1. Seed production stands of S 37 cocksfoot were obtained with varying plant densities by utilizing two drill widths, removing sections of drill, or over-sowing drilled material. All density treatments were operative at two levels of N, 87 or 174 lb. N per acre per annum.2. Tillers in selected quadrats were labelled at monthly intervals during autumn and/or winter for 3 years. Performances of tiller populations were assessed from these quadrats.3. Seed yields were increased in many cases by reducing plant density from a continuous drill pattern. Increased plant density reduced yields. With plant communities on a 1 ft. square arrangement at the high level of nitrogen, an increase of 33%, or 243 lb. seed, per year over a 3-year period was obtained compared with continuous rows at any level of N. The yield of gapped stands increased over the 3-year period, whilst the yields of continuous rows dropped in the final year.4. Nitrogen significantly increased the yield of cocksfoot, except in the third year, by increasing the weight of seed per ear.5. Tiller numbers per quadrat increased in most treatments over the course of the experiment, both within years and from year to year; seasonal peaks of tillering were apparent. The effect of N on tiller numbers differed each year, presumably due to the state of the populations when the N was applied.6. Higher tiller numbers per plant were obtained with lower plant numbers per unit area. Percentage fertility of tillers was generally higher with lower plant densities, and lower tiller numbers per plant, other factors being equal. The only significant effect of N on fertility was to decrease it in the third year.

Three experiments are described, two with S215 meadow fescue and one with S37 cocksfoot, all grown for seed, during which all new tillers, soon after their appearance, were labelled at intervals of a month—a total of nearly 12,000 tillers. Whatever the first date of observation, the earliest tillers were always found to have contributed the largest proportion of the ears present at harvest. In one experiment applied nitrogen caused an increase in the number of tillers and ears, without however affecting the percentage contribution of the earliest tillers to the final crop of ears. The importance of the autumn period of tillering is stressed.

1. Pure swards of S. 48 timothy and S. 215 meadow fescue receiving approximately 52 or 156 lb. N per acre over a period of 8 months were cut (a) at anthesis and twice thereafter or (6) every 4 weeks. The number and weight of tillers and leaves and annual plot yields were determined.2. Tiller numbers rose to their highest in spring and then declined throughout the summer. The higher rate of nitrogen increased tillers in the meadow fescue more than in the timothy; the system of frequent defoliation resulted in enhanced production of tillers in the low nitrogen swards of both species, so that maximum populations within a species were similar under the two levels of nitrogen.

The first part of this paper (Lambert, 1967) described the purpose and layout of the experiment, and presented data on the vegetative growth of S. 48 timothy at a low plant density (30 cm x 30 cm square pattern) for production of seed. The treatments involved were (a) irrigation to field capacity for a period from about 1 week before initiation of inflorescences until 2 weeks before harvest, except for periods of profuse an thesis, and (6) no irrigation; these treatments were applied at three levels of nitrogen: 0, 87 and 261 lb N/acre (0, 97-5 and 292-5 kg N/ha) per annum designated, NO, N l and N2 respectively. The nitrogen was applied in two equal doses, in mid-September and at the stage of initiation of inflorescences in May.This paper describes the effect of the treatments on reproductive development, the components of yield, and the yield of clean seed. METHODSThe course of reproductive development was determined for each treatment by a series of apical dissections and by observation. From late April until inflorescences were completely differentiated, tillers were cut from plants in the first or sixth row of the treatments in one replicate on two occasions each week, and the apices of the ten largest tillers in each treatment were dissected out under a microscope. When seven of the ten tillers had apices with spikelet initials or complete floret initials it was accepted that the plants in that treatment had initiated or completely differentiated inflorescences respectively, provided that the subsequent dissections indicated at least the same stage of development.Estimates of the date of emergence of inflorescences, and of general anthesis were based on five inflorescences per plant; because local weather conditions may affect the date of anthesis (Emecz, 1961), the process may be spread over a considerable period in timothy. The duration of anthesis was recorded as that period when there was at least one inflorescence with fresh anthers on at least half of the plants; the date on which anthesis occurred in the majority of inflorescences was recorded as the date of general anthesis. The timothy was harvested when the majority of the seed was light brown. An area of 4 drills x 7 ft (2-1 m) was used for determination of yield of seed (Lambert, 1967). Material was stored in muslin bags, subsequently threshed in a machine built at N.I.A.E. (Chalmers & Billington, 1961), and the seed was cleaned by aspiration and sieving in apparatus slightly modified from that described by Chalmers & Kemp (1964). One drill of seven plants was harvested and, after the ears were counted, was threshed separately to determine the weight of seed produced per ear.The ears from the central plant in the areas used for determination of yield of seed were cut separately; these central plants were the ones used in spring for counts of numbers of tillers (Lambert, 1967). The ears from these plants were counted and their lengths were measured, and from each plant ten ears of graduated lengths were selected. Each ear was stripped to the rac...

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