Submitted to: Natural Organic Matter in Soils and Water North Central Region Symposium
Publication Type: Abstract Only
Publication Acceptance Date: January 27, 2003
Publication Date: March 21, 2003
Citation: PIKUL JR, J.L., JOHNSON, J.M., CAESAR, T., WRIGHT, S.E., ELLSBURY, M.M. SOIL ORGANIC MATTER AND AGGREGATE STABILITY AFFECTED BY TILLAGE IN THE NORTHERN CORN BELT. NATURAL ORGANIC MATTER IN SOILS AND WATER NORTH CENTRAL REGION SYMPOSIUM. 2003. p. 20. Technical Abstract: Soil organic matter (SOM) contains a complex pool of humic materials having important beneficial properties linked to soil function and productivity. Loss of SOM has been associated with increased tillage intensity. Objectives were to determine effect of tillage on composition of soil organic components and stability of soil aggregates. Measurements were made on two adjacent farms under a corn-soybean rotation in eastern South Dakota. Soil is a Vienna-Brookings complex having a clay loam texture. At three times during the 2-year rotation, soil was collected from the top 50 mm of no tillage (NTF) and conventional tillage (CTF) farms. No tillage has been used for 10 years on NTF. Soil was air-dried and a rotary sieve was used to separate samples into aggregate groups. Group 1 was soil <0.4 mm, group 2 was 0.4-0.8 mm, group 3 was 0.8-2.0 mm, group 4 was 2.0-6.0 mm, and group 5 was 6.0-19.0 mm. Water stability of dry and pre-moistened aggregates were determined by wet-sieving. Total soil carbon (C) was measured by combustion. Immunoreactive total glomalin (IRTG), a glycoprotein originating from hyphae of arbuscular mycorrhizal fungi, was measured with an enzyme-linked immunosorbent assay on all aggregate groups. The ELISA method was used to detect the presence of soil aggregating basidiomycete fungi in water stable aggregates. Humic acid (HA) was extracted from soil with 0.5 M NaOH and precipitated with concentrated HCl4. Average (all groups) soil C was 4% greater under NTF, compared with CTF, and IRTG was 46% greater under NTF compared with CTF. Basidiomycete population was about 20% greater under NTF compared with CTF. There were no differences in HA concentration between NTF and CTF. However, group 5 aggregates had 17% more HA compared to group 3 and 13% more compared to group 4 (p=0.08). Water stability of dry aggregates from NTF was twice that of CTF. Aggregate stability increased with aggregate size on both NTF and CTF. Dry and wet sieving show that soil aggregates from NTF resisted breakdown when compared with aggregates from CTF. Group 5 aggregates had 6% more C (p=0.058) and 43 % more IRTG (p=0.03) under NTF compared with CTF. Differences in properties among aggregates show that organic cementing agents (humic materials or microbial exudates) are not uniformly distributed among aggregate groups. Results show a link between reduced tillage and improved soil aggregate stability.