A large number of agronomic factors can influence maize yield, many of which are within a farmers control given the climatic and soil conditions. A balanced crop nutrition programme is essential to ensure the crop achieves its potential.
Forage maize yield is influenced by the same nutrients as the grain maize, however the difference in nutrient removal between the two types needs to be considered when planning the nutrient programme of the following crop.
Nitrogen is important to achieve high maize yields. It fuels crop growth and development and needs to be readily available. Nitrogen is important to build and maintain green leaf, maximizing photosynthetic assimilation and maize crop yields
Phosphorus is particularly important for root development and good crop establishment. Crops planted in cold or wet soils are often slow to establish and phosphorus is often the limiting factor. Similarly on dry soils where P availability is also limited.
Phosphate availability is also greatly influenced by both soil pH and by soil temperature.
Foliar application of phosphate is the best way to overcome these early deficiencies and will help the crop develop a better root system to support later growth.
Research has shown that phosphate deficient maize plants growing in cold and/or acid soils utilise phosphate applied to the leaf at twice the rate of control plants without any deficiency; much more phosphate was translocated from the leaf, particularly to the roots, which maximises early root development.
Potassium, like nitrogen, also boosts crop development, and large amounts are taken up by the growing plant. Supplies need to be balanced alongside those of nitrogen. Good potassium nutrition can also help minimise the effects of frost damage and reduces lodging. Potassium is most important for stomatal closure and low supplies result in loss of water from the plant.
Forage maize removes significantly higher amount of potassium than grain maize (see Maize nutritional summary) and this must be taken into account when assessing fertiliser needs of the following crop.
Sulphur supply is particularly important in the conversion of nitrogen to protein and helps improve nitrogen use efficiency. Manures tend to be a poor source of sulphur this needs to be supplied together with nitrogen.
Zinc has an important role in both shoot and root growth and development. In the above pot experiment maize plants weregrown ina nutrient solution without zinc and the 20 days after sowing sprayed withYaraVita Zintrac 700 at 1 l/ha then shoots and root weighed 5 weeks later.
Unavailability of any micronutrient can restrict growth processes and subsequent maize yield.
Manganese and iron increase photosynthetic activity and maintain good growth for high yields. Calcium ensures good plant strength, protecting root, leaf and stalk production. Boron is required for pollen tube growth and good grain set. Zinc is important for photosynthetic activity.
Manganese has a direct effect on plant development and growth. It is involved in chlorophyll production and photosynthesis, and acts as a catalyst in many plant growth processes including the metabolism and synthesis of proteins.
Maize plants are only slightly sensitive to lack of iron. Where deficiencies do occur, foliar applications – particularly those made at later stages of leaf growth and at early stem extension – have been shown to increase maize yield. Iron is important to plant metabolism as a component of enzymes and protein, and in nitrate reductase for reduction of nitrate to ammonium and then amino acids