When Paul Kato plants maize on his land in Katikara Village in Kyabigambire, Hoima District, he already knows what he will harvest. Whether he applies fertiliser or not, the yield rarely changes. Season after season, Kato bags between 17 and 18 bags of maize per acre. That consistency, he says, is the most frustrating part.
‘I have tried applying fertiliser several times but nothing changes,’ he explains. ‘I assume when I go the extra mile to apply fertiliser, I should be getting like 30 bags. But I end up with the same 17 or 18. To me, it feels like a waste of money.’
Across Bunyoro, many farmers share Kato’s experience. Some have given up on fertiliser entirely, convinced that it simply doesn’t work in their soils. But agronomists insist something else is at play.
Beneath the surface
According to Dr Joseph Ekwangu, a crop agronomist at Bulindi Zardi, what farmers see as ‘fertiliser failure’ is often caused by soil conditions they cannot see with the naked eye.
‘When you do all the recommended agronomic practices, you get the desired yields. But some soils are naturally fertile and may not need fertiliser at all. Others need it in smaller amounts. This can only be known after soil testing,’ Dr Ekwangu says.
Much of Bunyoro has soils with low pH, meaning they are acidic. Acidic soils create a major problem for phosphorus, one of maize’s most important nutrients. When the pH is low, phosphorus becomes fixed in the soil and cannot be taken up by the maize roots, even if applied in the right quantities.
‘You may actually be wasting fertiliser for no good reason. If your soil is acidic to the point where nutrients get locked up, you should not be applying fertiliser blindly. Bring your soil for testing so we can advise you properly,’ Dr Ekwangu explains.
This trend is not unique to Uganda. FAO reports and fertiliser manuals across East Africa confirm that acidic tropical soils often retain or ‘lock up’ phosphorus, reducing fertiliser efficiency by up to 40 per cent.
Maize needs fertiliser in small meals
To reduce nutrient loss in such soils, Dr Ekwangu recommends a technique gaining ground across Africa: split fertilisation.
‘The maize plant isn’t greedy. It eats slowly. If you apply everything at once, more will be wasted, especially in acidic soils. When you split, you give the crop what it needs at the right time,’ he says.
Traditionally, farmers apply 50kg of DAP per acre at planting. But Dr Ekwangu says this is where most of it goes to waste.
Instead, he advises: apply 25kg at planting, then apply 25kg at first weeding, around three to four weeks later.
This, he says, ensures nutrients reach the plant during the most critical growth stages.
Studies from Tanzanian and Kenyan maize research stations show that splitting nitrogen and phosphorus doses can increase yields by 15-30 per cent, especially in regions with rainfall variability or acidic soils.
Soil testing
Despite its importance, soil testing remains rare among smallholder farmers. Yet it is the first step in unlocking better fertiliser performance and often in saving money.
A soil test reveals the soil’s nutrient levels, pH and organic matter content. Most maize thrives in soils with a pH between 5.5 and 7.0, but many parts of Bunyoro fall below this range.
‘Before you invest in fertiliser, spend a small amount on a soil test. It might show your soil is already fertile, or that you only need small doses of fertiliser,’ Dr Ekwangu says.
Without this knowledge, farmers may apply fertiliser year after year without any benefit.
Beyond fertiliser
Even with the correct fertiliser and split application, maize still demands proper agronomy. Poor spacing, late weeding, and low-quality seed can all undermine fertiliser efficiency.
Maize responds best when: spaced correctly, weeded early, planted using improved seed varieties and grown in well-prepared soils with good moisture.
Without these conditions, even the best fertiliser cannot push yields beyond a certain point.
Turning point
After learning about soil acidity and split application, Kato says he is willing to try a different approach.
‘Maybe my soil is already fertile. Or maybe I’ve been applying incorrectly. I want to know the truth before I spend more money,’ he says.
Agronomists say this shift in mindset is critical. Fertiliser is not a one-size-fits-all solution. It is a targeted tool that works only when applied correctly and under the right soil conditions.
‘When farmers understand their soil, they stop wasting money. And when they apply fertiliser using split doses, they finally start seeing the yields they expect,’ Dr Ekwangu says.
PRACTICAL APPLICATION
Small change, big difference
A smallholder farmer can save a significant amount of money on an acre of maize simply by changing how they approach fertiliser use. The first and most important step is soil testing, which costs between Shs20,000 and Shs30,000. This small investment provides crucial information about soil pH and nutrient levels. Many soils in Bunyoro are naturally fertile or only slightly deficient, meaning they do not require the full one-bag fertiliser dose that most farmers apply by default. A soil test can therefore save a farmer from buying fertiliser unnecessarily, potentially saving up to Shs120,000 before planting even begins.
Savings continue when the farmer uses the findings from the soil test to apply fertiliser more efficiently. Instead of buying a full 50kg bag of DAP, which costs about Shs150,000, a farmer may only need 25-35kg depending on the soil’s nutrient status. This reduces spending by an additional Shs60,000. When fertiliser is applied in a single dose at planting, much of it is lost due to leaching or fixation in acidic soils. Splitting the application, half at planting and the rest during first weeding, ensures that more nutrients reach the crop at the time when it needs them most. This increases fertiliser efficiency without increasing fertiliser cost.
The benefits of these two practices extend beyond savings.
Farmers, who currently harvest 17 to 18 bags of maize per acre regardless of whether they use fertiliser, often see yield improvements when they combine soil testing and split fertiliser application. Many farmers in similar soils in western Uganda report harvesting between 22 and 25 bags per acre after adopting these practices. Even a modest increase of three bags translates into an additional Shs270,000 in income, given current maize prices.
In total, a smallholder farmer can earn and save an extra Shs450,000 on a single acre through soil testing and correct fertiliser management. These gains can be channeled into preparing land for the next season, buying improved seed, expanding acreage, or supporting household needs.