Estimate of Soybean Yield with Site Property for Delineation of Management Zones.

The spatial variability of crop yield is related to terrain attributes and to physical- chemical properties of the soil. The objective of this study was to determine if the site properties (topography and soil apparent electrical conductivity; ECa) can allow estimating the spatial variability of soybean yield to delineate management zones in commercial fields. The research was carried out in a 37 ha field located in southeastern Cordoba Province, Argentina (33°31.285'S; 62°53.626'W). The field was composed of different soils (Entic Haplustoll and Typic Haplustoll). Soil ECa measurements were made using the Veris 3100® (Veris 3100, Division of Geoprobe Systems, Salina, KS). Elevation dates were collected at the same times that ECa data, using a differential GPS (vertical accuracy of 3–5 cm). A yield monitor coupled to a harvester was used to quantify the soybean yield during three years (soybean campaign 2005/06- 2007/08 and 2008/09). Multiple regression analysis with a backward variable selection with a significance level of 0.15, to eliminate variables (SAS, 2006) was used to estimate the spatial behavior of soybean yield. Models explained and significantly estimated (p <0.05) soybean yield variability for each year and the average of the three years (temporal model stability). The ECa and terrain elevation showed highly significant correlations (p <0.05) with the contents of clay, organic material, P-bray and pH. The ECa and terrain elevation are useful tools for characterizing the spatial variability of soil and delineate management zones with different soybeans yield potential. Therefore, Precision Agriculture provides the opportunity to apply differential agronomic practices, hence allows increasing the efficient use of inputs, improving profitability and the protection of the environment. Key words: spatial variability, Precision Agriculture, management zones.