Effect of Potassium and Nitrogen Fertilization on Lysine, Methionine, and Total Protein Contents of Wheat Grain, Triticum aestivum L. em. Thell.1

Abstract

AbstractAn irrigated, split‐plot field experiment was conducted at Pahlavi University, Shiraz, Iran to study the effects of N and K fertilization on the lysine, methionine, and total protein contents of wheat (Triticum aestivum L. em. Theil., var. ‘Roushan’). The soil was calcareous silty clay loam. The area was flood irrigated once before seeding and four times during the growing season. Rainfall totaled 49 cm. The amino acids were assayed microbiologically.Yield of grain was not affected by application of 50 or 100 kg/ha of N, but decreased at the 200‐kg level. The ratio of grain to total dry matter decreased consistently with increasing application of N, showing that N stimulated the vegetative growth much more than seed production. Application of K did not show any significant effect on the yield of grain or on total dry‐matter production.Protein content of the grain was consistently increased by each additional increment of N, and so were the lysine and methionine contents. The increase in protein was about 1% for each addition of 50 kg N/ha. Percentage of lysine in the protein showed an inverse relationship with the N applied or the protein content of the grain. However, K significantly increased the lysine percentage in the protein. Percentage of the methionine in the protein did not change with varying rates of N or K.