Durum grain quality as affected by nitrogen fertilization near anthesis and irrigation during grain fill

Nitrogen fertilization and irrigation practices can affect durum [Triticum turgidum subsp. durum (Desf.) Husn.] grain quality, especially protein cont ent. The purpose of this study was to determine if irrigation frequency dur ing grain fill influences the effectiveness of N applied near anthesis in i ncreasing durum grain quality. A field study was conducted at Maricopa, AZ on a Casa Grande sandy loam soil (fine-loamy, mixed, superactive, hyperther mic, Typic Natrargid). Durum was grown with recommended amounts of N fertil izer until anthesis when 0, 3.4, and 6.7 g N m(-2) were applied and irrigat ion based on 30, 50, and 70% depletion of plant-available soil water was in itiated. Irrigation during grain fill had no effect on grain yield or grain quality except in 1996, when irrigating at 30, 50, and 70% depletion resul ted in hard vitreous amber counts (HVAC) of 813, 870, and 934 g kg(-1), res pectively. Nitrogen application near anthesis of 0, 3.4, and 6.7 g N m(-2) resulted in grain protein contents of 115, 127,and 140 g kg(-1) in 1995 and 132, 141, and 151 g kg(-1) in 1996, respectively. Nitrogen application nea r anthesis increased grain protein yield and HVAC in both years of the stud y and increased grain yield, grain volume weight, and kernel size in 1995. The results of this study suggest that N fertilizer application near anthes is has a primary influence on durum quality and that effects of irrigation frequency during grain fill are inconsistent or relatively minor.