Survey of the impact of cropping on soil carbon and aggregate stability
2002
Serohijes, R.C. | Almendras, A.S. (Leyte State Univ., Baybay, Leyte 6521-A (Philippines). Dept. of Agronomy and Soil Science) Blair, G. | Whitebread, A. | Lefroy, R.
Upland crop production in the Philippines is generally constrained by infertility and low organic matter of the soil. Continuous cultivation generally leads to a declining soil organic matter content and quality, reduced soil carbon, lower biological activity and deteriorated soil structure. A survey was conducted in Leyte, Cebu and Davao to investigate the impact of cropping on soil carbon and aggregate stability. Soil samples (0-10 cm depth) were collected from adjacent uncleared and cropped areas for analysis of total and labile carbon and wet aggregate stability. Total organic carbon (CT) was analyzed by combustion method. The labile carbon (CL) by oxidation with 333 mM KMnO4. Aggregate stability were measured using a wet sieving technique with five sieve sizes (125, 250, 500, 1000 and 2000 mm). Mean weight diameter (MWD) was calculated by getting the average of soil mass in each aggregate size fraction. Of the 18 sites surveyed, there was loss of both CL and CT as a result of cropping at 16 sites. The average loss of CL (43.4%) was greater than the average loss of CT (37.5%). In Leyte and Cebu, the overall sites, the correlation between MWD was stronger with CL than with CT. The correlation coefficients MWD-CL and MWD-CT for the Davao sites were slightly different. The survey indicates that the farming common to the areas surveyed had detrimental impact on soil organic carbon and aggregate stability
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