Tillage effects on rainfall partitioning and sediment yield from an ultisol in central Alabama

ABSTRACT:

Coastal Plain soils in the Southeast have been intensively cropped, traditionally managed under conventional tillage practices, and are susceptible to erosion. Conservation tillage systems have significant potential as a management tool for row crop production, especially on sandy surface soils of the Coastal Plain because they reduce soil loss and conserve water. We quantified rainfall partitioning and sediment delivery from a Plinthic Paledudult-Typic Hapludult soil complex (loamy sand surface) located in the Coastal Plain region of Alabama managed under conventional- and no-till systems for 10 years. Conventional till and no-till treatments were evaluated with and without surface (Black Oat, Avena strigosa Schreb.) residue (0-9600 kg ha⁻¹) and with and without paratilling (non-inversion subsoiling to 40 cm). Field plots (∼60 m²) represented eight treatment combinations, two tillage treatments (conventional till, no-till), two residue management treatments, residue removed or left in place (+R), and two non-inversion, deep tillage treatments, paratilled, non-paratilled, with each treatment combination replicated four times. Two 1-m² rainfall simulator plots were established on one tillage-residue-deep tillage treatment replicate. Each 1-m² plot received 2 h of simulated rainfall (50 mm h⁻¹). Runoff and sediment delivery were continuously measured from each flat, level-sloping 1-m² plot (slope = 1 percent). No-till plots had at least two times less runoff and four times less sediment delivery compared to conventional till plots. Runoff was greatest for conventional till, residue removed, non-paratilled plots (58 percent of the rainfall amount), and lowest for no-till, residue left in place, paratilled plots (4 percent of the rainfall amount). About 42 percent of the rainfall infiltrated in the conventional till, residue removed, non-paratilled plots (worst-case scenario) compared to about 96 percent for the no-till, residue left in place, paratilled plots (best-case scenario), resulting in only 2.8 days of water for crop use in conventional till, residue removed, non-paratilled plots and 6.9 days of water for crop use in no-till, residue left in place, paratilled plots (2.5-fold difference). Removing residue resulted in 18 percent more runoff as a rainfall percentage (18 percent less infiltration) for no-till plots and 25 percent more runoff (25 percent less infiltration) for conventional till plots, and accounted for 38 to 76 percent of the differences in runoff and sediment transported from no-till and conventional till plots. For conventional till and no-till plots, removing surface residue increased sediment yields by 1.5 and 7 times. Paratilling resulted in 10 percent less runoff as a rainfall percentage (10 percent more infiltration) for no-till plots and 26 percent less runoff (26 percent more infiltration) for conventional till plots. Compared to non-paratilled conventional till and no-till plots, paratilling caused runoff rates to increase at a slower rate, and increased steady-state runoff rates by 40 percent and 400 percent, respectively. Paratilling reduced bulk density (0 to 12 cm) and soil strength 0 to 50 cm) by at least 15 percent compared to non-paratilled treatments. Combining residue management and paratilling through conservation tillage in row-crop agriculture in the Coastal Plain region of Alabama reduces runoff and soil loss for conventional till and no-till systems by improving soil properties and maintaining infiltration, resulting in increased estimates of plant available water.