Spatial Relationship Between Soil Electrical Conductivity and Soybean Grain Quality in the Argentinean Pampas.

Apparent electrical conductivity [ECa] of the soil profile can be used as an indirect indicator of a number of soil physical and chemical properties. We hypothesize that the ECa in combination with spatial analysis of soybean crop properties, can be used to understand the variability of protein and oil contents in soybean grains within a field. The objective of this work was to characterize the spatially relationship between soybean grain composition and soil properties. ECa data were collected with a coulter-based sensor [Veris 3100] on two fields of the Argentinean Pampas [Mercapire:Lat: -33.522, Lon: -62.910; San Esteban:Lat: -33.524, Long: -62.763]. In both fields, the soils are excessively drained with high sand content, their use is limited by low moisture retention and rainfall. Soil samples were taken at 30 and 90 cm deep in 8-16 sampling sites to determine soil properties. Plant samples were obtained from the same sampling sites to determine biomass, grain number and weight, and grain quality. Correlations of ECa with sand content and soil organic matter contents [MO] were generally highest and most persistent across two fields and ECa data types. Crop properties [Biomass, grain number and weight] were strongly related to ECa in both fields. Regressions estimating soil fine fraction and MO as a function of ECa90cm across two study fields were reasonably accurate [r²>0.6]. Areas of high ECa generally have a higher content of clay, loam and MO. The regression analysis indicated that ECa90cm explain soybean protein and oil concentration more consistently than ECa30cm. In general, areas of lower ECa90cm have a higher oil content. Zones with higher content of clay, loam and MO have a higher biomass and grain number and weight. These relationship, suggest that spatial variability of ECa can be an indicator of the spatial distribution of soybeans protein or oil concentration