Farmers need proper advice on soils

What you need to know:

  • If every farmer had a soil test done that prescribes the needed inputs, they would be able to allocate their limited funds effectively and stakeholders such as agrovets, fertiliser manufacturers and the government would get the crucial business information on which inputs and blends to import, produce and stock.
  • Soil testing recommendation always starts with the pH of the soil. Soil pH is the measurement of hydrogen cations in the soil. In simple language, it measures the acidity or alkalinity of the soil.
  • Blanket recommendations do not stand a chance with the latest breed of farmers who are realising that their yields have been going down despite their best efforts.

Crops are like babies that need tender care and proper feeding from the start for them to grow properly.

Since feeding of crops happens through the soil, farmers need to take care of their soils to successfully grow healthy plants. Kenyan farmers have for a long time neglected their soils, relying on government blanket recommendations for fertiliser application.

In the same way that a sick person cannot simply go to the pharmacy to buy some drugs, blanket recommendations might be the wrong “drug” as well as the wrong “dose” for a particular crop or soil.

A sick person should always go and see a doctor first, have a blood test done if necessary, and then the expert can prescribe medicine and the right dose.

If every farmer had a soil test done that prescribes the needed inputs, they would be able to allocate their limited funds effectively and stakeholders such as agrovets, fertiliser manufacturers and the government would get the crucial business information on which inputs and blends to import, produce and stock.

Accurate information on soil fertility and crop management, thus, comes hand-in-hand with a business plan in modern farming.

SOIL TESTING

Soil testing recommendation always starts with the pH of the soil. Soil pH is the measurement of hydrogen cations in the soil. In simple language, it measures the acidity or alkalinity of the soil.

Most Kenyan soils show pHs below 5, which means they are acidic. With the exception of tea, many crops need to be grown at pH levels of between 5 and 7.

At a low pH, the amount of hydrogen cations in the soil is very high and it, thus, locks up nutrients in the soil. These nutrients might be available in the soil or provided by fertiliser application, but they cannot be taken up by the crop because their capacity to be exchanged is disabled.

The exchange points (negative charges on organic matter aggregates) are blocked by high numbers of hydrogen cations. This phenomenon is called nutrient fixation due to low pH.

The only solution to this problem is adequate liming. Lime chemically reacts with the hydrogen cations in the soil and binds them up.

The hydrogen is removed from the soil and the pH is raised. The cation exchange capacity of the soil is freed up again and nutrients can be exchanged from the soil to the crop.

Fertiliser recommendation, therefore, always has to take pH and cation exchange capacity into consideration to give an accurate picture of the soil fertility status. The recommendation is based on calculation of the gap between the nutrient needs of a particular crop and how much of the nutrients found in the soil can be provided to the crop in the next growing season.

On top of that, any sensible recommendation should also take into account what the current yield potential of the field is, and, therefore, how much a farmer can earn from that field with that particular crop.

FINANCIAL VIABILITY

Input recommendation that costs more than the farmer will ever earn from that field is not financially viable. The recommendation’s task is to increase the current yield potential but also to take into consideration how the soil fertility status of that field can be raised long-term. The overall fertility status of a soil can only be improved if organic matter content and cation exchange capacity are brought to an optimum.

This cannot be achieved in one season but needs close cooperation between the soil testing laboratory and the farmer over a number of years to reach the soil fertility maintenance level. Once this is reached, optimum yields are obtainable. Bringing up the fertility level of your soil is, thus, the first step to successful farming.

Blanket recommendations do not stand a chance with the latest breed of farmers who are realising that their yields have been going down despite their best efforts. These farmers are asking themselves the right questions such as what they are doing wrong and what the problem might be.

They realise they are missing crucial information on which they could base their farming decisions and are sometimes unable to access basic soil testing facilities. Innovations such as mobile laboratories have to drive the industry if we are to have our farmers able to use modern tools in farming.

Ms Weber is the country manager of SoilCares Limited