Abstract
a USDA-ARS, George E. Brown, Jr., Salinity Lab., 450 West Big Springs Rd., Riverside, CA 92507-4617
b USDA-ARS, Water Manage. Res. Lab., 9611 S. Riverbend Ave., Parlier, CA 92648
* Corresponding author ( dcorwin{at}ussl.ars.usda.gov )
Received for publication March 22, 2002.
Crop yield inconsistently correlates with apparent soil electrical conductivity (EC a ) because of the influence of soil properties (e.g., salinity, water content, texture, etc.) that may or may not influence yield within a particular field and because of a temporal component of yield variability that is poorly captured by a state variable such as EC a . Nevertheless, in instances where yield correlates with EC a , maps of EC a are useful for devising soil sampling schemes to identify soil properties influencing yield within a field. A west side San Joaquin Valley field (32.4 ha) was used to demonstrate how spatial distributions of EC a can guide a soil sample design to determine the soil properties influencing seed cotton ( Gossypium hirsutum L.; ‘MAXXA’ variety) yield. Soil sample sites were selected with a statistical sample design utilizing spatial EC a measurements. Statistical results are presented from correlation and regression analyses between cotton yield and the properties of pH, B, NO 3 –N, Cl - , salinity, leaching fraction (LF), gravimetric water content, bulk density, percentage clay, and saturation percentage. Correlation coefficients of -0.01, 0.50, -0.03, 0.25, 0.53, -0.49, 0.42, -0.29, 0.36, and 0.38, respectively, were determined. A site-specific response model of cotton yield was developed based on ordinary least squares regression analysis and adjusted for spatial autocorrelation using maximum likelihood. The response model indicated that salinity, plant-available water, LF, and pH were the most significant soil properties influencing cotton yield at the study site. The correlations and response model provide valuable information for site-specific management.
Abbreviations: EC a , apparent soil electrical conductivity • EC e , electrical conductivity of the saturation extract • GIS, geographical information systems • GPS, global positioning systems • LF, leaching fraction • OLS, ordinary least squares • SP, saturation percentage • g , gravimetric water content • b , bulk density