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Title: Nitrogen and harvest effects on soil properties under rain-fed switchgrass and no-till corn over 9 years: implications for soil quality

Author
item Stewart, Catherine
item FOLLETT, RONALD - Collaborator
item Pruessner, Elizabeth
item Varvel, Gary
item Vogel, Kenneth
item Mitchell, Robert - Rob

Submitted to: Proceedings Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/4/2014
Publication Date: 3/4/2014
Citation: Stewart, C.E., Follett, R.F., Pruessner, E.G., Varvel, G.E., Vogel, K.P., Mitchell, R. 2014. Nitrogen and harvest effects on soil properties under rain-fed switchgrass and no-till corn over 9 years: implications for soil quality. Proceedings Great Plains Soil Fertility Conference. 1-4.

Interpretive Summary: Nitrogen fertilizer and harvest management will alter soils under bioenergy production. The long-term effects of the timing, harvest, and residue removal rates remain relatively unknown. Compared to no-tilled corn (Zea mays L.), switchgrass (Panicum virgatum L.) is predicted to have a greater positive effect on soil properties (i.e. soil organic C [SOC], soil microbial biomass (SMB-C), and soil aggregation) due to its perennial nature and deep-rooted growth form, but few explicit field comparisons exist. When all metrics were combined, NT-C with 120 and 180 kg N ha-1 did not affect 'SQI, but 60 kg N ha-1 decreased 'SQI (0-30cm) due to lower SOC and aggregate stability. Even with best-management practices such as NT, bioenergy corn production and corn stover removal will have to be carefully managed to prevent soil degradation. Long-term N and harvest management studies that include biological, chemical, and physical soil measurements are necessary to accurately assess bioenergy impacts on soils.

Technical Abstract: The long-term effects of nitrogen (N) fertilizer rate, harvest timing and residue removal remain relatively unknown under bioenergy crop production but do alter soil properties. Although few explicit field comparisons exist, switchgrass (Panicum virgatum L.) is predicted to improve soil properties such as soil organic C [SOC], soil microbial biomass [SMB-C], and soil aggregation when compared to no-tilled corn (NT-C, Zea mays L.). We measured several soil properties over a nine year rain-fed study of N fertilizer rate (0, 60, 120, and 180 kg N ha-1) and harvest management on switchgrass (harvested at Aug. and post-frost) and NT-C (with and without 50% stover removal) in eastern NE. We measured SOC, aggregate stability, SMB-C, bulk density (BD), pH, P and K in the top 0-30 cm. All measured soil parameters were evaluated individually and collectively in the Soil Management Assessment Framework (SMAF). Both NT-C and switchgrass increased SOC content and aggregate stability over the nine years, reflecting improvement from previous conventional management. Increased N fertilizer rate increased SOC and available P, but decreased SMB and pH. When all metrics were combined, NT-C with 120 and 180 kg N ha-1 did not affect 'SQI, but 60 kg N ha-1 decreased 'SQI (0-30cm) due to lower SOC and aggregate stability. Even with best-management practices such as NT, bioenergy corn production and corn stover removal will have to be carefully managed to prevent soil degradation. Long-term N and harvest management studies that include biological, chemical, and physical soil measurements are necessary to accurately assess bioenergy impacts on soils.