|Powell, J mark|
Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/25/2005
Publication Date: 6/15/2005
Citation: Grande, J.D., Karthikeyan, K.G., Miller, P.S., Powell, J.M. 2005. Crop residue level and manure application timing effects on runoff and sediment losses from no-till corn. Journal of Environmental Quality. 34:1337-1346. Interpretive Summary: Many dairy farmers are expanding herd size and devoting more of their cropland to corn silage production. This shift to corn silage, which removes more plant material from fields than corn grown for grain, leaves soil surfaces exposed and could increase erosion. This study examined the effects of residue cover and manure application on runoff and sediment losses from no-till corn fields. Treatments included corn grown for grain (G), silage (SL), and high-cut (60-65 cm) silage (SH). Three manure treatments were also included in the study: no manure (N), manure applied in the fall (F), and manure applied in the spring (S). Simulated rainfall was applied in the spring and fall for 2 years and runoff from experimental plots was collected. As residue cover increased (G >SH > SL), runoff decreased. Fall runoff from SL was 4-6 times greater than SH, and was unaffected by manure application. Spring runoff from SL plots that received manure was 62-88% less that SL plots that did not receive manure. Spring-applied manure reduced sediment concentration by 60-71% compared to non-manured and fall-manured plots. Spring runoff in G plots had 82% less sediment compared to SL plots. Sediment loads in spring runoff from S was 87-92% lower and, in 2003, 82% lower in fall runoff compared to N plots. This study showed that dairy farmers could reduce most negative erosive effects of corn silage harvest by applying manure in the spring and by leaving more crop residue in the field by increasing silage cutting height.
Technical Abstract: There is growing interest in corn silage utilization due to changes in animal farm dynamics and favorable economics compared to alfalfa. Since the extent of residue cover influences runoff production and soil losses, and since high-cut silage will increase residue cover, this harvesting method could conceivably minimize water quality degradation that would otherwise result from harvesting corn for silage. We examined the effects of crop residue level and manure application timing on runoff and sediment losses from no-till fields planted in corn. Treatments included conventional corn grain (G) and silage (SL) and non-conventional, high-cut (60-65 cm) silage (SH). Each treatment also received one of three manure treatments: no manure (N), application in fall (F) or spring (S). Simulated rainfall (76 mm/hr; 1 h) experiments were performed in the spring and fall for 2 years, runoff from 2.0 m x 1.5 m plots collected, and a sub-sample analyzed for sediment concentration, load, and particle size distribution. Both residue cover and manure were found to affect runoff and sediment losses; however, the observed effect varied by season. Runoff was inversely related to residue cover (G < SH < SL). Fall runoff from SL was 4-6 times greater than SH but was not significantly affected by manure. However, manure reduced spring runoff from silage plots by 62-88% compared to plots not receiving manure. Reductions were lower when manure was applied to G. Differences in sediment concentration between SH and SL were not significant in any season. In 2002, higher residue in G reduced the sediment load in spring runoff by >82% compared to the silage plots; reductions were lower in spring 2003. The sediment load in fall runoff from SH was 76% lower than SL. Spring-applied manure had the greatest influence on sediment export; the sediment concentration in spring runoff was 60-71% lower for S compared to N or F plots. Similarly, the sediment load in spring runoff from S was 87-92% lower and, in 2003, 82% lower in fall runoff compared to N plots. Nearly identical particle size distributions of sediment were observed for sediment from SH and SL plots. Finally, higher levels of crop residue and manure, particularly when spring-applied, lead to enrichment in the clay-sized fraction of runoff sediment.