Impact of Thirty Four Years of Tillage and Cover Crop Management on Soil Physical Properties.

Soil physical properties are significant soil quality indicators which experience gradual improvement under conservation agriculture. Previous short-term studies revealed inconsistent results on the impact of conservation agriculture on soil physical properties. The main objective was to investigate the long-term impacts of cover crops and no-tillage on soil physical properties and their relationships with soil water availability and cotton productivity. We collected our data from a cover crop, N rate, and tillage experiment conducted on cotton continuously on a Lexington silt loam at Jackson, TN for 34 years. The combinations of no cover crop, hairy vetch, and winter wheat with two tillage systems of no-tillage (NT) and conventional tillage (CT) were used in this study. Soil samples were collected in four replicates from 0-15cm and 15-30cm soil depths. Soil physical properties, including bulk density, total and macro-porosity, gravimetric moisture content, penetrability, particle size distribution, aggregate stability and size distribution, water retention, water infiltration and hydraulic conductivity, were measured and analyzed statistically as an RCBD split-split plot design. Bulk density values for CT immediately before the annual tillage did not differ significantly (P>0.05) from NT. In general, soil aggregate stability, field capacity moisture, and cumulative infiltration  under NT and cover crops showed significantly higher mean values (P<0.05) compared to CT and no-cover crops, respectively. Cone penetrability shows a higher spatial variability in NT compared to CT. However, penetrability was not significantly different between tillage managements. First year results are in accordance with previous studies indicating that in long term NT management, the ideal improvement in soil physical properties obtained whenever it is combined with cover crops and in particular with nitrogen fixing cover crop (hairy vetch) even with lower inorganic N fertilization.