Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2005
Publication Date: January 21, 2006
Citation: Williams, J.D., Wuest, S.B., Schillinger, B.F., Gollany, H.T. 2006. Rotary subsoiling newly planted winter wheat fields to improve infiltration in frozen soil. Soil & Tillage Research 86 (2006) 141-151. Interpretive Summary: Producers of dryland crops in the Pacific Northwest (U.S.A.) continue to seek new or improved soil and water conservation techniques. Once such practice is subsoiling - the practice of ripping continuous channels or creating pits using a rotary subsoiler to penetrate plow-pans and improve root penetration of, and water infiltration into the soil profile. When water infiltrates into the soil profile, it becomes soil water and contributes to crop production, and it does not runoff and carry topsoil from a field. Data for this experiment was collected during six years of the seven-year period between 1996 through 2003. The rotary subsoiler created 16-inch deep pit with a 1.0-gallon capacity every 7.5 ft^2. Runoff and erosion were not recorded at any location because of natural rainfall over the seven-year period. Wheat grain yield was not improved or damaged due to subsoiling steep slopes. Over-winter water storage was improved by rotary subsoiling in two of the six-years of the experiment. In 2003, we simulated rainfall using a machine specifically developed for this purpose. Rotary subsoiling significantly reduced runoff during the final 50 min of rainfall simulation. Erosion was significantly reduced only during the 20 to 45 min period after runoff had begun. Based on the results of rainfall simulation, rotary subsoiling offers valuable soil and water saving benefits during intense, short duration rainstorms to farmers of newly fall planted wheat fields, fallowing a year of fallow, on steep slopes.
Technical Abstract: Ripping continuous open channels or creating pits in the soil surface penetrates plow-pans for the purpose of improving root penetration of, and water infiltration into the soil profile. In the Pacific Northwest, precipitation ranges from 150 - 350 mm, and falls predominately from November to March creating sever runoff and erosion from frozen or partially frozen soils. Experiments were conducted in six of seven years from 1996 through 2003 at six on-farm sites in eastern Washington to determine if rotary subsoiling reduced runoff and erosion, improved soil water storage, or affected crop yields. There were two treatments, rotary subsoiling and control. The rotary subsoiler created 40 cm deep pit with a4-L capacity every 0.7 m^2. Runoff and erosion did not occur in either treatment at any location because of natural rainfall over the 7-year period. No differences in wheat grain yield were found between subsoiled and control plots when averaged over six years. Rotary subsoiling increased water stored over winter (P<0.05) in 2 of 6 years. In 2003, rainfall was simulated for approximately three hours at a rate of 18 mm/hr on both subsoiled and control plots to determine runoff and erosion responses. Rotary subsoiling significantly reduced runoff during the final 50 min of rainfall simulation. Erosion was significantly reduced only during the 20 to 45 min period after runoff had begun. Rotary subsoiling can reduce runoff and increase water stored in the soil profile, and, during short duration, intense rainstorms, it provides valuable soil-saving benefits, in fall planted wheat fields on steep slopes, following summer fallow.