How Soil Loses Fertility

Soil is the base or mother of agriculture in Uganda, however, most soils in Uganda are dead. They are less productive than they were a few years ago.

Organic matter which is always on top of the soil is washed away through erosion. Bush burning leads to loss of nutrients such as nitrogen and sulphur.

When these are missing from the soil, its fertility is lost.

• Soil erosion—loss of top fertile soil, occurs when it rains heavily.
• Bush burning causes loss of nitrogen.
• Over tillage /over ploughing, leads to loss of soil structure due to over compaction. It is similar to over using the soils.
• Over grazing leaves the soils bare, hence it is affected by direct sunshine and soil erosion.
• Clean weeding where the soil is left bare before planting and after planting leads to loss of nutrients.
• Not replacing removed nutrients leads to negative nutrient balance of -21, -8 and -43 for NPK.
• Mono-cropping every season deprives soils of nutrients. This is why intercropping is important. You can, for example, plant legumes such as beans, soya or maize with bananas and coffee. Beans too can be planted on top of potato mounds etc.
• Use of non-biodegradable materials – polythene, because they prevent water from sipping into the soils.
• Concrete structures near the farmland, for example graves. Cement affects the nutrients in the soils because it sucks out water.
• Over compacted soils cannot allow root penetration, but also the larger spaces that take in air, will be blocked and nutrients including oxygen will not find their way in the soil to get to the roots. Continuous tillage/ploughing affects the larger spaces for air, which tend to disappear, especially where there is clay. This affects fertility.
• Weeding by removing all the weeds and placing them on the boundary exposes the soil to direct heat and rains. This again takes away fertility in the top soils. The best thing is to weed and leave cut grass decompose in the garden.