Mitigation of ammonia and nitrous oxide emissions from pasture treated with urine of sheep fed diets supplemented with sodium chloride

Abstract

This study was conducted to evaluate the effects of the inclusion of sodium chloride (NaCl) in the diet on growth performance and nitrogen (N) balance in sheep and subsequent ammonia (NH3) and nitrous oxide (N2O) emissions from pasture treated with urine of sheep. A total of 30 Ujimqin male sheep (a local breed, average body weight 15±1.3kg) were equally divided into three groups. The control group (C) was fed a standard NaCl diet (3g NaCl/kg DM), and the treatments were a medium salt group (MS, 4.5g NaCl/kg DM) and high salt group (HS, 6g NaCl/kg DM). Urine samples collected from the control and HS groups were used for land application in a field experiment, which consisted of 5 treatments: soil group (S, soil without treatment), distilled water group 1 (W1, 326mL), distilled water group 2 (W2, 458mL), urine of sheep in control group (C, 326mL, 102kgN/ha), urine of sheep in HS group (HS, 458mL, 92kgN/ha). The supplementation of NaCl had no adverse effects on growth performance and N balance in sheep. The high NaCl diet increased total urine volume (P<0.05) and average urine volume (P<0.05) and reduced urinary pH (P<0.05) and the N concentration in the urine (P<0.05) compared with standard NaCl diet. Compared with the C treatment, the HS treatment resulted in a delay of the peak N2O emission and decreased the average emission rates of NH3 by 48% (P<0.05) and N2O by 26% (P<0.05) from soil. In conclusion, high NaCl diet of grazing sheep (6g/kg DM) seemed to be a feasible means of reducing emissions of NH3 and N2O from urine treated pasture by increasing urine volume and decreasing total N concentration in urine.