Nutrient, Sediment, and Bacterial Losses in Overland Flow from Pasture and Cropping Soils Following Cattle Dung Deposition
Communications in Soil Science and Plant Analysis , 37 , 2006
McDowell, R.W., Muirhead, R.W., Monaghan, R.M.
The loss of phosphorus (P), suspended sediment (SS), ammonia (NH4þ-N), nitrate (NO3 2-N), and Escherichia coli in overland flow (OF) from dairy cattle dung can impair surface water quality. However, the risk of P and N loss from grazed pastures varies with time. Current practice in southern New Zealand is to select a field, cultivate, sow in Brassica spp., and graze in winter to save remaining pasture from damage. This deposits dung when soil is wet and OF likely. Hence, we determined P, NH4þ-N, NO3 2-N, and E. coli loss from dung in OF via simulated rainfall from intact grazed pasture and cropland treatments of a soil. Analysis of OF, 0, 1, 4, 11, 24, and 43 days after dung deposition at the upslope end of soil boxes indicated that total P (TP), NH4þ-N, and SS concentrations decreased sharply from day zero and leveled out after 11 days. More particulate P and SS were lost from the cultivated than pasture treatment, whereas the reverse occurred for dissolved organic P because of greater sorption of phytase active materials. Escherichia coli losses were high (1 105 100mL21) in both treatments throughout. Using the equations of fit in an example field site indicated that management of dung deposition could affect up to 25–33% of TP lost in OF