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SUMMARY

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eturn to table of contents Table 1. Average nitrate-nitrogen content (ppm) in the top 2-foot soil layer for three stover removal rates during six growing seasons at Arlington and Lancaster. Soil Organic Matter (%) Arlington Lancaster Removal Rate (%) 0 50 100 0 50 100 5 4 3 2 1 0 —— ppm —— —— ppm —— 2010 49 59 65 30 31 39 2011 70 67 61 37 44 59 2012 86 101 86 49 54 37 2013 4 11 12 5 15 6 2014 16 13 11 10 13 6 2015 17 21 13 31 42 16 0% 50% 100% 2010 2011 2012 2013 2014 2015 Figure 3. Soil organic matter content (0-6 inches) for three stover removal rates during six growing seasons at Arlington. Soil Organic Matter (%) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0% 50% 100% 2010 2011 2012 2013 2014 2015 Figure 4. Soil organic matter content (0-6 inches) for three stover removal rates during six growing seasons at Lancaster. • Soil organic matter content was generally greater at Arlington than Lancaster given the differences in soil origin and slope (Figure 3, 4). • A slight decrease in soil organic matter with increasing stover removal rate was observed at Arlington after 4 years, while at Lancaster a similar decrease was observed after 3 years of stover harvest (Figure 3, 4). Soil Phosphorus (ppm) 120 100 80 60 40 20 0 0% 50% 100% 2010 2011 2012 2013 2014 2015 Figure 5. Plant available phosphorus concentrations in soil (0-6 inches) for three stover removal rates during six growing seasons at Arlington. Soil Phosphorus (ppm) 30 25 20 15 10 5 0 0% 50% 100% 2010 2011 2012 2013 2014 2015 Figure 6. Plant available phosphorus concentrations in soil (0-6 inches) for three stover removal rates during six growing seasons at Lancaster. • Soil test phosphorus concentrations at Arlington varied among years, but no pattern was observed other than a general decrease in soil test phosphorus over six growing seasons. In general, soil phosphorus concentrations ranked as excessively high at this site (Figure 5). • At Lancaster, soil phosphorus concentrations decreased with increasing stover harvest rate after three growing seasons. Soil test phosphorus concentrations were considered optimal during all six years (Figure 6). • All treatments at both study sites received 13 lb/acre of total phosphorus as starter fertilizer annually. • The potassium content in soil at Arlington was reduced with stover harvest after three years but only dropped below optimal levels at the end of the six growing seasons (Figure 7). • Potassium soil concentrations at Lancaster decreased with increasing stover harvest rate after three growing seasons and overall were below optimal concentrations (Figure 8). • All treatments at both study sites received 25 lb/acre of potassium as starter fertilizer annually. 38

eturn to table of contents Soil Potassium (ppm) 180 160 140 120 100 80 60 40 20 0 Figure 7. Plant-available potassium concentrations in soil (0-6 inches) for three stover removal rates during six growing seasons at Arlington. Soil Potassium (ppm) 0% 50% 100% 2010 2011 2012 2013 2014 2015 Figure 8. Plant-available potassium concentrations in soil (0-6 inches) for three stover removal rates during six growing seasons at Lancaster. Soil Bulk Density (grams/cc) 120 100 80 60 40 20 0 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0% 50% 100% 2010 2011 2012 2013 2014 2015 0% 50% 100% 0-3 inch 3-6 inch Figure 9. Effect of three stover harvest rates on soil bulk density at two different depths after six growing seasons at the Arlington study location. Soil Bulk Density (grams/cc) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0% 50% 100% 0-3 inch 3-6 inch Figure 10. Effect of three stover harvest rates on soil bulk density at two different depths after six growing seasons at the Lancaster study location. • Soil bulk density at the two depths measured at Arlington increased as stover harvest rate increased; however, the observed bulk density is not considered root restrictive (Figure 9). • No clear trend in soil bulk density with stover harvest treatments was observed at the Lancaster location (Figure 10). Plots at this site were established on the contour given the sloping field typical of this region, which might have increased traffic across treatment areas and could have contributed to the lack of differences at that field site. Nevertheless, the magnitude of the bulk density values were not indicative of compaction. CONCLUSIONS AND RECOMMENDATIONS • There were some statistically significant differences in corn grain yield with stover harvest rate, but no clear trend was discernable. In some years, the 100% stover harvest rate had numerically greater yields at both sites. • Soil organic matter, phosphorus, and potassium were reduced to some degree at both sites after multiple years of stover harvest (3 years or more). • Soil bulk density increased after six years of stover harvest, possibly due to the additional harvest traffic and reductions in organic matter. However, soil bulk density values at both sites were within an acceptable range for crop growth. • Although yields were not clearly reduced with stover harvest in the six-year study period, given some of the trends in soil properties with stover harvest, it is possible that yield could be suppressed if stover harvest is conducted continuously for longer periods of time. • Other soil types or soils with marginal productivity potential would most likely be more negatively affected by continuous 100% stover harvest. However, the 50% stover harvest rate had comparable results to the 0% harvest rate. • Given the data presented here, it seems feasible to harvest half of the corn stover biomass after or during grain harvest for biofuel production or other uses. However, it is recommended to restrict the 50% biomass harvest to no more than three consecutive years and to incorporate management techniques to mitigate long-term negative impacts to the soil, such as use of cover crops, crop rotations, and reduced tillage. 39

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