Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 2, 2011
Publication Date: May 11, 2011
Citation: Griffith, S.M., Banowetz, G.M., Dick, R.P., Mueller Warrant, G.W., Whittaker, G.W. 2011. Western Oregon Grass Seed Crop Rotation and Straw Residue Effects on Soil Quality. Agronomy Journal. 103:1124-1131. Interpretive Summary: As grass seed crop field burning in western Oregon was phased-out, alternative non-thermal practices, such as post harvest straw residue removal or incorporation to the soil, and crop rotations were being developed. There is little information available on the practicality and impacts of non-thermal grass seed cropping systems on soil quality. Consequently, in 1992, the multidisciplinary non-thermal cropping systems project was initiated USDA-ARS (Corvallis, OR) at three diverse sites in the Willamette Valley, Oregon. This platform provided an excellent opportunity to evaluate soil quality indexes which are useful to aid agriculturists to identify early indicators of changes in soil management. Soil carbon is an important factor in soil quality. Understanding how it changes with respect to soil crop rotation or crop residue management is important to maintaining high agricultural sustainability. We found that soils of grass seed production systems in western Oregon are high in soil quality, rich in C, and improved over tilled conventional annual cropping systems of the same climatic zone. Temperature perennial grasses, unlike annuals, have characteristically extensive roots systems, and under Marine climate conditions remain biologically active year-around, thus continuously interacting with the soil ecology. Increasing C inputs (e.g., residue return) can enrich the soil system further. Data indicates that straw removal for value-added use like bioenergy production or livestock feed can be accomplished without appreciably affecting soil quality. Furthermore, grass seed cropping systems play an important role in soil carbon (C) storage and enhancement, a valuable ecosystem service in this region where grass seed is produced in on land that is not suitable for production of crops.
Technical Abstract: Little is known about the impact of crop rotation and post-harvest residue management on the agricultural sustainability of conventional grass seed cropping systems in the Willamette Valley of western Oregon, U.S.A. The effects of a six-year rotation (continuous grass versus diverse crop species rotation), and post-harvest residue management (straw remaining or removed) on soil quality were investigated at three locations, each contrasting in soil drainage classification. The crop rotations were continuous grass seed production, grass/legume, and grass/legume/cereal. The species of grass grown at each site were different and represented those most commonly produced in each environment. They included perennial ryegrass, tall fescue, and creeping red fescue. Residue treatments included low residue (grass straw removed by raking and bailing) versus high residue (flail chopped onto the field). All grass seed crop rotations maintained high soil quality under conventional tillage and each residue treatment, but under some situations, soil quality was enhanced with continuous grass rotation and high residue management, particularly under moderately drained soil conditions where tall fescue seed was produced. These studies suggest that straw removal for value-added use like bioenergy production or livestock feed can be accomplished without appreciably affecting soil quality. Furthermore, grass seed cropping systems play an important role in soil carbon (C) storage and enhancement, a valuable ecosystem service in this region where grass seed is produced in on land that is not suitable for production of crops that require better-drained soils. Western Oregon’s marine climate and poorly drained soils offer a unique environment to study crop production and soil quality due to the mild temperatures and high amounts of annual precipitation often associated with semi-flooded field conditions. No such climatic and soil conditions like this exist elsewhere in the world.