Snowmelt runoff, sediment, and phosphorus losses under three different tillage systems

In cold climates, snowmelt runoff often exceeds rainfall runoff during the year. Conservation tillage practices may he effective in reducing runoff du ring the cropping season but not during the snowmelt period. A plot study w as conducted on a cropped hillslope to assess how tillage practices affect snowmelt runoff and the associated losses of sediment, phosphorus (P), and chemical oxygen demand (COD). Tillage systems were fall moldboard and chise l plowing with spring disking, and a ridge till system utilizing only the t illage associated with summer row cultivation. Tillage and planting were do ne up and down the slope. Ridge tilled plots had higher fall residue cover, retained more snow, had less surface roughness, and consequently produced more runoff than the moldboard plow treatment. The amount of runoff from ch isel plowed plots was similar to runoff from ridge tilled plots despite a r elatively rough surface and moderate amount of residue cover. Phosphorus lo sses in runoff were higher for the ridge till and chisel plow systems than for the moldboard plow system. for all tillage systems, soluble P represent ed a major portion (75%) of the total P loss in snowmelt runoff, Although e rosive losses in snowmelt were low, the P losses were substantial and merit consideration in studies evaluating management systems impact on surface w ater quality in regions where snowmelt runoff is important. (C) 2000 Elsevi er Science B.V. All rights reserved.