Reservas de carbono organico y de fracciones humicas en un Vertisol sometido a siembra directa | Soil organic carbon and humic fraction stocks in a Vertisol under non-tillage management
2006
Garcia-Silva, R. | Espinosa-Victoria, D. | Figueroa-Sandoval, B. | Garcia-Calderon, N.E. | Gallardo-Lancho, J.F.
Since the decade of the nineties, direct sowing over crop residues or non-tillage management (NT) was intensified in the State of Guanajuato, Mexico, as a means to increase soil organic matter (SOM) and to improve its properties. With this idea, a field experiment with NT was established in 1994 and conducted to date, in Valle de Santiago (Guanajuato, Mexico). The present work was carried out during the fall-winter period of 2003; the main objective was to evaluate the effect of the NT management on soil organic carbon (SOC) and on SOM fraction stocks, referred to the ploughing layer of 0-15 cm and in a Typic haplustert profile (Vertisol). Treatments considered in this study were: a) non-tillage with maize residues on the soil (NTR); b) non-tillage with some of the non-packed crop residues on the soil (NTr); c) conventional tillage with straw burning (CT), and a non-cultivated soil (NCS) as a control. Treatments were established in a completely randomized block experimental design, with four replications. Parameters measured were soil clay content, soil bulk density, pH, SOM and total N content, C/N ratio, and soil stocks of SOC, fresh organic matter (FOM), fulvic acids (FA), humic acids (HA), and humin (Hn). The highest SOC and humic fraction stocks in the 0 to 15 cm layer were found in NCS; with no significant differences between SOC content of the NCS and NTr management. About 70% of the SOC was FA in NTR. NTr increased SOM with 1% in relation to CT. However, reserves of SOC, FOM, FA, HA, and FA+AH of the epipedon of the Vertisol decreased by 33, 57, 35, 47, and 38%, respectively, in relation to NCS; SOC content reduction represented 1.6% of SOM. SOC reserves of Vertisol solum (1 m) were 154 Mg ha-1.
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