|Karlen, Douglas - Doug|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2004
Publication Date: 9/1/2004
Citation: Clark, J.T., Russell, J.R., Karlen, D.L., Singleton, P.L., Busby, W.D., Peterson, B.C. 2004. Corn Stover Grazing Effects on Soil Physical Properties and Subsequent Soybean Yield. Agronomy Journal. 96(5):1364-1371. Interpretive Summary: Stored feed costs represent one of the largest expenses associated with beef cow-calf production. Winter grazing of corn crop residue can substantially reduce these costs, but will that practice subsequently reduce soybean yield in a two-year corn-soybean rotation? Scientists at the National Soil Tilth Laboratory in cooperation with colleagues at Iowa State University and in New Zealand conducted a three-year on-farm study to determine how grazing corn crop residues during the winter affected various soil physical properties and soybean yield during the following year. Grazing increased soil surface roughness and compaction, especially if it occurred when soil moisture was high and soil temperatures were above freezing. However, with or without preplant tillage, the overall effects of grazing on subsequent soybean stand establishment, growth, and yield were small compared to the added benefit of using the crop residue as an inexpensive feed source. For producers who want to graze corn crop residue without sacrificing soybean yield, we recommend that they should restrict grazing to periods when soil temperatures are below freezing and/or plan to till the surface soil prior to planting soybeans.
Technical Abstract: There is concern that compaction and/or surface roughness caused by winter grazing of corn (Zea mays L.) crop residues may reduce soybean [Glycine max (L) Merr.] yields. A three-year, on-farm study was conducted near Atlantic, IA, to address this concern. Two 19.4-ha fields with Marshall (silty clay loam), Minden (silty clay loam) and Corley (silt loam) soils managed in a corn-soybean rotation were split into four replicate blocks of six paddocks. For five, 4-week intervals cows grazed one paddock at a stocking rate of 3.7 cows ha**-1. The sixth paddock provided a non-grazed control. Soil bulk density, aggregate stability, moisture content, penetration resistance, surface roughness, residue cover, soybean plant population and yield were evaluated for disked and no-tillage treatments following grazing. Grazing corn crop residue did not affect soil bulk density but increased penetration resistance to a depth of 10.5 cm in paddocks grazed in October and November. Surface roughness increased quadratically (r**2 = 0.27) as the proportion of time that soil temperature was below 0 deg C increased, reaching a maximum of 60%. Cattle grazing had no effect on subsequent soybean plant population, but yield decreased with increased soil penetration resistance (r**2 = 0.36). Soybean yields also increased as the proportion of the time soil temperature was below 0 deg C increased (r**2 = 0.72). Effects of grazing of corn crop residues on subsequent soybean yield will be minimal if grazing is restricted to periods when soils are frozen.