Spatial variability of microbial biomass and organic matter labile pools in a haplic planosol soil

• Published in: Bragantia 2010, Vol.69 (suppl), p.85-95
• Main Authors: Loureiro, Diego Campana, De-Polli, Helvécio, Ceddia, Marcos Bacis, Aquino, Adriana Maria de
• Format: Article
• Language: English
• Subjects: AGRICULTURE, MULTIDISCIPLINARY
• ISSN: 0006-8705; 1678-4499; 0006-8705
• DOI: 10.1590/S0006-87052010000500010

The objective of this work was to study the spatial variability of soil microbial biomass (SMB) and labile soil organic matter pools (labile SOM), under different management systems and plant cover. The experiment was conducted in a Haplic Planosol soil on an Integrated Agroecological Production System (SIPA), in Seropédica, Rio de Janeiro. The evaluated management systems were: alley cropping, pasture, and bush garden, the late one was used as reference area. Three grids of regular spacing of 2.5 x 2.5 meters were used for sampling, consisting of 25 georeferenced points each, where soil samples were taken at 0-10 cm depth. The following labile constituents of soil organic matter were determined: free light fraction (FLF), water soluble C and N, C and N of SMB (SMB-C and SMB-N), and glomalin content. The textural fractions (sand, silt, and clay), pH in water, and chemical attributes (organic C, total N, Ca, Mg, Al, P, K, and CEC-cation exchange capacity) were also determined. The areas of alley cropping and pasture showed spatial dependence to the attributes of SOM. The occurrence of high spatial dependence for the attributes associated to microbial biomass in the alley cropping system (C, FLF, SMB-N and respiration), probably was due to external factors related to management, such as: intensive rotational cropping system, diversity of crops and different inputs of organic matter to soil such as pruning material and organic compost. O objetivo do trabalho foi estudar a variabilidade espacial da biomassa microbiana do solo (BMS) e dos constituintes lábeis da matéria orgânica do solo (MOS), sob diferentes sistemas de manejo e cobertura vegetal. O experimento foi instalado em um Planossolo Háplico no Sistema Integrado de Produção Agroecológica (SIPA), em Seropédica (RJ). Os sistemas de manejo avaliados foram: cultivo em aléias, pastagem e, horto florestal como área de referência. Para a amostragem utilizaram-se três grades regulares com espaçamento de 2,5 x 2,5 metros, composta de 25 pontos georreferenciados para cada grade, onde se coletou amostras de terra na profundidade de 0-10 cm. Em cada amostra determinaram-se os seguintes constituintes lábeis da MOS: fração leve livre, formas de C e N solúveis em água, C e N associado à BMS e teor de glomalina. Determinaram-se também as frações granulométricas areia, silte, argila, umidade gravimétrica, bem como os atributos químicos de rotina. Somente as áreas de cultivo em aléias e pastagem tiveram dependência espac