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Consequences of Changes in Particulate Organic Carbon in Vertisols under Pasture and Cropping
Author(s) -
Chan K. Y.
Publication year - 1997
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1997.03615995006100050013x
Subject(s) - vertisol , pasture , soil water , agronomy , environmental science , total organic carbon , soil carbon , soil health , particulates , soil organic matter , mineralization (soil science) , soil science , chemistry , environmental chemistry , biology , organic chemistry
Soil organic C levels are generally low in Vertisols and, under cropping, they decline rapidly, resulting in N deficiency limiting crop production. The pools of soil organic C lost during cropping of native pasture soils need to be identified so that management strategies can be developed to reverse this loss. Changes in particulate (>53‐µm) organic carbon (POC) under different histories of cropping and pasture were monitored in two Vertisols with contrasting C and N status in the semiarid subtropical area of Australia and the changes were related to N availability and aggregate stability. Results indicate POC was the form of organic C that was preferentially lost under cropping; on average it made up 70% of the difference in organic C between native pasture and cropped soils in the 0‐ to 5‐cm layer. It was also the form of organic C regained when cropped soils were returned to pasture. Particulate organic C was significantly related to N mineralization, indicating the importance of this fraction to N availability in the Vertisols. Particulate organic C was more significantly related to the water stability of the >250‐µm size fraction than that of the <50‐µm fraction and thus indicates the importance of POC in maintaining the stability of the macroaggregates of these soils. Regression analyses indicated that, for Vertisols, POC is equally sensitive to changes in these important soil properties under different management practices as TOC. Results also demonstrated the effectiveness of pasture in restoring POC and therefore its usefulness in maintaining and restoring the fertility of V ertisols.