LOSS OF GREEN COLOR AND CHANGES IN KERNEL WEIGHT FOLLOWING WINDROWING OF IMMATURE WHEAT

Abstract

A field study was conducted to determine the effects of stage of maturity at harvest on kernel weight and color of two cultivars each of hard red spring (Triticum aestivum L.) and durum (T. turgidum L. var. durum) wheat dried in windrows or artificially following threshing. Plots were cut at kernel water concentrations (KWC) ranging from approximately 160 to 2200 g water per kilogram kernel dry weight and left in the field to dry in simulated windrows. A subsample was threshed and the grain dried in a forced-air oven at 40 °C and under ambient laboratory conditions of 25–30 °C. Percent green kernels and kernel weights were determined on the field- and artificially-dried samples. Differences among cultivars in green kernel percentage appeared to be largely related to maturity differences. Green kernel percentage dropped below 0.75 (top commercial grade tolerance) at higher harvest KWC in the windrowed samples than in the artificially dried samples. In unevenly matured crops, green kernel percentages in excess of 0.75% remained a risk even at harvest KWC approaching combine ripeness (170 g kg−1). There was little difference in green kernel percentage of the ambient-air-dried and oven-dried grain when harvested at commercially realistic KWC less than 250 g kg−1. Kernel weight increased in windrowed wheat harvested at KWC greater than 1200 g kg−1, presumably through translocation of assimilates from the straw. No such translocation was detected in wheat windrowed within the recommended KWC range of 640–670 g kg−1.Key words: Ambient air drying, artificial drying, windrowing, wheat (hard red spring), wheat (durum)