Interference Effects and Economic Threshold of Solanum nigrum in Processing Tomato Under Different Planting Densities

Abstract

Interference effects and economic threshold of Solanum nigrum in processing tomato were evaluated under different planting densities to understand weed–crop competition dynamics and optimize weed management strategies. Field experiments were conducted with varying tomato planting densities under naturally infested conditions of S. nigrum. Weed density, biomass accumulation, crop growth parameters, and yield attributes were recorded to quantify competitive interactions. Results indicated that S. nigrum exerted significant interference on tomato growth, with increased weed density leading to substantial reductions in plant height, canopy development, and fruit yield. Higher planting densities of tomato reduced weed biomass and improved crop competitiveness by enhancing early canopy closure and limiting resource availability for weed establishment. Economic threshold analysis demonstrated that allowable weed density decreased with lower planting densities, highlighting the importance of crop spatial arrangement in weed management decision-making. The interference intensity was strongly influenced by early-season competition, where S. nigrum establishment prior to crop canopy formation resulted in maximum yield losses. Regression analysis revealed a negative correlation between weed density and tomato yield, supporting the predictive value of threshold-based management approaches. The study emphasizes the role of planting density as a cultural practice influencing weed suppression efficiency and economic return. These findings provide a basis for integrated weed management strategies aimed at minimizing S. nigrum impact in processing tomato systems while optimizing input costs and crop productivity.