2018 ASHS Annual Conference

Bioprocessing byproducts, including corn gluten meal (CGM) and soybean meal (SM), are often used as organic fertilizers and also have demonstrated herbicidal potential. Using these products to integrate weed and nutrient management may increase the profitability of vegetable farms by reducing labor required to control weeds and apply fertilizer. Our research objective was to determine the effects of different bio-based products and application rates on weed suppression, mineral soil nitrogen (N), and crop yield in tomato (Solanum lycopersicum ‘Defiant’) and broccoli (Brassica oleracea var. italica ‘Arcadia’). Four rates of CGM and SM were applied to each of 10 plants in a 15 ft linear bed to achieve 0.5 g, 1 g, 2 g, and 5 g N/plant. These treatments were compared to weedy, weed-free and synthetic fertilizer controls. Velvetleaf (Abutilon theophrasti) was seeded into each planting hole prior to treatment application, and emergence recorded weekly. Soil N was measured continuously for 4-8 wks after treatment application with ion-exchange resin membranes. Tomato fruit and broccoli heads were removed at harvest maturity and weighed. Weed emergence was reduced up to 60% and 75% with the highest rates of SM and CGM, respectively. Soil N increased with amendment rate and spikes in ammonium may have contributed to weed suppression; however, amendment type and rate did not influence crop yield. A minimum of 180 g of CGM/ft² was required to achieve consistent weed suppression, which is 4.5 to 9 times greater than current industry recommendations (20-40 g/ft²).