Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/1998
Publication Date: N/A
Citation: Interpretive Summary: An on-farm study was performed to examine the impacts of tillage practices on biologically-active soil organic matter, a possible indicator of soil quality. Thirty-six fields in four regions of Illinois were sampled for analysis of three components of biologically-active soil organic matter, including particulate organic matter (POM), potentially mineralizable organic matter (PMN), and soil microbial biomass (SMB). Two of the components, POM, and PMN were more abundant in the surface layer of soils under no tillage, whereas there was no effect of tillage on SMB at any depth. Overall, tillage affected the vertical distribution of components of biologically-active soil organic matter, but had no effect on the total quantities present. The results of this study show that in poorly drained areas, which are common in Illinois, conservation tillage practices, such as no till, may not result in greater organic matter accumulation, but rather stratification of organic matter in the soil profile, with the greatest concentration at the soil surface. Use of the technology could, however, benefit agricultural producers economically, without the effect of accumulated organic matter in the soil profile.
Technical Abstract: This study evaluated the impacts of tillage practices and soil texture on biologically-active SOM in Illinois by characterizing particulate organic matter (POM), potentially mineralizable N (PMN), and the soil microbial biomass (SMB). Thirty-six fields in four regions of Illinois were sampled during spring and summer of 1995 and 1996. Each field had been under either conventional tillage (CT) or no-till (NT) management for at least five years. Fields were sampled in the corn (Zea mays L.) or soybean [Glycine max (L.) merr.] phase of their rotation. No-till fields contained slightly more soil organic C (SOC) and total N than CT fields in the 0-5 cm depth. There were no significant impacts of tillage practices on SOC contents in the 5-15 or 15-30 depths, nor in the overall sampling depth (0-30 cm). Fields under NT contained more POM and PMN in the 0-5 cm depth but there was no impact of tillage practices on POM contents over (0-15 cm). The SMB did not differ in NT and CT systems in any depth. Results suggest that in Illinois soils, tillage practices have impacted the vertical distribution, not the total accumulation, of biologically-active and total SOM. Analysis of covariance was used to investigate how texture influenced the impacts of tillage practices on total and biologically-active SOM. The soils studied ranged in texture classes from silt loam to clay. Sand content which ranged from 10 to 212 g kg-1 soil, was a more effective textural covariate than silt or clay. In low sand content soils, NT fields contained greater SOC, total N, and POM contents in the 5-15 cm depth than CT fields. In higher sand content soils, tillage practices had no impact on the vertical distribution of total SOC, total N, or POM.