Test for active organic carbon as a measure of soil quality.

摘要

Soil properties functionally associated with soil quality are largely controlled by active organic carbon. In this study a simple test of active carbon was evaluated as a of soil quality. Sixty-one soils representing a wide range of properties were analyzed for total and active microbial biomass, basal respiration rates, arginine ammonification rates, dehydrogenase activity, nitrogen mineralization rates, and macroaggregate stability. Ratio of microbial biomass over total organic carbon, and maintenance respiration rates were calculated. Using an inductive additive approach, soil properties were normalized relative to their maximum value in the data-set, and then summed and averaged to calculate a soil quality index. Among the soil properties, active microbial biomass, ratios of total and active microbial biomass over total organic carbon, basal and maintenance respiration rates, and macroaggregate stability accounted for 97.2, active microbial biomass, ratio of total microbial biomass over total organic carbon, and macroaggregate stability accounted for 85.2 and active microbial biomass as the single most sensitive indicator accounted for 75.1% of the variation in the soil quality index, respectively. The soil quality indices were higher in conservation vs. conventional management, and spring vs. fall-sampled soils. The soil quality index values for spring or fall-sampled soils were correlated (r{dollar}sp2{dollar} = 0.828) to each other. Total organic carbon, 0.5M K{dollar}sb2{dollar}SO{dollar}sb4{dollar} extractable carbon before and after microwaving of soil, 0.5M H{dollar}sb2{dollar}SO{dollar}sb4{dollar} and 0.5M NaHCO{dollar}sb3{dollar} extractable carbon, and anthrone reactive carbon in 0.5M K{dollar}sb2{dollar}SO{dollar}sb4{dollar} extracts after microwaving of soil were determined on field-moist or air-dried soils. Although the anthrone procedure measured a smaller pool of soil organic carbon than did the others, it was the most sensitive to prior soil management and significantly discriminated among treatments in replicated field experiments. Among the measures of carbon, the anthrone reactive carbon gave the best prediction of the soil quality index (r{dollar}sp2{dollar} = 0.736 for field-moist, and 0.653 for air-dried soils, 0.774 for spring and 0.61 for fall-sampled soils. On average, anthrone reactive carbon was higher in conservation vs. conventional, and spring vs. fall-sampled soils. Anthrone reactive carbon well correlated between field-moist and air-dried soils (r{dollar}sp2{dollar} = 0.53) and between the spring and fall-sampled soils (r{dollar}sp2{dollar} = 0.724). The approach used to test the soil quality index was based on subjective, a-priori judgement of expected soil quality and does not include all the parameters of soil quality. However, the procedure is adaptable to integrate most soil properties and applicable to diverse soil-crop management systems. A soil test based on anthrone reactive carbon might be useful in monitoring soil quality and identifying fields in which organic matter management is a limiting factor for agricultural production.