Use of geophysical survey as a predictor of the edaphic properties variability in soils used for livestock production

The spatial variability in soils used for livestock production (i.e. Natraquoll and Natraqualf) at farm and paddock scale is usuallyvery high. Understanding this spatial variation within a field is the first step for site-specific crop management. For this reason,we evaluated whether apparent electrical conductivity (ECa), a widely used proximal soil sensing technology, is a potential estimatorof the edaphic variability in these types of soils. ECa and elevation data were collected in a paddock of 16 ha. Elevation wasnegatively associated with ECa. Geo-referenced soil samples were collected and analyzed for soil organic matter (OM) content, pH,the saturation extract electrical conductivity (ECext), available phosphorous (P), and anaerobically incubated Nitrogen (Nan).Relationships between soil properties and ECa were analyzed using regression analysis, principal components analysis (PCA), andstepwise regression. Principal components (PC) and the PC-stepwise were used to determine which soil properties have an importantinfluence on ECa. In this experiment elevation was negatively associated with ECa. The data showed that pH, OM, and ECextexhibited a high correlation with ECa (R2=0.76; 0.70 and 0.65, respectively). Whereas P and Nan showed a lower correlation (R2=0.54and 0.11 respectively). The model resulting from the PC-stepwise regression analysis explained slightly more than 69% of the totalvariation of the measured ECa, only retaining PC1. Therefore, ECext, pH and OM were considered key latent variables because theysubstantially influence the relationship between the PC1 and the ECa (loading factors>0.4). Results showed that ECa is associatedwith the spatial distribution of some important soil properties. Thus, ECa can be used as a support tool to implement site-specificmanagement in soils for livestock use