Soil Erosion from Tillage and Planting Systems Used in Soybean Residue: Part I - Influences of Row Spacing

A rainfall simulator was used to compare soil losses from various tillage and planting systems used in residue from soybeans which had been grown in both wide and narrow spaced rows the previous season. Up and- down hill tillage and planting treatments ranging from a double disk system to no-till planting were evaluated using replicated plots on a silt loam soil in the Nora Series having a 10% slope. Tillage and planting systems used in soybean residue from narrow spaced rows had soil erosion and soil erosion rates that were reduced by approximately 50% compared to the same systems used in residue from wide spaced soybeans. However, the reductions were significant only for the double disk tillage system. There was a trend for the start of runoff to be delayed and for residue cover, accumulated runoff, runoff rate, and sediment concentration to be reduced for tillage systems used in narrow row soybean residue compared to the same systems used in residue from wide spaced rows. INTRODUCTION Most soybeans produced in the Midwestern United States are grown in a corn-soybean rotation. In Nebraska, soybean production grew to a record of nearly one million hectares in 1982 (NCLRS, 1984), nearly double the area of 197S. Several studies (Dickey et al., 198S; Laflen and Colvin, 1982; Laflen and Moldenhauer, 1979; Siemens and Oschwald, 1978) have shown that soil erosion following soybeans can be more than double the erosion following corn. Tillage and planting systems which leave a protective cover of crop residue on the soil surface have been shown to reduce soil losses, and are among the least costly erosion control practices (Nicolet al., 1974; Seay, 1970). Leaving as little as 20% of the soil surface covered with corn or soybean residue reduced erosion by 50% of that which occurred from a cleanly tilled, residue free surface (Dickey et al., 1984, 198S). Similarly, a no-till system which left a 95% cover of wheat residue, reduced erosion by 99.8% of that which occurred from a moldboard plow system (Dickey et al., 1983)