A comparison of animal output and nitrogen leaching losses recorded from drained fertilized grass and grass/clover pasture

Abstract

Annual liveweight gain of beef cattle (steers) grazing grass pasture fertilized with 200 kg N\ha was compared over a period of 7 years with that of steers grazing grass\white clover pasture given no artificial N fertilizer at North Wyke, Devon, UK. Nitrogen lost by leaching over the ensuing winter drainage periods was monitored from both pastures. Nitrogen leaching loss from the fertilized pasture over an extended period of 13 years (1983-95) is also reported.The average annual liveweight gain of the steers grazing the grass\clover pasture (0n81 t\ha) was 19 % lower than that of the steers grazing the N-fertilized grass pasture (1n00 t\ha). The average annual loss of nitrate-N by leaching in winter drainage from the grass\clover pasture (13 kg\ha) was only 26 % of that recorded from the fertilized grass (50 kg\ha). A possible reason for this difference may arise from the previous history of the grass\clover pasture which had been ploughed in 1982, causing a flush of N mineralization and consequently greater immobilization of N in the soil in subsequent years.Losses of N each winter by leaching measured over a 13-year period from the fertilized grass were highly correlated (P 0n001) with the preceding summer's soil moisture deficit, with the highest losses following dry summers. The nitrate-N concentration in the drainage water exceeded the European Union limit in drinking water (11n3 mg\l) in the initial 25 mm of drainage during 11 of the 13 autumns. The average loss of N each winter (53 kg\ha) was equivalent to 26 % of the fertilizer-N applied annually. Immediate losses of N by leaching of fertilizer applied in early spring and throughout one very wet summer (1993) were minimal.

Forms of phosphorus transfer in hydrological pathways from soil under grazed grassland

“…Surface water flowed from the drained plots on 21 days during the year. In 1994 there was more rain and drainage than usual: the 30‐year mean rainfall (1966–95) is 1055 mm, with 480 mm excess drainage, occurring over 139 days (Tyson et al . 1997).…”

Grazing legumes in Europe: a review of their status, management, benefits, research needs and future prospects

“…Nevertheless, it is now generally believed that the smaller N losses with grass‐clover swards are due to the lower level of livestock production and that the two systems (grass‐clover swards receiving no N fertilizer and N‐fertilized grass swards) would release similar amounts of nitrate at equal levels of livestock production per hectare (Cuttle et al. , 1992; Tyson et al. , 1997; Hooda et al.…”

Impact of agronomic practices of an intensive dairy farm on nitrogen concentrations in a karst aquifer in Ireland

“…Soil moisture stress has also been linked with NO3 -leaching. Tyson et al (1997) found that NO3 -leaching over a 13-year period from the fertilized grassland was significantly correlated with the preceding summer's soil moisture deficit (SMD), with the highest losses after dry summers. Soil moisture stress can contribute to increased NO3 -leaching through reducing crop uptake and/or organic N released from the soil microbial biomass during soil rewetting (Halverson et al, 2000).…”