Nitrogen losses from outdoor pig farming systems

Abstract

Abstract. Nitrogen losses via nitrate leaching, ammonia volatilization and nitrous oxide emissions were measured from contrasting outdoor pig farming systems in a two year field study. Four 1-ha paddocks representing three outdoor pig management systems and an arable control were established on a sandy loam soil in Berkshire, UK. The pig management systems represented: (i) current commercial practice (CCP) -25 dry sows ha 71 on arable stubble; (ii)`improved' management practice (IMP) -18 dry sows ha 71 on stubble undersown with grass, and (iii)`best' management practice (BMP) 12 dry sows ha 71 on established grass. Nitrogen (N) inputs in the feed were measured and N offtakes in the pig meat estimated to calculate a nitrogen balance for each system.In the first winter, mean nitrate-N concentrations in drainage water from the CCP, IMP, BMP and arable paddocks were 28, 25, 8 and 10 mg NO 3 l 71 , respectively. On the BMP system, leaching losses were limited by the grass cover, but this was destroyed by the pigs before the start of the second drainage season. In the second winter, mean concentrations increased to 111, 106 and 105 mg NO 3 -N l 71 from the CCP, IMP and BMP systems, respectively, compared to only 32 mg NO 3 -N l 71 on the arable paddock. Ammonia (NH 3 ) volatilization measurements indicated that losses from outdoor dry sows were in the region of 11 g NH 3 -N sow 71 day 71. Urine patches were identified as the major source of nitrous oxide (N 2 O) emissions, with N 2 O-N losses estimated at less than 1% of the total N excreted. The nitrogen balance calculations indicated that N inputs to all the outdoor pig systems greatly exceeded N offtakes plus N losses, with estimated N surpluses on the CCP, IMP and BMP systems after 2 years of stocking at 576, 398 and 264 kg N ha 71, respectively, compared with 27 kg N ha 71 on the arable control.These large N surpluses are likely to exacerbate nitrate leaching losses in following seasons and make a contribution to the N requirement of future crops.

Effect of nose ringing and stocking rate of pregnant and lactating outdoor sows on exploratory behaviour, grass cover and nutrient loss potential

“…Williams et al (2000) showed that nitrate leaching can be greatly reduced by using a management system that stocks pigs on established grassland compared to arable stubbles. After 6-month stocking, the vegetative cover on the grass system had been destroyed so in the following winter nitrate losses were similar from both systems.…”

Nutrient excretion by outdoor pigs: a case study of distribution, utilization and potential for environmental impact

“…I n response to consumers'demand for`naturally' raised pigs, an increasing number of breeding sows is being kept outdoors in Europe, especially in the UK, France and Denmark (Mortensen et al 1994;Denmat et al 1995;Watson & Edwards 1997). Outdoor pig production has benefits in terms of animal welfare and low costs of buildings and equipment (Deering & Shepherd 1985), but it may have hidden costs due to losses of nutrients to aquifers used for public water supply (Worthington & Danks 1992) or to the atmosphere (Petersen et al 1999;Sommer & MÖller 1999;Williams et al 2000).…”

Soils and nitrous oxide research

“…Grasslands are the most important sources of N 2 O emissions in temperate systems, and the effects of grassland management on N 2 O emissions have been extensively reported (Merino et al, 2005;Dobbie & Smith, 2006;Jones et al, 2006;Ball et al, 2007). The large amounts of N input received by grasslands, together with the excreta returned by grazing animals and thus concentrated in small areas have been identified as particularly important causes of high rates of N 2 O emissions Williams et al, 2000). This heterogeneity makes an assessment of emissions from grazed areas with the conventional cover box measurements particularly challenging.…”

“…The large amounts of N input received by grasslands, together with the excreta returned by grazing animals and thus concentrated in small areas have been identified as particularly important causes of high rates of N 2 O emissions (Oenema et al. , 1997; Williams et al. , 2000).…”