Landscape control of nitrous oxide emissions during the transition from conservation reserve program to perennial grasses for bioenergy. Issue 4 (12th September 2016)

• Record Type: Journal Article
• Authors: Saha, Debasish; Rau, Benjamin M.; Kaye, Jason P.; Montes, Felipe; Adler, Paul R.; Kemanian, Armen R.
• Is Part Of: Global change biology. Volume 9:Issue 4(2017)
• Page Start: 783
• Page End: 795
• Publication Date: 2016-09-12
• Subjects: conservation reserve program -- energy crops -- land use change -- landscape position -- Miscanthus -- switchgrass; Biomass energy -- Periodicals; Biomass energy -- Environmental aspects -- Periodicals; Energy crops -- Periodicals; 662.88
• DOI: 10.1111/gcbb.12395
• Languages: English
• ISSNs: 1757-1693

Abstract

Abstract: Future liquid fuel demand from renewable sources may, in part, be met by converting the seasonally wet portions of the landscape currently managed for soil and water conservation to perennial energy crops. However, this shift may increase nitrous oxide (N2 O) emissions, thus limiting the carbon (C) benefits of energy crops. Particularly high emissions may occur during the transition period when the soil is disturbed, plants are establishing, and nitrate and water accumulation may favor emissions. We measured N2 O emissions and associated environmental drivers during the transition of perennial grassland in a Conservation Reserve Program (CRP) to switchgrass ( Panicum virgatum L.) and Miscanthus x giganteus in the bottom 3‐ha of a watershed in the Ridge and Valley ecoregion of the northeastern United States. Replicated treatments of CRP (unconverted), unfertilized switchgrass (switchgrass), nitrogen (N) fertilized switchgrass (switchgrass‐N), and Miscanthus were randomized in four blocks. Each plot was divided into shoulder, backslope, and footslope positions based on the slope and moisture gradient. Soil N2 O flux, soil moisture, and soil mineral nitrogen availability were monitored during the growing season of 2013, the year after the land conversion. Growing season N2 O flux showed a significant vegetation‐by‐landscape position interaction ( P < 0.009). Switchgrass‐N and Miscanthus treatments had 3 and 6‐times higher cumulative flux respectively than the CRP in the footslope, but at other landscape positions fluxes were similar among land uses. A peak N2 O emission event, contributing 26% of the cumulative flux, occurred after a 10.8‐cm of rain during early June. Prolonged subsoil saturation coinciding with high mineral N concentration fueled N2 O emission hot spots in the footslopes under energy crops. Our results suggest that mitigating N2 O emissions during the transition of CRP to energy crops would mostly require a site‐specific management of the footslopes.