Spatial Variability of Selected Soil Properties in an Olive Orchard in Tarom Region, Zanjan Province, Iran

An experiment was carried out in order to study the spatial variability of soil fertility variables in an irrigated mature olive tree (Olea europea cv. ‘Zard’) orchard. The orchard is located in the Tarom area of Zanjan Province (48° 56′ to 50° 5′ E and 36° 47′ to 37° 36′ N) and i s under olive with trees planted 7×7 m. Soil parameters - including K, P, Na, Cl, EC and OM - were determined in soil samples from 0-60 cm depth in late February 2011. A regular 98×98 m sampling grid was established and the intersection points were georeferenced. The data were analyzed using both classical statistics and geostatistical methods. Maps were created as a basis for orchard soil sitespecific management. Interpolations were realized according to thresholds and standard deviation of every parameter. Estimates were used to draw variation maps of each soil fertility component based on Kriging method. High geo-distribution variation was detected. The results showed that an important area is menaced by K deficiency.
Indeed, in this area soil K was revealed to be under the 70 ppm threshold level. The geostatistical analysis indicated different spatial distribution models and spatial dependence levels for the soil properties. Sodium and OM were strongly distributed in patches. Phosphorous was moderately spatial dependent, and K did not follow a spatial correlated distribution.