Spatial variability of soil attributes by an electromagnetic induction sensor: A framework of multiple fields assessment under Brazilian soils

Abstract

Soil apparent electrical conductivity (EC a ) to survey soil has been demonstrated to be a valuable tool for mapping the soil attributes. Whereas the correlation between EC a and soil attributes is well documented, the practical usage of EC a data to characterise soil properties on individual fields or across many fields is still not recognised in Brazil. Including EC a data from several fields could increase the capacity to characterise soil properties compared to a within-field approach. The objective of this study was to deliver a framework to allow the characterisation of soil spatial variability using EC a data from multiple fields. The ability of EC a to map the content and variability of soil attributes was assessed in six fields, totalling 412 ha and 2000 soil samples. The results indicate a significant correlation between EC a and selected soil properties. EC a data is useful to predict and characterise the content and variability of soil attributes according to EC a classes. Sites with relatively low EC a values presented greater spatial variability of those attributes, which requires more intensive sampling for proper spatial characterization. The amplitude of variation of EC a was directly correlated to clay content ( R 2 = 0.95), SOM ( R 2 = 0.65) and CEC ( R 2 = 0.76) ranges, where 1.0 mS m −1 corresponded to 1.5 g kg −1 , 0.12 g dm −3 and 0.25 mmol c dm −3 , respectively. The spatial variability of those attributes remained stable over different sampling times. The significant correlation of EC a readings to soil attributes indicates a potential framework to manage soil fertility in multiple fields. • ECa are an excellent alternative to establish fertility zones. • ECa can be used to guide soil sampling processes. • Low ECa classes presented greater spatial variability. • High ECa values have higher soil fertility levels. • Spatial patterns were temporally maintained.