MANURING AND SOIL TYPE INFLUENCE ON SPATIAL VARIATION OF SOIL ORGANIC-MATTER PROPERTIES

The spatial variability of microbial biomass C and three humification indexes (the degree of humification, DH; the index of humification, HI ; and the humification rate, HR) were investigated in order to evaluat e their usefulness as indicators of the response of soil organic matte r to altered soil environments. The investigation was carried out by e xamining the topsoil layer of an experimental field characterized by t he presence of four phases of one soil series and, except for the addi tion of cattle manure in part of the field, by fairly uniform agricult ural practices. A rectangular area of 350 by 800 m was sampled on a sq uare grid scheme coupled with nesting. The experimental objective was to determine if the investigated properties were influenced by changes in soil type and bu the addition of cattle manure. All properties mea sured showed spatial dependence at the sampling distances adopted, Two groups of properties were identified based on their degree of spatial variability: microbial biomass C, DH, and HI exhibited short-range va riability, whereas HR varied across longer distances. Microbial biomas s C and FIR showed a spatial pattern related to soil amendment and soi l types, respectively. Therefore, these variables provided complementa ry information about the condition of soil organic matter in the study area.