Responsiveness of miscanthus and switchgrass yields to stand age and nitrogen fertilization: A meta‐regression analysis. Issue 5 (4th March 2022)

• Record Type: Journal Article
• Authors: Sharma, Bijay P.; Zhang, Na; Lee, DoKyoung; Heaton, Emily; Delucia, Evan H.; Sacks, Erik J.; Kantola, Ilsa B.; Boersma, Nicholas N.; Long, Stephen P.; Voigt, Thomas B.; Khanna, Madhu
• Is Part Of: Global change biology. Volume 14:Issue 5(2022)
• Page Start: 539
• Page End: 557
• Publication Date: 2022-03-04
• Subjects: age -- meta‐analysis -- meta‐regression -- miscanthus -- nitrogen -- switchgrass -- yield; Biomass energy -- Periodicals; Biomass energy -- Environmental aspects -- Periodicals; Energy crops -- Periodicals; 662.88
• DOI: 10.1111/gcbb.12929
• Languages: English
• ISSNs: 1757-1693

Abstract

Abstract: Optimal management of the perennial bioenergy crops, miscanthus and switchgrass, requires an understanding of their responsiveness to nitrogen (N) fertilizer at different maturity stages across locations and growing conditions. Earlier studies that have examined the yield response of these crops to N and stand age using field experiments or meta‐analysis techniques provide mixed evidence. We extend earlier studies by applying a multi‐level mixed‐effects (MLME) meta‐regression model to conduct a more extensive multivariate regression of yield response of these crops to N and stand age, while controlling for climate and location conditions and unobserved factors related to study design. Our findings are based on 1403 and 2811 yield observations for miscanthus and switchgrass, respectively, from experiments conducted between 2002 and 2019 across the rainfed region in the United States. We find statistically significant evidence that an additional year of maturity increases miscanthus and switchgrass yields but at a decreasing rate; yields peak at the 7th and 6th year respectively, for the observed range of applied N rates and stands. We also find that an increase in N application increases yield by a statistically significant level, but at a declining rate; the magnitude of the yield response to N is, however, small and varies with the age of the crop. The impact of N is larger on older compared to younger and middle‐aged stands of miscanthus. In contrast, the impact of N on switchgrass is larger on middle‐aged compared to younger and older stands of switchgrass. We do not find a statistically significant effect of soil productivity on yield for either crop. This analysis provides a basis for developing N application recommendations and optimal rotation age for miscanthus and switchgrass and shows that these energy crops can grow just as productively on low productivity land as on high productivity land. Abstract : Optimal management of miscanthus and switchgrass requires an understanding of their responsiveness to N at different maturity stages and growing conditions. Our paper evaluates whether yield of miscanthus and switchgrass declines with stand age and if N fertilization can offset this age effect and increase yields. We provide a basis for developing N recommendations and optimal rotation age for these crops, which will optimize feedstock production for lignocellulosic biofuels. Our estimates lead toward improved assessment of optimal N use, rotation age, farm profitability, and GHG reduction, which researchers and policymakers require for incentivizing and upscaling lignocellulosic biofuel production.