Site-specific Management of Pastures Based on Soil Apparent Electrical Conductivity Survey

Fertilization is the main cost of maintenance of permanent pastures. Its incorrect use results in important direct economic losses and in environmental pollution. Usually, soils utilised for pasture and livestock production in Southern region of Portugal have high spatial variability. Consequently, it is necessary to determine the spatial patterns of the main soil properties as the first stage in implementing site-specific management strategies. However, this has to be performed using an inexpensive technique because the profitability in this type of farms are very low, so owners need an economical, effective, and reliable method to know which zones have similar potential management. The use of soil apparent electrical conductivity (ECa), as it integrates many soil properties affecting crop productivity (for instance, soil texture, organic matter and cation exchange capacity), constitutes one of the most appropriate soil variables to characterize the management zones of a field. In the present study ECa measurements obtained with a Veris 2000 XA contact-type sensor and soil samples taken at 0-0.30m depth in two permanent pastures were used. The aim was to assess the spatial pattern of some soil properties, based on ECa measurements as ancillary information and a guided soil sampling. Relationships between ECa and some important soil properties were analyzed and, later, some maps were produced to visualize the spatial variability of the soil properties. Finally, homogeneous zones were delimited for attaining a site-specific management of the fields. Results showed that ECa is associated with some important soil properties and, consequently, can be considered as support information with the aim of obtaining data to be used to implement site-specific management (intelligent soil sampling or differential and optimal fertilization), in soils with permanent pastures and to contribute to the increased sustainability of the pasture grazing systems.