SPATIAL STRUCTURE OF AVAILABLE MICRONUTRIENT CONTENTS AND THEIR RELATIONSHIPS WITH OTHER SOIL CHARACTERISTICS AND CORN YIELD

Improved nutrient management in precision agriculture is important for achieving high yield and protecting environmental quality. The objectives of this study were to explore the spatial distribution of soil-available microelements and investigate the spatial relationship between corn yield and soil properties. The topsoil was sampled according to a nested sampling pattern (20*20 m), to describe the spatial variability by geostatistical techniques from 0 to 220 m. The mean plant-available Cu, Zn, Fe, and Mn contents were 1.91, 0.63, 16.88, and 11.93 mg kg -1 , respectively, being at medium or at high levels. The results indicated that coefficient of variation for soil properties varied from 1.28 (pH) to 47.51 % (EC). Within the field studied, moderate spatial dependence was found for many of the variables, but at different spatial scales. The semivariance analysis showed that available Zn and Mn were spatially correlated at the greater distances of 155.8 m and 379.8 m, hence requiring the largest sampling interval, and available Cu and Fe were at shorter distances of 95.3 and 57.1 m, respectively. Yield map showed few consistent high or low yielding areas of the field. Although no correlation was found between Zn content and corn yield, inadequate Zn and the lowest yield amount were clustered in the northern corner of the study area. The clustering nature of data probably resulted from the differences in soil characteristics of the study area. The results revealed that available macro and micronutrient status showed wide variations across the study area which was mainly associated with the variation in soil texture, organic matter and calcium carbonate contents of the field. The spatial variation in soil characteristics within the field has clearly been reflected in the yield of corn.