| Popis: |
Spatial characterization of crop residues and agrichemicals incorporated by tillage is needed to interpret biomass-related soil processes. This study presents such a characterization. We first described oat residue (Avena sativa L.) and green-sphere distributions produced by chisel plow (CP) and moldboard plow (MP) tillage and then described red-sphere distributions when incorporated during secondary tillage. Finally the co-location of incorporated oat residue and colored spheres was characterized. Green and red ceramic spheres were surrogates for shoot residue and incorporated agrichemical, respectively. Characterizations were derived from weights of soil and residue and counts of spheres in soil cores (1.84 cm diam. by 30 cm long, sectioned into 15 sublengths each 2 cm long). Penetration with MP was 25 cm, CP was 15 cm, and cultivator was 17 cm. The MP incorporated 67% of residue in the 10- to 20-cm depth, while more that 90% of the incorporated residue in the CP was between 1 and 11 cm deep. Secondary tillage had negligible influence on these depth distributions. Green-sphere distributions were related more closely to tool penetration than those of oat residue because root and shoot tissue were not distinguished. Fractional porosity of the 5.32-cm 3 volumes, adjusted to account for oat residue and sphere volumes, was increased 12% due to these materials. Many 5.32-cm 3 volumes contained no oat residue, whereas only a few volumes had concentrations ≥ 4 times the mean residue concentration. Although oat residue was incorporated with primary tillage, residue and herbicide surrogates were co-located in 35% of the volumes, many of which contained large concentrations of residue. Exclusive use of either primary tillage with the same secondary tillage produces an environment for characteristically different bioactivity in the upper 10 cm. |
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