|Douglas Jr, Clyde|
Submitted to: World Fertilizer Congress of International Scientific Centre of Fertilizers
Publication Type: Proceedings
Publication Acceptance Date: 3/31/1997
Publication Date: N/A
Interpretive Summary: Nitrogen and phosphorus loss from agricultural fields is an important issue. Most of the runoff and erosion in the Pacific Northwest occurs during the winter months when rain falls on frozen soils or on snow on frozen soils. Tillage/crop residue management can have a big impact on runoff and erosion from agricultural fields. We need to know how tillage systems and crop residues left on the soil surface affect runoff and erosion and subsequently nutrient loss. This research utilizes rainfall simulation on frozen field soils to evalute the effect of four tillage/residue treatments on nitrogen and phosphorus in runoff and erosion. This information is important in our development of management systems to help control erosion in the wintertime rainfall regime of the Pacific Northwest
Technical Abstract: In Eastern Oregon and Washington, USA, greater than 60% of the annual precipitation occurs from November through April. Approximately 85% of the erosion in the Pacific Northwest (PNW) occurs during this time as a result of rainfall and snowmelt on frozen soil. Rainfall simulation was used to evaluate runoff and erosion from tillage and crop residue management treatments in 9 m by 1.5 m plots with frozen soils and/or snow on frozen soils in 1996 and 1997. Simulation was performed at two different locations in producers fields. Plots were located on a 26% slope on a north aspect in 1996 and a 14% slope on a west aspect in 1997. Stephens variety soft white winter wheat was seeded in each field. Tillage and residue treatments were moldboard plow (MP), chisel plow (CP), mow-plow-2100 (MP2), and mow-plow-6200 (MP6) kg residue kg/ha. The mow-plow system is where standing wheat stubble is cut with a harvester-header mounted on the front of a tractor and distributed to the side onto moldboard plowed ground, while a moldboard plow is being pulled behind the same tractor. Runoff samples were taken from each treatment on Feb. 5 and 7, 1996, and Jan. 15, 17 & 30, 1997, at ten min. intervals for 90 min. after start of runoff. Preliminary data analysis indicates that runoff nutrient loss was inversely related to the percentage of surface soil covered with crop residue. Soluble N and P concentrations increased in the order CP < MP6 < MP < MP2. Sediment N and P concentrations increased in the order CP < MP6 < MP2 < MP.