Understanding the impact of crop rotation and residue management in grass seed production systems on soil quality and, in particular soil C dynamics, is critical in making long-term soil management decisions supporting farm sustainability. The effects of a 6-yr rotation and residue management (high vs. low residue) on soil quality were investigated at three locations in Oregon, each contrasting in soil drainage classification. The crop rotations were continuous perennial grass seed production, grass/legume seed production, and grass/legume/cereal seed production. The grass species grown at each location were different and represented those most commonly produced in each environment; perennial ryegrass ( Lolium perenne L.), tall fescue [ Schedonorus phoenix (Scop.) Holub], and creeping red fescue ( Festuca rubra L.). All three grass seed crop rotations and residue methods maintained high soil quality in conventional or direct seeded soils, but under some situations, soil quality was higher with continuous grass rotation and high residue. Data suggest that straw removal for value-added use, like bioenergy production, can be accomplished in the Pacific Northwest Marine climate without appreciably affecting soil quality. Furthermore, grass seed cropping systems play an important role in soil C storage and enhancement, a valuable ecosystem service in this region where grass seed is produced on land that is not suitable for production of conventional crops that require better-drained soil. We conclude that by nature perennial grass seed crops promote high soil fertility and enriched soil C pools and consequently contribute to the tolerance of these systems to the use of less conservation-oriented crop management methods at times when crop loss could be potentially high. This attribute provides producers greater latitude in selecting soil and crop management options to address issues of soil fertility, pest, weed, or seed certification to minimize economic crop yield losses.
