What Are the Impacts of Long-Term Tillage Systems on Soil Compaction in Nebraska?.

Soil compactibility (soilÕs susceptibility to compaction) could vary among tillage systems due to differences in soil organic C concentration and related soil properties. For example, a few studies have suggested that no-till management may reduce soil compactibility by increasing soil organic C concentration relative to conventionally tilled systems. More data from different soils, crop rotations, and climates are needed to understand how tillage systems affect soil compactibility. Reduced soil compactibility is important to root growth and overall crop production. The objectives of our study were to determine Proctor bulk density (soil compactibility) on two ongoing long-term (>30 yr) tillage experiments and study its relationships with changes in soil organic C concentration among tillage systems in the western Corn Belt. The long-term tillage experiments are located at Haskell Agricultural Laboratory (HAL) near Concord, NE, and was established in 1985 and managed by Charles A. Shapiro, while the experiment at Rogers Memorial Farm (RMF) near Lincoln, NE, was established in 1981 and managed by Paul Jasa and Stuart Hoff. At the HAL site, there were four treatments: 1) moldboard plow, 2) disk, and 3) no-till under corn-soybean rotation. At the RMF site, treatments were 1) chisel plow, 2) moldboard plow, 3) no-till, and 4) disk under corn-soybean rotation. Proctor test was conducted for samples collected from 0 to 15 cm and 15 to 30 cm soil depth. Data showed that Proctor bulk density was generally higher under no-till than under plow till, but differences among no-till, disk, and reduced tillage were not significant. The critical water content (the water content at which maximum compaction occurs) increased with a decrease in tillage intensity. The Proctor bulk density decreased as the soil organic C concentration increased with a reduction in tillage intensity. Overall, no-till management can reduce soilÕs susceptibility to compaction in corn-soybean rotations compared with plow tillage, but it may differ from reduced till.