Impact of late -season irrigation management on malting barley yield and quality

Last irrigation application time, its impact on crop yield, quality, and economic benefits were studied in 2000, 2001, and 2002 cropping seasons. Two different water management experiments were designed based on last irrigation cutoff time with full water requirements and deficit irrigation practices during the grain formation period. Four irrigation cutoff times were selected based on the different stages of crop production during grain formation period. Last irrigation was cutoff at milk, pre-soft dough, soft dough, and post soft dough grain formation stages. Deficit irrigation was designed using 50%, 60%, and 70% depletion of water holding capacity before next water application. Effects of different water stress levels were evaluated during very sensitive grain formation stages.;Field experiments over the three years indicated that last irrigation at soft dough stage produced the highest grain yield of two-row malting spring barley. Water cutoff before or after soft dough stage reduced the grain yield significantly at p < 0.05 but the quality of grain for malt production was not significantly different when water was cutoff at pre-soft dough or post-soft dough stages. Irrigation cutoff at milk stage produced the lowest grain yield with lowest quality. It was observed that the decrease in grain yield at post-soft dough was due to the moisture related grain diseases that decreased the weight and quality of the kernels for malt extraction. Economic value of the crop was 13% greater with irrigation cutoff at soft dough rather than at post soft dough. Last irrigation practice at pre-soft dough cutoff also proved 10% better than the post soft dough cutoff. Water use efficiency during individual years was highest with cutoff at milk stage but the grain quality was the lowest.;Irrigation practices with irrigation at 50% and 60% depletion were not significantly different in terms of water use, grain yield, and grain quality. However, irrigation at 50% depletion produced higher mean yield in three years. Water management at 70% depletion significantly reduced grain yield and quality due to smaller grain size. Therefore, it is not a suitable practice to let soil water deplete to the 70% level during grain formation periods if sufficient water supply is available. On average, soft dough (40%), 50%, and 60% water management practices produced 13%, 10%, and 8% more crop value than 70% depletion. An analysis of crop yield response to water supply indicated that irrigation at 70% depletion and milk stage cutoff provided almost the same relationship. Pre-soft dough and 50% depletion water management also behaved in similar fashion.;Crop yield response factor ky for pre and post soft dough cutoff is 0.06 and 0.07 while for milk cutoff it is 0.23. Water stress treatments were started at the same time and were applied for whole grain formation period. An average ky value for stress treatment is estimated as 0.25 during the grain formation period.