PHOSPHORUS LOSSES AS AFFECTED BY TILLAGE AND MANURE APPLICATION

There is a lack of data on conservation tillage under field conditions characteristic of a dairy operation. Thus, simulated rainfall was used to compare total P (TP), algal-available P (AAP), and dissolved molybdate-reactive P (DMRP) losses from the conventional, chisel, and no-till systems for corn both with and without surface-applied manure prior to tillage. Rainfall was applied at several times during the growing season of 1978 and 1979. A portion of the previous year's residue was removed in 1978 and all the residue was left in 1979. Concentrations and losses of TP and AAP among unmanured tillage treatments were similar to trends observed for sediment concentrations and losses. In 1978, the chisel and no-till systems were ineffective in reducing TP and AAP losses relative to the conventional system.