van Ygem

Analysis results and assessment:

Determination Determination result Target figure* Assessment
Soil type 35 -- Light loam
Acidity: pH-KCl 6,4 6,4 - 6,9 Favorable
Humus: carbon 1,8 1,2 - 1,6 Normal.
Phosphorus (P) 37 13 - 21 High.
Potassium (potash) (K) 42 16 - 23 High.
Magnesium (Mg) 14 10 - 17 Normal.
Calcium (Ca) 167 183 - 403 Fairly low.
Sodium (Na) 4,6 3,5 - 6,9 Normal
Boron (B) -- -- --

Liming advise (total dosage): 1300 kg acid binding value (abv) per hectare (as maintenance liming)

Fertilization advice: in kg/ha for:

first crop second crop third crop
(7/89, leek) (5/90, parsley) (4/91, spinach)
lime 1300 kg a.b.v. 0 kg a.b.v. 0 kg z.b.w.
Nitrogen 200 kg N 150 kg N 150 kg N
Phosphorus 40 kg P2O5 40 kg P2O5 80 kg P2O5
Potassium 90 kg K2O 40 kg K2O 190 kg K2O
Magnesium 130 kg MgO 130 kg MgO 80 kg MgO
Sodium 0 kg Na2O 0 kg Na2O 0 kg Na 2O
Boron -- -- --

Importance of the nutritional elements

Main elements

Nitrogen (N): Nitrogen is of great importance in the plant for the formation of proteins, chlorophyll and other organic compounds. It promotes the development of leafs and stem. When there is a nitrogen deficiency, the above-ground parts stay small and branch little. Too little leaves develop which also stay small. Leave stems remain short and are pointed steeply upwards. The plant gets a bright green color (chlorophyll deficiency). Excess nitrogen can be recognized due to a strong vegetative growth with long dark green leaves and soft shoots. Sometimes bloom delays occur and there is a reduced fertility. Woody stems ripen slowly and are therefore susceptible to frost. There is also a greater risk of infestation by aphids and mildew fungi. Too much N also reduces the absorption of potassium, so that potassiumdeficiency occurs.

Phosphorus (P): Phosphorus is necessary for the formation of core proteins and plays a role in the assimilation and respiration by the plant. It has a favorable influence on the development of the root system and promotes the ripening of the crop. It increases the sugar and starch content in roots and tubers. A lack of phosphorus is most recognizable in a young crop. When there is a deficiency, the leaves turn purple and reddish-brown at the bottom of the leaf. Poor rooting and low yields also accompany phosphorus deficiency. Plants remain small and delicate. Flowers are also smaller than normal.

Potassium (K): is important in the metabolic processes in the plant. It therefore has a beneficial effect on the yield and the quality of the crops. It promotes the production of carbohydrates. It reduces the sensitivity to drought and frost. When there is a potassium deficiency, the leaves keep behind in growth and are puckered or curled. The color of the leaves are darker than normal. The leaf edges are colored yellow and also withered. Potassium deficiency leads to poor maturation of woody plants in the autumn, making them sensitive to frost.

Sulfur (S): Both sulfur deficiency and excess sulfur give no specific symptoms. The signs of deficiency have some similarity to N-deficiency.

Magnesium (Mg): Magnesium is important as a building element for chlorophyll. With a magnesium deficiency, the leaves retain a yellow discoloration along the leaf edges or between the leaf veins. Later-on, a brown discoloration occurs. Along the leaf veins, the leaves remain green. The uptake of Mg occurs mainly in cold wet summers. At a soil pH lower than 5, there is almost no more absorption of Mg.

Calcium (Ca): Calcium is important for the plant to neutralize acids. It is a component of the cell walls. Calcium deficiency is little observed. With some fruits (eg tomato), the deficiency of calcium is expressed by nose rotting. Ca is of more importance to the soil.

Trace Elements

Copper (Cu): promotes the formation of chlorophyll and is part of some enzymes. Deficiency symptoms are mostly found at sandy soils that are poor in humus content. One sees a poor development of growing tissue sections. Leaves are sometimes chlorotic and/or necrotic and curled or twisted.

Zinc (Zn): Zinc deficiency can occur in poor soils and soils with a high pH. Usually there is a compact growth and chlorotic spots in older leaves. A fertilisation with an organic manure is often sufficient to eliminate the problems.

Boron (B): Boron plays a role in the transport of carbohydrates in the plant. Boron deficiency often leads to the death of the growpoints and young shoots, after which they start to decay (affects cell division). Borondeficiency occurs mainly on light sandy soils, especially during dry periods. At a high pH the risk of deficiency is also increased.

Molybdenum (Mo): Molybdenum deficiency leads to a keeping behind in growth, leaves that become pale and wither eventually. Symptoms often appear in the middle and oldest leaves. They are yellow to yellowish-green and the leaves curl. Mo deficiency usually occurs on soils with a low pH, the remedy will mainly consist of bringing up the pH.

Manganese (Mn): Manganese is necessary for the formation of chlorophyll and plays a role in the physiology of the plant. With manganese deficiency, the young leaves become yellow spotted, with veins that remain green. With manganese deficiency, the plant produces too little carbohydrates which renders the plant limp and ragged due to a lack of formed cellulose.

Iron (Fe): Iron is needed in the formation of the green color of the leaves. Iron deficiency expresses itself as a yellowing (chlorosis) in the young leaves, where the veins remain green. With serious deficiency, the growth comes to a halt and white coloration of the leaves occur.

Deficiencies

Cause P K Mg Ca B Fe Mn Zn Cu Mo
low pH x x x
high pH x x x x x
too dry x x x x
too wet x x
light soil x x
cold ground x x x
too high N x
too high P x x x x
too high K x x x
too high Fe x x

Determination method for defficiencies

A. Symptoms firstly occuring on older leaves

  • Abnormally formed leaves, reduced growth, no necrosis
    • Yellow, monocotyledons: V-shaped yellowing starting at the top: N
    • Purple or very dark green coloring of the leaves: P
  • Necrosis and/or chlorosis
    • Brown bronze necrosis starting on the leaf edge or top: K
    • Between-vein chlorosis: Mg

B. Symptoms firstly occuring on younger leaves

  • Dead end bud; especially with dicotyls: B
  • Weakened stem, angled at the top: tomato (nose rotting), apple (spots): Ca
  • Shortening of the internodes: Zn
  • Young leaves wilted, poor flowering and setting of seeds: Cu
  • Between-vein chlorosis: Fe

C. Symptoms throughout the entire plant

  • Legumes and coal (clamping heart): Mo

Organic fertilizers

Organic fertilizers workings

Organic fertilizers are important as they:

  • Improve the structure of the soil. On heavier soils de the adhesion of the particles is reduced so that the manipulatability is improved. On light soils, the adhesion between the particles is increased so that a stable crumb structure is obtained.
  • Increase the water-holding capacity of the soil
  • Promote soil life: soil organisms use organic materials as food
  • Contain plantfeeding elements: the mineralization occurs slowly and is spread over several years (up to 3 years after administration), thus only a part is directly absorbable by the plant. The organic nitrogen compounds are first converted to ammonia and then further converted by microorganisms to nitrate, which is absorbable by the plant.

Soil improvers

As soil improvers, the following are usable: - Compost - Stable manure - Green manure These soil improvers also contain plant food, but in many cases it will be necessary to also use concentrated fertilizers. In the private garden, we can best work with concentrated, organic, slow-acting fertilizer like blood meal, bone meal, horn meal instead of fast-acting fertilizers.

A. Compost Good compost is a living whole of a variety of bacteria and other organisms that constantly convert plant waste into humus. Compost is ready for sale at a garden center, but it is also well possible to make it yourself. Making compost yourself: The place where the compost pile will come needs to be well protected and half shaded. Otherwise the compost pile dries out too much and the composting is significantly delayed. A suitable place can be made by placing a hedge or some shrubs around the compost pile. One can also use a composting barrel. In such a container a sheltered and fairly humid climate is present. We then dig a hole of 15 cm deep wherein we place a 10 cm thick layer of compost or old manure. On this old layer, a new thick (20 cm) layer of organic material is placed (eg leaves, weeds, vegetable waste, potato peels, ...). Cooked food and potato peels treated with a growth inhibition medium should not be added here (cooked leftover food starts to rot and smell and the treated peels slow down the composting). Also, diseased plant remains (with fungus or viral diseases) do not belong in the compost pile so as to prevent their spreading in the garden. The pieces of organic material must not be too long, these digest very slowly (compost shredders are for sale, the length of the waste must not exceed 20 cm). The composting runs best if fresh waste is mixed with dry waste. Piles with dry waste do not digest, piles with too much wet waste start to smell. On top of the organic matter, a layer of lime (agricultural lime), no thicker than a sheet of paper, is placed. On top of this limestone layer, a layer of soil or old compost (one finger thick) is placed. Then we again introduce a layer of organic material and the sequence of layers is repeated over and over. We pile it up to about 150 cm in height. Once and a while, we compress the pile and ensure that the base is wider than the top. The pile is covered with a layer of soil (one finger thick) and a layer of mowed grass. The composting then commences, after a few days the temperature will rise to 40-50°C. With composting temperatures above 50°C, weed seeds and pathogens can be destroyed. Sometimes it may be necessary to water the pile every now and then as it becomes dryer as time goes by (dry piles can be recognized as they don't sink in ater a few weeks). After 1 to 4 months, we can convert the pile, it will have done sunk in a little. We place the upper part of the pile at the bottom and bring the outer portion of the pile to the interior portion. The temperature will again rise slightly, as time passes, the compost pile sinks in, the temperature is reduced and worms begin to digest the pile further. After about six months the compost pile begins to smell like forest soil and it is then ready for use.

B. Stable manure Compost is a better soil improver than stable manure, especially on more acid soils. Fresh manure from the stables will contain many nutrients (especially N) and too fresh organic material. Therefore, the manure can best be left to settle. We make good old manure by mixing cow manure (main component) with an other type of manure, compost and organic material. We place this in a pile and cover it with a finger-thick layer of soil. After 3 months, the manure is ready for use. Old manure contains, similar to compost, a rich whole of soil organisms and brings these, besides nutrients, into the soil.

C. Green manure To protect the soil organisms in the winter, the soil is best kept covered. For this purpose we sow green manure such as winter rye or ryegrass in late summer that we then dig under in the spring. It also acts as a catch crop for the nutritional elements present in the soil. The green manure takes up the nutritional elements from the soil and it will release these in the spring, after mineralization (especially N). We can also sow leguminous plants (such as clover, vetches, ...) in early spring and dig these under later-on in early spring. The root nodules gather N-gas from the air and lock it in the soil. This is especially interesting for leafy vegetables.

Concentrated organic fertilizers

The shortage in certain nutrients can often not be remedied with the use of compost and old stable manure. We will then need to resort to fertilizers that contain specific nutrients in higher concentrations.

Name Nutrients Remarks
Bone meal 5% nitrogen, 15% phosphorus and lime Quantities vary
Byobact trace elements --
Cacao waste 8-10% acid binding constituents Suitable for calcium-poor soils
Dendrovorm 7% nitrogen, 5% phosphorus and 5% potassium --
Dolomitic lime 20% carbonic magnesium and 30% carbonic calcium --
Guano 14% nitrogen --
Hoof meal 13-14% nitrogen Works slower than blood meal
Blast furnace silica lime 50% acid binding constituents Suitable for acidic soil
Maerl 45% acid binding constituents, 6% magnesium and trace elements --
Magnesite allot of magnesium Quantity varies
Natural phosphate 13% phosphorus --
Serpentine rich in magnesium, silica and trace elements Composition varies
Thomas slag meal 3% magnesium, 17% phosphorus and calcium --
Feather meal 12 to 14% nitrogen --

What's in manure, compost and waste compounds ?

Per 100 kg nitrogen (in kg) potassium (in kg) phosphoric acid (in kg) calcium (in kg) organic matter (in kg)
potato foliage 0,6 0,8 0,18 1,0 20
brown coal ashes -- 1,0 0,6–1,5 16,0 --
core wood ashes -- 10,0 3,4 30,0 --
conifer tree wood ashes -- 6,0 2,5 35,0 --
coal ashes -- 0,1–0,5 0,8 3,5–8,5 --
peat ashes -- 1,0 1,2 15–30 --
basalt meal -- 1,51 0,87 12,63 --
bone meal 4,0 0,2 21,0 31,0 --
cesspit sludge 0,36 0,15 0,16 0,11 15–10
cesspit sludge (with peat) 1,0 0,25 1,1 0,06 20-30
leaves 1,0 0,29 0,22 1,41 85
blood meal 15,0 0,7 1,3 0,8 60
pine and spruce needles 0,9 0,13 0,2 1,6 80
pigeon manure 1,76 1,0 1,78 1,6 30
duck manure 1,05 0,63 1,4 1,7 26
egg shells traces -- -- 40 --
goose manure 0,55 1,0 0,55 0,85 25
(Stinging nettle ?) extract 0,25 0,5 0,01 0,03 5 – 8
plaster -- -- -- 35,0 --
green manure yield luguminous crops: 150–250 kg/ha
vegetable waste 0,4 0,5 0,2 0,5 30
soil compost 0,02 0,15 0,15 0,6 8
Fabaceae 0,7 0,5 0,1 0,3 20
wool waste 3–9 0,1 0,5 0,5 85
soapy water -- 0,6 -- -- --
sea sludge 0,35 0,7–0,92 0,2–3,5 6–8,12 40
sea weed 0,19 0,29 0,04 0,54 5
hair 3-9 -- -- -- present
hoof chips 11,0 -- 6,0 6,6 80
horn meal 10,2 -- 5,5 6,6 85
horn chips 17,0 -- 8,0 6,6 85
wood chips 0,1 0,003 0,001 -- 80
chicken manure 1,63 0,85 1,54 2,4 26
cow manure
cow manure (without digging under) 0,3 0,5 0,17 0,35 25
cow manure (with digging under) 0,42 0,5 0,25 0,48 25
leather meal 7,0 -- -- -- present
lye water -- 0,8-1,2 -- -- --
tannery waste 1,4 -- 1,3 1,2 30
molasse rinse 3,0 10,5 -- -- 40
marl -- -- -- 20-90 --
mussel meal -- -- -- 60 --
weed (crushed) 0,5 0,7 0,2 0,2-1,0 2
horse manure 0,44-0,58 0,35-0,53 0,28-0,36 0,21 30
apple porridge 0,26 0,24 0,1 0,04 70
debris (sifted) -- -- -- 20-60 --
reed 0,6 0,26-0,67 0,2 traces 50
sewage sludge 0,36 0,16 0,15 2,1 19
soot 3,5 1-2 0,5 4-10 90
sheep manure (without digging under) 0,56 0,16 0,32 0,28 32
sheep manure (with digging under) 0,83 0,66 0,23 0,35 32
foamy soil 0,2-0,5 -- 0,5-1,5 15-30 15-30
rinse -- 0,5 -- -- --
stable manure
stable manure (3 to 5 months) 0,55 0,65 0,3 0,73 30
street waste 0,5 -- 1-10 present present
straw
rye 0,45 1,0 0,26 0,29 85
wheat 0,45 0,9 0,2 0,28 85
barley 0,5 1,0 0,2 0,33 85
peas 1,4 0,5 0,35 1,82 80
trimming waste material traces 0,74 0,3 present 20-60
urine 0,35 0,21 0,27 0,02 2
pig manure 0,45 0,61 0,19 0,08 30
meat meal 5,8 0,3 17,4 22,3 40
fly ash 0,5 12,0 0,5-1,5 15 traces


When and how to fertilize

The timing: depends on the soil type. Sandy soils are best foreseen of compost or old manure in february. On clayish soils this is best done in autumn. When we would fertilise sandy soils in autumn, a large part would be rinsed to deeper soil layers, where it is unreachable by the plant roots. This is an issue specific to light/sandy soils due to their already loose structure. On clayish soils with a a dense structure, the trough-flushing is low. By already fertilising in autumn, the clods produced by the soil improver can freeze-break in winter.

The digging-in of the manure. In most gardens the manure is simply dug in, this is however not recommended. By simply digging-in, we destroy many of our soil organisms. Each type of micro-organism lives at its own depth in the soil. By digging and turning the soil around, we bring the topsoil a depth where many micro organisms suffocate. A good way to process manure and compost, without disturbing the soil too much is to dig shallowly. It is sufficient to dig in the fertilizer in the 5 to 10 cm-layer under the soilsurface.

Agriculture manual 1 2 1 image 8.JPG

Fertilizers

Artificial fertilizers

Nitrogen: several N-compounds exist: - Nitric N: works fast, but washes out easily - Ammoniacal N: works slow (needs to be converted to nitrical first), washes out less easily (locked to clay-humus-complex) - Urea N: works rather slow (needs to be converted to ammoniacal and then to nitric N first) - Amidic N: works very slow (needs to be converted to ureum, then to ammoniacal, and then to nitric N first)

Fertiliser Main constituents Base equivalent *
Nitrogen fertilisers:
ammonia nitrate 22% N ½ ammoniacal nitrogen -2
ammonia nitrate 26% N ½ nitric nitrogen -12
ammonia sulphate 21% N ammoniacal nitrogen -62
ammonia sulpho nitrate 26% N ammoniacal + nitric nitrogen -54
Liquid ammonia 82% N ammoniacal nitrogen -82
Calcium nitrate 15,5% N nitric nitrogen +12
Chili nitrate 16% N nitric nitrogen +17
Kalcyanamide 18% N amidic nitrogen +40
Ureum 46% N ureum nitrogen -46
Phosphorus fertilisers:
Superphosphate 18% P2O5 -- -2
Metal slags 15-18% P2O5 -- +40
Rhenaniaphosphate 38% P2O5 -- +22
Triple superphosphate 43% P2O5 -- 0
Soft phosphates (minimum 25%) -- +33
Potassium or potash fertilisers: a distinction is made between chlorinated and non-chlorinated potassium/potash fertilisers
Potassium chloride 40, 50 or 60% K2O KCl 0 to +2
Potassium sulphate 48% K2O K2SO4 -1
Potassium soda 20% K2O and 28% Na2O KCl + NaCl +1
Patented potassium 26% K2O and 8 to 12% MgO K2SO4 + MgSO4 +0
Magnesium fertilisers:
Magnesium sulphate 16% MgO MgSO4 +0
Kieserite 27% MgO MgSO4 +0
Magnesite 90% MgO MgO +126

For magnesium limes: see lime and soil improvers

  • If the base-equivalent is negative, the fertilizer is acidifying

Complex compound fertilizers

Complex compound fertilizers contain NPK (Mg) in each pellet. eg: 10-15-20(5) means 10% N, 15% P, 20% K, 5% Mg

Calculation of the fertilizing

Eg: A crop like cauliflower requires 3 kg of N per are 100 kg of ammonia contains 20 kg of N 10 kg of ammonia contains 2 kg of N To obtain 3 kg of N, we thus need to provide 15 kg of ammonia.

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Lime fertilizers

Workings of lime in the soil

  • Structure: Ca makes heavy clayish soils less stiff, and improves the coagulation.
  • pH: lime fertilizers increase the pH when the soil is too acidic
  • Enriching of the soil with N: a reduction of the level of acidity promotes the development of N-binding bacteria , hereby improving the the binding of N
  • Mobilization of plant nutrition: the present food supplies are rendered absorbable

At a low pH, the uptake of N, K, Mg, S decreases and the solubility of trace elements is increased with a too acidic pH. At a high pH, the uptake of Fe, Mn, Cu, Zn decreases.

Liming is more focused on improving the soil structure and soil pH then the supplying of crops with Ca.

Lime fertilizers

  • Slaked agricultural lime powder Ca(OH)2: abv= 50-60
  • Calcium carbonate lime such as marl lime, chalc, carbonated agricultural lime CaCO3 abv= 35-52
  • Calcium and magnesium carbonates such as dolomitic lime MgCO3 and CaCO3 abv= 45-60
  • Magnesium lime powder Mg(OH)2 -Ca(OH)2 abv= 50-60
  • Foaming soil CaCO3 abv= 20-40

Acid binding value

In a liming advise, the lime dosage is given in kg abv per ha. Eg: calcium dosage of 1000 kg abv per hectare, with the use of agricultural lime powder with a abv=50 means the administration of 2000 kg/ha .

Agriculture manual 1 2 1 image 10.JPG

When to administer ?

Repair liming: When the pH is too low and allot of lime needs to be administered, it is best done in late summer or autumn, and spread over 2-3 years. The lime needs to be scattered and well mixed with the soil. Maintenance liming: slight limings to supplement the lime store is best done in early spring after plowing and then well mixed.

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