EFFECT OF MOISTURE, TEMPERATURE, AND NITROGEN ON YIELD AND PROTEIN QUALITY OF THATCHER WHEAT

Abstract

Soil moisture level was the most important factor controlling plant and grain yields while nitrogen fertilizer had the greatest influence on protein content and sedimentation value. Lower temperatures and nitrogen fertilization favored plant development at medium and high soil moisture levels but did not significantly alter the yield of plants subjected to periodic moisture stress. Temperature was the only treatment to have a consistent effect on kernel weight. However, seed yields were more closely associated with total plant weight and number of culms than kernel size.The sedimentation values of the flour, which ranged from 33.8 to 70.7 ml, were highly correlated with protein content. The wide range of sedimentation values approached the maximum range reported for very weak and very strong wheats. Within treatments receiving the same nitrogen applications, the sedimentation values and protein content were inversely related to grain yield.Variations in glutamic acid and proline content of the hydrolyzed flour proteins were positively associated with protein content and sedimentation value. Amino acids which were negatively correlated with protein content included alanine, arginine, aspartic acid, cystine, glycine, and lysine. Contrary to previous reports the lysine content varied over the complete range of protein content in the flours. The significance of these variations in amino acid composition are discussed in relation to recent studies on the fractionation of flour proteins.