TEMPLATE DESIGN © Cover Crop Influences on Organic Grain Crop Production Emily Bruner, Laura Harris, Larry Grabau, Greg Schwab, and Chad Lee Plant & Soil Sciences, University of Kentucky, S126 Ag North, Lexington, KY Abstract Organic grain cropping systems use a variety of mechanisms to meet crop fertility needs and control pests. In order to assist farmers in the transition to organic production, research is needed to discover which systems can increase yields, while minimizing weed pressure (1). This report compares five different productivity-related dependent variables for two different cropping rotations. The rotations discussed in this preliminary report were winter rye followed by soybean and vetch followed by corn. Cover cropping practices, planting rates, and N application rates were treated as independent variables and their effect on the dependent variables measured were reported for the first two years of the study. Analysis revealed that the only significant difference consistent across the two years evaluated was for canopy closure at soybean flowering in response to soybean planting rates. While other significant differences were noted, more seasons of study are needed to reach consistent conclusions. Introduction Materials and Methods This study was conducted at the University of Kentucky’s North Farm, in Fayette County, Kentucky. The plots examined for this preliminary report have been in transition to organic production for the past three years. In the cropping systems analyzed, two grain crops were produced in each two year rotation, starting in the fall of In this moderate grain intensity system, corn ( Zea mays L.) planting followed a hairy vetch ( Vicia villosa ) cover crop and soybean [ Glycine max (L.) Merr.] planting followed a winter rye ( Secale cereale L.) cover crop. Both rotations were planted in 11.0 m by 24.4 m blocks and four replications of each rotation were instituted, for a total of eight blocks. Cover crop residues were removed from one strip within each block and then placed uniformly on top of a different strip, creating three treatments: roots only, roots and shoots (RS), and roots, shoots, plus extra shoots (RS plus extra shoots) for both corn and soybean rotations. Corn seeding rates were uniform in all plots with early N fertilizer rates applied at 45 kg ha-1 on all plots, followed by randomized rates of 0, 45, 90, and 135 kg ha-1. Soybeans were planted in 0.76 m wide rows at four different planting rates of 185, 309, 432, and 556 thousand viable seeds ha-1. Corn and soybean yields were estimated from the middle two rows of each 4-row wide plot, and biomass of corn, soybeans, broadleaves, and grasses was estimated using 0.5 m by 0.76 m sample areas. Corn plant height was measured to the top of tassel at harvest, and canopy closure percentages were visually estimated at time of flowering, growth stage R1. Independent variables were rye cover cropping practices and soybean planting rates for the rye-soybean rotation, and vetch cover cropping practices and N application rates for the vetch-corn rotation. Dependent variables were crop biomass, broadleaf biomass, grass biomass, and grain yield for both rotations, canopy closure for soybean, and plant height for corn. All variables were analyzed using the general linear models function in PC-SAS (SAS Institute Inc., 1997) according to a split plot design with vetch or rye treatments as whole plots, and N application or planting rates as split plots. Results Discussion References For the rye-soybean rotation, grass biomass was significantly lower in the RS plus extra shoots treatment (Table 1). There were no significant differences among treatments for the other four dependent variables measured in the rye-soybean rotation (Table 1). For the rye-soybean rotation, there were no significant differences found among cover cropping practices for any of the dependent variables measured (Table 2). Canopy closure was significantly higher in the 556,000 seeds ha-1 planting rate for the rye-soybean rotation. Soybean yields were significantly lower at the lowest planting rate for the rotation, but there were no other significant differences between planting rates noted for the remaining independent variables (Table 1). Canopy closure tended to be higher in the highest planting rates for the rye-soybean rotation; however, there were no other significant differences noted between planting rates for the other independent variables analyzed (Table 2). Among the dependent variables measured for the vetch cover cropping practices, corn plant height, corn biomass, and corn yield were all significantly higher in the RS plus extra shoots treatment (Table 3). Grass biomass was significantly lower for this treatment, while broadleaf weed biomass showed no significant differences among treatments in the vetch-corn rotation (Table 3). There were no significant differences among cover cropping practices for the independent variables measured in the vetch-corn rotation (Table 4). N application rates did not cause any significant differences in the 5 independent variables measured for either rotational year analyzed for the vetch-corn rotation (Tables 3 and 4). Canopy closure was significantly higher for elevated planting rates in both years, showing the expected relationship between planting rates and canopy closure. In , the difference in canopy closure at the time of soybean flowering was related to grass biomass and soybean yield, indicating that, in some environments, increased soybean planting rates may help with the control of grassy weeds. For the vetch-corn rotation, the highest level of vetch application resulted in the greatest corn plant height, corn biomass, corn grain yield, and the lowest grass biomass (Table 3). This may have been related to improved soil water conservation in this vetch treatment, as the soil surface was covered with a thick mulch of hairy vetch residue. The rotation data may offer some insights into consistent differences among the cover cropping practices, soybean planting rates, and N application rates examined. If continued, this study should offer insights into yield increases and weed control strategies during the transition to organic cropping systems. The large scale adoption of herbicides and synthetic fertilizers has completely changed not only the practice of farming itself, but the very landscape on which it depends. With limited arable land becoming an increasingly relevant issue, transitioning to more dynamic, sustainable farming practices could provide a viable outlook for the future. Organic farming mimics biological processes for the production of crops and growers utilize a range of cultural practices and natural inputs to manage fields (4). It has been estimated that crop yields nationally would decline by 20 % if herbicides were replaced by hand labor and cultivation strategies currently employed by organic producers (3). Organic crop growers tend to utilize increased tillage and hand weeding at a greater cost and with lower yields. These intensive cultivation practices can also contribute to soil erosion and land degradation (6). To support expansion of organic cropping systems, research on minimizing weed competition and crop yield losses during transition needs to be increased (5). Organic farming has been one of the fastest growing segments of U.S. agriculture for over a decade (2). In order to convince large scale producers to transition into organic production, overall systematic approaches need to be identified and developed into profitable planting cycles in order to assist farmers into transition. The objective of this report is to investigate organic grain cropping systems on a research farm in Kentucky, and to assess cover cropping methods and their influences on the dependent variables measured. In this study, two crop rotations, with three cover cropping practices employed in each, were analyzed to determine which rotation increased yields and minimized weeds. Fold or cut poster here Image of the Study Location Study location after cover crops have been plowed into the field. 1. Delate, K., C. A. Cambardella, and D. L. Karlen Transition strategies for post-CRP certified organic grain production. Crop Management doi: \CM RS. 2. Economic Research Service USDA data sets: Organic production. Verified on November 2, Gianessi, L. P., and N. P. Reigner The value of herbicides in U.S. crop production. Weed Tech. 21: Kuepper, G Organic field corn production. Verified on November 2, Karlen, D. L., C. A. Cambardella, C. T. Bull, C. A. Chase, L. R. Gibson, and K. Delate Producer- researcher interactions in on-farm research: A case study on developing a certified organic research site. Agron. J. 99: Peigne, J., B. C. Ball, J. Roger-Estrade, and C. David Is conservation tillage suitable for organic farming? A review Soil Use and Management 23: