Delineating site-specific management zones on pasture soil using a probabilistic and objective model and geostatistical techniques

In recent years, different algorithms have been utilised to delineate management zones, areas with similar properties, within agricultural fields. However, there are few applications in pasture systems. In this work, the formulation of the Rasch model, as an objective and probabilistic technique to integrate different soil properties, provided measures of pasture soil fertility that were used to analyse spatial variability throughout a field. To illustrate the proposed approach, a case study was conducted in a pasture field. Ten soil properties (sand, silt, and clay contents, moisture content, pH, organic matter, nitrogen, phosphorus, potassium, and soil apparent electrical conductivity) were measured at 76 locations in a pasture field; after their integration in the model, a classification of all sampling locations according to pasture soil fertility was determined, and the influence of each soil property on the soil fertility was highlighted, with the soil moisture, clay, and sand contents and nitrogen being the most influential properties and the silt content being the least influential property. Then, an ordinary kriging algorithm was used to estimate pasture soil fertility throughout the field, and homogeneous zones were delimited from the kriged map. The possibility of using probability maps to determine management zones and provide information for hazard assessments of pasture soil fertility in the field was also shown. Finally, NDVI data at each sampling location were utilised to verify the differences between the management zones.