152-13 Nitrogen and Harvest Treatment Effects On Soil Properties Under Non-Irrigated Switchgrass and Maize After 9 Years.

Poster Number 2811

See more from this Division: SSSA Division: Soil & Water Management & Conservation
See more from this Session: Bioenergy Crops, Biomass Production, and Soil and Environmental Quality

Monday, November 4, 2013
Tampa Convention Center, East Exhibit Hall

Catherine E. Stewart1, Ronald F. Follett2, Elizabeth Pruessner2, Gary E. Varvel3, Kenneth P. Vogel4 and Robert B. Mitchell4, (1)Soil Management and Sugar Beet Research, USDA-ARS, Fort Collins, CO
(2)Soil Plant Nutrient Research, USDA-ARS, Fort Collins, CO
(3)Agroecosystem Management Research Unit, USDA-ARS, Lincoln, NE
(4)Grain, Forage, and Bioenergy Research Unit, USDA-ARS, Lincoln, NE
Abstract:
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.  We assessed soil properties over 9-years for a 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 no-till corn (with and without stover removal) in eastern, NE. We measured SOC, aggregate stability, microbial biomass, bulk density (BD), pH, P and K in the top 0-30 cm. Both no-till corn (NT-C) and switchgrass increased SMB-C, SOC, and aggregate stability over the nine years, reflecting improvement from previous conventional management. However, the soils under switchgrass had double the percent aggregate stability, 1.3 times more microbial biomass, and a 5-8% decrease in bulk density in the 0-5 and 5-10 cm depths compared to NT-C. Cumulative soil P loss was significantly greater beneath NT-C (-14.79 kg P ha-1) compared to switchgrass (-9.30 kg P ha-1) after 9 years. When all measured soil parameters were included in the Soil Management Assessment Framework (SMAF), switchgrass improved soil quality indicators (SQI) over time and NT-C decreased soil quality (0-30cm), or had no effect. NT-C residue removal of 50% decreased SQI. Long-term N and harvest management studies that include a diverse set of field measurements - biological, chemical, and physical – are necessary to accurately assess bioenergy impacts on soils.

See more from this Division: SSSA Division: Soil & Water Management & Conservation
See more from this Session: Bioenergy Crops, Biomass Production, and Soil and Environmental Quality