Above and Belowground Drivers of Weed-Soybean Competition in a Long-Term Organic Cropping Systems Experiment

Increased weed free production capacity and decreased weed-crop competition intensity could help explain apparent crop tolerance of weeds in organic systems. The weed community and soil environment are affected by management history and could influence weed-crop competition relationships. We investigated weed-soybean competition in four organic cropping systems: (i) High Fertility (HF), (ii) Low Fertility (LF), (iii) Enhanced Weed Management (EWM), and (iv) Reduced Tillage (RT). In our experiment, the RT system had greater weed-free soybean production capacity, greater soil health, but also greater weed abundance and diversity than the EWM system. Soil inorganic N, K, Ca, and respiration were positively related to weed-free soybean production capacity. Unexpectedly, we observed positive relationships between weed-soybean competition intensity and several soil nutrient and organic matter indicators. Our research highlights connections between management history and weed-crop competition in organic systems, which could inform integrated weed management strategies.