Impact of variable NPK source on water use efficiency and growth rates of winter grasses (cereals): Wheat, rye, barley and oats

Growth analysis [absolute growth rate (AGR), crop growth rate (CGR), and net assimilation rate (NAR)] and water use efficiency (WUE) response of four cool season C3-cereals viz. wheat (Triticum aestivum L.), rye (Secale cereale L.), barley (Hordeum vulgare L.) and oats (Avena sativa L.) at 30, 60 and 90 days after emergence (DAE) under eight NPK sources [S1 = 20-20-20, S2= 20-27-5, S3 = 7-22-8, S4 = 10-10-10-20S, S5 = 11-15-11, S6 = 31-11-11, S7 = 24-8-16, and S8 = 19-6-12] in pot experiment. The experiment was conducted in the green house of Dryland Agriculture Institute, West Texas A&M University, Texas, USA during winter 2009-10. The results confirmed significant variations in AGR, CGR, NAR and WUE among the four crops at different growth stages and NPK source. Barley and wheat were dominant crops under each NPK source in terms of higher AGR, CGR and WUE than rye and oats at 30 DAE. The AGR, CGR and WUE at 60 DAE decreased for each crop species with application of NPK 31:11:11 and 24:8:16 having more nitrogen content. At 90 DAE, both CGR and WUE ranked first for barley with NPK 20:20:20, for wheat with 24:8:16 and NPK 10:10:10 for oats. The increase in AGR and CGR had positive impact on WUE. Interestingly, the AGR, CGR and WUE increased whereas NAR decreased with the passage of time. The S6 NPK fertilizer, known as an acid loving fertilizer had harmful effects on the growth and WUE of different crop species in this study. Key words: Triticum aestivum, Secale cereale, Hordeum vulgare, Avena sativa, growth stages, NPK source, absolute growth rate (AGR), crop growth rate (CGR), net assimilation rate (NAR), water use efficiency (WUE).