ABSTRACT
One of the rst steps in maximizing nutrient energy efciency is maintaining soil organic carbon (SOC). Tillage and cropping systems play signicant role in affecting soil carbon dynamics and carbon dioxide (CO2) °ux. The evaluation of various tillage systems can help determine the effectiveness of conservation practices in sustaining soil productivity and enhancing environment quality. Soil C storage and CO2 emission respond to conservation tillage differently from conventional tillage because of their differential effects on soil properties. The
14.1 Executive Summary ...................................................................................... 235 14.2 Introduction .................................................................................................. 236 14.3 Methods ........................................................................................................ 237
14.3.1 Determination of Soil and Crop Residue Organic Carbon ............... 238 14.3.2 Soil Carbon Loss due to Tillage ....................................................... 239 14.3.3 Quantifying Soil Carbon Loss ..........................................................240
14.4 Results and Discussion ................................................................................. 241 14.4.1 Tillage Depth Effects on Soil Organic Carbon ................................ 241 14.4.2 Tillage Effects on Total Carbon Input from Crop Residue .............. 243 14.4.3 Tillage Effect on Soil Carbon Loss .................................................. 243 14.4.4 Soil Organic Carbon Pool Loss ........................................................ 247 14.4.5 Tillage Impact on Mineralizable C ...................................................249
14.5 Conclusions ...................................................................................................250 14.6 Calculating Mineralizable C and the Michaelis-Menten Constant ............. 251 Acknowledgments .................................................................................................. 252 References .............................................................................................................. 252
purpose of this study was to determine the impact of tillage on soil C storage and CO2 emission in Clarion-Nicollet-Webster soil association in a corn [Zea mays L.]–soybean [Glycine max (L.) Merr.] rotation in Iowa. Soil CO2 emission was lower for less intensive tillage treatments compared with moldboard plow, with the greatest differences occurring immediately after tillage operations. Cumulative soil CO2 emission was 19%–41% lower for less intensive tillage treatments than moldboard plow, and it was 24% less for no-tillage with residue than without residue during the 480 h measurement period. Findings suggest that adopting less intensive tillage such as no-tillage and strip-tillage, and better crop residue cover are effective in reducing CO2 emission and thus improving soil C sequestration in a corn-soybean rotation. This case study demonstrates how mineralizable carbon and turnover can be calculated using the Lineweaver-Burk transformation of the Michaelis-Menten equation.
