Amelioration Strategies After Corn Residue Removal

 

In two other articles in this week's CropWatch authors share research results regarding corn stover removal and impacts on nutrient, soil erosion, soil organic carbon, and the succeeding crop yields. Most of the studies include continuous corn and stover removal each year to determine the potential worst-case scenarios and recommendations for producers. Some have studied how amelioration practices, such as adding cover crops and/or manure, may positively or negatively offset any effects of stover removal. The university research described below on amelioration effects has been published in the past year and is ongoing. 

 

 

One study from 2013-2016 looked at soil property changes and corn yield with five corn residue removal rates (0%, 25%, 50%, 75%, and 100%) and the addition of three cover crop treatments (no cover; early cereal rye terminated two to three weeks before corn planting; late cereal rye terminated most often terminated within 10 days after corn was planted). This was studied in a non-irrigated (Rogers Memorial Farm near Lincoln) and an irrigated environment (South Central Ag Lab near Clay Center), both in no-till continuous corn systems. Both locations had silt loam soils. Residue was removed in mid- to late-October each year and cereal rye cover crop treatments were drilled shortly thereafter. The cover crops were not irrigated for establishment or additional growth.

 

For soil properties, wet aggregate stability (to determine potential for water erosion), concentrations of particulate organic matter, soil organic carbon, and total soil N after three years of management were measured.

 

With complete residue removal, wet aggregate stability was reduced at the non-irrigated site over three years, suggesting the potential for increased water erosion. Irrigated soils may be more resilient in their response to wet aggregate stability to residue removal, suggesting that in the short-term more residue could be removed from irrigated sites compared to non-irrigated sites. Early termination appeared to have no effect on offsetting the corn residue removal effects on water erosion potential. Later termination of the cover crop resulted in increased wet aggregate stability at both locations. On average, later cover crop termination resulted in 0.7 tons/acre biomass compared to 0.2 tons/acre under early termination.  Cover crop biomass increased where residue was removed compared to where it had not been removed. The authors suggest that a cover crop biomass yield above 0.4 tons/acre may offset the water erosion potential effects of crop residue removal. 

 

Soil organic carbon and total nitrogen concentrations weren’t significantly affected by either residue removal or timing of cover crop termination in either site after three years. This suggests that in the short term, even high rates of residue removal do not reduce these concentrations. At both sites adding cover crops after residue removal increased soil organic carbon concentrations. A 13.5% increase in particulate organic matter was observed with later termination over early termination and the control treatments at the irrigated site at the 1-foot depth. There were no effects at the 2-foot depth.

 

Residue removal and cover crop termination date did not affect corn yield when all three years were combined. There were individual year and location effects on corn yield, suggesting these effects may be year and/or site-specific. It was noted that corn was shorter in the non-irrigated field at 0% residue removal versus 50% and 100% residue removal early in the season; however, the heights were consistent by tasseling. This is similar to the irrigated field in which corn was taller early in the season at the 100% residue removal compared to 0% and 50% with similar heights for all residue removal treatments by tasseling. Residue removal and cover crop termination date also didn’t affect the amount of residue the corn plants produced each year.

 

The overall conclusion of the study suggested that higher than the suggested 30-50% of residue removed may be possible in some soils (such as silt loam) when cover crops are used to help ameliorate the effects of removal.

 

 

Another Nebraska study near Bellwood looked at the effects of aerial interseeded cereal rye versus no cover crop into a standing corn crop in late August/early September from 2013-2015. Corn was harvested as high moisture corn followed by residue removal treatments of 71% corn residue removal or no removal on a sandy loam soil.  This study was conducted on strip-till, irrigated, continuous corn. 

 

Researchers found that the treatments did not affect fertility properties or subsequent corn yield.  However, increased wind erosion was noted when 71% of the residue was harvested on sandy loam soils compared to no residue harvest or addition of the rye cover crop. Adding the rye cover crop did not significantly impact soil properties on a sandy loam soil within three years, but it tended to reduce soil erosion.

 

It also was noted that biomass production by aerially interseeding rye into standing corn vs. the authors’ other studies of drilling the rye after harvest didn’t appear to increase cover crop biomass in spite of being seeded two months earlier. This could be due to variability of establishment and biomass production of the aerially interseeded rye each year, which may have also been a limitation on impacting soil properties in a more positive way.

 

 

An on-going six-year study at the university’s South Central Ag Lab near Clay Center looked at interactions between corn residue removal and irrigation rate (full or 60%), fertilizer management (112 lbs N/ac versus 180 lbs N/ac) and amelioration practices of a winter cover crop, manure, or no amelioration practice on continuous irrigated corn yield from 2011 to 2016. Cereal rye was drilled in late October after harvest at a rate of 100 lbs/acre and was terminated two weeks prior to planting corn. For the manure treatment, sheep or cattle manure was applied following corn and stover harvest in the fall every two years based on phosphorus removal.

 

Statistical yield increases occurred with stover removal and the 180 lbs N/ac nitrogen rate, suggesting these yield increases could be expected in irrigated, no-till, continuous corn systems where residue was removed on silt-loam soils. Grain yields were similar by irrigation rate (full versus limited) and amelioration practice. Adding cover crops or manure as amelioration practices did increase nitrogen recovery measured in the study while maintaining soil organic carbon and reducing soil erosion.

 

These Nebraska studies suggest that adding a cover crop or manure after corn stover removal does not negatively impact the subsequent corn yield where water is not limiting and can help reduce erosion on all soil types. Higher amounts of cover crop biomass (over 0.4 tons/acre) may be necessary to offset any negative effects of water erosion after residue removal. It also may positively affect soil properties in the top foot of soil in the next three to five years. Studies are ongoing to determine additional and consistent impacts over time.  An economic component of amelioration practices would also be beneficial.