Forage Utilization and Beef Cow Nutrition
Beginning in 1999, two locations in Iowa (Chariton, Atlantic) were used to study the effects of corn residue grazing by beef cows on soil characteristics and soybean yields the following growing season. Cows were allowed to graze inside selected paddocks at monthly periods throughout the fall and winter. For a grazed and ungrazed comparison, grazing exclosures were used inside the grazed paddocks while one paddock was left ungrazed for a control. The use of this design was to determine if grazing had any adverse effects on soil characteristics and at what date and weather conditions did they occur. Also equal portions of the fields went to no tillage and disked soil the following year before soybean planting to compare effects of corn residue grazing on tillage treatments. Soil was analyzed for soil bulk density, moisture, penetration resistance, roughness, texture, and type. Corn crop residues were also collected for yield, cover and composition. The following year, soybeans were harvested using a combine equipped with a yield monitor and global positioning system. Crop residue grazed at the Atlantic site had a decrease in the organic matter yield in grazed paddocks, but no difference in the nutritional quality of residue between grazed and ungrazed paddocks. Soil bulk density data collected from the Atlantic site showed a significant difference between the 0-4 and 4-8 inches depths (P<.01) and tillage treatments (P=.04) apparently caused by soil types because no tillage treatment was given until the following spring. Bulk density and penetration resistance ratios inside and outside exclosures did not differ between periods grazed indicating there was no effect of grazing on soil compaction. However, there was an effect of grazing period on soil roughness. Like the Atlantic site, crop residue organic matter yields at Chariton decreased over the winter. Unlike the Atlantic site, there was an increase in concentrations of NDF and ADF and a decrease in CP concentration in crop residue for the grazed paddocks over the ungrazed paddocks. Pre-grazing, post-grazing and post-planting corn crop residue cover did not differ between paddocks grazed and ungrazed, but was different between tilled and no tilled plots after soybeans were planted. Soil bulk density data at Chariton were not affected by grazing date. However, penetration resistance in the upper 6 inches in periods grazed at the beginning and end of the season were greater than paddocks ungrazed or grazed in January or February (P=.077). Soil roughness, however, was lower in these paddocks. Regardless of the effects of crop residue grazing on soil characteristics, soybean yields subsequent to grazing date did not differ between paddocks that were ungrazed or grazed at different periods of the winter.
Iowa State University
Clark, Justin; Russell, Jim; Karlen, Douglas; Busby, Darrell; Secor, L. James; Peterson, Brian; Pellack, Larry; Olsen, Carroll; and Shouse, Shawn, "Effects of Corn Crop Residue Grazing on Soil Physical Properties and Subsequent Soybean Production in a Corn- Soybean Crop Rotation (A Progress Report)" (2002). Beef Research Report, 2001. 13.