Abstract
AbstractSoil‐test biological activity (STBA) is a key indicator describing the functions of soil to catabolize organic amendments, promote soil organic C sequestration, and cycle nutrients. We explored how climatic zone, land use, and physiographic region affected the relationship of STBA with several soil fertility properties and processes. Soils from Georgia, North Carolina, Pennsylvania, and Virginia (wet climate) were Aquults, Fluvents, Udalfs, Udepts, and Udults and soils from Nebraska and Oklahoma (dry climate) were Udolls and Ustolls. Annual cropland and perennial pasture were the land uses. The Prairie region had silt loam and silty clay loams, the Ridge–Valley region had silt loams, and the Piedmont and Coastal Plain regions had fine sandy loam, loam, sandy clay loam, and sandy loams. Across all locations, STBA with the flush of CO2 during 3 d following rewetting of dried soil was most strongly associated with cumulative C mineralization, basal soil respiration, particulate organic C, potential N mineralization during 24 d of aerobic incubation, residual soil ammonium, soil microbial biomass C, and total soil N. Climatic zone modified the association between STBA and net N mineralization, possibly caused by greater N immobilization in drier soils with 2:1 clays. Physiographic region had a small effect on the relationship between STBA and net N mineralization. Land use did not alter this relationship significantly. Soil‐test biological activity was verified as a robust indicator of soil organic N supply, as well as of general soil biological condition to assess the soil's catabolic potential and potential C storage.
Highlights
Soil health evaluation is an important step towards understanding how to develop and promote sustainable agricultural systems, since many conservation management approaches can result in site-specific changes in Abbreviations: Dry matter (DM), dry matter; Soil-test biological activity (STBA), soil-test biological activity soil function (Snapp et al, 2005; Wander & Bollero, 1999)
The variation explained by STBA alone would have been 80, 81, 65, 88, 68, and 58%, respectively. These results suggest that some form of biologically active C or N fraction should be determined in all physiographic regions and land uses; since STBA is a relatively simple, rapid, reliable, and direct measure of the biological fraction, it would be a logical choice
Soil-test biological activity was supported as a robust indicator of soil N availability from the mineralization of soil organic N during aerobic incubation, as well as from plant N uptake in an unamended greenhouse bioassay
Summary
Soil health evaluation is an important step towards understanding how to develop and promote sustainable agricultural systems, since many conservation management approaches can result in site-specific changes in Abbreviations: DM, dry matter; STBA, soil-test biological activity soil function (Snapp et al, 2005; Wander & Bollero, 1999). Describing changes in how well soil functions should be the goal of soil health evaluation. Indicators of soil function should be easy to measure, reasonably indicate changes in soil function, be applicable to field conditions, be sensitive to variations in management, and encompass key ecosystem processes that are relatable to processoriented modeling (Franzluebbers, 2016). Numerous soil health indicators have been proposed and used under.
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