Rotational No-Tillage Management for Reducing the Carbon Footprint of Organic Corn-Soybean Based Cropping Systems.

Altering cropping practices to reduce greenhouse gas (GHG) emissions and increase soil carbon (C) sequestration is one of several key strategies for mitigating global climate change. When such changes in practices are applied to important crops like corn and soybean (planted on over 67 million ha in the US in 2008) the potential for impact is large. To this end, our work focuses on quantifying the effects of different corn-soybean production methods on energy requirements, GHG emissions, and soil C sequestration. Recent advancements in cover crop utilization for weed suppression in no-till planted organic corn and soybean have made it possible to produce competitive yields, while reducing GHG emissions associated with pre-emergence and inter-row cultivation. Moreover, because mulch from mechanically-killed cover crops is used for weed suppression, this system has potential to sequester more C than traditional no-tillage or organic production systems. Despite the high level of weed suppression that is possible with cover crop mulches, tillage is still required at some points in the rotation to avoid pest and fertility problems. Specific information on crop and soil management practices, energy requirements, GHG emissions, and soil C sequestration in such cover-crop based systems is lacking in the literature. In this study, we parameterize a simple static-deterministic model to compare the C footprint of organic and conventional corn and soybean production with varying levels of soil tillage and cover cropping. In the model, cropping system energy requirements and GHG emissions are estimated by summing values associated with each management operation. Preliminary results indicate that integrating cover crops and other practices that are central to organic rotational no-till systems can effectively reduce the C footprint of corn and soybean production.