Midwest Cropping System Effects on Soil Properties and on a Soil Quality Index

Cropping systems may improve or decrease soil quality depending on the specific crop rotation, nutrient amendments, and tillage practices employed. We conducted this study to determine the effect of six cropping systems in the Wisconsin Integrated Cropping Systems Trial on soil properties aft er 18 yr of continuous treatments. We sampled soils (0-5 cm and 5-20 cm depths) following the corn (Zea mays L.) year of three grain-based systems (continuous corn and two grain rotations), aft er both corn and alfalfa (Medicago sativa L.) in two forage-based systems (organic and conventional), and in grass-legume pasture. Extractable P and K, pH, total organic carbon (TOC), total N, active soil C, potentially mineralizable nitrogen (PMN), water-stable aggregates (WSA), bulk density (BD), penetrometer resistance, and total microbial biomass (TMB) were measured, and the Soil Management Assessment Framework (SMAF) soil quality index (SQI) was determined. The pasture (0-5 cm) was significantly better than all other systems in almost all soil quality indicators and had the highest SQI (96 vs. mean of 87 for others). The alfalfa-based systems had more total N, TOC, active C, PMN, and WSA and higher BD in one or both depths than did the grain-based systems but SQIs were not different. Among the grain systems, there was less variation and few significant differences were observed. While there were significant differences among systems for most soil properties, a SQI based on a composite of seven soil properties, showed few differences on this well managed, productive, prairie-derived soil.