Maize usually responds well to fertilizers, provided other growth factors are adequate. Improved varieties can only reach their high yield potential when supplied with sufficient nutrients.
A maize crop of 2 t/ha grains and five t/ha stover removes about 60 kg N, 10 kg P2O5 and 70 kg K2O from the soil. Nitrogen6 uptake is slow during the first month after planting, but increases to a maximum during ear formation and tasselling.
Maize has a high demand for nitrogen, which is often the limiting nutrient. High nitrogen levels should be applied in three doses, the first at planting, the second when the crop is about 50 cm tall, and the third at silking.
Many soils provide substantial amounts of the phosphorus (P2O5) and potassium (K2O) but this is not adequate enough, especially at the seedling stage. Apply P2O5 near the seed for early seedling vigor. K2O is taken up in large quantities but plants’ requirement can usually be estimated by soil analysis.
K2O deficiency results in leaves with burnt edges and yellow or light green colour and empty cob ends, while P2O5 deficiency results in purple tinged leaves and hollow grains.
Nitrogen deficiency shows as yellow or light green stunted plants.
Phosphate is not taken up easily by maize and, moreover, some tropical soils are deficient in available phosphate.
Zinc deficiency symptoms include shortening of internodes and light streaking of leaves followed by a broad stripe of bleached tissue on each side of the leaf midrib. Occasionally the leaf edges and interior of the stalk at the nodes appear purple.
It is advisable to apply organic manures to improve soil structure and supply nutrients, all before ploughing. Nitrogen can be applied in organic farming via green manure (legumes fixing N directly from the atmosphere), farmyard manure (FYM) or compost. Phosphorus can be supplied through FYM, compost, and in the form of rock phosphate (available in East Africa as Mijingu rock phosphate). Rock phosphate should be applied in the rows or planting holes at planting to promote root formation. Potassium can be supplied through FYM, compost and ashes. However, fertilizer recommendations based on soil analysis provide the very best chance of getting the right amount of fertilizer without over or under fertilizing. Ask for assistance from a local agriculturist office.
In rain-fed maize growing areas, plant seeds along with the first rain.
This will allow roots to absorb the natural nitrates formed with bacterial action in the soil. Roots are susceptible to poor drainage, which causes stunted and yellowing of leaves. Stagnant water results to loss in N through leaching and denitrification