Nitrogen Balance in Urine‐affected Areas of a New Zealand Pasture¹

Abstract

The high rates of urine‐N deposited during grazing offers the potential for considerable N loss through volatilization, leaching, and denitrification. A field experiment was conducted to evaluate the magnitude and pathways of N transformations and losses under warm, moist conditions. Urine was applied to 3‐m2 plots in a ryegrass (Lolium perenne L.)‐white clover (Trifolium repens L.) pasture at 300 or 600 kg N/ha. These rates simulate the urine affected area of sheep and cattle, respectively. Ammonia volatilization, inorganic N in the soil profile, symbiotic nitrogen fixation (by acetylene reduction assay), and herbage N yields were measured over 53 days. Four days after application from 30 to 35% of the added N could not & accounted for as either soil mineral N or volatilized NH3‐N. Ammonia‐N evolution was rapid only for the first 2 days, and I5 to 18% of the N was volatilized as NH3. Profile NH4‐N was completely nitrified by 21 days. Considerable amounts of the applied N was lost from the 0 to 45 cm profile by 53 days. Since rainfall and irrigation exceeded estimated evapotranspiration, leaching of NO3‐N is the probable loss mechanism. The apparent recovery of N in herbage was 37 and 22% of that added. Acetylene reduction was substantially less in the urine‐treated swards. From 30 to 35% of the urine‐N was not accounted for as inorganic N early in the experiment; immobilization and rapid leaching of urine below 45 cm are probable loss mechanisms. The experiment indicated that in a warm, moist environment, typical of late spring‐early summer in New Zealand, more than half of the N in urine voided by sheep or cattle can be lost, and that an intensively grazed grass‐legume system is far from a closed system, or cycle, with respect to N.

Isotopic composition of soil, vegetation or cattle hair no suitable indicator of nitrogen balances in permanent pasture

“…grazed' was identical to that of the 'mean urine ? grazed since 2003' patches (Ball et al 1979). In intensive dairy farming, urine affecting 40% of the pasture area has been estimated to decrease N fixation by at least 10% annually (Ledgard et al 1982).…”

“…Ball et al 1979;van Beek et al 2003). Where N inputs exceed N outputs, surpluses are assumed to result in N accumulation in the soil and/or in increased N transfer to the environment.…”

Evaluating the lingering effect of livestock grazing on functional potentials of microbial communities in Tibetan grassland soils

“…It has been reported that grazing could cause considerable N loss under warm and moist conditions through leaching and denitrification (Ball et al 1979). However, grazing reallocates N between aboveground and belowground ecosystems, which could compensate soil N loss.…”

A lysimeter study of the fate of15N‐labelled nitrogen in cow urine with or without farm dairy effluent in a grazed dairy pasture soil under flood irrigation

“…In intensively grazed dairy pasture systems, although the amount of NO3--N leached is affected by inputs of N fertilisers and organic waste effluents (Scholefield et al 1993;Di et al 1998aDi et al ,b, 1999Ledgard et al 1999a;Silva et al 1999;Monaghan et al 2000), the largest contribution comes from the N returned from the animal urine (Ball et al 1979;Ryden et al 1984;Field et al 1985;Silva et al 1999;Di & Cameron 2000, 2002b. In a grazed pasture, between 60-90% of the N ingested by the grazing animal is returned to the pasture in the urine and dung and more than 70% of the N returned is in the urine (Haynes & Williams 1993;Jarvis et al 1995).…”