A small-plot experiment was made to assess the influence on dry-matter output from grass of a wide range of fertilizer nitrogen and defoliation interval treatments. There were five defoliation treatments, 22, 28, 45, 75 and 112-day regrowth intervals throughout the growing season each at six levels of nitrogen application, ranging by 300 kg increments from 0 to 1500 kg/ha/year.There was a marked interaction effect between treatments; a positive dry-matter response was maintained to a higher level of applied nitrogen with more frequent defoliation. In 2 years out of 3 maximum dry-matter yield was produced under a 75-day defoliation interval although the mean yield advantage over a 45-day defoliation system was only 11 %. Mean yield of digestible dry matter appeared to reach a maximum under a 45-day defoliation interval at 600 kg N/ha but at the lower levels of N the maximum yield was reached at the longest growth interval.Seasonal response to nitrogen under the 22-and 28-day defoliation systems measured as the increase in yield resulting from increased N at each cutting date reached its peak in July-August. Application for these short growth periods early and late in the growing season appeared to be a relatively inefficient use of nitrogen.The less frequently the sward was harvested and the higher the nitrogen application the greater was the reduction in ground cover as estimated by eye at the end of the growing season, this reached an estimated 25% reduction under 112-day defoliation at 300 kg N/ha/year.In relation to published figures nitrate content of herbage did not reach dangerous levels until nitrogen application reached levels beyond those at which maximum dry-matter yield was achieved.

Persistence and productivity of pastures containing mixtures of warm and cool‐season forages may be compromised by interspecific competition when growing periods overlap. An ability to predict the onset and termination of growth of component species would facilitate timing of management interventions to minimize harmful competition in mixed pastures. Experiments were undertaken in controlled environment to assess the use of accumulated temperature values to indicate development stages in three cool‐season grass species, and to evaluate the consistency of this relation under a range of temperature regimes that included variable exposure to below‐freezing temperatures. When grown under light and dark temperature regimes of 22.5 and 7.5, 17.5 and 12.5, 15.0 and 0.0, or 10.0 and 5.0°C, respectively, leaf appearance in Italian ryegrass (Lolium multiflorum Lam.), tall fescue (Festuca arundinacea Schreb), and tall wheatgrass [Elytrigia elongata (Host) Nevski] showed a close linear relationship with accumulated temperature, within each temperature regime. The interval between appearance of successive leaves on seedling mainstem (phyllochron) was increased by increased average daily temperature. In seedlings grown under a 15.0 and 0.0°C temperature regime, phyllochron was increased linearly by up to four 15‐h exposures to −5.0 or −7.5°C dark‐cycle temperatures in successive 24‐h periods. The effects of variation in mean daily temperature and of plant exposure to below‐freezing temperature on phyllochron should be considered if accumulated temperature is used to predict development stage of cool‐season grasses in the field.

Limited availability of herbage during the cool season creates a problem of a supply of nutrients for livestock producers throughout the southern Great Plains of the USA and, particularly, on small farms where resource constraints limit possible mitigating strategies. Six coolseason grasses were individually sown into clean-tilled ground, no-till drilled into stubble of Korean lespedeza [Kummerowia stipulacea (Maxim) Makino] or no-till over-sown into dormant unimproved warm-season pastures. The dry matter (DM) yields of mixtures of cool and warm-season herbage species were measured to test their potential for increasing cool-season herbage production in a low-input pasture environment. Only mixtures containing Italian ryegrass (Lolium multiflorum Lam) produced greater year-round DM yields than undisturbed warm-season pasture with all establishment methods. When cool-season grass was no-till seeded into existing warm-season pasture, there was on average a 0AE61 kg DM increase in year-round herbage production for each 1AE0 kg DM of cool-season grass herbage produced. Sowing into stubble of Korean lespedeza, or into clean-tilled ground, required 700 or 1400 kg DM ha )1 , respectively, of cool-season production before the year-round DM yield of each species equalled that of undisturbed warm-season pasture. Productive pastures of perennial cool-season grasses were not sustained beyond two growing seasons with tall wheatgrass [Elytrigia elongata (Host) Nevski], intermediate wheatgrass [Elytrigia intermedia (Host) Nevski] and a creeping wheatgrass (Elytrigia repens L.) · bluebunch wheatgrass [Pseudoroegneria spicata (Pursh)] hybrid. Lack of persistence and low productivity limit the usefulness of cool-season perennial grasses for overseeding unimproved warm-season pasture in the southern Great Plains.

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