Poor nitrogen supply during grain fill leads to lower grain proteins. A balanced nitrogen topdressing during stem elongation can improve grain protein content and provide the right amount of nitrogen to sustain the grain corn filling.
Good potassium nutrition can increase protein content of the grain and the levels of proteinogenic amino acids, cystine and methionine.
Sulfur supply is particularly important in the conversion of nitrogen to protein and in improving grain corn quality. S also helps in the process of amino acid production, ensuring high nitrogen use efficiency.
Iron is important to plant metabolism as a component of enzymes and proteins, and in nitrate reductase for reduction of nitrate to ammonium and then amino acids.