Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 23, 2003
Publication Date: March 17, 2004
Citation: Pikul Jr, J.L., Johnson, J.M., Ellsbury, M.M., Wright, S.E., Caesar, T. 2004. Soil organic matter and aggregate stability affected by tillage. Abstracts, Humic Substances Seminar VII. Boston, MA, March 17-19, 2004. p. 54. Technical Abstract: Soil organic matter (SOM) is important to soil function and productivity. Loss of SOM is linked to increased tillage intensity. Objectives were to determine effect of tillage on components of SOM and stability of soil aggregates. Measurements were made on two adjacent farms under a corn-soybean rotation in eastern South Dakota. Soil is a clay loam. About 10 kg of soil from the top 5 cm was collected from 4 locations of no tillage (NTF) and conservation tillage (CTF) farms. A rotary sieve1 was used to separate soil 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, group 5 was 6.0-19.0 mm, and group 6 was >19.0 mm. Water stability of aggregates from groups 3, 4, and 5 was measured by wet-sieving2. High energy moisture characteristics (HEMC)3 were measured on groups 1 and 2. Humic acid (HA) was extracted from soil with 0.5 M NaOH4. Total carbon (C) and nitrogen (N) of soil and HA were measured by combustion. Immunoreactive total glomalin5 (IRTG) was measured with an enzyme-linked immunosorbent assay (ELISA). The ELISA method was used to detect the presence of soil aggregating basidiomycete fungi. Particulate soil organic matter (POM) was isolated by sieving6. Soil C was significantly (p=0.001) greater under NTF, compared with CTF, in aggregate groups 1-5. There were no differences between NTF and CTF in basidiomycete population. There was a significant difference (p=0.01) in C:N of HA between NTF and CTF. There was a significant difference between NTF and CTF in IRTG, but that difference depended on sampling time (spring or fall). Fine POM and water stability of aggregates were significantly (p=0.001) greater under NTF, compared with CTF, in aggregate groups 3-5. Aggregate stability increased with aggregate size on both NTF and 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 improved soil aggregation under no tillage.