How Much Fertilizer Does Maize Need in Kenya? Application Rate Guide

Maize is Kenya's most important food crop, grown on over 2 million hectares. Yet average yields remain below 2 tonnes per hectare — less than half what improved varieties can deliver with proper fertilization. The difference often comes down to applying the right amount of the right fertilizer at the right time.

Maize Nutrient Requirements

To produce one tonne of maize grain, a crop removes approximately 20 kg of nitrogen (N), 8 kg of phosphorus (P2O5), and 15 kg of potassium (K2O) from the soil. For a target yield of 5 tonnes per hectare — achievable with good management — the crop needs roughly 100 kg N, 40 kg P2O5, and 75 kg K2O per hectare.

In practice, not all applied nutrients are taken up by the crop. Nitrogen use efficiency is typically 40-60 %, meaning you need to apply more than the crop removes. The common recommendation for Kenyan maize is approximately 120-150 kg N per hectare.

Recommended Fertilizer Programme

The standard Kenyan recommendation for maize, based on KALRO research, is as follows:

· At planting: Apply DAP at 100-150 kg/ha (18-27 kg N + 46-69 kg P2O5)

· At knee-height (4-6 weeks): Top-dress with urea at 100-150 kg/ha (46-69 kg N)

· At tasselling (8-10 weeks): Optional second top-dress with urea at 50-75 kg/ha (23-34 kg N)

The Role of Nitrogen in Maize

Nitrogen drives vegetative growth — stalk height, leaf area, and ultimately grain fill. A nitrogen-deficient maize crop shows yellowing of the lower leaves starting from the leaf tip, progressing along the midrib. By the time symptoms are visible, yield loss has already begun.

Urea (46:0:0) is the most cost-effective nitrogen source per unit of N. At 46 % nitrogen content, 100 kg of urea delivers 46 kg of nitrogen. Apply urea when the soil is moist and incorporate it lightly to reduce ammonia volatilization losses, which can reach 30 % on the soil surface in hot, dry conditions.

Micronutrient Boost for Higher Yields

Research from KALRO and IITA shows that adding zinc and sulphur to the standard NPK programme can increase maize yields by 15-25 %. Ammonium sulfate as a partial nitrogen source provides both nitrogen (21 %) and sulphur (24 %), addressing the sulphur deficiency that is widespread in Kenyan soils.

A practical approach: replace 30-40 % of the urea top-dressing with ammonium sulfate. For example, instead of 150 kg/ha of urea alone, use 90 kg/ha of urea plus 100 kg/ha of ammonium sulfate. This delivers similar total nitrogen but adds 24 kg/ha of sulphur.

Summary

Kenyan maize needs approximately 120-150 kg of nitrogen per hectare for optimal yields. The standard programme uses DAP at planting and urea as top-dressing. Substituting part of the urea with ammonium sulfate adds sulphur — a nutrient increasingly recognized as limiting in Kenyan soils.

FAQ

Q: When is the best time to top-dress maize with urea?

A: Apply the first top-dressing when maize is at knee-height (4-6 weeks after emergence), ideally just before rain or irrigation. The second application, if needed, should be at tasselling (8-10 weeks). Never apply urea to dry soil in hot conditions — nitrogen losses can exceed 30 %.

Q: Can I use ammonium sulfate instead of urea for all the nitrogen?

A: You can, but ammonium sulfate has only 21 % nitrogen versus urea's 46 %. You would need more than double the weight (and cost) to deliver the same nitrogen. A 60:40 urea-to-ammonium sulfate ratio is the most practical approach.

Q: Is DAP still the best basal fertilizer for maize?

A: DAP is widely used and effective, but it does not supply potassium or micronutrients. On soils testing low in K, consider using NPK 17:17:17 instead, or supplementing DAP with muriate of potash (MOP).

Maxing supplies urea and ammonium sulfate for East African maize production. Contact ops@qdmaxing.com for Kenya-specific fertilizer recommendations and pricing.