Microbial use of root-derived carbon and litter-derived carbon in conventional and no tillage soils.

摘要

Understanding interactions among microorganisms, soil fauna, soil organic matter, plant roots and biogeochemical cycles are essential in developing sustainable agroecosystems. Two localized areas of increased activities are associated with the roots and plant residues. By using {dollar}sp{lcub}14{rcub}{dollar}C tracer methods in conventional tillage and in no tillage soils, the relative contributions of root-derived C and litter-derived C can be made for the two tillages.; A method for simultaneously field pulse-labeling maize plants in CT and in NT plots was developed. Maize plants in root-derived C plots were pulse-labeled in July. Maize plants grown in lined, raised beds were multiply pulse-labeled, harvested, dried, chopped, and applied to litter-derived C plots in November. {dollar}sp{lcub}14{rcub}{dollar}C was measured in aboveground maize biomass, roots, soil, microbial biomass, particulate organic matter, and soil respiration, in order to calculate turnover rates and develop a {dollar}sp{lcub}14{rcub}{dollar}C budget.; Microbial turnover of root-derived C was found to be similar between tillages. The distribution of label among the measured compartments did not differ between tillage treatments. Of the applied label in the root-derived C plots, 35-55%, 6-8%, 3%, 1.6% and {dollar}<{dollar}1% was recovered in the shoots, roots, soil, cumulative respiration, and microbial biomass, respectively. Microbial turnover of litter-derived C in CT was 7 times faster than in NT. By day 97, 67.5% of the applied label had accumulated in the CT soil, while only 28.9% had accumulated in the NT soil. Results agree with microarthropod data indicating little tillage effect on rhizosphere food webs, but distinctly different soil organisms active in buried versus surface litter.