Submitted to: Journal of Production Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/1999
Publication Date: N/A
Interpretive Summary: Grain-yield mapping has demonstrated to farmers that much of the yield variability within fields is associated with water-related soil and landscape properties. Inexpensive and accurate methods for measuring and mapping water-related soil properties within fields are needed and would greatly help those interpreting yield maps and developing plans for site- specific management. The objective of this research was to evaluate the relationship of grain yield and soil electrical conductivity (EC)on claypan soils. We found that differences in soil EC were related strongly to the depth of topsoil. We also found that within-field differences in corn and soybean grain yields were related to soil EC measurements. Areas within fields prone to the risk of yield reduction from deficient or excessive water were apparent from the soil EC measurements. Without irrigation, management to improve production on high soil EC areas (areas with low topsoil depth) might include increasing water infiltration and water conservation by using conservation tillage methods and/or planting more drought-tolerant crops like soybean or grain sorghum. Management options for improving production in areas of low soil EC where runoff water was at times excessive might include improving surface and/or subsurface drainage. We feel the trend of decreasing corn grain yield with increasing soil EC is a common occurrence on claypan soils and has the potential of being a basis for variable-rate nitrogen application. The results of this study will benefit farmers and crop consultants by helping them understand variations in within-field crop production. As a result, they will be able to develop improved site-specific management plans that are more efficient and environmentally friendly.
Technical Abstract: An inexpensive and accurate method for spatially measuring water-related soil properties associated with variability in grain crop production would greatly enhance interpretation of yield maps and improve planning for site- specific management. This study was conducted to investigate the relationship between soil electrical conductivity (EC) and grain yield on claypan soils (Udollic Ochraqualfs). Grain yield data for 13 site-years over four claypan soil fields were obtained by combine yield monitoring and soil EC was measured by a mobile, electromagnetic induction (EM) sensor. The relationship between grain yield and soil EC was examined for each site-year in a scatter plot. A boundary line function was fit to the upper edge of data in the scatter plots. A significant relationship between grain yield and soil EC (boundary lines with r**2 > 0.25 in 9 out of 13 site- years) was apparent, but climate, crop type, and specific field information nwas needed to interpret the relationship. Each site-year was characterized into one of four condition categories: Condition 1) site-years where yield variation was mostly unrelated to soil EC (meaning soil water variation within the field had little influence on yield); Condition 2) site-years where yield increased with decreasing soil EC (meaning soil water was mostly deficient over the field); Condition 3) site-years where yield mostly decreased with decreasing soil EC (meaning soil water was mostly excessive over the field); and Condition 4) where yield was less at low and high soil EC values and higher at some mid-range values of soil EC (meaning soil water was excessive, deficient, and optimal within the field). Soil EC data on claypan soils can help diagnose likely water-related problem areas (i.e. water deficiencies and excesses) affecting grain crop production.