Comparison of Grid Soil Sampling and E.C. Generated Zone Soil Sampling in a Highly Variable Flood Plain Soil.

The rapid adoption of remote sensing and other tools for predicting soil management zones within a production field has been observed in many areas of Texas. The producers utilizing these tools often question the mechanisms behind the measurements and how the developed zone management maps relate to both soil test data and yield. This field study utilized one primary location and two secondary fields to evaluate how direct current generated electrical conductivity (E.C>) data (Veris Technologies) and the subsequent zone management soil sampling data relates to soil test data collected on sub-hectare grid soil sampling. The primary study side is comprised of an irrigated 15 ha-1 field in the Brazos River floodplain near College Station, TX. The soils in the study location vary from deep clays to shallow clays over loamy sands historically cropped to corn (Zea mays), grain sorghum (Sorghum bicolor), or cotton (Gossypium spp.). The field E.C. data was collected by a Veris 3100 pulled through the field on 21.3m centers prior to the development of six management zones. Soil samples were collected from 10 discrete locations across the management zones, along with 18 define grid sampling points. Soil samples were collected at depths of 0-15, 15-30, 30-60, 60-90 and 90-120 cm. The shallow Veris E.C. data was highly correlated with 0-15 and 15-30 cm sand, clay, organic matter and Mehlich III extract K and Mg. The soil test properties for the lower depths and the relationships between cotton yield of the zone and grid fertilized areas will also be reported.