Soil Conductivity as a Measure of Soil and Crop Status—A Four-Year Summary

Animal manure can be an important resource providing soil avail-able N for plant needs, but determining the nutrient availability re-sulting from such amendments is difficult. A study was conducted to examine changes in electromagnetic induction (EMI) soil conductivity and available N levels during four growing seasons in relation to ma-nure or compost application and use of a green winter cover crop.With simultaneous soil samples, a series of soil conductivity maps of a re-search cornfield were generated using a global positioning system (GPS) and EMI methods. The Clay Center, NE, site was treated dur-ing a 10-yr period with a winter wheat (Secale cereale L.) winter cover crop (1CC) and no-cover crop (2CC). The site was split for sub-treatments of manure and compost at rates matching either the P or the N requirements of silage corn (Zea mays L.). Differences between the 1CC and 2CC treatments for values of NO3–N and water-fille