Effects of maize residue removal on soil quality and greenhouse gas emissions in Iowa

Mahdi Al-Kaisi,Jose Guzman

doi:10.31285/agro.16.559

Abstract

Maize residue is an important component of soil carbon (C) budget and development of soil quality indices. However, maize residue in recent years has been considered as another potential feedstock source for ethanol production in addition to or alternative to maize grain. The current emphasis on using maize residue as a feedstock for future ethanol production presents a soil and environmental challenge that needs to be addressed. Additionally, there have been few studies that examine greenhouse gas (GHG) emissions from agriculture soils under different residue removal rates, various N rates, and tillage practices and their interactions effects on soil C dynamics and GHG emissions. The objective of this study was to examine potential changes in soil C sequestration and GHG emissions under no-tillage (NT) and conventional tillage (CT) and nitrogen fertilization rates of 0, 170, and 280 kg N ha-1 with variable rates of residue removal (0, 50, and 100%). Field studies were established in fall of 2008 on two sites, a poorly-drained soil at the Iowa State University Agronomy Research Farm (North central, IA) and a well-drained soil at the Armstrong Research and Demonstration Farm (Southwest, IA) in continuous maize. After two years of residue removal, soil C, water inﬁ ltrations, aggregate stability and bulk density was measured. After every harvest, crop measurements included maize grain yield, above-ground biomass, and root-biomass. Weekly measurements of soil surface CO2, and N2O emissions coupled with soil moisture and temperatures were collected. Additionally, C budgets were calculated for different treatments. These measurements provide insights on whether these management practices resulted in net gains or losses of C sequestration and atmospheric CO2. Findings suggest that sites for this study were a signiﬁcant net sink for atmospheric CO2-C, even when maize residue was removed and under different tillage and N fertilization (when applied) management. Applications of N had the largest effect on N2O-N emissions, where greater N2O-N emission was associated with high N rates. In addition, signiﬁcant declines in soil quality properties were observed after only two years of residue removal. The severity of soil quality deterioration due to residue removal varied with different tillage and N managements.

Highlights

Maize residue left on the surface after harvest is a potential feedstock source for bioethanol production which can contribute to the reduction of fossil fuel use and net greenhouse gas (GHG) emissions (1)
After three years of maize residue removal, significant decreases in soil total organic carbon (TOC) varied with tillage and N fertilization management
Adoption of NT in general reduce significant losses of TOC when 50 % of the residue was removed in both sites, significant decreases similar to CT were observed when 100% of residue was removed

Summary

Introduction

Maize residue left on the surface after harvest is a potential feedstock source for bioethanol production which can contribute to the reduction of fossil fuel use and net greenhouse gas (GHG) emissions (1). It is currently more expensive to produce ethanol from lignocellulosics than from starches, it is projected that improvements in technology and scale of production will improve these costs (2). It is projected that lignocellulosic ethanol production will become a viable option and could create an annual market for crop residue from approximately 143 million tons to 583 – 805 million tons (3). The removal of crop residue, may require farmers to change their current tillage and fertilization practices to prevent against potential soil erosion and other soil and environmental negative effects. Since current agriculture practices are responsible for large proportion of N O emissions, 2 changes in management practices can have significant

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