By Joshua Kato
Soil is like a bank account, and if poorly fed, it can deplete or fail to sustain the growth of a plant. Experts say soil reaches a certain point and gets ‘useless’ after nutrients are depleted.
“The causes of degradation cut across so many factors in Uganda. These include poor tillage and poor choice of crops, as well as overgrazing in case of the cattle corridor, bush burning and non-application of fertility enhancers,” Dr Robert Muzira, a soil scientist from Mbarara Zonal Agricultural Research Institute, says.
Soil consists of different nutrients. Organic matter that is always on top of the soil is washed away through erosion, and bush burning. This leads to the loss of nutrients, such as nitrogen and sulphur. When these components are missing from the soil, the fertility is lost.
- Soil erosion-loss of top fertile soil occurs when it rains heavily.
- Bush-burning causes loss of nitrogen and potassium.
- Over tillage/over ploughing (loss of soil structure due to compaction, which affects the absorption of nutrients).
- Overgrazing leaves the soils bare and moisture is lost due to the direct heat.
- Not replacing removed nutrients leads to negative nutrient balance of around; -21, -8 and -43 for NPK.
- Practise inter-cropping because mono-cropping deprives soils of possible nutrient-enhancing crops, such as legumes.
- Use of undegradable materials, such as polythene, which prevent water from seeping into the soils.
- Cemented elements near the farmland, for example, graves. Cement affects the nutrients in the soil. Such soils cannot allow root penetration because the larger spaces that take in the air will be blocked. Therefore, nutrients, including oxygen, will not find their way to the roots in the soil.
- Continuous tillage/ ploughing affects the larger spaces for air that tend to disappear, especially where there is clay, affecting fertility.
- While weeding, let the grass stay on top of the soil to avoid exposure to direct sunlight that depletes fertility from the top soils.
