Soil surface property and soybean yield response to corn stover grazing

Farmer concern that compaction and/or surface roughness caused by winter grazing of corn (Zea mays L.) crop residues may reduce subsequent soybean [Glycine max (L.) Merr.] yield prompted this 3-yr, on-farm study near Atlantic, IA. Two 19-ha fields with Marshall silty clay loam (fine-silty, mixed, superactive, mesic Typic Hapludolls), Minden silty clay loam (fine-silty, mixed, superactive, mesic Aquic Hapludolls), Corley silt loam (fine-silty, mixed, superactive, mesic Argiaquic Argialbolls), and Colo silty clay loam (fine-silty, mixed, superactive, mesic Cumulic Endoaquolls) soils managed in a corn-soybean rotation were chisel-plowed and split into four replicate blocks of six paddocks. Five paddocks within each block were grazed in consecutive 4-wk intervals at a stocking rate of 3.7 cows ha(-1) while the sixth provided a nongrazed control. Following each grazing season, two blocks were disked, and two received no-tillage before soybean planting. Soil bulk density, aggregate stability, moisture content, penetration resistance, surface roughness, residue cover, soybean plant population, and yield were evaluated for each grazing by tillage treatment. Soil bulk density was not affected, but penetration resistance to a depth of 10 cm increased in paddocks grazed in October and November. Cattle grazing had no effect on subsequent soybean plant population, but yield decreased with increased soil penetration resistance (r(2) = 0.36). As the proportion of time soil temperature was below 0degreesC during the grazing period increased, soybean yield increased (r(2) = 0.72). Effects of grazing corn crop residues on subsequent soybean yield will be minimal if grazing is restricted to periods when soils are frozen or if the soil is disked before soybean planting.