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Long Term Effect of Corn Residue Grazing on Crop Yields
A 36 ha irrigated field was used to study long term effects of grazing corn residue on crop yields. Half of the field was planted to corn and the other half was planted to soybeans and crops were alternated yearly. Each half was divided into 2 replicates of 3 grazing treatments beginning in 1997: 1) fall/winter grazed (FG) in November to mid-February, 2) spring grazed (SG) in mid-February to April, and 3) not-grazed (NG). Calves (227-319 kg BW) were stocked at 3 hd/ha in FG and 3 hd/ha in SG up until 2000 (5 years) and then increased to 7.4 hd/ha in SG. For FG, no-till planting was utilized throughout the 16 years. However, yield data in FG is only available from the harvest of 2004 through 2013 (10 years). Within the SG and NG, 3 tillage treatments: no-till, ridge-till or spring disk-till, were imposed after corn with no-till being used following the soybean crop. These tillage treatments were maintained through 2007, at which time only the no-till treatments were continued. Therefore, the comparison of SG vs. NG under no-till is available for 16 years, the split plot comparison of SG vs. NG under three tillage strategies is available for 9 years, and the comparison of SG, FG, and NG under no-till is available for 10 years. No interaction (P ≥ 0.55) between tillage and grazing was observed for soybean or corn yield. Across all tillage treatments SG of corn residue increased (P < 0.01) soybean yields and had no effect (P = 0.58) on corn yields. Similarly, over 16 years SG under no-till increased (P = 0.03) soybean yields (3.90 vs. 4.00 ± 0.036 t/ha for NG and SG, respectively) and had no effect (P = 0.96) on corn yields. Over 10 years, FG (4.41 t/ha) improved (P < 0.01; SEM = 0.053) soybean yields over both SG (4.28 t/ha) and NG (4.18 t/ha), whereas SG tended (P = 0.07) to increase soybean yields when compared to NG and no effects (P= 0.55) of grazing in either season were observed on corn yields (12.8, 13.0, 13.1 ± 0.24 t/ha for NG, SG and FG, respectively). These data suggest that grazing of corn residue at stocking rates that would result in consumption of approximately half of the leaf and husk appears to have slightly positive or no impacts on subsequent soybean or corn yields.
Keywords: Corn residue, Crop Yield , Grazing