Soil Test—Why Is It So Important?

"I am a Maize and Coffee farmer in Kirinyaga County. I have been told that I should test my soil and then buy a fertilizer specifically manufactured for my farm. What's your advice?"

Soil testing is certainly an important practice for farmers. This is because the results will give an indication on the potential of the soil to supply nutrients, as well as give an indication of the soil properties important in making certain Agronomic decisions.

However, having said that, please remember that even on your ONE or TWO  acre piece of land, you can still get different soil Test results from different parts of the field, which then begs the question; Would you then have to buy TWO or more different types of fertilizer for your ONE acre piece of Land ? And if the same case applies to all the farmers in Kirinyaga for example, where we have more than Half a million farmers, would they also need different fertilizer types ?

And finally, would the fertilizer manufacturers then have the ability and flexibility to manufacture all these thousands or more different grades of fertilizers ? To answer these questions we need to understand the process of fertilizer manufacturing.

Fertilizer Manufacturing 

There are many different types of fertilizers, made in different manufacturing processes, with basic natural raw materials such as Air, Water, Natural Gas and mineral deposits like rock phosphate. A full production run is required to make a specific grade of a fertilizer, and this means only one grade can be produced at a time.

Therefore, to produce different grades would mean that the factory would have to clean the lines after every grade to manufacture the next one. This is true even for the Blended products. For this reason it is not commercially viable for a factory to manufacture hundreds or thousands of grades to suit the soil needs of every other farmer. 

The solution

Application of fertilizers is meant to principally feed the crops and not the soil. Therefore it is more important to consider the crop’s Nutrient requirements, and supply these through a crop specific fertilizer.

Different crops have different Nutrient requirements, and therefore its vital that this factor is considered in deciding what fertilizer to apply to which crop.

Soil test results are indeed a useful tool in making the fertilizer recommendation, but its use is limited if it is used as a stand-alone decision making factor for deciding the fertilizer type to apply.

Instead, the Crop Nutrient requirement should be the background and the application of a crop specific fertilizer considered, and the rates adjusted based on the local soil conditions as well as the Yield targets of the farmer.  So the more your yield target, the higher rate of the nutrients ( Fertilizer ) you would have to apply up to the economic optimum level.

In conclusion therefore, Crop specific fertilizers, with rates adjusted for the soils conditions will certainly give you better value in your Maize and coffee farming business. Such crop specific fertilizers are available from most Agrovets around the country.

By: Vitalis Wafula

East Africa Regional Agronomist

Yara