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Fluid Journal : Fluid Journal 2008-2009
WINTER 2008 Fluid Journal 9 SUMMARY There are potential soil and environmental problems associated with the removal of crop residue from croplands for the production of ethanol, as being urged upon agriculture by portions of the public and political world. Removal of corn residue leads to decreases in soil organic matter (SOM). Decreases in SOM reduce water-holding capacity and the ability of a plant to extract water during short-term water deficits. Placement of residue on the soil surface protects the surface from water and wind erosion and also moderates the extremes in soil temperature and moisture required for optimal microbial activity. Decline in SOM and extreme microclimate can lead to crusting, which limits water infiltration and gas exchange. Both have an impact on crop production and environmental quality. tillage during times in which the soil has a minimal soil residue cover and the potential for soil erosion may exist during times of intense rainfall. This aspect begins to demonstrate the potential environmental consequences of biomass removal. Removal effects On crop production. Studies have shown that removal of one pound of biomass has reduced subsequent grain production by 0.13 lb and stover production by 0.29 lb. One aspect of biomass removal could be to reverse the increasing trend shown in Figure 1 of annual increases because of the cumulative impact of bio mass removal on soil- plant interactions. Such reduction could be caused by changes in SOM, nutrient availability, soil water, and general soil condition. It has been shown that SOM is one of the primary factors affected by management of crop residues. Differences are dependent upon the initial organic matter content in Figure 1. Annual increase in corn stover biomass production for U.S. corn production, 1949 through 2006. Table 1. Amount of nutrients removed in the 2006 corn stover and wheat straw production season across the U.S. Nutrient Corn (lbs/A) Wheat (lbs/A) N 115.00 27.20 P 2O5 40.00 6.80 K 2O 167.00 47.60 Ca 30.00 8.16 Mg 23.00 4.08 S 16.00 6.80 Cu 0.06 0.01 Mn 1.72 0.22 Zn 0.34 0.20 the soil profile. Another parameter affected by residue removal is the impact on soil compaction. Change in management and harvesting methods could potentially increase the number of harvest trips across a field and could cause compaction. Research has shown that wheel- induced compaction could impact water runoff and soil erosion and concluded that more harvest trips, with the potential for more wheel- tracked areas, would increase potential for runoff. On soil organic matter. Changes in SOM levels will be one of the first noticeable changes to occur within the soil. Soil organic matter provides a valuable asset to the soil in terms of soil structure, water- holding capacity, and energy source for microbial activity. Corn Production Year 1940 1950 1960 1970 19801 9902 000 2010 Biomass (lb/A) 2000 4000 6000 8000 10000 12000 Data Biomass = -259554.7 +134.46 Yr r2= -.93
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