Thursday, 10 November 2005 - 9:15 AM
307-4

Predicting Spatial Yields from Potential Water Supplies.

Scott Staggenborg, Gerard Kluitenberg, and Lloyd Stone. Kansas State University, Dept of Agronomy, 2004 Throckmorton, Manhattan, KS 66506

In rainfed environments, soil water holding capacity influences grain yields. Therefore, the ability to spatially estimate soil water holding capacity will enhance a producer's ability to characterize spatial yield goals and yield stability. The objective of this study was to evaluate the influence of spatial soil water holding capacity as an indicator of spatial and temporal yield patterns. A previous study examined the use of pedotransfer function to estimate this information. Soil texture, organic matter, bulk density and water content at -33 kPa and -1.5 MPA were determined from fifty-three soil samples collected from a 63 ha field near Manhattan, KS. Plant available water (PAW) was calculated as the differences ins soil water contents at -33 kPa and -1.5 MPA. Soil water contents at -33 kPa and -1.5 MPA increased as silt (y = -0.2222x2 + 0.3685x + 0.0267; R2 = 0.9145), clay (y = -4.0044x2 + 1.5641x + 0.0155; R2 = 0.8896) and organic matter (y = -0.0521x2 + 0.2103x - 0.0472; R2 = 0.8104) increased and decreased as sand content increased (y = -0.1623x + 0.2098; R2 = 0.8892). Yield was determined at each sample site from yield monitor data for corn (4 yr) and soybean (1 yr) by summing the mass flow data in 21 m circles centered on the point. Yields had higher correlations to PAW in the corn (r=0.27) than the soybean (r=0.01) and increased in the corn as yields increased. These results suggest that under high yielding conditions, it may be more profitable to exploit spatial soil water information.

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