No-till green manure termination influences soil organic carbon distribution and dynamics

Abstract

There is continued interest in adopting no-till practices in organic agriculture. One way to decrease tillage is to implement no-till termination of green manures. Studies on this novel approach have focused primarily on cash crop performance and weed control. The objective of this study was to examine soil organic C distribution and dynamics as influenced by different methods of green manure termination of a spring-planted green manure. In this green manure–wheat (Triticum aestivum L.)–fall rye (Secale cereal L.)–soybean [Glycine max (L.) Merr.] rotation three green manure termination methods were compared (no-till crop roller, spring tillage, and fall tillage). A mixture of hairy vetch (Vicia villosa Roth)–oat (Avena sativa L.) was seeded in late May in two trials, the first commencing in 2013 and the second in 2014. Soil organic C was monitored for 3 yr after green manure termination. In Trial 2, total organic C was greater under no-till green manure termination compared to fall and spring-till termination (by 2.4 ± 1.2 Mg C ha–1 and 2.3 ± 1.3 Mg C ha–1, respec-tively) and the effect remained significant in all 3 yr. In Trial 1, particulate organic matter C was stratified in no-till and concentrated at the soil surface (0–5cm) and higher overall in no-till in Trial 2. Overall soil organic C was higher under no-till green manure termination and the more labile pool of POXc appeared less responsive to termination treatments.