The aim of this study was to evaluate the spatial variability of some soil physical attributes and its effects on the development of rubber trees cultivated with leguminous cover crops. The experiment was conducted at Pólo Regional de Desenvolvimento Tecnológico dos Agronegócios do Centro Norte, located in Pindorama, SP, Brazil, on a Typic Kandiudalf. Saturated infiltration rate was evaluated at 0.10 and 0.20cm depth while macro and micro porosity and bulk density were evaluated at 0-0.10, 0.10-0.20, 0.20-0.40 and 0.40-0.60 m layer. Rubber tree plant development was evaluated for four years (1996-1999) through plant stem perimeters and its increase with time. Descriptive statistics was used to calculate and analyze the dispersion and central limit parameters. Geostatistics was used to evaluate the spatial dependence through semivariograms, to perform interpolation using kriging and to construct contour maps for georeferenced data. Spatial dependence was found for all soil physical properties with the range of spatial dependence varying between 15 and 90m. Saturated infiltration rate showed spatial dependence with no relation with plant development evaluations or with any other soil physical attributes. High values for bulk density and micro porosity at 0.20-0.40 m indicate soil compaction at this layer. The plant stem perimeter increased linearly with time while the rate of increase in perimeter decreased with time. The mean increase in plant perimeter was smaller for the winter as compared with the summer measurements. The spatial distribution for rubber tree growth as a function of time presented high continuity as measured by the low nugget effect values and it showed close relation with bulk density values, as the regions with low bulk density showed large values for rubber tree stem perimeter.
Infiltration rate; hydraulic conductivity; hevea brasiliensis; soil physical properties
