Contribution of above- and belowground bioenergy crop residues to soil carbon

Author(s)

Carvalho, Joao L. N. ; Hudiburg, Tara W. ; Franco, Henrique C. J. ; DeLucia, Evan H.

• Document type: Journal article
• Source: Global Change Biology Bioenergy; v. 9, n. 8, p. 1333-1343, AUG 2017.
• Web of Science Citations: 31

Abstract

GHG mitigation by bioenergy crops depends on crop type, management practices, and the input of residue carbon (C) to the soil. Perennial grasses may increase soil C compared to annual crops because of more extensive root systems, but it is less clear how much soil C is derived from above-vs. belowground inputs. The objective of this study was to synthesize the existing knowledge regarding soil C inputs from above-and belowground crop residues in regions cultivated with sugarcane, corn, and miscanthus, and to predict the impact of residue removal and tillage on soil C stocks. The literature review showed that aboveground inputs to soil C (to 1-m depth) ranged from 70% to 81% for sugarcane and corn vs. 40% for miscanthus. Modeled aboveground C inputs (to 30 cm depth) ranged from 54% to 82% for sugarcane, but were 67% for miscanthus. Because 50% of observed miscanthus belowground biomass is below 30 cm depth, it may be necessary to increase the depth of modeled soil C dynamics to reconcile modeled belowground C inputs with measured. Modeled removal of aboveground corn residue (25-100%) resulted in C stock reduction in areas of corn-corn-soybean rotation under conventional tillage, while no-till management lessoned this impact. In sugarcane, soil C stocks were reduced when total aboveground residue was removed at one site, while partial removal of sugarcane residue did not reduce soil C stocks in either area. This study suggests that aboveground crop residues were the main C-residue source to the soil in the current bioethanol sector (corn and sugarcane) and the indiscriminate removal of crop residues to produce cellulosic biofuels can reduce soil C stocks and reduce the environmental benefits of bioenergy. Moreover, a switch to feedstocks such as miscanthus with more allocation to belowground C could increase soil C stocks at a much faster rate. (AU)

• FAPESP's process: 13/13451-0 - Use of isotopic discrimination to evaluate the contribution from above and belowground plant parts to provide carbon to the soil
• Grantee: João Luís Nunes Carvalho
• Support Opportunities: Scholarships abroad - Research
• FAPESP's process: 02/10534-8 - Sugar cane yield in subsequent cycles associated to the residual effect of N and S and their transformations in the soil, on conservation system
• Grantee: Paulo Cesar Ocheuze Trivelin
• Support Opportunities: Research Projects - Thematic Grants