WHAT is soil testing?

SOIL analysis is a set of various chemical processes that determine the amount of available plant nutrients in the soil, but also the chemical, physical and biological soil properties important for plant nutrition, or “soil health”. So basically, soil sampling and testing provide an estimate of the capacity of the soil to supply adequate nutrients to meet the needs of crops.

Chemical soil analysis determines the content of basic plant nutrients; nitrogen (N), phosphorus (P2O5), potassium (K2 O), pH, humus content, total CaCO3, available lime, organic matter, total sulphur (S), trace elements, and other physical characteristics (capacity, permeability, density, pH – value).

Soil analysis implies:

• taking soil samples

• Laboratory analysis of samples

• the interpretation of the results by the issuance of fertilizer recommendation

Why soil testing is important

The purpose of soil testing in highyield farming is to determine the relative ability of a soil to supply crop nutrients during a particular growing season, to determine lime needs and for diagnosing problems such as excessive salinity or alkalinity. Soil testing is also used to guide nutrient management decisions related to manure and sludge application with the objective of maximising economic/agronomic benefits while minimising the potential for negative impacts on water quality.

What to know about your soil

To find out what you need to do to improve your soil’s quality, you should know each of the following attributes of the soil; that is current pH levels of soil, fertility levels of the principal nutrients, type and quantity of lime your soil needs, nutrients need to be added to your soil as fertilizer and amount of fertilizer your crop and soil need.

If you do not have this information, a soil test may help.

Limitations of soil testing

Soil testing can let you know where your soil needs treatment or improvement. However, a soil test cannot tell you which crop to grow, prevent poor crops caused by drought, disease, insects, too much water, or other problems, substitute for proper cultural practices, and replace good management.

How to take a soil sample

The sampling process is very simple and can be done by anyone with the right tools. Lime may need up to six months to produce the full effect in raising the soil pH. Be sure to send samples to the laboratory well before it’s time to fertilize so that you can use the results to determine what kinds of fertilizer to buy.

Samples are taken by probe, but can also be taken by a shovel. If the sample is taken by shovel, the procedure is as follows dig a pit, vertically cut the soil along the pit wall, the shovel must be pulled out so that the soil does not slip off and forming of sample — longitudinally along the middle of shovel soil width 5cm is allowed, and left and right of the sample soil is cropped and removed

A sample is taken to a depth of normal tillage i.e, to rooting of plants, for field crops 0-30 cm, for permanent crops (orchards and vineyards) 0-30cm and 30-60cm. Taking soil samples for analysis is done after harvesting of crops and before any fertilizing, at optimum soil moisture.

Samples must be taken at regular intervals of between 10-20m apart in the field.

The samples are mixed and up to 1 kg of the taken soil. Thus separated sample is placed in a plastic bag on which write the following information: name of farmer, name of farm and date of sampling. There are several ways of taking samples: (a)network, (b) Z-scheme, (c) diagonally (d) in permanent crops