Soil microbial and macrofauna dynamics under different green manure termination methods

No-till green manure (Gmr) termination creates a unique situation compared to conventional no-till crop management due to the surface mulch generated. However, the impact this practice has on soil biota has been little researched, despite the important role soil biota play in soil ecosystem functions such as decomposition and pest control. This study examines how termination management of Gmr can affect soil biota and their population dynamics. Over two trials, Gmr tillage regimes of fall tilled, spring tilled, or no-till were applied to a spring planted Gmr of hairy vetch/oat (HVO) along with a typical regional practice of tilled red clover Gmr within a four-year grain rotation. Soil microbial biomass (SMB), earthworm density, and beetle and spider activity density were assessed up to three years following Gmr termination. SMB was greatest in the spring for no-till and fall tilled HVO Gmr treatments, but the effect was transient, disappearing after two months. Earthworm densities were negatively affected by tillage (88% and 86% less than no-till in Trial 1 and 2, respectively) but densities recovered three years after tillage to that of the no-till treatment. Beetle activity density was largely unaffected by Gmr termination. Spider captures were more numerous in no-till plots compared to spring tilled in one trial. Impacts of Gmr termination on soil organisms vary by taxa and earthworms were the most sensitive, taking two years to recover from tillage. No-till Gmr termination does not show clear benefits to soil biota.