Spatial Relations between Oat Residue and Ceramic Spheres when Incorporated Sequentially by Tillage

Abstract

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‐cm3 volumes, adjusted to account for oat residue and sphere volumes, was increased ≈12% due to these materials. Many 5.32‐cm3 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.

How can straw incorporation management impact on soil carbon storage? A meta-analysis

“…NT treatment resulted in the absence of soil disturbance, with the straw remaining on the soil surface. In contrast, under RT and PT treatments, an excess of 90 and 60 % of incorporated straw might be buried at depths of 0-11 cm and 10-20 cm, respectively (Allmaras et al 1996). Li et al (2001) reported straw decomposition rates were closely related to SI depths, in decreasing order from 5 to 15 cm to the surface soil.…”

Tillage effects on soil hydraulic properties in space and time: State of the science

“…Allmaras et al (1996) characterized the depth distributions of oat residues and ceramic spheres incorporated by tillage into the top 30 cm. Green spheres served as a residue tracer under primary tillage, followed by secondary tillage of red spheres as a tracer or surrogate for herbicides.…”

Mineralisation of crop residues on the soil surface or incorporated in the soil under controlled conditions

“…the presence or absence of mulch on the soil surface or the spreading of fragments in the soil, modifies the physical, biological and chemical properties of soil, such as water content, temperature, O 2 content (Allmaras et al 1996), N content, pH and the composition of the decomposer community (Holland and Coleman 1987). The reduced rate of decomposition usually observed under field conditions on the surface (Seneviratne et al 1998) may be attributed to a limited contact between soil and plant residues.…”