**2.7 Pre-plant blended fertilizers and nitrogen topdressing**

The right fertilizers must be applied at the right rate and at the right time, following best agronomic practices before smallholder maize producers across Africa can

**Figure 7.** *Dry rotary system used in small-scale fertilizer blending.*

optimize grain yields. Shortages of soil nitrogen (N), phosphorus (P), and potassium (K) result in weak roots, stunted growth, greater vulnerability to pests and disease, reduced photosynthetic efficiency, fewer and smaller ears, and incomplete grain fill. Sub-Saharan Africa is facing food security challenges due, in part, to decades of soil fertility depletion. Applying mineral fertilizer, in conjunction with better management of organic resources and increasing Biological Nitrogen Fixation (BNF) can increase crop yields, replenish soil nutrients, increase soil organic carbon sequestration, and reduce N and C losses [41, 42]. Too few farmers in Sub-Saharan Africa use appropriate fertilizer formulations, dosages, and schedules, leading to lower yields, reduced profits, and nutrient-depleted soils [43].

Specialized blends of common fertilizers that contain N, P, K, and other nutrients such as sulfur, magnesium, and zinc are developed for basal application to maize crops. Applying blended fertilizers before planting can help to ensure a more balanced availability of nutrients for maize crops [44]. This is important because nitrogen fertilizer is one of the largest investments maize farmers make, and it can be lost due to drought or excessive rainfall. To overcome this inefficiency, it is widely recommended that nitrogen fertilizer be applied in two or more split applications throughout the growth cycle. This practice ensures that crops have a continuous supply of nitrogen, which can help mitigate financial risks to farmers and improve yields [45].

Many agro-dealers and manufacturers offer specially designed pre-plant fertilizer blends for maize. These formulations are adjusted to local growing conditions and soils and promote early crop development, stress resilience, and grain production by effectively delivering nutrients throughout the growing season. Top dressing N fertilizer later in the season better matches soil availability to the demand pattern of maize crops (**Figure 7**). The optimum time for top-dressing N fertilizer is when maize crops have eight to ten fully developed leaves. In this way, African farmers can obtain higher maize yields with lower rates of nutrient inputs when using blended fertilizers at planting instead of single fertilizers and splitting their nitrogen applications instead of a one-time input.
