Soil is like a bank account, and if poorly fed, it can deplete or fail to sustain a plant’s growth. 

Experts say soil reaches a certain point and gets ‘useless’ after nutrients are depleted and this renders growing crops on it difficult.  

Therefore, according to experts who facilitated a soil management session under the Dutch Village during the 2024 Harvest Money expo, to keep it on the right track, the addition of fertilizers is inevitable and additional proper management practices.   

According to Julius Twinamwijuka, from Ferti-plus, who exhibited in the Dutch village and trained soil management, farmers can reboot soils by adding calcium and fertilizers to them. 

He explained that inadequate calcium in the soil can be identified when plants or flowers start withering.

“Farmers must take good care of their soils by avoiding practices that may reduce nutrients. And if they notice any signs of deficiency in their crops, they must add fertilizers but most especially after doing a soil test,” Twinamwijuka said. 

A soil test sample costs between sh30,000 to sh50,000. 

While training expo goers, Michael de Voogdm, also from the Dutch village, who had come for the expo from Netherlands said without good soils, farmers are bound to register losses. 

He defined soil health as the continued capacity of the soil to function as a vital living ecosystem that sustains plants, animals, and humans.

“It allows good root growth and plant productivity and improves drainage and soil aeration,” he explained. 

Voogd remarked that when soils become too acidic, plants struggle to get nutrients. This explains why, in some places, plants wither even when there is rain. 

However, he said that even though Ugandan soils are healthy, they need to be boosted with updated nutrients to keep them productive.

Using technology to manage soil health

The Dutch soil specialists also encouraged farmers to look into new forms of technology to manage soils and improve quality. 

Save for a few countries where ‘soilless’ farming is taking root, 100% of farming in Uganda still depends on natural soils. This means that agriculture can only be sustained through proper management of the soils. 

“We cannot talk about sustainable agriculture when we have soils with negative nutrient balances, that cannot yield well,” Alex Lwakuba, commissioner in the Ministry of Agriculture says. 

He thus advised farmers that usage of soil fertility enhancers like fertilizers of any type is now a must. 

Ugandan soils at a glance

According to soil scientist Professor Julius Kitungulu, Uganda`s soils are currently depleted; 

-Very old therefore deeply weathered – hardly stores nutrients.

-Inadequate supply of the major nutrients.

-Low nutrient holding capacity – poor retention of water resulting in poor yields

-Deficient or toxic of trace elements – being acidic means that even if you use fertilizers, they will not be effective. 

-Soluble nutrients prone to leaching – losses especially to nitrogen and potassium.

-These above characteristics show major shortcomings relating to plant growth requirements. 

So what determines soil fertility?

Soil has large and small spaces. The small spaces take in water, while the large spaces take in oxygen. For the plants to grow as expected, the soils must have all the nutrients like nitrogen, phosphorus and potassium (NPK). 

Other nutrients are magnesium, calcium and sulphur, required in small quantities. Iron, copper, manganese, zinc, chlorine and sodium are required in minute amounts. All these contribute to the growth of crops.

-There is a misconception among farmers that NPK is a single fertilizer or nutrient for the soil, whereas not. Kitungulu says NPK is a combination of three nutrients needed by plants for the different stages of growth.

-When planting, the first interest is root formation, so farmers should apply phosphorus. 

-When leaves start to show, nitrogen should be applied and when it comes to fruiting, that is when potassium can be added to make a complete set of NPK. 

How does soil lose fertility?

“The causes of degradation cut across so many factors in Uganda. These include poor tillage and poor choice of crops, over grazing in case of the cattle corridor, bush burning and non-application of fertility enhancers,” says Dr Robert Muzira, a soil scientist from Mbarara Zonal Agricultural Research Institute.  

Soil is made up of different nutrients as seen above, organic matter which is always on top of the soil is washed away through soil erosion, and bush burning leading to loss of nutrients like nitrogen, sulphur as these escape. This leaves the soil bare; when these are missing from the soil, the fertility of the soil 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 compaction, which affects absorption of nutrients 

-Over grazing leaves the soils bare, hence affected by direct sunshine, which leads to loss of moisture.  

-Not replacing removed nutrients leading to negative nutrient balance of around: -21, -8 and -43 for NPK. 

-Mono cropping deprives soils of possible nutrient enhancing crops like legumes. This is why intercropping is important. 

-Use of undegradable materials – polythene, because they prevent water from seeping into the soils. 

-Cemented elements near the farmland, for example graves. Cement affects the nutrients in the soils. 

Such 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, affecting fertility.  

-Weeding by removing all the weeds and placing them onto the boundary exposes the soil to direct heat and rains. This again takes away fertility in the top soils. Best thing to do is to weed, but let the cut grass remain and rot on top of the soils.