Increasing grain maize number and size
Nitrogen, phosphorus, potassium and boron have a particular impact on grain set and size, thereby influencing maize yield.
Crop Nutrition and Grain Maize Number and Size
Nitrogen
Nitrogen is essential for plant growth, being one of the main building blocks of proteins. In grain maize, the highest yields generally come from N-rates of 200-250kg/ha. Rates need to be high enough to maximize plant growth. Lack of nitrogen results in short cobs with a low number of grains.
Phosphorus
Applications up to 150kg/ha of P2O5 provide positive yield responses in trials on low P index soils However, even at very high P index soils a starter application of about 20kg P2O5/ha is required to achieve high yields.
Potassium
Trials commonly show large responses to high rates of potassium. Annual rates in most countries will range from 150 to 250kg K2O/ha. maize requires potassium and nitrogen in similar quantities for high yields and low N application will reduce K uptake, restricting growth. A lack of potassium and phosphorus can lead to incomplete grain set at the point end of the maize cob.
Boron
Boron is involved in cell extension and pollen tube growth; hence, it has a direct effect on grain set. A lack of boron can lead to a restricted grain set, with the cob having many missing kernels and a few large grains. Foliar or soil applied boron during stem elongation (V5 to V7) can contribute to higher grain maize yield.
