Weeds, nitrogen, and yield: Measuring the effectiveness of an organic no-till system

Previous research in the mid-Atlantic and midwestern USA has identified advantages and drawbacks of "organic no-till" vegetable production, but few studies have been conducted in the warmer southeastern region. The purpose of this study was to examine the effects of tillage [no-till (NT) vs. conventional tillage (CT) of a cereal rye/crimson clover cover crop] and three nitrogen fertilization rates on organic tomato (Solanum lycopersicum L.) and summer squash (Cucurbita pepo L.) yield, weed suppression, and soil N dynamics in two years in a soil series in Clemson, SC. Squash yields were similar between tillage treatments in both years. NT tomato yields were 43% greater than CT yields in 2014, whereas CT tomato yields were 46% greater than NT yields in 2015. Squash and tomato yields per unit of management labor (time) were significantly greater in NT compared to CT treatments for both years. There were no statistical differences in squash and tomato yields between N fertilization treatments in either year. Pre-season soil N levels were significantly higher in NT tomato plots in 2014 but similar between tillage treatments in tomato plots in 2015 and in squash plots both years. Post-season soil N levels in tomato plots were similar between tillage treatments both years. Post-season soil N levels were significantly higher in NT squash plots in 2014 and in CT squash plots in 2015. Roller-crimped NT mulches provided adequate early-season weed suppression in both years and saved considerable weed management and seedbed preparation labor. Overall, the results demonstrated that organic no-till is a viable method for reduced tillage summer vegetable production in the South Carolina Piedmont region.