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Soil & Water Management & Conservation

Impact of Tillage and Residue Burning on Carbon Dioxide Flux in a Wheat–Soybean Production System

Univ. of Arkansas, Fayetteville, AR 72701

^* Corresponding author (kbrye{at}uark.edu)

Burning of wheat (Triticum aestivum L.) residue followed by plowing is a common management practice in wheat–soybean [Glycine Max (L.) Merrill] production systems in the mid-southern USA. However, this residue management practice is not environmentally friendly and may not be sustainable. The objectives of this study were to (i) evaluate the effects of N fertilization of wheat, residue burning, and tillage on soil surface carbon dioxide (CO₂) flux in a wheat–soybean double-crop production system, and (ii) evaluate the role of soil temperature and soil moisture in controlling CO₂ flux in a relatively warm, subhumid environment. Soil surface CO₂ flux was measured nine times between June 2002 and October 2003 during the soybean growing season under all combinations of conventional- (CT) and no-tillage (NT) at high and low N fertilization levels with and without residue burning at two locations in the Mississippi River delta region of eastern Arkansas. Soil surface CO₂ flux was 37.6% higher (P < 0.01) from CT than from NT and 6.1% higher (P < 0.05) from the low than the high N rate treatment at one location, but not at the other. Burning did not affect soil surface CO₂ flux except for a significant burning x N rate (P = 0.016) and burning x time interaction (P = 0.032) at one location, but not at the other. Both soil temperature and moisture parameters were significantly negatively correlated with temperature-normalized soil surface CO₂ flux, but soil temperature, particularly at the 10-cm depth, explained more of the variation than did soil moisture parameters. The results of this study indicate that tillage and N fertilization of prior wheat, but not residue burning, affect the loss of C as CO₂ from the soil and that there are additional soil and/or environmental factors, other than near-surface soil moisture and temperature fluctuations, perhaps microbial biomass, that contribute to controlling soil surface CO₂ flux in wheat-soybean production systems in the subhumid region of southern USA.

Abbreviations: ASPB, Arkansas Soybean Promotion Board • CBES, Cotton Branch Experiment Station • CT, conventional tillage • CTIC, Conventional Tillage Information Center • IPCC, Intergovernmental Panel on Climate Change • NT, no-tillage • NOAA, National Oceanic and Atmospheric Administration • OM, organic matter • PTBS, Pine Tree Branch Experiment Station • VWC, volumetric water content • WFPS, water-filled pore space