Estoque e fraÃÃes da matÃria orgÃnica e suas relaÃÃes com o histÃrico de uso e manejo de latossolos. / Organic matter storage and fractions and the historic of Latosol use and management

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

In cultivated areas, the reductions in the storage of soil organic matter (SOM) in average are 50%, in a period of cutting of the native vegetation and subsequent cultivation inferior to 10 years. The soil use and management practices exercise great influence on the MOS storage and fractions, since the vegetable covering and the soil management they modify the additions and the losses of the soil carbon. This study was carried out to evaluate organic matter storage and fractions of typic dystroferric Red Latosol (Oxisol) submitted to different use and management systems, in the south of the Minas Gerais state, Brazil. In Lavras, MG, six use and management systems were sampled: forest native (MTN), eucalyptus (EUC), pinus (PIN), pasture (PAS), corn in the minimum tillage system (MCM) and corn in the conventional tillage system (MPC). It was also sampled plots of one experiment (11 years of implantation) in an area of Experimental Farm of EPAMIG, in Machado (Minas Gerais State-Brazil), with the objective of evaluated the influence of planting densities (12 treatments) on the productivity of coffee plants (Coffea Arabica L.). In that experiment, the soil samples were collected in the interline (IL) and in the canopy projection (CP) of coffee plants. These soil samples were were used to determine the content and stocks of carbon (C) and total nitrogen (TN), C-microbial biomass (Cmic), degree of oxidation of C and physical fractionation of SOM. The experimental results have revealed that the variation in the distance between on line and another of coffee plants was not efficient in changing the C and NT contents and storage. The largest contents of C and NT were observed in the treatments related to the space of 3.5 meters among the coffee plant rows. The cultivation of corn (MCM e MPC) in Lavras caused a fast decline in the soil C and NT contents and storage. The C and NT contents tended to increase soil samples or systems with larger entrance of vegetable residues, and the highest differences among treatments happening wer verified, mainly, in the soil superficial layers. The decrease in the space between line plants was efficient in increasing the Cmic contents, mainly for soil sample collected in the interline of coffee plants. The highest Cmic content was verified in the treatments where the distances of coffee plant lines were 2 and 2.5 meters. In the two Latosol evaluated, the largest proportion of C of the soil was associated to the high oxided fractions (F1 and F2). The vegetable cover influenced the C degree of oxidation, since the less bioavailability forms prevailed in the systems under natural vegetation. The physical fractionation of organic matter revealed a high reduction in the carbon associated the light fraction with the soil cultivation, which contributed with 1,1 the 16,4% of the total C present in two Latosols. The reached results allow classifying the Cmic, the C in the light fraction and the C in the F1 fraction as adequate index for determining changes in the SOM amount and quality in different soil management systems.

ASSUNTO(S)

pastagem matÃria orgÃnica carbono carbon stocks mata eucalipto biomassa microbiana organic matter pasture corn cultivation systems grau de oxidaÃÃo da matÃria orgÃnica estoque de nitrogÃnio sistemas de cultivo do milho microbial biomass nitrogen stocks fracionamento fÃsico da matÃria orgÃnica cafeeiro physical fractionation of organic matter coffe estoque de carbono eucalyptus ciencia do solo degree of oxidation of organic matter pinus pinus mata carbon

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