Soil Compaction, Both an Environmental and Agronomic Culprit: Increased Nitrous Oxide Emissions and Reduced Plant Nitrogen Uptake

With a burgeoning world population and growing demand for agricultural products, it will be necessary to strike a judicious balance between maintaining adequate N inputs and minimizing gaseous N losses in farming systems. Our objective in this study was to quantify the effects of soil compaction, N fertilization, and clay content on N2O emission from soil. Soil cropped to maize (Zea mays L.) was compacted by tractor wheel traffic or not compacted for consecutive years, and N fertilizer was applied at 0, 75, 150, and 300 kg N ha(-1) to both compaction treatments. Variability in clay content across the experimental plots allowed us to assess of the effects of texture on N2O response to compaction and N fertilization. Compaction, increasing N fertilization, and their interaction all significantly increased cumulative emissions of N2O during the growing season. There was a significant carryover effect, with higher N2O emissions observed in previously compacted soils in a subsequent year when soybean [Glycine max (L.) Merr.] was grown and no compaction or N fertilizer was applied. Nitrous oxide emissions scaled against plant N uptake showed significant positive response to both compaction and N fertilizer. Clay content did not significantly affect N2O emissions, but its role became apparent when the emissions were scaled by N uptake. This scaling amplified the deleterious effects of compaction on gaseous N losses from soil because compaction both increased N2O emissions and decreased yield and plant N uptake. In contrast, increasing N fertilizer increased both and therefore did not have as large an effect on the scaled N2O emissions.