Conservation Practices in Western Oregon Perennial Grass Seed Systems: II. Meadowfoam Rotation Crop Management

Rapid changes in practices used to produce perennial grass seed crops in the U.S. Pacific Northwest region and shortened lengths of time that perennial grass seed fields remain in production have increased the need for additional rotation crops that are adapted to the poorly drained soils found in western Oregon. This research was conducted at three sites to determine ways to manage meadowfoam (Limnanthes alba Hartw. ex Benth.) as a component in perennial grass seed rotation systems. Experiments were conducted in 1997, 1998, and 2001 to investigate combinations of spring-applied herbicide and N fertilizer and times of applications, direct-seeded and conventional tillage establishment methods, and previous crop residue management on meadowfoam seed yield, seed oil concentration, and oil yield. No spring-applied fertilizer or herbicide produced responses for all yield components as great as or greater than any other treatment combination. Direct-seeded meadowfoam yielded more oil than the conventional establishment treatment. There was no effect of residue management amounts from grass seed grown in the previous rotation sequence on meadowfoam production; however, maximal residue management, especially if used in combination with direct-seeded meadowfoam, should reduce annual soil erosion. Meadowfoam is suited to low-input production and is adapted to the use of conservation practices including direct seeding and maximal residue management in perennial grass seed systems. THERE has been a rapid change in the practices used to produce perennial grass seed crops in the U.S. Pacific Northwest. Because of air quality and public safety concerns, postharvest straw burning was reduced to 10% of the historic high by 1998 in maritime western Oregon. Also, a majority of the grass seed crop now being produced is private turf-type cultivars with increased market demands for new cultivars, in contrast to earlier times when public forage cultivars dominated the market (Meyer and Funk, 1989). As a result, the length of time that seed fields remain in production has shortened to as few as 3 or 4 yr, compared with times past when stands were established for 10, 20, or more years. Because grass seed crops readily shatter when reaching maturity, added pressures have been placed on seed growers to meet genetic purity standards when changing cultivars of the same grass species (Mueller-Warrant et al., 1995; Young and Youngberg, 1996). Grass seed crops are adapted to the poorly drained soils found throughout the southern Willamette River basin of western Oregon. The economic value of grass seed crops combined with limited choices of alternative rotation crops that are adapted to these conditions greatly limit the rotation crop options available to growers. When rotation crops are used, the primary selections have been white clover seed (Trifolium repens L.) or wheat (Triticum aestivum L.). Meadowfoam has emerged as an additional rotation crop option for perennial grass seed production systems. This crop is a small herbaceous winter–spring annual that grows 20 to 401 cm tall. Native meadowfoam was originally found in vernal pools in northern California and southern Oregon pastures, with its name derived from the white blooming canopies of plants that give the image of white foam covering the ground. Flowering stems arise in late winter to early spring from a rosette. The leaves are pinnately dissected with incisely toothed, lobed, or parted stems. The fibrous root system penetrates the soil to a depth of 150 cm. Vegetative growth is terminated in late spring when temperatures rise. Meadowfoam favors low temperatures during flowering and seed formation (Pearson, 1983; McGahuey, 1986; Franz and Jolliff, 1989; Franz et al., 1992), which can be problematic for pollinator bee (Apis mellifera L.) activity needed to ensure pollination (Jahns and Jolliff, 1990). Meadowfoam damaged by springtime-applied herbicide is characterized by buttonrather than pear-shaped buds that either do not open or have shriveled or distorted flower petals (O.G. Hoffman, personal communication, 2005). Meadowfoam produces high quality oil comprised of C20 and C22 fatty acids, with D 5 unsaturation (Miller et al., 1964; Higgins et al., 1971; NikolavaDamyanova et al., 1990). These oil characteristics give this crop potential for use in the production of lubricants, cosmetics, rubber additives, and plastics (Hirsinger, 1989; Burg and Kleiman, 1991), or biodiesel. There is limited information available describing how meadowfoam would respond in perennial grass seed production systems. Perennial grass seed crops typically require N fertilizer applications to achieve optimal economic yields, but there is a growing amount of evidence that excess residual N in the soil following seed production may have an adverse affect on meadowfoam yields (G.D. Jolliff, personal communication, 2005). Meadowfoam seed yield and seed oil USDA-ARS, National Forage Seed Production Research Center, 3450 SW Campus Way, Corvallis, OR 97331. The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the USDA or the ARS of any product or service to the exclusion of others that may be suitable. Received 15 Dec. 2005. *Corresponding author ([email protected]). Published in Agron. J. 98:1501–1509 (2006). Cropping Systems doi:10.2134/agronj2005.0342 a American Society of Agronomy 677 S. Segoe Rd., Madison, WI 53711 USA Abbreviations: H1F1, herbicide plus fertilizer applied at the normal time; H1F2, herbicide applied at the normal time but without fertilizer; H1Fd, herbicide applied at the normal time with fertilizer application delayed; H2F1, fertilizer applied at the normal time without herbicide; H2F2, no herbicide or fertilizer applied; HdF1, fertilizer applied at the normal time but the herbicide application delayed; HdF2, herbicide application delayed and no fertilizer applied. R e p ro d u c e d fr o m A g ro n o m y J o u rn a l. P u b lis h e d b y A m e ri c a n S o c ie ty o f A g ro n o m y . A ll c o p y ri g h ts re s e rv e d . 1501 Published online October 3, 2006