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The cents and sense in soil testing

By Alex Wachira
Nursery preparation experts tend to a Squarefoot box Garden farm . [David Gichuru, Standard]

A new farmer looking to venture into farming a soil test would be important to know what inputs are needed, how much is needed, are there soil borne diseases, are there nematodes in the soil, is the soil texture okay.

For example, a fruit or an avocado farmer how is the subsoil where the roots grow deep into, in a soil with a lot of clay sub soil and whose soil texture is not good, avocado farming would not be good.

When it’s very dry the sub soil will be very dry for roots to thrive properly and when it’s very wet the sub soil will be too wet and there will be water logging and drainage is affected which leads to root diseases.

Experts can also advice on which other crops a farmer can grow in the soil, but in most cases it’s the farmer who decides which crop they would like to grow and analysis is done based on that plant.

If the soil is not favorable for the farmer’s choice of crop the scientists can suggest crops which can do well instead.

For example, for extremely salty soils crops suggested would have to be more salt tolerant other than the farmers’ choice of crops.

Soil testing prices are competitive and affordable for instance for a complete soil analysis it costs about 5,000 Kenya Shillings per sample with accurate recommendation.

 A farmer should carry out soil testing to:

  • To save money: Using fertilisers without soil testing could mean you are applying the wrong quantity, type at the wrong stage.  

           Soil testing ensures a farmer grows with less by saving on using fertilizers or manure. A farmer uses                           less inputs as they give crops what they need and get more production, saving money and minimizing                          wastage.

  • To succeed in soil correction: If the PH is wrong it needs to be corrected using lime. Lime needs to be applied before planting to correct the PH and fertility.  If the sodium levels are high in the soil they need to be displaced by applying gypsum.
  •  To determine if the electrical conductivity is high in which case the application of any fertilizer is not recommended because the EC comes from the inputs that farmers put in the soil.
  • For high value crops like capsicum farmers are recommended to do soil test before planting. Farmers are recommended to do soil testing after harvesting.
  • For permanent or perennial crops like coffee, citrus tree farmers are recommended to do soil test at least once a year
  • If you don’t do soil-test before planting, you either over-fertilise or under-fertilise your soil. For example, you may have too much nitrogen in maize, get delayed maturity, lodging of crops like grasses.
  • Due to excess nitrogen you may get insect damage on crops as the insects are able to bite and penetrate into crops quickly which affect yields.
  • If you put less you may suffer from problems like diseases which in the long run affect your yields. For instance, very low amount of calcium may lead to deficiency problems causing diseases to arise which lower the production.
  • Excess fertilizers are not consumed by plants as crops take up only what they need leaving the other elements in the soil which can go down through drainage and you lose nutrients.

This also has another effect as it’s an environmental issue leading to too much fertilizers into the water body affecting the aquatic life.

A farmer needing soil correction may need weeks or months before the next planting for incorporation of nutrients e.g. putting lime in the soil during land preparation.

Checking the nutrition status of the soil takes 7 working days or shorter depending with the condition of the soil if it’s dry or not. There are no mobile testing kits, experts use wet chemistry where the sample goes to the lab and is taken through the various stages of analysis.

There are agronomists in every county who visit farmers once in a while and take them through soil analysis reports to make sure the farmer understands the report results and implement them to get an impact to the farmer and output of the investment. This is free as an after sale support.

It is also important to test irrigation water as it has a direct effect on the status of the soil and should thus be tested on its’ suitability. For example, if the irrigation water has a high level of sodium it will not be suitable.  

 

 

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