Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 24, 2009
Publication Date: June 2, 2009
Citation: Bartholomew, P.W., Williams, R.D. 2009. Establishment of Italian ryegrass (Lolium multiflorum Lam.) by self-seeding as affected by cutting date and degree of herbage removal in spring in pastures of the southern Great Plains of the United States. Grass and Forage Science. 64(2):177-186. Interpretive Summary: Most natural or improved pasture in the southern great plains is comprised of warm-season grasses that do not grow during the cooler months of the year. Each year livestock producers throughout the southern plains have to overcome problems of shortage of feed for their stock during the months of October to March. Farmers commonly provide cool-season feed supplies in the form of home-produced hay, purchased feedstuffs or as grazed winter cereal or forage grass. The need for winter feed imposes a cost burden on all livestock producers, but especially on small and limited resource farmers. Home-grown cool-season pasture for grazing is likely to provide the least costly method of winter feeding, but most small livestock producers do not have the field equipment necessary for cultivation and planting of annual cereal crops, and cool-season perennial pasture grasses do not persist well in the southern plains environment. Italian ryegrass is an annual cool-season pasture grass that is productive in the southern plains and can produce seed and may regenerate itself from year to year, without the need for cultivation and sowing. We carried out experiments with Italian ryegrass to examine how the timing of harvest and the proportion of the crop harvested would affect available of forage and the production of necessary seed for re-establishment of a productive crop in the following year. Although we found that ryegrass could reseed itself for up to two years after initial sowing, the amount of seed needed for establishment of a productive crop varied widely from year to year. The success of self-seeding appears to depend on the weather conditions during July and August, after seeds have been shed, and on the survival of seed until the cool temperatures of fall arrive. We estimated that in just over 40% of cases a self-seeded crop would fail to establish and concluded that over time any cost savings with self-seeding are likely to be offset by its unreliability, so that annual planting will be the more effective method of re-establishment of ryegrass.
Technical Abstract: Annually-sown cool-season small grain cereals can provide a valuable source of cool-season feeding for livestock in the southern Great Plains of the USA, but for many farmers limited access to field equipment for cultivation and planting is an obstacle to their use. Italian ryegrass (Lolium multiflorum Lam.) [IRG] can persist through volunteer seeding and may offer an alternative source of cool-season herbage. The effects of initial harvests in mid-April, early-May or mid- to late-May following planting, and of partial-harvest treatments that removed an average 0.57, 0.73 or 1.00 of standing crop, on seed deposition, seedling reestablishment and forage yields of IRG were measured. Delay in initial harvest reduced seed production, seed deposition, 1000 seed weight and eventual seedling re-establishment. Partial harvest did not compensate for reduced seed deposition arising from late harvest. Seedhead and seed numbers required to achieve a self-seeded target population of 500 established seedlings m-2 ranged from 885 to 5650 seedheads m-2 and 3360 to 5850 deposited viable seeds m-2. Volunteer seeding showed an establishment failure rate of 0.43, indicating that self-seeded IRG will need periodic resowing. Any economic benefit derived from self-seeded IRG will depend heavily on the success of re-establishment of the volunteer crop.