Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/1996
Publication Date: N/A
Citation: Interpretive Summary: Crop residue placement in soil has a major impact on the biological reactions that control residue decomposition, structure of the soil, water movement, and efficacy/degradation of agrichemicals. Research and extension has focused on the soil surface covered by crop residue but has not evaluated the placement in the soil as controlled by tillage tools/systems. Measurements in this study show that each tillage tool gives a specific pattern of buried residue--information which can forecast degradation of agrichemicals, soil quality responses to tillage/organic matter and many other biotic responses in the plow layer. This information should help project the value of various tillage systems to control soil quality, water quality, and soil carbon accumulation relative to the global carbon problem.
Technical Abstract: Spatial characterization of incorporated crop residues and agricultural chemicals is needed to interpret the many biomass-related soil processes. Our objective was to characterize oat-residue distribution produced by chisel and moldboard primary tillage, and then to characterize the co- location of incorporated oat residue and a surrogate for herbicide incorporated during secondary tillage. Green spheres traced oat shoot- residue and red spheres traced an incorporated agrichemical. Characterizations were derived from weight of soil/residue and sphere counts in 5.32-cm**3 volumes from soil cores (1.84-cm diam.) 30 cm long and sectioned into 15 sublengths each 2 cm long. Moldboard penetration was 25 cm; chisel, 15 cm; and cultivator, 17 cm. The moldboard incorporated 67% of the oat residue below 10 and above 20 cm, while 67% of the chisel- incorporated residue was between 1 and 11-cm depth. Secondary tillage had negligible influence on these depth distributions. Sphere distributions with depth were related more closely to tool penetration than measured oat residue because root tissue was not distinguished from shoot tissue. Fractional porosity of the 5.32-cm**3 volumes, corrected for oat residue and sphere volumes, was increased about 12% due to these extraneous materials. Frequency distributions of oat-residue concentration in these 5.32-cm**3 volumes, fit to an exponential saturation curve, displayed many volumes without oat residue and a few volumes with concentrations at least 4 times the mean. Although oat residue was incorporated with primary tillage, oat residue and red spheres were co-located in volumes with large concentrations of oat residue.