| Summary: | Malting barley is not a widely planted crop in the Southwest, due to grain protein contents that can sometimes exceed the industry standard of 11.4 %. To achieve < 11.4% grain protein, careful nitrogen (N) management is needed. Tissue testing guidelines for N management for reduced grain protein and acceptable yields have not yet been determined for malting barley in the Southwest. The objectives of this study were to: (i) correlate NO₃-N in dried stem tissue with sap NO₃-N, and (ii) develop stem NO₃-N guidelines for N management in malting barley. In November 1997 two varieties of malting barley, Morex and Crystal, were planted at the Maricopa Agricultural Center. Five N rates (0, 60, 120, 180, and 240 lbs/acre) were applied in four split applications. Each treatment was replicated three times in a randomized complete block design. Samples were collected from lower stems at the 3-4 leaf 2 node, and flag leaf visible growth stages. Grain yields ranged from 1765 lbs/A to 3439 lbs/A for Morex and 2104 lbs/A to 4274 lbs/A for Crystal. Grain protein ranged from 7.6- 10.5% (Morex) and 7.0- 10.7% (Crystal). Correlation coefficients between stem NO₃-N and sap NO₃-N were 0.80 for Morex and 0.84 for Crystal. For Morex and Crystal, grain protein was within the malting industry grain protein range of 10.5- 11.4% at 240 lbs N/A, and yield was optimized at 180 lbs N/A. Sap NO₃ analysis can be a useful tool for determining N status of malting barley. Stem NO₃-N concentrations at 180 lbs N/A were generally within the optimum range for NO₃-N in small grains.
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