Weeds and soil-borne pathogens are limiting factors in organic watermelon (Citrullus lanatus) production. Yellow nutsedge (Cyperus esculentus) is a problematic weed for Southeastern watermelon growers. Fusarium wilt caused by Fusarium oxysporum f.sp. niveum (FON), is responsible for significant yield loss in watermelon production. Inefficient non-chemical tactics are an impediment to curtail weeds and soil-borne diseases in organic watermelon; and necessitate the adaption of an alternative strategic and holistic approach. Anaerobic soil disinfestation (ASD) has the potential to control weeds and soil-borne pathogens across a range of environments and crop production systems. ASD is a preplant chemical independent technique, which requires incorporation of labile organic carbon (C) sources into the soil, followed by tarping the soil with plastic mulch, and irrigating the soil to the saturation. Shifts in soil microbial communities and production of volatile organic compounds during ASD process are the main mechanisms that are believed to kill soil-borne pathogens and weeds seeds. The objectives of this study were to 1) determine whether ASD can suppress the emergence of yellow nutsedge, 2) compare the efficacy of locally available C sources, 3) evaluate if ASD can influence grafted and non-grafted watermelon yield. A field trial was conducted at Clemson University’s, Coastal Research and Education Center in Charleston, South Carolina in 2023. The study was arranged in a randomized complete block design with four replications. Main C sources were subjected to control (CT) with no C, chicken manure molasses (CMM), and cotton seed meal (CSM). All treatments were assigned as ASD with non-grafted (Powerhouse) and grafted (Carolina strongback) rootstock grafted to scion Powerhouse. Indicators of reduction in soils (IRIS) tubes paint removal (%), yellow nutsedge shoot count, and crop yield data were recorded. Higher anaerobic soil conditions and lower yellow nutsedge shoot count were observed in ASD plots. At the time of watermelon harvest, total number of yellow nutsedge shoot count were recorded as 65, 25, and 22 in CT, CSM, and CMM, respectively. Higher marketable fruit yield was recorded in ASD plots treated with CMM. Based on weed control and yield assessments, CMM to facilitate ASD is an ideal practice for growing organic watermelon in South Carolina.
