Cotton seed meal and chicken manure + molasses-induced anaerobic soil disinfestation improved weed and root-knot nematode management in sweetpotato

Abstract

Managing yellow nutsedge and southern root-knot nematode (SRKN) is particularly challenging in organic sweetpotato production. Anaerobic soil disinfestation (ASD) has emerged as a promising nonchemical pest management strategy that entails incorporating labile carbon amendments into the soil, covering the soil with impermeable plastic mulch, and irrigating the amended soil to saturation. Field studies were conducted at Clemson University in Charleston, South Carolina, in the 2023 and 2024 growing seasons, to evaluate the effect of ASD on yellow nutsedge and SRKN. Treatments were structured as a factorial arrangement of three carbon amendments ( Brassica residue [BR], chicken manure + molasses [CM+M], and cotton seed meal [CSM]) and an unamended control (UC) by four sweetpotato clones (Bayou Belle, Monaco, Murasaki-29, and USDA-18-040) with four replications using a randomized complete block design. ASD was terminated 3 wk after initiation, and sweetpotato slips were planted 1 wk after ASD termination. Greater cumulative anaerobicity was observed in the CM+M and CSM treatments with increments exceeding 220% relative to UC at ASD termination. Six weeks after planting, yellow nutsedge densities across all sweetpotato clones were significantly lower with CM+M (4 to 10 plants m ⁻² ) and CSM (6 to 8 plants m ⁻² ) treatments than the UC (21 to 27 plants m ⁻² ). Both bunch cultivars (Monaco and USDA-18-040) and spreading cultivars (Bayou Belle and Murasaki-29) sweetpotato clones resulted in similar yellow nutsedge densities. Soil population densities of SRKN at 16 wk after planting were reduced by 23% to 44% in CM+M treatments and by 29% to 46% in CSM treatments, relative to the UC. Marketable sweetpotato yield rose from 47% to 131% with the CMM and CSM treatments compared with UC yield. The findings of this study demonstrate that CM+M and CSM-induced ASD have the potential to suppress yellow nutsedge and SRKN in organic sweetpotato production systems while increasing the marketable sweetpotato yield.