Selected soil properties' variability and their relationships with yield in three Mississippi fields

For site-specific soil management to be effective, soil factors must vary within a field and potentially be limiting to crop production. The objectives of this two-year study were the following: (i) to determine the amount of variability in selected soil physical and chemical properties in three typical Mississippi fields and (ii) to determine which soil factor or factors were influencing crop yields. Three fields were sampled on a 1-ha grid and analyzed for pH,in water (1:1), Ca, K, Mg, Na, P, clay content, and elevation. Variability in the soil parameters, as evidenced by coefficient of variation (CV), differed among the soil factors measured, with pH having the lowest CV, and P having the highest CV. This was true in all the three fields for the two years of this study, with only one exception. Principal component analysis was used to group highly correlated variables into new and independent variables that could then be used in regression analysis. Stepwise regression using these latent variables found that the yield variability tended to be explained by the principal components representing topography, clay content, and P and K soil test levels, with topography having an influence in all the three fields. Relationships between yield and P and K fertility indicated that these two nutrients were not yield limiting. It is felt that identifying the topographic and soil texture effects on yield can be helpful in defining how site-specific soil management can be used to influence crop yield.