INTERACTION BETWEEN MANURE AND TILLAGE SYSTEM ON PHOSPHORUS UPTAKE AND RUNOFF LOSSES

Application of manure on soils having high P test has raised concerns over the eutrophication of lakes and rivers. The objective of this stu dy was to evaluate the effects of one time application of 164 kg P ha( -1) from solid beef (Bos taurus L.) manure on soil Olsen P dynamics, P uptake by corn (Zea mays L.) grain, and P losses as total P (TP), par ticulate P (PP), and dissolved molybdate reactive P (DMRP) in both sno wmelt and rainfall runoff under ridge tillage (RT) and moldboard plow (MP) systems from 1992 to 1994. Soil P was consistently higher in the manure than no manure treated plots (17.9 vs. 12.3 mg kg(-1) in 1993 a nd 23.7 vs. 13.8 mg kg(-1) in 1994), Phosphorus uptake was greater fro m the manure than no manure treated plots (24.5 vs. 19.8 kg ha(-1) and 23.5 vs. 18.8 kg ha(-1)). Annual PP and TP losses were either similar or lower from manure than no manure treated plots. Particulate P loss es by rainfall runoff were lower from the RT vs. MP systems (0.25 vs. 1.95 kg ha(-1) in 1993 and 0.06 vs. 0.65 kg ha(-1) and 1994), The oppo site was apparent for DMRP losses in snowmelt, which were higher from the RT than MP system (0.11 vs. 0.01 kg ha(-1) and 0.14 vs. 0.03 kg ha (-1)). The RT system is an environmentally better system than the MP s ystem due to its substantial reduction in annual PP and TP losses.