Crop residue management effects on crop production, greenhouse gases emissions, and soil quality in the Mid-Atlantic USA
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Cellulosic biomass-to-bioenergy systems can provide environmental and economic benefits to modern societies, reducing the dependence on fossil-fuels and greenhouse gas emissions while simultaneously improving rural economies. Corn (Zea mays L.) stover and wheat straw (Triticum aestivum L.) residues have particular promise given these crops are widely grown and their cellulosic fractions present a captured resource as a co-product of grain production. Annual systems also offer the ability to change crops rapidly in response to changing market demands. However, concerns exist about residue removal effects on soil health, greenhouse gases emissions and subsequent crop productivity. The carbon footprint and the crop yield productivity and soil health responses resulting from the removal of crop residues has been studied extensively over the last 20 years, but this research has been largely conducted in the Corn Belt. To investigate the impact of crop residue removal in the Mid-Atlantic USA, combinations of corn stover (0, 3.33, 6.66, 10 and 20 Mg ha-1) and wheat straw (0, 1.0, 2.0, and 3.0 Mgha-1) were soil applied in a corn-wheat/soybean (Glycine max L. Merr.) rotation in Virginia's Coastal Plain. Corn stover (0, 3.33, 6.66, 10 and 20 Mg ha-1) was applied in a continuous corn cropping system in the Ridge/Valley province. For each system, residues were applied following grain harvest over two production cycles. Each experiment was conducted as a randomized complete design with four replications. The highest rates of stover retention resulted in greater greenhouse gas emissions in year 1, but not year 2 of these studies and did not affect overall global warming potentials. Stover application also increased soil carbon but had little effect on other measures of soil quality. Stover K levels were greater with high rates of stover retention. Overall, these studies indicate little effect of residue removal or retention (above typical residue production rates) on subsequent crop production, greenhouse gas emissions, or soil health measures in the short term. This study is one of the first to assess residue removal in the Mid-Atlantic USA and is the first study to investigate the impacts that managing more than one crop residue in a multi-crop system. Longer-term research of this type may be warranted both to determine the consequences of residue management and to start building a regionally-specific body of knowledge about these practices.
General Audience Abstract
Over the last decade, strategic economic and environmental concerns have increased interest in the use of crop residues as sustainable, renewable sources for bioenergy and bio-products. Most of the work investigating the sustainability of residue removal has occurred in the US Corn Belt, where corn stover and wheat straw (the part of the plant that is not grain) supplies are abundant. Although the research data from the Corn Belt provide guarded optimism about residue harvest systems in the Midwest, it is not suitable to extrapolate these results to the South because of differences in soils, climate, and cropping systems. Cooler, humid conditions can sustain higher levels of soil organic matter, lessening but not eliminating concerns about stover removal. Current research from the Midwest region suggests routine stover harvest – within limits – can be sustainable. The development of new bioenergy and bioproduct industries in the Southeast region is leading to a growing expectation that regional cropping systems will supply the millions of tons of biomass needed for these new businesses. However, few data are available regarding sustainable crop residue harvest from the Southeast. Sustainable levels of residue removal may be quite low given regional soil and climatic conditions, and the effects of residue removal on soil health parameters and greenhouse gas emissions remain to be defined. The purpose of this project was to determine the amount of corn stover and wheat straw can sustainably be harvested from Virginia’s grain-based cropping systems without reducing plant productivity or soil quality or increasing GHG emissions. This research generated regionally relevant information on the impacts of crop residue removal to help determine whether harvesting wheat straw and corn stover can be a sustainable practice for the region’s cropping systems. In a first stage, short term impacts of residue removal on soil quality and greenhouse gases were measured in Blacksburg and New Kent, VA, over the period 2015-2017.
- Doctoral Dissertations