|Novak, Jeffrey - Jeff|
Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2005
Publication Date: 3/19/2005
Citation: Ding, G., Liu, X., Herbert, S., Novak, J.M., Amarasiriwardena, D., Xing, B. 2006. Effect of cover crop management on soil organic matter. Geoderma. 130:229-239. Interpretive Summary: Soil organic matter (SOM) is a very important component of soil because it influences many chemical and physical properties that affect the quality of soil. Agricultural practices such as cover crop and nitrogen (N) management will influence the amount of plant residue returned to soil and the N available to convert this residue into organic matter. Thus, it is important from a crop productivity and soil quality standpoint to determine how changes in cover crop and N management will influence the amount and chemistry of SOM. Studying the chemistry of SOM is complex. The SOM must be extracted from soil using various solutions, and the fractions obtained are characterized using sophisticated analytical equipment. We characterized the SOM fractions obtained from soils under a vetch/rye, rye alone and no cover crop. After characterization, we found that there was more SOM under the vetch/rye and rye alone treated with N fertilizer and it was chemically different than SOM under no cover crop. Our results mean that to maintain a soil's high agricultural productivity, it is prudent to continue using a cover crop with N fertilizer management.
Technical Abstract: Characterization of soil organic matter (SOM) is important for determining the overall quality of soils, and cover crop system may change SOM characteristics. The purpose of this study was to examine the effect of cover crops on the chemical and structural composition of SOM. We isolated humic substances (HS) from soils with the following cover crop treatments: a) Vetch (Vicia Villosa Roth.)/Rye (Sesale cereale L.), b) Rye alone, and c) Check (no cover crops) that were treated with various nitrogen (N) fertilizer rates. CPMAS-TOSS (Cross-Polarization Magic-Angle-Spinning and TOtal Sideband Suppression) 13C NMR results indicated that humic acids (HA) from soils under rye only were more aromatic and less aliphatic in character than the other 2 cover crop systems without fertilizer N treatment. Based on the DRIFT (diffuse reflectance Fourier transform infrared) spectra peak O/R ratios, the intensities of oxygen-containing functional groups to aliphatic and aromatic (referred to as recalcitrant) groups, the highest ratio was found in the HA from the vetch/rye system with fertilizer N. The lowest ratio occurred at the vetch/rye system without fertilizer N treatment. The O/R ratio of fulvic acids (FA) can be ranked as: vetch/rye without fertilizer > vetch/rye with fertilizer > no cover crop without fertilizer > rye alone (with or without fertilizer) soils. Both organic carbon (OC) and light fraction (LF) contents were higher in soils under cover crop treatments with and without fertilizer N than soils with no cover crop. These chemical and spectroscopic data show that cover crops had a profound influence on the soil SOM and LF characteristics.