Weed Management Lessons from the Cornell Organic Grain Cropping Systems Experiment.

Long-term impacts of crop and soil management on weed populations, weed communities, and weed-crop competition are critical to understand when designing successful organic cropping systems. A long-term experiment at the Cornell University Musgrave Research Farm was initiated in 2005 and compared four organic cropping systems that differed in soil fertility inputs and intensity of weed management.  A three-year rotation of corn—soybean—spelt/red clover was grown in all systems, and the experiment included two crop rotation entry points. The High Fertility system received fertility inputs based on soil testing and Cornell University recommendations, whereas the Low Fertility system received fewer inputs. Standard physical and cultural weed management practices were applied in these two systems. The Enhanced Weed Management system aimed to maximize weed suppression with additional weed management practices, whereas the Reduced-Tillage system aimed to maximize soil health with fewer tillage and cultivation practices. Standard soil fertility management practices were applied in these two systems. Crop performance and weed suppression data were collected annually in all systems and crops. Weed-crop competition intensity, pooled across years, was also quantified in each crop and each system. Management system affected weed-crop competition, weed abundance, and weed community composition. Results show that managing soil fertility in organic cropping systems is important for suppressing weeds and maximizing profitability. Crop performance in the Reduced-Tillage system was poor, which was mainly a result of ineffective weed suppression. During the first two crop rotations, profitability of each crop was maximized in different systems, indicating that attributes of each system are important for optimizing overall performance.