Wednesday, November 15, 2006

Evidence for Wind-Driven Rain Erosion on Sunflower Stubble Land in the Northern Great Plains.

Stephen Merrill, Ted Zobeck, Donald Tanaka, Simon Van Donk, Lawrence Hagen, Joseph Krupinsky, Brenton Sharratt, and John Stout. USDA-ARS, PO Box 459, Mandan, ND 58554

Soil-crop production systems in the northern Great Plains have undergone species diversification to include those with non-durable residues. To assess hazards when lands with such crops are tilled or fallowed, a wind erosion study was established in central North Dakota on silt loam soil (Haplustoll) that had no-till sunflower in the previous season. April tillage treatments consisting of no-till (NoT), single pass disking (MedT), and two pass heavy disking with rotary harrow (MaxT) were followed by chemical fallow with glyphosate. Soil losses were measured with BSNE-type sediment samplers in square 1.4 ha replicate plots. The majority of the 3- to 10-day collection periods appeared to be largely unaffected by rainfall. Soil losses for the relatively dry top 3 windstorm periods in 2003 averaged 3.3, 12.7 and 46.5 kg/m for NoT, MedT, and MaxT treatments, respectively; MedT:NoT and MaxT:NoT ratios were 3.8:1 and 14.1:1, respectively. Soil losses (and ratios of tilled to NoT losses) for a rain-affected period in May 2003 were 1.8, 4.4 (2.4:1) and 3.7 kg/m (2.1:1) for NoT, MedT, and MaxT treatments, respectively. Comparable figures for a rain-affected period in Aug. 2004 were 2.5, 2.9 (1.2:1), and 3.9 kg/m (1.6:1). We hypothesize that wind-driven rain erosion (WDRE) contributed to soil losses during periods when heavy rains and strong winds occured together. Reductions in differences of MaxT to NoT and MedT to NoT ratios during rain-affected periods are taken as evidence of WDRE occurence. Wind tunnel studies have shown that WDRE results in higher saltation trajectories than dry erosion. Transport by WDRE, being initiated by rainsplash emission, is less dependent on wind energy than dry erosion and is evidently less sensitive to standing residue and roughness. It appears that WDRE partially overcame protective effects of residues in NoT and roughness in MedT here. We speculate that WDRE could accelerate erosion on wind-exposed summit positions on conservation-tilled lands currently considered less vulnerable to water erosion.

Handout (.pdf format, 817.0 kb)