Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/20/2001
Publication Date: N/A
Citation: Interpretive Summary: Soil organic matter (SOM) is an important component of soil because it has a large influence on a soil's productivity. The quality of SOM, therefore, may be strongly influenced by agricultural management practices such as tillage. Some conventional forms of tillage such as disking will hasten SOM decomposition while other minimal tillage practices leave more plant residue on the soil surface. Tillage management may determine long-term quality of soil to produce a good crop yield. We investigated the influence of tillage on SOM chemical characteristics in a sandy Coastal Plain soil under long-term conventional and minimal tillage management. We determined that tillage influenced the chemical qualities of SOM and influenced its ability to store nutrients and water.
Technical Abstract: Soil organic matter (SOM) is of primary importance in maintaining soil productivity and its characteristics are subject to chemical change with agricultural management practices. This may significantly influence short-term changes in SOM chemical properties that can have an influence on C sequestration. Nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy were used to evaluate the impacts of tillage (conventional vs. conservation) management on the structural and compositional characteristics of SOM. Both physically and chemically isolated SOM fractions were extracted from a Norfolk soil series under long-term tillage management (20 yrs). The physical fraction of SOM (light fraction, LF) was isolated using a density gradient technique employing a 1.5 g/mL NaBr solution while the chemical fraction (humic acid, HA) of SOM was extracted using alkali treatment. The NMR results indicate that HA from conventional tillage (0-5 cm deep) was less aliphatic and more aromatic than HA from conservation tillage. The aliphatic carbon content decreased with increasing soil depth (0-15 cm) for both conventional and conservation tillage treatments. The reverse trend was true for aromatic carbon content for both treatments. Using the reactive/recalcitrant (O/R) peak ratio data obtained from the IR analysis, we found that the HA was more reactive in the top (0-5 cm) soil depth under conservation than under conventional tillage. Both soil organic carbon and LF material were higher in the top 0-5 cm soil under conservation than conventional tillage. Our results show that long-term tillage management can significantly influence the characteristics of both physical and chemical fractions of the SOM pool.