Soil and nutrient runoff losses with in-row, chisel-planted soybeans

ABSTRACT:

Coulter, in-row chiseling 20 centimeters (8 inches) deep in rye stubble effectively controlled runoff (less than or equal to 13%) on rainulator plots (10.7 and 21.4-meter slope lengths) with a 7 percent slope until water content in the topsoil approached 14.2 percent (about 0.1-bar suction). In-row chiseling and soil cover (rye mulch as well as rye mulch plus 68% soybean canopy) collectively reduced soil losses during rainulator runs to less than 0.5 metric ton per hectare (0.2 ton/acre) on both slope lengths. Increased slope length led to increased runoff, even with low soil water content during soybean canopy development. Removing crop residue and destroying the chisel slot with complete tillage caused soil losses exceeding 40 metric tons per hectare (17.8 tons/acre). Runoff-weighted nutrient losses related positively to soil losses. Increased slope length consistently increased nutrient losses during all tillage-soil cover sequences. Most nutrient loss variation was accounted for by treating soil loss as an independent variable during the rye mulch cover period. Phosphorus losses were correlated better to soil losses among tillage-soil cover sequences than to the cations. Coulter, in-row, chisel-planted soybeans through rye residue following winter-spring cattle grazing of rye effectively controlled runoff as well as soil loss and some nutrient losses.