Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 2014
Publication Date: April 23, 2014
Citation: Grabber, J.H., Jokela, W.E., Lauer, J. 2014. Soil nitrate and forage yields of corn grown with clover or grass companion crops and manure. Agronomy Journal. 106:952-961. Interpretive Summary: Corn silage is the predominant forage fed to cattle in the Midwestern United States, but its production can contribute to groundwater contamination, eutrophication of natural ecosystems, and hypoxia in coastal waters by soil, phosphorus, and nitrate. The production of silage corn with companion crops (e.g., cover crops or living mulches) is therefore widely recommended for reducing soil and nutrient losses from cropland and for maintaining or improving crop yields, nutrient cycling, and soil quality. We evaluated the agronomic and environmental performance of five companion crop systems for corn during a four-year study in south central Wisconsin. In two rotational systems, corn was grown for one year with either kura clover living mulch or interseeded red clover followed by one year of clover production. Three continuous corn systems employed interseeded ryegrass, fall-seeded rye, or no companion crop. Because forages are usually heavily manured on farms, we also assessed the effects of fall versus spring manure applications on the performance of these corn companion crop systems. In previous papers from this study, we reported the off-season herbage production and soil nitrogen uptake of companion crops fertilized with manure and their effects on spring runoff and soil quality. The current paper examined the soil nitrate levels and forage yields of these corn companion crop systems fertilized with spring versus fall manure in relation to continuous corn fertilized solely with inorganic fertilizer. Overall, we found that no companion crop or manure management system was clearly superior in all attributes related to forage production, nitrate leaching potential, runoff, and soil quality. Thus the most appropriate choice of companion crops and manure management for no-till silage corn will depend on producer requirements for feed production and on site-specific requirements to remediate nitrate leaching and runoff of soil and nutrients from cropland. In ongoing studies we are working to improve the practicality, reliability, and yield of silage corn grown in rotation with interseeded forage legumes. Such systems should improve the profitability of corn-legume rotations for farmers while helping to protect cropland, natural ecosystems, and water resources.
Technical Abstract: Few studies have compared the agronomic performance of cover crop and living mulch systems for no-till silage corn (Zea mays L.). In a four-year Wisconsin study, we compared soil nitrate levels, dry matter yields (DMY) and crude protein yields (CPY) from five such corn-companion crop systems amended yearly with manure as well as continuous corn fertilized solely with inorganic nitrogen (N). Two rotational companion crop systems employed corn grown with kura clover (Trifolium ambiguum Bieb.) or interseeded red clover (Trifolium pratense L.) followed by one year of clover production. Three continuous corn companion crop systems utilized interseeded ryegrass (Lolium multiflorum Lam.), fall-seeded rye (Secale cereale L.), or no companion. Use of companion crops influenced spring and fall soil nitrate concentrations to a 30-cm depth, but had little effect on residual fall nitrate to a 1.2-m depth. Residual fall nitrate was related to N balance (inputs minus outputs) for continuous corn fertilized solely with inorganic N, but not for companion crop systems amended with manure. Corn-clover rotations provided 23% less DMY, but 26 to 60% more CPY than continuous corn treatments. Rotations with red clover produced the highest and most consistent yields of silage corn. Spring vs. fall manure application had no effect on soil nitrate and only influenced yields of continuous corn grown with grass companion crops. Overall, no system excelled in all traits, thus selection of companion crop and manure management systems for silage corn will depend on feed production and environmental goals.