Cropping Systems for Perennial Ryegrass Seed Production: II. Minimum Tillage Systems for Changing Cultivars in Certified Seed Production

Few studies have been conducted to evaluate certified grass seed crop establishment under no-till systems. Four field studies were conducted near Corvallis, OR, between 1985 and 1989, to evaluate the acceptability of 1- and 2-yr no-till crop rotation systems between two perennial ryegrass (Lolium perenne L.) cultivars grown for certified seed production under the genetic purity requirements of Association of Official Seed Certifying Agencies (AOSCA). Four rotation systems were used: 1- and 2-yr red clover (Trifolium pratense L.), 1-yr meadowfoam (Limnanthes alba L.), and 2-yr meadowfoam-spring pea (Pisum sativum L.). Afterharvest residue from a diploid perennial ryegrass was either burned or flail-chopped (nonburned) before drill-seeding the rotation crops. A tetraploid perennial ryegrass followed after rotation crops to assess contamination from seedlings of the first perennial ryegrass (diploid) seed crop. For all rotation sequences, the number of ryegrass plants growing between planted rows and the percentage of diploid seed in the harvested tetraploid seed crop exceeded AOSCA seed certification standards. Burning the stubble did not reduce the number of volunteer seedlings to the level acceptable for seed certification. We concluded that 1- or 2-yr rotation sequences out of perennial ryegrass seed production using minimum tillage systems were not sufficient to meet the cultivar purity standards for production of certified seed, even when burning preceded establishment of the rotation crops. Also, burning ryegrass stubble prior to establishment of the rotation species had little effect on seed yield of the following ryegrass crop. Burning the stubble of the first-year ryegrass crop established after rotation species, however, improved the seed yield of the second-year crop. Contribution from the Oregon Agric. Exp. Stn., Tech. Paper no. 10662.