Conventional Vs Low External Input Cropping Systems: Soil Biology and Nutrient Cycling.

Low external input (LEI) systems have been proposed as a solution to reducing dependency on artificial fertilizers and reducing negative environmental impacts associated with conventional farming systems. A long-term cropping experiment located in Central Iowa was used to compare two treatments: 1) an inorganically-fertilized, 2-year corn-soybean rotation (conventional system, characteristic of the Midwestern United States), and 2) a manure-fertilized, 4-year corn-soy-oat/alfalfa-alfalfa rotation (our LEI system). Previous studies demonstrate consistent increases in yield and nitrogen cycling efficiency in the LEI system, and suggest a healthier soil in the LEI versus the conventional system. We present differences in biological indicators of soil health between conventional and LEI systems – including soil mesofauna, earthworms, and microbial biomass – and attempt to link these indicators to differences in yield and nitrogen cycling efficiency.