A Rhea Africa staff testing soils on a farm using the Agripad, a soil testing device.

Why a soil test is crucial


With any mention of reducing crop harvests or problems with soils, the first question on any experts’ lips is: Have you tested your soil?

Soils do get sick due to a myriad of reasons mentioned elsewhere in this edition. And just like a human needs a doctor to analyse symptoms, so is there need to find out what ails your soil.

One of the main reasons why our soils are sick is precisely because we continue to deplete them without testing to see what they need.

Soil testing allows for optimised and efficient crop production, the optimal and correct use of fertilisers, and reduces costs by applying only the amount of fertiliser needed.

Soil testing is done:

  • 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 (EC) in the soil is high in which case the application of any fertiliser 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 a soil test before planting. Farmers are recommended to do soil testing after harvesting.
  • For permanent or perennial crops like coffee and citrus trees, farmers are recommended to do a soil test at least once a year.
  • Because if you do not do a soil-test before planting, you either over-fertilise or under-fertilise your soil. For example, you could have too much nitrogen in maize that could lead to delayed maturity and lodging of crops like grasses.
  • Due to excess nitrogen, you could get insect damage on crops as the insects are able to bite and penetrate crops quickly, which affects yields.
  • If you put less, your crops could suffer from diseases, which in the long run affect your yields. For instance, very low amounts of calcium could lead to deficiency problems, causing diseases to arise and lower your production.
  • Excess fertilisers are not consumed by plants as crops take up only what they need, leaving other elements in the soil, which can go down through drainage and you lose nutrients.
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