NITROGEN NUTRITION ON LEAF CHLOROPHYLL, CANOPY REFLECTANCE, GRAIN PROTEIN AND GRAIN YIELD OF WHEAT VARIETIES WITH CONTRASTING GRAIN PROTEIN CONCENTRATION

Wheat cultivars ('AC Barrie', 'Brook Field', 'Hoffman', and 'Norwell') with different protein concentrations were compared under four nitrogen (N) levels (0, 50, 100 and 150 kg ha-1) in an environment-controlled greenhouse, and the same experiment with an additional N level (200kg N ha-1) was repeated in the field in 2007. In the greenhouse experiment, application of 100 kg N ha-1 resulted in significantly greater grain yield due mainly to higher number of grains per spike and heavier mean grain weight; in the field study, the 150 kg N ha-1 treatment produced the greatest yield (P0.01) primarily due to more number of grains per spike. Crude grain protein percentage was increased significantly with each increment of N up to the highest level; however, protein yield (kg ha-1) increased significantly with fertilizer up to 150 kg N ha-1. Leaf chlorophyll contents were increased linearly with increment of N levels up to 150 kg ha-1 both in the greenhouse and field trials while leaf area indices continued to increase up to the highest application rate (200kg N ha-1). Canopy reflectance, expressed as normalized difference vegetation index (NDVI), attained maximum value with 150 kg N ha-1 in the field experiment. Among the varieties tested, oHoffmano out-yielded other three varieties due to heavier grain weight. Although highest grain and/or plant crude protein content were recorded in 'AC Barrie', it was the variety 'Hoffman' that produced the highest total protein (kg ha-1) with largest NDVI and leaf area index (LAI) values.