Nitrogen and phosphorus losses from a feedlot for suckler cows

Summary

The raising of cattle outdoors in winter is becoming more common in temperate areas, although there is little information available on the effects of this practice on forested environments. In this study, the concentrations of ammonium acetate extractable phosphorus (P AAAc )and mineral nitrogen (NH 4-N and NO 3-N) in soil and the quality of percolation water from an open feedlot were studied in eastern Finland in 1997–2000. In each of four pens (975–1300 m2) eight suckler cows were fed in winter from 1995 in the case of the first two pens and from 1996 in the remaining two. The suckler cows usually stayed in the front part of the feedlot. Therefore the nutrient loading was also the highest in this part of the lot. When the pens had been used for 1–2 winters, the mean contents of PAAAc, NH 4-N and NO 3-N in the surface soil (0–5 cm)were 14,73 and 3.0 mg l–1 respectively, compared to only 3.0, 4.2 and 0.06 mg l–1 in the control forested area. In the front part of a 1-m-deep soil layer, the mean amounts of NH 4-N, and NO 3-N were 410 and 28 kg ha–1 respectively after 1–2 years of use of the feedlot. In percolation water, too, the mean concentrations of total phosphorus and total nitrogen were high in the front part: 1.7 –28 and 210–1400 mg l–1 respectively. The minimum requirement is cleaning of the dung, and even then loading may be substantial.