Influence of Tillage Systems and Residue Levels on Runoff, Sediment, and Phosphorus Losses

Abstract

ABSTRACT Arainfall simulator was used to study the effects of conventional tillage and no-till on the losses of runoff, sediment, and phosphorus (P) from agricultural lands. Three rye crop residue levels, 0, 750, and 1,500 kg/ha, were studied within each tillage system. Phosphorus fertilizer was applied at a rate of 46 kg/ha. A total of 100 mm of rainfall, with an intensity of 50 mm/h, was applied to 12 0.01 ha plots, located on a silt loam soil. Water samples were collected from H-flumes and later analyzed for sediment and P contents. No-till was found to be effective in reducing runoff and sediment losses. Runoff and sediment losses decreased as residue level increased, regardless of the tillage system. Increasing crop residue level from 0 to 750 kg/ha caused a decrease in average orthophosphorus (PO4) concentration for both tillage systems. However, as the crop residue level increased, from 750 to 1,500 kg/ha, the PO4 concentrations increased. Both PO4 and total-P (P4) losses were greatest with the 0 kg/ha residue treatment, intermediate with 1,500 kg/ha residue, and least with 750 kg/ha residue. The greater P losses from the 1,500 kg/ha, relative to the 750 kg/ha residue treatment, were attributed to higher P leaching from the crop residue of the 1,500 kg/ha treatment and insufficient suspended sediment to sorb P from solution for this level. No-till was very effective in reducing PO4, sediment-bound P (Psb), and Pj losses. Averaged over all residue levels, no-till reduced PO4, P^b, and Pj losses by 91, 93, and 97%, respectively, compared to conventional tillage.