Effect of gibberellic acid and nitrogen application on biomass and nutritive value of annual ryegrass

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AbstractEnhancing the growth of annual ryegrass (Lolium multiflorum Lam.) would be beneficial to livestock producers to decrease supplementation. The objective of the study was to examine the effects of nitrogen (N) and gibberellic acid (GA) in biomass production and nutritive. We evaluated the application of N (0, 20, and 40 lb N acre–1) and RyzUp Smartgrass (RYZ) [gibberellic acid (gibberellin A3)] at a rate of 0.4 oz acre–1 across two growing seasons (2011–2012 and 2012–2013). The experimental design was a split‐plot replicated four times. The main plots consisted of four treatment application dates (mid‐December, early and late January, and mid‐February) and the subplots consisted of four treatments (RYZ, 40 lb N acre‐1 [40N], 20 lb N acre‐1 [20N] plus RYZ, and 40N plus RYZ) and untreated control (UC). Seasonal dry matter (DM) yield was not different between UC and RYZ treatments, while N treatments had significantly greater biomass production but were not different from each other. RYZ had a 5% yield increase while 40N+RYZ had a 26% yield increase compared with UC. Treatment had a significant effect on crude protein (CP) (P < .01), neutral detergent fiber (NDF) (P = .02), and water‐soluble carbohydrate (WSC) (P < .01). No differences in WSC were detected between UC and RYZ treatments, while the treatments containing N had a slight decrease in concentration. Data suggests that temperatures in the southern United States during annual ryegrass production might be too mild to observe a GA response at the applied rates.