Phosphorus Losses in Runoff As Affected by Tillage

Abstract

Little data are available on P losses in runoff from land under conservation tillage (CT) where the surface‐applied fertilizer variable has been eliminated. Thus, simulated rainfall was used to evaluate the comparative effects of four tillage systems on the losses of total P, dissolved molybdate‐reactive P (DMRP) and algal‐available P (AAP) where fertilizer was subsurface banded at planting. Tillage treatments included conventional (CN) and three CT systems: chisel plow (CH), till‐plant (TP) and no‐till (NT). Above‐ground portions of corn (Zea mays L.) plants were removed prior to simulation. Trials were conducted over a 4‐yr period, with individual trials being performed in June and July, September, or October of various years. The NT, CH, and TP treatments reduced total P losses by an average of 81, 70, and 59%, respectively, relative to CN. Concentrations and losses of total P among tillage treatments followed those for sediment concentrations and losses. Concentrations of DMRP were, in most cases, lowest for CN, although differences among treatments were generally small and not significant. With the exception of the first simulated rainfall trial (September 1980), no significant correlation was observed between DMRP concentrations and residue cover. Losses of DMRP for the CT treatments were similar to, or significantly lower than those for CN. Differences in AAP concentrations varied among treatments and sampling periods, although concentrations were usually lowest for NT. The relative percentage of AAP concentrations to total P concentrations increased over the course of this study. This increase was 6, 8, 26% higher for CH, TP, and NT, respectively, relative to CN. Relative to CN, the NT, CH, and TP treatments reduced AAP losses by an average of 63, 58, and 27%, respectively. These results indicate that CT systems can effectively reduce AAP losses in runoff relative to CN, especially at times when high sediment concentrations and losses occur from conventionally tilled land.

BMP Optimization to Improve the Economic Viability of Farms in the Upper Watershed of Miyun Reservoir, Beijing, China

“…This indicated that less soil disturbance allows more crop residue to remain on the soil surface, which reduces soil erosion and facilitates better infiltration of precipitation. The observed reductions in sediment, PP, and TP loss with conservation (or reduction) compared to conventional tillage are supported by similar findings from field studies [37,38]. These studies also found P and sediment loss to be highly related for all tillage systems, as reduced tillage systems greatly reduce sediment-P losses and in turn TP losses.…”

Phosphorus fertilization, soil stratification, and potential water quality impacts

“…No-till has often been shown to decrease TP and sediment losses compared to tillage (Andraski et al 1985;McIsaac et al 1995; . Previous studies also found that no-till generally increased SP losses compared to tillage.…”

“…However, this treatment did result in significantly greater sediment concentrations than the other treatments. Similarly, the disked DAP treatment resulted in the greatest TKN load and FWMC.No-till has often been shown to decrease TP and sediment losses compared to tillage (Andraski et al 1985;McIsaac et al 1995; . Previous studies also found that no-till generally increased SP losses compared to tillage.…”

Controlling Sprinkler Irrigation Runoff, Erosion, and Phosphorus Loss With Straw and Polyacrylamide

“…However, applying PAM to straw-covered soil decreased sediment concentrations for irrigations 1 and 2 compared to untreated bare soil or untreated strawcovered soil. Typically sediment and total-P concentrations are directly related (Andraski et al, 1985;Carter et al, 1974). Significant relationships (P < 0.01) between sediment concentration and total-P concentration occurred for both PAM-treated and untreated soil, but sediment concentration only explained 37 and 18% of the total-P concentration variability, respectively ( fig.…”