A lysimeter study of the impact of cow urine, dairy shed euent, and nitrogen fertiliser on nitrate leaching

Abstract

The effect of cow urine, dairy shed effluent (DE), and urea fertiliser on nitrate leaching was determined using undisturbed soil lysimeters (500 mm diameter by 700 mm deep) with ryegrass (Lolium perenne)–white clover (Trifolium repens) pasture. Cow urine was applied to the lysimeters, at rates of 0 and 1000 kg N/ha in May 1996. Urea and DE were applied to urine-applied and non-urine-applied lysimeters at rates of 0, 200, and 400 kg N/ha in 4 split equal applications in May, August, and November 1996 and February 1997. Natural rainfall was supplemented with simulated rainfall in winter and spring (May–October) to achieve the 75th percentile of winter–spring rainfall records in the region. Flood irrigation was applied 6 times during summer–autumn (November–April) at 100 mm per application, which is a typical practice used by dairy farmers in the region. Drainage water was collected and analysed for nitrate, nitrite, bromide (added tracer), and ammonium. Over the first year of the experiment (May 1996–April 1997), 12% of the urine-N applied was lost through leaching, mainly in nitrate form. When urine (1000 kg N/ha) was applied in combination with DE (200 kg N/ha) and urea (200 kg N/ha), the mineral N leaching loss increased to 14% of the total N applied. The annual average nitrate concentrations in the drainage from the lysimeters that received urine alone, or urine+DE and/or urea, were 33–57 mg N/L, with a mean peak concentration of 110 mg N/L. These nitrate concentrations were significantly higher than in those treatments that did not receive urine (1–5 mg N/L). Because, on average, about 25% of the area of a grazed dairy paddock receives urine per year, the field-scale leaching losses were calculated by taking into account the dilution effect of drainage water from non-urine patch areas of the paddock. The calculated annual paddock losses were 33–60 kg N/ha, and on average the annual paddock nitrate concentrations were 10–17 mg N/L. This demonstrates the importance of accounting for the dilution of nitrate in the leachate from non-urine patch areas of the paddock. The annual average concentration from the treatment DE at 400 kg N/ha was significantly lower than that from the urea treatment at the same rate. This was probably because of the different chemical forms of N in each material, and needs to be taken into account when developing regional rules for land application of urea and effluents.

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

“…Previous studies have shown that NO3--N leaching from cow urine patches in grazed dairy pastures is a major contributor to high NO 3 --N leaching losses in free-draining dairy pasture soils (Silva et al 1999;Di & Cameron 2002b). Results from this study show that between 6.4 and 9.1% of the 15 N-labelled urine N may be leached.…”

“…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).…”

Land application of farm dairy effluent: Results from a case study, Wairarapa, New Zealand

“…The majority of the nitrogen applied in the effluent is in a relatively immobile organic form due to the dung component (Di et al 1998;Silva et al 1999;Barkle et al 2000;Longhurst et al 2000). Hence, it is likely that the effluent application has resulted in increases in microbial biomass carbon and nitrogen which has, consequently, increased gross nitrogen mineralisation rates.…”

“…The management of nitrogen and phosphorus to prevent possible groundwater or surface water contamination is a key issue for the long-term sustainable use of effluent-irrigated land (Falkiner & Polglase 1997). To avoid adverse effects on the environment and human health, rules have been set by some regional councils to restrict the rate of FDE application; however, such rules fail to take into account the heterogeneous nature of soil (Silva et al 1999).…”

A mechanical hoof for simulating animal treading under controlled conditions

“…For example, we were able to make direct measurements of nitrate leaching from grazed dairy pasture systems using undisturbed soil monolith lysimeters. Urine and farm dairy effluent were collected and applied to the lysimeters, with animal treading simulated using the mechanical hoof (Di et al 1998Silva et al 1999). The capacity to control the treading effects has greatly enhanced our ability to assess the effects of animal grazing on soil and environmental quality (e.g., Di & Cameron 2000).…”