a Yekzaban - Department of Soil Science, Faculty of Agriculture, University of Guilan, Rasht, IRAN.
m Shabanpour - Department of Soil Science, Faculty of Agriculture, University of Guilan, Rasht, IRAN.
n Davatgar - Department of Soil and Water Research, Rice Research Institute of Iran (IRRI), Rasht, IRAN.

Soil aggregate is one of the most important soil properties governing most of the physical, chemical, hydrological and biological properties of soils. Also soil particle size distribution (PSD) is one of the fundamental physical properties affecting aggregate stability. Characterizing the variation of both properties is very important in environmental research. The objective of this study was to assess effects of (PSD) on soil aggregates stability (i.e. MWD) and to compare spatial pattern these properties at agricultural field in North of Iran. From the study area 75 soil samples were sampled by a systematic sampling strategy at 0 to 30 cm depth below the surface on a regular grid spacing of 10m×10m and transported to laboratory. Soil mean weight diameter (MWD) was negatively correlated with silt (-0.424; p < 0.01) and positively correlated with clay (+0.454; p ˂ 0.01). The semivariograms analysis showed moderate to strong spatial dependency for all soil properties. The soil properties with strong spatial correlations were clay and silt content, whereas sand and MWD were moderately correlated. The range spatial dependence for soil properties varied from 31m for MWD to 58m for silt content. The results showed that areas with higher silt and clay are always associated with the lower and higher MWD, respectively. Therefore we assume that the areas associated with the lower clay might be due to the effect of soil erosion or leaching in rainy season.

Interpolation , Ordinary kriging , Semivariogram , Soil texture ,