Spatial variability on soil pH gradient: a case study in vineyards
Scannavino, JR; Perez-Kuroki, AJ; Ghobakhlou, A; Sallis, P; Shanmuganathan, S; Cruvinel, PE
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Soil pH gradient is an indicator of microorganisms and bacteria population in root zones with effects on the growth of plants, such as grapevine (Fernandez-Calviño, 2010). The pH gradient analysis can be used to determine management strategies – root development and soil quality - to reach the most suitable balance for a specific vineyard. Custom built management strategies lead to high vineyard productivity and avoid undesirable environmental impacts caused by surplus-nutrient runoff into streams, ground water reservoirs and the micro-fauna population. However, the pH gradient in agricultural soil varies in a spatialtemporal way, making its studies difficult and timeconsuming. Given this scenario, the interpolation techniques have been used to build spatial maps of soil attributes by sampled locations values. Such spatial maps give the soil condition of whole agricultural field, allowing the estimation of non-sampled locations values. A common methodology of spatial interpolation is the kriging, a popular statistical method that is grounded within the geostatistics field. Exemplifying, the Figure 1 shows the 2D maps of soil macronutrients spatial variability analyzed by kriging method (Cruvinel, 1999). The objective of this study is to evaluate the spatial variability of pH gradient in soil based on the use of geostatistical mapping obtained by pH measurements and semi-variogram models. For the analysis of the pH gradient, the soil samples were collected in 58 points considering three different horizons:~5-15 cm, ~15- 25 cm, and ~25-35 cm depths. To minimize error the soil pH gradient analyses were duplicated in the vineyard soils and at laboratory. The preliminary results have shown the existence of a significant pH gradient with values in the top layers of soil lower than the bottom layers. Therefore the pH level from top layers was more acid than the bottom ones. This study is part of “Enometrica Project”, which is an ongoing research project on micro-climate monitoring and modelling in vineyards and orchards to positively influence crop management and resulting quality production.