The effects of nitrogen and irrigation on timothy (Phleum pratense) grown for production of seed: II. Reproductive growth and yield of seed

Abstract

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...

Irrigation frequency and seasonal timing effects on perennial ryegrass (Lolium perenne L.) seed production

“…Lambert (1967) found that irrigation increased the proportion of heavy seed in timothy (Phleum pretense L.) and Chynoweth et al (2012) demonstrated that seed yield increases resulting from irrigation in perennial ryegrass were associated with increases in seed weight. Rowarth et al (1997) did not observe differences in seed weight from seed harvested from water-stressed and non-stressed perennial ryegrass plants grown under greenhouse conditions.…”

“…Later senescence of the irrigated stands of perennial ryegrass may have led to increased seed weight as a result of a longer seed fill period. Delayed harvest has been reported in irrigated stands of timothy (Lambert, 1967) and perennial ryegrass (Hebblethwaite, 1977).…”

“…There is limited information available on the effects of irrigation frequency and seasonal timing on perennial ryegrass seed crop production. In England, seed yield of timothy (Phleum pratense L.) and perennial ryegrass (Lolium perenne L.) was reported to increase with irrigation (Lambert, 1967;Hebblethwaite, 1977;Hebblethwaite and McGowan, 1977). Work done recently in New Zealand showed that first-year perennial ryegrass seed yields are increased with spring irrigation (Chynoweth et al, 2012).…”

Nitrogen studies in Lolium perenne grown for seed III. The effect of nitrogen and water stress

“…1965;Lambert, 1967). Hebblethwaite (1977) found that irrigation of S23 perennial ryegrass increased seed yield by up to 52% but the magnitude of the response depended largely on the amount of rainfall during the experimental year.…”

“…The seed yields of herbage species respond to nitrogen (N) application (Evans, 1954;Roberts, 1966;Hebblethwaite and Ivins, 1977) and to irrigation (Rampton. 1965;Lambert, 1967). Hebblethwaite (1977) found that irrigation of S23 perennial ryegrass increased seed yield by up to 52% but the magnitude of the response depended largely on the amount of rainfall during the experimental year.…”