Proof of the SoilCares Concept

The British are used to saying “The proof of the pudding is in the eating”. For SoilCares, the proof is in the crop yield, as our ultimate goal is to increase yields at a minimum of costs.

The benefits that can be obtained through SoilCares depend on the situation of the farmers applying the services. 

For example, a small scale farmer that is still at the very beginning of the yield response curve, can expect to benefit from a large yield increase. On the other hand, for high-end precision farmers, who are already close to an optimal yield the impact will be more on the cost reduction by applying more precise amounts of fertilisers.

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Figure: The effect of improved fertilisation on yield levels will be most pronounced at the very low and low soil test levels.

The yield response curve is also dependant on the types of soils and crops. Some soils will highly respond to fertiliser applications, while others might show no or very little response.  These effects are also considered for the calculation of our fertiliser recommendations.

Crop growth only responds to scarce nutrients, this is known as the Law of the Minimum or as the Liebig’s barrel. 

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Figure. Liebig’s barrel visualizes the Law of the Minimum: yield levels will only increase when applying scarce nutrients. At higher yield levels other nutrients become limiting.

In this concept a barrel with different staves is a metaphor for yield levels and yields (water level) can only be increased by increasing the limiting stake. By knowing the soil fertility status and the crop specific nutrient requirement SoilCares identifies the limiting nutrients and provides targeted recommendations. Thereby, losses of added nutrients are prevented and cost effectiveness is increased.


In Burundi SoilCares services were tested amongst 22 farms in 2 regions (Makamba and Vigizo).

Three treatments were applied: the farmer's traditional practices, the governmental recommendations and those of SoilCares. The trial was first performed on maize and stepped to beans in the second season. The trials were performed by independent researchers and practitioner organisations.

The SoilCares recommendations engendered a yield increase of on average of 80%. The initial application of fertilisers also influenced the following season: without having to apply additional fertilisers, the bean yields increased by another 80% on the same plots.

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Figure. Maize yields obtained from different fertiliser recommendations in two regions in Burundi. In Makamba yields were also measured in the subsequent season which showed a residual positive effect. The numbers on the x-axis represent the different farmholds.