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NEWS & CURRENT AFFAIRS

The Nairobian

The ABC of soil testing

Crop

By Alex Wachira | Jul 02, 2019

**Joseph Odhiambo harvests sukuma wiki from his farm (Photo: Denish Ochieng/ Standard)**

Soil testing is the process of analysing soil sample for fertility which entails determining its acidic or alkalinity (PH), nutrients and organic matter.

There are 10 to 15 different parameters that need to be examined to determine whether your soil is for your crop or not.

Soil testing is important to a farmer because without it farmers will simply be guessing what fertilisers to buy.

Without soil testing you don’t have the information required to understand which nutrients are needed, how much lime is needed, how much nutrients to apply and ultimately which fertilisers to buy.

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When farmers bring their soil samples to be tested they are passed through a technical desk where agronomists discuss with the customers to understand what they are going through as farmers. If there are any challenges they are facing they are advised on what analysis can be done.

The samples are then taken to the lab, to the sample intake. The samples are then put into a system where they are moved to various stages of sample preparation like passing them through different sieves. This is to get the right size of particles to move to the next stage.

The samples then go to sample weighing where there is weighing of the correct amount of soil sample that goes to the machine.

From there the sample is taken to the lab machines to get the data. The data is then verified by the laboratory team making sure it’s correct and okay.

The soil sample report is then moved to approval stage. At the approval stage soil scientists and other technical experts come up with recommendations which farmers are given based on the analysis report. The farmers are advised on the type of fertilisers to put and the amount and the stage of the crop growth when they should apply fertilisers.

Experts look at the nutrition which is called complete soil analysis with recommendations. The scientists look at PH, the EC (electrical conductivity) which is an indicator of salts in the soil, micro and macro nutrients, carbon nitrogen ratio (CN ratio).

Macro means the major elements that are needed by plants in large quantities like calcium, phosphorous etc. The micro nutrients are nutrients required by plants in smaller quantities but are very essential and valuable. Examples include Boron, Zinc etc.

This is usually considered as the fertility status of the soil or its nutritional status. Experts are then able to advise on the next step which is the analysis and recommendations.

Basically the analysis will be based on the concentration of those various elements in the soil.

There is then another analysis called pathology. This is analysis reveals plant diseases which are very key depending on the crop to be grown based on the farmer’s response on what they would like to plant. This ensures the farmer checks for nematodes and pathology which is diseases.

Therefore, based on the crop a farmer plans to grow for example growing tomatoes experts recommend that the farmer schedules for pathology screening because there are some of the diseases that attack tomatoes and have no cure once the crop is infected. For example, bacterial and verticillium wilts. Once a crop is infected you need to uproot and throw away that plant as it spreads from one plant to another.

Thus it’s very important for a farmer to do pathology screening before planting because at that point one will be able to do drenching or treat the soil to make sure that it is disease free before planting.

For nematodes, based on the crop one is growing for instance in potatoes, the test for a notorious nematode called sisnematode is a must.

Based on the farmer’s prospects on what they want to grow they are advised on various analysis and key things they have to look for as noticed in soil analysis.

Diseases affect the plant but there are diseases that are soil-borne for example fusarium which attacks the crop. Once the crop is planted into the soil and grows, it is a good host and accommodates the diseases.

To be continued….