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ARS Home » Plains Area » Lincoln, Nebraska » Agroecosystem Management Research » Research » Publications at this Location » Publication #327945
Title: Ruminant urine increases uptake but decreases relative recovery of nitrogen by smooth brome grass

Author
item SNELL, LAURA - University Of Nebraska
item GURETZKY, JOHN - University Of Nebraska
item Jin, Virginia
item DRIJBER, RHAE - University Of Nebraska
item MAMO, MARTHA - University Of Nebraska

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2016
Publication Date: 12/2/2016
Citation: Snell, L.K., Guretzky, J.A., Jin, V.L., Drijber, R.A., Mamo, M. 2016. Ruminant urine increases uptake but decreases relative recovery of nitrogen by smooth brome grass. Crop, Forage & Turfgrass Management. A0022.

Interpretive Summary: Pasture management in eastern Nebraska supports the state’s $12 billion beef cattle industry, which is the largest single industry in Nebraska and ranks 1st in commercial red meat production in the United States. Little is known about how pasture fertilization rates and grazer urine inputs affect the efficiency of fertilizer and urine use by smooth brome, a common forage grass in eastern Nebraska. This research showed that smooth bromegrass responds well to fertilizer applications up to 180 kg N/ha (e.g. about 160 lb N/ac). Grass growing in areas affected by grazer urine inputs will have higher crude protein content but less efficient nutrient use compared to areas without urine inputs. The implication of these findings is that risks for nitrogen losses from fertilizer and urine will be higher in urine-affected areas.

Technical Abstract: Nitrogen (N) fertilizer application and excreta return may contribute to poor nutrient recovery and use efficiencies in pastures. From 2011-2012, we investigated the effects of ruminant urine input (urine and distilled water control) and N fertilizer rate (0, 40, 80, 120, and 160 lb N/acre) on N responses of smooth bromegrass (Bromus inermis Leyss.) in eastern Nebraska. Response variables included crude protein (CP) concentration, N uptake, apparent N recovery (ANR), and N use efficiency (NUE). In 2011, CP concentrations and N uptake increased linearly with N fertilizer rate on most harvest dates in urine- and distilled water-treated plots. In 2012, only urine had an impact as drought limited forage accumulation. Apparent N recovery averaged 42% and 63% in urine and distilled water-treated plots, respectively, in 2011 but did not differ between treatments in 2012, averaging 24%. Meanwhile, NUE was similar among treatments averaging 13.0 lb dry matter (DM)/lb N fertilizer applied in 2011 and 6.5 lb DM/lb N fertilizer applied in 2012. In years with favorable growing-season precipitation, producers can expect CP and N uptake in smooth bromegrass pasture to increase with fertilizer applications up to 160 lb N/acre in eastern NE. Pasture areas impacted by urine will have greater CP and N uptake but will recover relatively less N than areas not impacted by urine.