Cover Cropping Systems for the Central Corn Belt

Corn (Zea mays L.) predominates in the central USA but grain sorghum [Sorghum bicolor (L.) Moench] may be preferable for cover crop systems. Effects of tillage (no-till and disk), cover crops, grain crop, planting date, and N fertilizer rate were investigated to compare grain sorghum and corn in cover crop systems. This 2-yr field study was conducted at Fisher, IL, on an Ashkum silty clay loam (fine, mixed, mesic Typic Haplaquolls); Toledo, IL, on a Cisne silt loam (fine, montmorillonitic, mesic Mollic Albaqualf); and Albion, IL, on a Belknap silt loam (coarse silty, mixed, mesic Aeric Fluventic Haplaquepts). Grain yield was not affected by tillage. Delayed planting of the grain crop increased cover crop biomass and N content at the expense of corn (128 vs. 106 bu/acre) and grain sorghum (94 vs. 89 bu/acre) yield. Grain yield following rye (Secale cereale L.) was less than when following hairy vetch (Vicia villosa Roth) or fallow. Optimal N rate was higher and yield was higher following hairy vetch (133 lb N/acre and 124 bu/acre) than following fallow (153 lb/N acre and 121 bu/acre) or rye (152 lb N/acre and 100 bu/acre), but cover crop establishment cost exceeded the benefit. Grain sorghum required less N than corn (108 vs. 180 lb N/acre), but the associated optimum yield (98 vs. 132 bu/acre) resulted in an economic advantage for corn. Thus, grain-sorghum-and-cover-crop systems are not attractive alternatives to corn-cover-crop or conventional-corn systems in the central Corn Belt. Research QuestionDue to environmental and economic concerns, interest in winter cover crops is increasing in the central USA. The purpose of this study was to evaluate the feasibility and compare the profit potential of corn and grain sorghum in cover crop systems in Illinois. Literature SummaryMany scientists and corn producers have concluded that cropping systems with corn and cover crops are less profitable than corn/fallow cropping systems in the central USA. Grain sorghum may be a better summer grain crop for such cover crop systems with hairy vetch or rye. Grain sorghum requires less N and water for an economically optimal yield and can tolerate a later planting date without suffering a yield loss. Grain sorghum and cover crop systems have been shown to work in Georgia, but farmers and scientists have little experience or research information to predict the outcome of such a system in the central Corn Belt. Study DescriptionThis field study was conducted during 1991 and 1992 on three farms in Illinois. Treatments consisted of hairy vetch (25 lb seed/acre) and rye (150 lb seed/acre) cover crops as well as winter fallow. The cover crops were killed 1 week prior to the appropriate corn planting date for each site or about 2 wk later. Corn and grain sorghum were planted no-till and conventionally 1 wk after the cover crops were killed. Four rates of N fertilizer (0, 80, 160, 240 lb N/acre) were applied as a sidedress. Plots were harvested at maturity. Applied QuestionsDid delayed planting of corn and grain sorghum result in increased cover crop production and N content? Delayed planting did increase hairy vetch and rye production and N content, but decreased corn (128 vs. 106 bu/acre) and grain sorghum yield (94 vs. 89 bu/acre). Thus, planting of corn or grain sorghum should not be delayed in an effort to increase cover crop biomass or N content. Are cover crops profitable? Grain yield following rye was significantly less than either fallow or hairy vetch and thus less profitable (Fig. 1). At the economically optimal yield level, grain yield following hairy vetch was 3 bu/acre greater than when following fallow but not large enough to compensate for seed and planting costs of hairy vetch. At economically optimal yield levels, we calculated that hairy vetch contributed only 20 lb N/acre to the subsequent summer grain crops. Soil erosion was not measured in this study, but it is reasonable to assume that no-till or cover crop systems would decrease soil erosion substantially. Fig. 1The effect of N fertilizer on mean grain yield of a summer grain crop following either a hairy vetch or rye cover crop or fallow. Is grain sorghum preferable to corn in a cover crop system? Grain sorghum required less N than did corn for an economically optimal yield (180 vs. 108 lb N/acre) (Fig. 2), but grain sorghum yield was so much less than corn (132 vs. 98 bu/acre at the economically optimal yield) that it was not competitive with corn regardless of the N rate used. Thus, grain sorghum is not preferable to corn for profitable cover crop systems in the central Corn Belt. Fig. 2The effect of N fertilizer on mean yield of corn and grain sorghum.