Agronomics of Corn Production under Different Crop Rotations in New York

The 1996 Federal Agriculture Improvement and Reform Act decouples support payments from production. Consequently, grain producers must devise rotations based on market prices. The objective of this study was to demonstrate to grain producers that soybean [Glycine max (L.) Merr.]-corn (Zea mays L.) or soybean -wheat/red clover (Triticum aestivum L./Trifolium pratense L.)-corn rotations under reduced inputs (banded herbicides plus cultivation, ∼105 lb N/acre) compared with continuous corn under full inputs (insecticide, broadcast herbicides, ∼-140 lb N/acre) maintains or enhances corn yields. Field-scale demonstrations, with participating farmers performing field operations, were established on four farms in New York in 1993. When averaged across years and sites, the soybean-wheat/clover-corn and soybean-corn rotations compared with continuous corn yielded 10% greater (141, 139, and 127 bu/acre, respectively). Grain yield, however, had site by rotation interactions. The soybean-wheat/clover-corn rotation yielded greater in eight of 12 site-year comparisons, and the soybean-corn rotation yielded greater in seven site-year comparisons with continuous corn. Major production challenges where corn did not respond positively to rotations include adequate stand establishment and weed control in the soybean-wheat/clover-corn rotation and adequate N fertility in the soybean-corn rotation. We successfully demonstrated that soybean-wheat/clover-corn or soybean-corn rotations with reduced inputs compared with continuous corn under full inputs enhanced or maintained corn yield. New York growers, who adopt soybean-wheat/clover-corn or soybean-corn rotations, have the opportunity to reduce corn inputs, thereby improving profitability and reducing potential environmental problems. Research QuestionThe 1996 Federal Agriculture Improvement and Reform Act allows planting flexibility, and eliminates target prices and loan rates for grain crops by the year 2002. Consequently, grain crop producers will have to devise the most profitable crop rotations based on market prices. In New York, a grain corn deficit state, cash crop producers have frequently grown continuous corn. Rotated corn, however, yields greater than continuous corn. Compared with continuous corn, rotated corn also requires less fertilizer N, corn rootworm insecticide, and herbicides. The objective of this study was to demonstrate to New York cash crop producers that rotated corn with reduced inputs compared with continuous corn under full inputs can maintain or enhance corn yields. Literature SummaryRotated corn following soybean yields greater than continuous corn by 5 to 25%, depending upon environmental conditions. Generally, corn following soybeans in low-yielding environments yields greater than continuous corn by more than 15%. In high-yielding environments, corn following soybeans yields greater than continuous corn by less than 15%. Rotated corn following wheat or wheat/clover yields greater than continuous corn by about 5%. It remains unclear whether there is an additional yield benefit to corn by removing corn from the rotation for two or more production years compared with one production year. Some studies have reported similar yields for rotated corn regardless of the number of years that corn has been removed from the rotation. Other studies have reported greater corn yields in a 4-yr compared with a 2-yr rotation. Study DescriptionA rotation × tillage study was established in 1993 on four farms in New York. Participating farmers performed all field operations including tillage, planting, spraying, fertilizing, and harvesting. Two tillage systems (moldboard plow and chisel) and three crop rotations (continuous corn, soybean-corn, and soybean-wheat/clover-corn) were evaluated in a randomized block design in a split-plot arrangement. Main plots, which ranged from 105 to 210 ft wide and from 400 to 1100 ft long, consisted of tillage systems. Subplots, either 15 ft (six rows) or 30 ft (12 rows) wide, consisted of rotations. Continuous corn received a corn rootworm insecticide at planting and preemergence herbicides. Rotated corn received no insecticide and the same preemergence herbicide rate in a 10 in. band at planting. Rotated corn also received a cultivation at the V4 stage. Rotated corn received about 30 lb/acre less fertilizer N than continuous corn. We measured plant populations at the V3 stage, soil nitrate N at the V4 stage, weed densities at the V8 stage, ear-leaf N at silking, grain yield, and grain N concentration at harvest. Applied QuestionsAre corn yields in soybean-corn or soybean-wheat/clover-corn rotations with reduced inputs equal or greater than continuous corn with full inputs? Corn in the soybean-wheat/clover-corn rotation with reduced inputs yielded greater in eight of 12 site-year comparisons and the same in the other four site-year comparisons with continuous corn with full inputs. Corn in the soybean-corn rotation with reduced inputs yielded greater in seven of 12 site-year comparisons, the same in four site-year comparisons, and less in one site-year comparison with continuous corn with full inputs. Obviously, rotated corn with reduced inputs compared with continuous corn with full inputs enhanced or maintained corn yields under New York growing conditions. New York growers, who adopt soybean-corn and soybean-wheat/clover-corn rotations, have the opportunity to significantly reduce corn inputs, thereby improving profitability and reducing potential environmental problems. Does a 3-yr compared with a 2-yr rotation provide an additional yield benefit to corn? When averaged across years and sites, corn in the soybean-wheat/clover-corn and soybean-corn rotations yielded the same, about 10% greater than continuous corn (141, 1139, and 127 bu/acre, respectively). Corn in the soybean-wheat/clover-corn and soybean-corn rotations yielded the same in nine of 12 site-year comparisons. The 3-yr compared with the 2-yr rotation did not provide an additional yield benefit to corn in this study. What were the major production challenges to rotated corn with reduced inputs? The major production challenges to corn in the soybean-wheat/clover-corn rotation were establishment of satisfactory corn stands and satisfactory weed control. When averaged across sites, the soybean-wheat/clover-corn rotation had the least corn populations in each year of the study. Greater seeding rates of corn in this rotation may partially compensate for reduced corn stands, presumably because of allelopathic effects of wheat straw. When averaged across sites, the soybean-wheat/clover-corn rotation had the greatest weed density in corn in 2 of the 3 yr. Apparently, growers have to closely scout corn in this rotation for potential weed problems. The major production challenge to corn in the soybean-corn rotation was establishing the correct fertilizer N to apply to corn. Soybean yields in 1993 poorly predicted N credits for the 1994 corn crop. The use of the presidedress N test may improve fertilizer N credits to corn following soybeans. How effective were the farmer-researcher partnerships in evaluating the different cropping systems? The farmer-researcher partnerships in this study were very effective in evaluating different cropping systems. The growers managed each site very precisely as evidenced by low CV values for corn yields. The growers also participated in field days and some cooperative extension winter workshops. We believe that this study had a significant impact because of the farmer-researcher partnerships, which contributed in part to the increased adoption of soybean-corn and soybean-wheat/clover-corn rotations in New York.