Designing Cropping Systems for Enhanced Soil Biological Function: Lessons Learned in Temperate and Tropical Agroecosystems.

Cropping system design has progressed from fallow-based systems to more temporally- and spatially-diverse systems aimed at enhancing soil health through increased carbon capture and greater biodiversity.  At the same time, many cropping system now feature less soil disturbance.  Over the past 20 years, our collaborative research group has tested the effects of these changes on various soil, ecosystem and crop parameters.  Crop rotations that include both annual and perennial crops provide among the largest improvement to total soil carbon, soil microbial and soluable carbon, and soil biota.  The Glenlea study showed that the positive effects of alfalfa (rotated with grains) were greater for organic compared with conventional management in surface soils, but less in the subsoil.  We are currently addressing this shortcoming through new forms of perennialization and alternative soil nutrient enhancement schemes such as night-time corralling of livestock.  Seeded and self-propagating cover crops are used around the world to “perennialize” cash crop systems.  Cover crops show significant promise for feeding soil biota, such as mycorrhiza, outside the active cash crop growth cycle.  Our ``Pesticide-Free Production`` study has discovered that weeds in no-till systems provide significant agronomic benefits that are linked to improvements in soil biology.  In monoculture systems, weeds may act as cover crops, providing low cost benefits to soil health.  The benefit of larger weed seedbanks is also being explored.  The introduction of grazing ruminants into various cropping system experiments offers new ways to enhance soil health but an important goal is to establish the level of integration needed for soil biota response.  Drawing on examples from northern and southern hemispheres, our group will discuss principles that enable diverse, no-till and perennialized cropping systems to enhance soil biological function.