Cropping Intensity Effects on Physical Properties of a No‐till Silt Loam

No-till cropping systems in the semiarid West have the potential to improve soil physical properties by increasing cropping intensity and crop diversity. An investigation at Akron, CO, compared soil conditions in winter wheat (Triticum aestivum L.)-summer fallow (WF) plots with soil conditions in wheat-corn (Zea mays L.)-fallow (WCF), wheat-corn-sunflower (Helianthus annus L.)-fallow (WCSF), wheat-corn-millet (Panicum miliaceum L.) (WCM), and a perennial grass/legume mix. The study began in 1990. Bulk density, pore size distribution, and saturated hydraulic conductivity were measured 7, 11, and 15 yr after inception. Bulk density in the grass plots decreased from 1.39 to 1.25 Mg m -3 in 15 yr. Bulk density in the annually cropped plots decreased from 1.38 to 1.30 Mg m -3 during the same time period. The pore size distribution became more uniform among the cropped treatments 15 yr after the start of the experiment. Saturated hydraulic conductivity increased in the grass plots from 27 mm h -1 to 98 mm h -1 in 15 yr. Saturated hydraulic conductivity in the annually cropped plots increased from about 14 to about 35 mm h -1 during the same period. The results from this study show that improving soil physical properties by cropping system alone may take many years. Perennial vegetation may be more effective than annually cropped systems at improving soil physical conditions because of less surface compaction from planting operations and the apparent ability of perennial root systems to create a more stable, continuous pore network.