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Nitrous oxide emissions from feces and synthetic urine of cattle grazing forage grass fertilized with hog slurry

Tremorin, Denis G., Tenuta, Mario, Mkhabela, Manasah, Flaten, Donald N., Ominski, Kim H.
Animal feed science and technology 2012 v.177 no.3-4 pp. 225-236
cattle, emissions, feces, field experimentation, forage grasses, grasslands, grazing, nitrogen content, nitrous oxide, pig manure, production technology, slurries, soil water, split application, spring, swine, urine
Effects of hog slurry application to fertilized grassland on emissions of nitrous oxide (N₂O) from feces and urine excreted by cattle grazing was determined. Feces from cattle grazing forage grass fertilized with two rates of plant available N from a hog slurry, (i) hog slurry as Split application in fall and spring, each 72kg N/ha (Split), and (ii) hog slurry each spring at 148kg N/ha (Single), and zero slurry (Control), were monitored in field experiments in 2004 and 2005. The slurry treatments resulted in total N of feces patches of 84 (Control), 86 (Split), and 106g N/m² (Single). Three synthetic urine treatments of (i) 136g N/m² (Low), (ii) 233g N/m² (Medium), and (iii) 329g N/m² (High) and no urine (Background) applied to simulate the range in levels possible for cattle grazing the grass fertilized with the slurry treatments were examined in 2005. Nitrous oxide emissions from feces of cattle grazing the Split and Single treatments were higher than Control. Cumulative N₂O emissions from feces additions in the studies were 7, 31, and 91mg N/m² for the Control, Single and Split treatments, respectively. Nitrous oxide emissions from feces increased with feces NO₃ ⁻ and soil NH₄ ⁺ concentrations, and decreased with feces and soil moisture. Cumulative N₂O emissions from urine treatments were much higher than from feces, being 165, 534 and 694mg/m². Nitrous oxide emissions from urine increased with soil NO₃ ⁻, NH₄ ⁺ and NO₂ ⁻ concentrations and decreased with soil moisture. Nitrous oxide emissions estimated for excreta of grazing cattle were 27g/kg of direct soil emissions for grassland receiving no slurry (Control) and 104 and 73g/kg of direct emissions of the Split and Single slurry treatments. Findings indicate direct N₂O emission estimates for hog cattle grazing production systems are enhanced more by hog slurry treatment than are emissions from excreta.