CROPPING SYSTEMS FOR PERENNIAL RYEGRASS SEED PRODUCTION .2. 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 held studies were conducted near Corvallis, OR, between 1985 and 1989, to evaluate the acceptabili ty of 1- and 2-yr no-till crop rotation systems between two perennial ryegrass (Lolium perenne L.) cultivars grown for certified seed produc tion 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 (Limnanth es alba L.),and 2-yr meadowfoam-spring pea (Pisum sativum L.). After-h arvest residue from a diploid perennial ryegrass was either burned or flail-chopped (nonburned) before drill-seeding the rotation crops. A t etraploid perennial ryegrass followed after rotation crops to assess c ontamination from seedlings of the first perennial ryegrass (diploid) seed crop. For all rotation sequences, the number of ryegrass plants g rowing between planted rows and the percentage of diploid seed in the harvested tetraploid seed crop exceeded AOSCA seed certification stand ards. Burning the stubble did not reduce the number of volunteer seedl ings to the level acceptable for seed certification. We concluded that 1- or 2-yr rotation sequences out of perennial ryegrass seed producti on using minimum tillage systems were nor sufficient to meet the culti var purity standards for production of certified seed, even when burni ng preceded establishment of the rotation crops. Also, burning ryegras s stubble prior to establishment of the rotation species had little ef fect on seed yield of the following ryegrass crop. Burning the stubble of the first-year ryegrass crop established after rotation species, h owever improved the seed yield of the second-year crop.