Basal Stem Nitrate Tests for Irrigated Malting Barley

Abstract

Nitrogen fertilizer use is essential for optimizing yield of irrigated malting barley (Hordeum vulgare L.) but must be managed carefully to achieve optimum grain protein concentrations demanded by the malting industry. Development of tissue tests, applicable for growing conditions in the desert Southwest, would be of benefit to growers for optimizing yield and grain protein of irrigated malting barley. Field experiments were conducted with two cultivars of malting barley [Morex (six row) and Crystal (two row)] under irrigated conditions in southern Arizona. The objectives were to (i) determine yield and grain protein response to N applications, (ii) determine the relationship between lower-stem tissue and sap NO3–N, and (iii) develop lower-stem and sap NO3 test guidelines for N management in malting barley. Yields ≥90% of maximum relative yield and grain protein concentrations acceptable for malting were achieved at N rates (kg ha−1) of 242 to 269 (1997–1998) and 205 to 269 (1998–1999) for Morex and 162 to 178 (1997–1998) and 166 to 181 (1998–1999) for Crystal. Stem and sap NO3–N were significantly correlated in both cultivars, with r2 values of 0.72 in Morex and 0.82 in Crystal. We propose that, to achieve acceptable grain yield and protein, lower-stem sap NO3–N in malting barley should be no less than 300, 180, and 120 mg L−1 and dry stem tissue NO3–N should be no less than 3000, 1000, and 800 mg kg−1 at Feekes growth stages 3, 7, and 10, respectively.