Soil quality

Soil quality is a term that is hard to explain, but reflects an understanding of the usability of a given soil.

In most situations, the most important use of a soil is as to grow food, so the quality of a soil is understood as the ability to grow the highest yielding crops.

A soil can be impaired in a large number of different ways. This can include the effect of the soil texture and mineralogy, the amount of soil organic matter, the droughtiness (how susceptible it is to drought), the risk of flooding, the local climate and so on. Some of these factors are discussed here.

It may also be affected by the way it has been managed and be impaired by high levels of Soil erosion, high salinity/sodicity, pollution, etc. It may also have known susceptibility to specific plant pathogens which prevent growth of crops.

It may also be considered to be of low quality due to a range of local cultural and religious factors.

Hence it is only really possible to understand the term in a holistic multi-dimensional way, including soil properties, biology, chemistry and physics, previous management and local perception.

In simplest form, the Soil Science Society of America defines Soil Quality as “the capacity (of soil) to function”. Of course, the problem with this definition is that the ability of a soil to function changes depending on what you want it to do, and one soil which functions well as an agricultural soil may be poor at another function.

Generally speaking, the highest quality soils are used for the highest valued soil activities in a given area. There is usually some kind of pyramid of behaviour, with soils that are valued less being used for lower value activities, sometimes if they are not even particularly suitable for that purpose.

It is therefore entirely possible that the whole concept is bunk.

In contrast, soil and plant nutrients are well understood chemical ions which have a measurable effect on plants. So it is possible for a soil to be highly fertile (high in measured plant nutrients) whilst being low quality for other reasons. It is also possible for a soil which is low in nutrients to be considered to be relatively high quality.

Determining the quality of the soil in practice

Before getting started to determine any soil of any particular land at at all, you may wish to first look into the plants you wish to grow. Different vegetables (assuming that is what you want to grow) will require different types of soil and (but this is a next step), different quantities of humidity/water and nutrients. Humidity/water availability can be changed by cultivation of the soil and/or by adding means to remove water from the soil more rapidly. The type of soil however, can not be changed at all or only to a very small amount.

If you work the other way around (getting any land you can get hold of for a low price or near in the vicinity of a house, ...) then obviously you don't need to look at the plants you want to grow. Actually, you won't be able to choose this at all, rather you'll need to plant whatever works on the specific type of soil you'll end up with after you purchased the land.

To get a rough estimate of the soil qualities/specifics in a country, we can first search online for maps. Basic maps should exist/be available which gives us a rough estimate of the types of soils

The shaking test allows us to determine on whether a soil ^{[1] [2] [3]}

More discussion of this concept

soilquality.org