WILD WHITE CLOVER SEED PRODUCTION

A survey, covering some 140 fields, totalling 1540 acres, in Kent was conducted in 1961 on the effect of different methods of management on yields of perennial ryegrass and white clover seed. The main results were: (a) the majority of seed growers harvested seed from short-term leys and only a limited acreage of permanent pasture was used for producing seed. Yields of both ryegrass and clover seed were considerably higher on the younger leys; (b) the highest seed yields in 1961 were obtained from fields where sheep grazing was stopped on 24 May. However, a large number of growers continued sheep grazing well after this date: (c) mechanical defoliation, especially when used to supplement sheep grazing, proved an effective method for producing high yields of clover seed; (d) honey bees are important in increasing seed yields, particularly on recently sown leys; (e) combine harvesting from the swath was the most common method of harvesting and no instance of the use of tripods was reported. Seed yields from baling methods were generally low, but direct combining produced a high average yield of clover seed. From these results it was concluded that there was much scope for raising the general level of clover seed yields, especially by giving greater attention to details of management.     

The effect of cutting and grazing managements on dry matter yield of white clover varieties (Trifolium repens) when grown with S23 perennial ryegrass

The effects of three defoliation treatments upon the performance of eight white clover varieties when grown with S23 perennial ryegrass were investigated. These treatments included a cutting only regime as used in National List trials and rotational and continuous sheep grazing.
There were significant ( P <0·001) differences between treatments, and the ranking of clover varieties also differed between the three treatments. The significance of this finding is discussed in relation to the evaluation of breeding material and varieties prior to recommendation to farmers.
Clover yields were less under grazing than cutting. This was due mainly to the selective grazing and removal of stolon material which occurred in the former treatments. Differences in the grass/clover balance resulting from the three treatments are discussed in relation to the degree of protection afforded to the clover stolons by the grass component.     

The effect of height and frequency of mowing on the yield and composition of perennial ryegrass—white clover swards in the autumn to spring period

Ninety-six plots (3 × 2 m) of well-established perennial rye grass/white clover pasture were mown to heights of 2·7 (Low) or 3·96 (High) cm (rising plate meter) at 14-, 28-, 84- or 112-d intervals in autumn-winter. A 7-, 14- and 28-d mowing interval was superimposed in spring on each autumn–winter mowing interval treatment with the low and high mowing heights altered to 2·92 and 4·80 cm, respectively.
With the low cutting height, accumulated herbage DM was more than doubled (1806 ± 79 kg DM ha^-1) compared to a 'high' (754 ± 49 kg DM ha^-1) cutting height in autumn–winter and this was due to increased harvesting efficiency rather than growth as estimated by leaf extension. Although defoliation interval had no effect on DM yield, the grass component increased and clover decreased. The composition effect carried over into spring. On average, 3·5 tillers were produced over winter for each ryegrass tiller present in autumn and tiller densities were higher in spring. Tillers produced over autumn–winter contributed more than 60% of ryegrass growth by early spring.
In early spring (16–30 September), the low cutting height increased herbage DM yield, in mid-spring (1–14 October) it reduced DM yields particularly in combination with short defoliation intervals, while in late spring (14 October to 11 November) cutting height had no effect on DM yields.
Over the entire spring period there was a very marked effect of defoliation interval on DM yields.     

Comparison of white clover varieties under cutting and grazing

Seven varieties of white clover ( Trifolium repens L.), of varying leaf size from large to small, were sown with perennial ryegrass ( Lolium perenne L.) in 1985, at an upland site, and compared over three harvest years under a cutting management (5-6 cuts), and under continuous grazing by sheep. Fertilizer N input totalled 80 kg ha⁻¹ in both the cutting and the grazing trial. The same varieties were included in two official National List (NL) trials sown the same year at a nearby site; these comprised a yield trial with 6-7 cuts and a persistency trial mown very frequently (17 cuts) to simulate intensive grazing.
At the upland site the large-leaved varieties, Milkanova and Blanca, were the highest yielding under cutting (mean 3·3 t DM ha⁻¹), and the small-leaved S184 and Kent the lowest yielding (mean 2·3 t DM ha⁻¹). The rankings were reversed under grazing (corresponding yields 1·1 and 2·1 t DM ha⁻¹). The medium-leaved varieties Donna, Menna and Grasslands Huia behaved similarly to the large-leaved varieties. Ranking order in the cutting trial was similar to that in the NL trial.
Ground covers after three harvest years differed significantly only under grazing, when the small-leaved varieties had a 2-3 times greater cover than the larger-leaved varieties. A poor separation of the varieties in the NL persistency trial suggests that defoliation was not sufficiently severe to simulate intensive grazing.
These comparisons indicate that the performance of clover varieties under the cutting regimes used should not be extrapolated to continuous sheep grazing.     

Managing grass/clover swards to produce differing clover proportions

Management treatments were applied to an established ryegrass/white clover sward with the aim of producing differences in clover content. The treatments were: mowing (M) with no fertilizer N (intended to give high clover), grazing by cattle (C) with no fertilizer N (medium clover) and grazing by sheep (S) with 300 kg N ha⁻¹ applied (low clover). Following treatments significant differences ( P < 0.001) were observed, with M, C and S containing respectively. 237, 81 and 3 kg DM ha⁻¹ of live clover. Treatment M swards had fewer ryegrass tillers but greater numbers of clover growing points than did treatment S, with values being intermediate on treatment C. Following overwintering most of the differences in the clover component between treatments C and M were lost, but those on treatment S still persisted. Management can be used to manipulate the botanical composition of ryegrass/white clover swards, but these changes may be only transient.     

Relationships between the yield of perennial ryegrass and of small-leaved white clover under cutting or continuous grazing by sheep

Seven varieties or advanced breeding lines of white clover ( Trifolium repens L.), all of small leaf size, were grown separately in mixtures with perennial ryegrass ( Lolium perenne L.) in an experiment encompassing three harvest years. Harvestable dry-matter (DM) yield measurements were taken of these mixtures and of perennial ryegrass monocultures under two management regimes: cutting and continuous sheep grazing. Considerable differences were observed in the harvestable DM yields of white clover, perennial ryegrass and total yields of the mixtures between plots containing different white clover varieties. White clover yields were generally higher under cutting, and perennial ryegrass yields were higher under grazing. The difference between perennial ryegrass yield in monoculture and in mixture was variable. In the second harvest year, a significant interaction effect was seen between management and white clover variety for white clover yield but not for perennial ryegrass yield. The relationship between clover yield and grass yield differed between the two management regimes. Under cutting, a negative correlation was observed, indicative of competitive effects. However, under grazing, no such correlation was seen. Possible mechanisms underlying these outcomes are discussed.     

Evaluation of white clover varieties under grazing and their role in farm systems

Four experiments were established in 1981–84 to investigate the effect of defoliation treatments on white clover varieties when grown with S23 perennial ryegrass. Treatments included a cutting only regime, as used in National List trials, and grazing systems simulating as near as possible those used on farms.
Differential effects of cutting and continuous sheep stocking on white clover varieties, together with significant variety × defoliation interactions, illustrated the importance of the grazing animal in the evaluation of white clover. Differential effects of cattle and sheep grazing were also evident. Cattle grazing was less detrimental to white clover than was sheep grazing, i.e. cattle were not selective, and less stolon was removed. In general, with both cattle and sheep grazing the larger the clover leaf size the greater the loss in stolons, which in turn decreased persistency. The results illustrate how alternating cutting, sheep grazing and cattle grazing managements can be used to maintain optimum clover/grass balance.
Successful clover/grass swards depend on the retention of clover, yet avoiding clover dominance. The difference in N transfer between clover varieties, especially those within the same leaf category, and the extra grass produced without fertilizer N, emphasized the importance of varietal choice. Breeding programmes have been concerned with the selection of larger-leaved, long-petioled varieties for growing in competition with grass in the presence of fertilizer N. However, the present results showed that, under continuous sheep stocking, increase in leaf size does not increase clover yield or persistency.
The results presented emphasize the importance of the grazing animal in the evaluation of white clover varieties and indicate that yield of clover dry matter should not be the major criterion for selection of varieties for farm systems.     

Productivity of mixtures of Italian ryegrass and red clover

Two red clover ( Trifolium pratense ) cultivars, Red Head (tetraploid) and Kuhn (diploid), were sown at a seed rate of 13 kg ha⁻¹ either alone or in mixture with Italian ryegrass ( Lolium multiflorum ) cv. RvP sown at seed rates of 10, 15, 20 or 30 kg ha⁻¹. RvP was also sown alone at a seed rate of 30 kg ha⁻¹ and received nil or 300 kg ha⁻¹ fertilizer a⁻¹ fertilizer N. All plots were established using the barley cultivar Midas sown at a seed rate of 100 kg ha⁻¹ as a nurse crop.
Neither clover cultivar nor ryegrass seed rate significantly influenced either dry matter harvested or botanical composition over the 3 harvest years. On average over all years the grass-clover mixtures produced 75% of the yield of the N-fertilized RvP, 125% of the clover monocultures and 225% of the unfertilized RvP. The red clover contribution to the total dry matter harvested of the mixtures averaged 45–60%. The dry matter concentrations of the mixtures were considerably higher than those of the pure clover stands. In the third year yields were markedly reduced in comparison with those in the first and second years.
It was concluded that Italian ryegrass can be a suitable companion grass for red clover. Its superior yielding capacity over other grasses such as perennial ryegrass or timothy under a conservation management can be coupled to advantage with red clover to give a sward which Is essentially stable, at least over a 2- to 3-year cropping period, although giving slightly reduced yields in the third year. Italian ryegrass-red clover mixtures, without the use of fertilizer N, can produce high DM yields of good quality herbage.     

The effect of companion perennial ryegrass cultivars on red clover productivity when timing of the first cut is varied

Replicated plots of Hungaropoly red clover were sown on a sterilized area in May 1975 alone (seed rate 11 kg ha^-1) or with one of six cultivars of perennial ryegrass (seed rate 3·5 kg ha^-1) viz. Cropper and S24 (early heading), Barlenna and Hora (medium heading) and Melle and Perma (late heading). In 1976 and 1977 primary growth was cut at one of four dates ranging from mid-May to mid-June and thereafter plots were harvested twice each year.
Varying the time of first cut did not have a significant effect on total dry matter (DM) yield in either year despite differences in means of cutting treatments on annual red clover yields of the order of 6–9%.
In some companion grass treatments total DM yield in 1976 was increased and total red clover yield and percentage red clover contribution were reduced relative to swards sown only with red clover. In 1977 a similar but non-significant trend was found. Swards containing early ryegrasses had higher total herbage DM yields but lower red clover yields and contents than all other swards at the first harvest in both years.
Delay in date of taking the first harvest in 1976 reduced DM digestibility in the first cut and increased it in the second in both years.
It is suggested that by cutting early and increasing the number of harvests from three to four per year, differences in the content of red clover between the first and second cut might be reduced, and it is concluded that more benefit is derived from red clover when medium or late heading ryegrasses are used as companion grasses.     

No relationship between leaf size and yield in medium leaf size white clover varieties under rotational sheep grazing and cutting

Nine medium leaf size varieties of white clover ( Trifolium repens L.) were grown in field plots with perennial ryegrass ( Lolium perenne L.) variety Fennema, and yield measurements were taken under both cutting and rotational sheep grazing. The sampling and management protocols in the cut plots mirrored those for the National List testing of white clover varieties in the UK. Dry-matter yields of the white clover and perennial ryegrass components of the mixture were recorded for six cuts in each of three harvest years. White clover yields were highest under cutting, perennial ryegrass yields under grazing. Significant differences were seen between the yields of white clover varieties, and significant interactions between white clover yields and management type were also observed. This interaction effect was not seen with respect to perennial ryegrass yields. No correlation was observed between leaf size and white clover dry-matter yield under either management type. The results suggest that leaf size, on the scale of variation represented within a leaf size category, is not a good predictor of yield under rotational sheep grazing or cutting. The significance of these results for varietal evaluation and for ascertaining the underlying bases for yield differences is discussed.     

Dynamics of perennial ryegrass and white clover in sown swards in NW Greece

Seasonal dynamics of white clover and perennial ryegrass were examined in sown perennial ryegrass/white clover swards subject to a 2 × 2 factorial treatment combination of defoliation (rotational grazing by sheep and cutting) and nitrogen fertilizer application (0 and 40 kg N ha^–1 year^–1) in NW Greece. Sward surface height and percentage cover were measured before and after five defoliation periods in 1996 within permanent microplots (30 × 30 cm, divided into nine cells) in which white clover was either initially present or absent. Both white clover and perennial ryegrass achieved maximum height and cover in April–May. Defoliation treatment and whether white clover was present initially significantly affected height and cover of both species. Total plant cover was similar prior to all defoliation periods except in July, a time of drought. Cover of perennial ryegrass was greater where white clover was initially absent, but total plant cover was greater in microplots containing white clover and the extent of the differences varied during the year. In contrast, N fertilizer application had little effect on species cover, other than small reductions in white clover cover. When white clover was present in April, it was found in virtually every microplot cell until July, but if it was absent in April there was little colonization of the microplot.     

THE EFFECTS OF CUTTING AND GRAZING SYSTEMS ON HERBAGE PRODUCTION FROM GRASS SWARDS

Studies were made on two perennial ryegrass–dominant swards of the effects of cutting and grazing systems of herbage production. A motor scythe was used for cutting and sheep in small enclosures for grazing. In both systems, herbage production was measured by a ground-level sampling technique, using sheep shears, and the difference between pre-treatment and post-treatment herbage was expressed as ‘utilized yield’. Correction for soil contamination is ensured by quoting all results on an organic-matter basis. Grazing treatments averaged 14–16% more organic matter and 36–45% more crude protein than cutting treatments in both experiments. These differences were ascribed to recycling of N under grazing. Infrequent defoliation gave higher yields than frequent, and severe defoliation higher yields than lenient under both cutting and grazing systems. The trends shown by cutting and grazing intensities are comparable and can be quantified. There is need to examine closely the relationships between the effects of cutting and grazing techniques on herbage production, since such knowledge would allow a more accurate prediction of the relevance to the grazing situation of results obtained under cutting.     

Effect of regrowth interval on the productivity of swards defoliated by cutting and grazing

Over three grazing seasons (1984-1986) a sward of perennial ryegrass, cv. Talbot, which received a total of 336 kg N ha^-1 each season, was cut or grazed with ewes at 3- or 4-week intervals on a rotational basis.
Sward productivity was higher under cutting than under grazing irrespective of the interval between defoliations. Under cutting, mean herbage organic matter (OM) yields over both intervals were 8·66, 9·62 and 8·17 t ha-¹ in 1984, 1985 and 1986 respectively while under grazing the corresponding yields were 7·65, 8·63 and 7·50 t ha^-1. The mean annual yield of herbage defoliated at 3-week intervals was 7·50, 8·64 and 7 ·20 t OM ha^-1 compared with 8·80, 9·60 and 8·46 t OM ha^-1 for swards defoliated at 4-week intervals in the three years respectively.
The nitrogen (N) content of both the available and the residual herbage was consistently higher under grazing than under cutting. Available herbage contained 31·3 and 27·7 g N kg OM^-1 and residual herbage 26·1 and 22·7 g N kg OM^-1 under grazing and cutting respectively.
The mean yield of N under cutting was 284 kg ha^-1 compared with 304 kg ha^-1 under grazing. Defoliation interval had no effect on N yield, the overall mean yield being 294 kg ha^-1 under both 3- and 4-week defoliation intervals. The effect of the treatments on tiller population was slight and inconclusive.
The process of grazing reduced yield probably as a result of damage to the sward through trampling; the positive effect of excretal N on yield was minimal on account of the short grazing periods.     

How does the vertical and horizontal structure of a perennial ryegrass and white clover sward influence grazing?

Mixtures of perennial ryegrass ( Lolium perenne L.) and white clover ( Trifolium repens L.) sown in alternate rows or in a thoroughly mixed matrix were grazed by sheep, either continuously or during short grazing tests, and were used to investigate the influence of the vertical and horizontal components of the sward structure on defoliation by sheep.
In an experiment under continuous grazing, the defoliation intensity was greater for white clover compared with perennial ryegrass leaves (0·80 and 0·58 respectively). In spring, perennial ryegrass leaves were more defoliated than white clover leaves, whereas the reverse was observed in summer. The ratio of the proportion of white clover to perennial ryegrass leaves grazed was negatively correlated with the difference between the surface height of the perennial ryegrass and white clover rows in spring. In both spring and summer, white clover leaves of the same extended leaf length had a higher proportion of them grazed than perennial ryegrass leaves.
In another experiment, during short grazing tests with perennial ryegrass–white clover swards that were grazed at the same sward surface height and at the same white clover content as in the previous experiment, there were no significant differences in the proportion of white clover and perennial ryegrass leaves grazed between strips of the two species and thoroughly mixed structures. The proportion of white clover leaves grazed was higher than that of perennial ryegrass leaves.
These results show that the differential defoliation by sheep of perennial ryegrass and white clover leaves varies according to their vertical distribution in the mixed canopy, but is little affected by their horizontal distribution. Even small differences in sward surface height between mixed perennial ryegrass and white clover can affect diet selection by sheep to a rather large extent.     

Breeding and evaluation of new white clover varieties for persistency and higher yields under grazing

Two experiments were established in 1989 and 1990 to evaluate the performance of white clover ( Trifolium repens ) varieties under grazing, using sheep and cattle, and also under a 'cutting-only' regime. The three potential medium/large-leaved varieties (AberVantage, AberCrown and AberDai) were selected and evaluated in a breeding programme that emphasized improving yield and persistency under grazing.
In Experiment 1, the potential varieties were sown with two different grass companions, and evaluated under a continuous cattle-grazing system, representative of their future role in actual farm practice, i.e. a set stocking system. Clover yield of the potential varieties in the second harvest year averaged 1–5 t ha⁻¹ more than the control variety Olwen. Total sward production of AberVantage, AberCrown and AberDai was 2.0–1.4 t ha⁻¹ higher than that of Olwen.
In Experiment 2, clover yields of the three potential varieties averaged 2.1 t more than Olwen in the second harvest year under continuous sheep grazing, but all three were lower yielding than Olwen in the cutting regime.
Both experiments illustrate how the use of grazing treatments during breeding and evaluation can improve the role of white clover varieties.     

Dry-matter yield and herbage quality of a perennial ryegrass/white clover sward in a rotational grazing and cutting system

The expected reduction in the use of fertilizer nitrogen (N) on grassland in the Netherlands has led to renewed interest in white clover. Therefore, the performance of a newly sown perennial ryegrass/white clover sward on clay soil was assessed during 4 consecutive years. The experiment consisted of all combinations of two defoliation systems, i.e. one or two silage cuts per year (S1, S2), spring N application rate, i.e. 0 or 50 kg ha⁻¹ year⁻¹ (N₀, N₅₀), and the management system, i.e. rotational grazing and cutting, or cutting only (RGC, CO). The overall mean white clover cover was 30%. All treatments affected white clover cover, which was 8% higher with S2 than with S1, 6% higher with N₀ than with N₅₀ and 12% higher with CO than with RGC. The overall mean annual dry-matter (DM) yield (13·1 t ha⁻¹ year⁻¹) was significantly affected only by the management system: in two relatively wetter years, the annual DM yield was 1·19 t ha⁻¹ higher with RGC than with CO, whereas there was no difference in two relatively drier years. Nitrogen application increased the DM yield in the first cut by 7·0 kg kg⁻¹ N applied, but had no significant effect on the annual DM yield. Herbage quality was not affected by the experimental treatments. The average in vitro organic matter digestibility was 0.801, and the average crude protein content was 193 g kg⁻¹ DM. With the expected reduction in the use of fertilizer N, perennial ryegrass/white clover swards should be seriously considered as an alternative option to perennial ryegrass swards on these clay soils.     

The liveweight gain of Limousin × Friesian heifers grazing perennial ryegrass/white clover swards of different clover content and the effects of their grazing on sward botanical composition

An experiment was carried out in 1992 and 1993 to examine the effect of white clover content of perennial ryegrass/white clover swards on the performance of Limousin × Friesian heifers. Swards with low (L), medium (M) and high (H) white clover contents were established and managed by continuous variable stocking. A compressed sward height of 5·5 cm was maintained using a buffer fence to vary plot areas, with herbage surplus to grazing requirements cut, removed and yields measured. The mean white clover proportions for treatments L, M and H were 0·02, 0·19 and 0·18 in 1992 and 0·13, 0·16 and 0·31 in 1993 respectively. White clover contents of the swards reached a maximum in August and September, and differences between treatments diminished. There was no significant difference between treatments in the content of white clover in the swards in autumn 1993.
Liveweight gains of heifers increased asymptotically with increasing white clover content of the sward. Below a white clover herbage mass of 300 kg DM ha^–1, there was little effect on liveweight gain, which was 0·70 kg day^–1 over the grazing season. Between 400 and 450 kg DM ha^–1 white clover, liveweight gains were 0·85–0·90 kg day^–1. While clover content of the sward did not significantly affect utilized metabolizable energy output; the mean output over the grazing season in the two years from liveweight gain and herbage yield was 78 GJ ha^–1. It is suggested that, using this grazing system, white clover reached an equilibrium with a mean herbage mass of about 400 kg DM ha^–1 over the grazing season.     

Soil N contributes to the oscillations of the white clover content in mixed swards of perennial ryegrass under conditions that simulate grazing over five years

The effect of the initial N-supplying capacity of soils (SoilN, 90–230 kg N ha^–1 year^–1) was tested on the dry-matter and N yields of pure or mixed white clover and perennial ryegrass swards, managed under simulated grazing over a 5-year period. The cumulated N harvested in the mixed swards was similar, both for white clover and perennial ryegrass, but the proportion of white clover showed oscillations over a 2-year period. In the first year, the SoilN effect was similar to that of fertilizer N. During the course of the experiment, the effect was always positive on the pure perennial ryegrass sward, alternately negative and nil for the white clover in the mixed sward and alternately positive and nil for the perennial ryegrass in the mixed sward; the period of these oscillations was 2 years. From the third regrowth period after sowing, the ratio between the actual N concentration and the concentration non-limiting to growth for the perennial ryegrass in the mixed sward, increased above that of the pure perennial ryegrass sward. It was in turn greater in the soils that were initially poor and then greater in those that were initially rich in soil N. The periodic oscillation of the initial SoilN effects implies that the initial SoilN gradient was alternately compensated and restored. It was concluded that N fluxes are partly responsible for the temporal oscillations in the proportion of white clover in mixed swards.     

Effects of pre-treatment, renovation procedure and cultivar on the growth of white clover sown into a permanent pasture under both grazing and mowing regimes

White clover ( Trifolium repens ) is a valuable pasture component that is frequently present in insufficient quantity for optimal animal nutrition. Several methods of reintroducing white clover into a permanent pasture without conventional tillage were investigated. Three seeders (Hunter, Vredo and a conventional seed drill), two white clover cultivars (Sacramento, and Sonja), two pasture pre-treatments (a hard spring grazing or grazing plus light harrowing) and two defoliation regimes (grazing or mowing) were used to determine optimal seedling establishment conditions. Defoliation treatments were used as a method of investigating pasture improvement experiments. Measurements were taken to determine proportion of white clover present and total herbage mass.
Plots renovated using a Hunter drill had the highest white clover content in the months immediately after renovation. Subsequently pre-treatment method appeared to have no significant effect on herbage mass or species composition. The proportion of white clover in plots sown with the cultivar Sacramento was frequently higher than that in plots sown with the cultivar Sonja, but, overall, herbage production of cultivars was not different.
Mowed plots had higher herbage production and tended towards a greater white clover content than grazed plots. Compaction of the surface to a depth of 10 cm in the grazed plots may have been a factor in the observed difference in herbage production. Regardless of management, within two years white clover content was similar among all treatments, including controls.     

SEED PRODUCTION STUDIES ON PERENNIAL RYEGRASS, TIMOTHY AND PRAIRIE GRASS

This paper considers the sequence of seed development by measurement and observation of ehanges in seed moisture content, weight, colour, endosperm consistency, germination capacity and yield in perennial ryegrass Grasslands Ruanui, timothy Grasslands Kahu and a New Zealand strain of prairie grass (Bromus unioloides). Seed moisture content was high (60–70%) after anthesis and declined at different rates, depending on the species and the weather. Maximum seed dry weight (maturity) was reached approximately 30 days after peak anthesis in all species and was influenced by N application and grazing. Colour changes in the seedhead and endosperm solidification proved unsatisfactory as measures of maturity. Endosperm solidification was reached 4, 11 and 12 days before maximum seed dry weight in ryegrass, timothy and prairie grass, respectively. Seeds removed from the plant as little as 7, 10 and 4 days after anthesis in ryegrass, timothy, and prairie grass, respectively, germinated, provided that dormancy was broken; but they did not retain viability after 3 months storage. Maximum viability of ryegrass, timothy and prairie grass seed tested immediately after harvest occurred 30, 38 and 16 days after anthesis, compared with 17, 35 and 12 days, respeetively, when germination testing was delayed for 3 months. In ryegrass, grazing caused a significant increase in seed yield in the second year while N application alone did not significantly increase yield. In timothy, grazing and to a lesser extent N, were both detrimental to seed yield in the second year. Highest yields were obtained in treatments not receiving either grazing or N. In prairie grass, grazing depressed and N application increased yields in both years. In all species similar or increased yield could be obtained by mowing the crop at, or slightly prior to, seed maturity and allowing seed development and ripening to continue on the cut straw for up to 10 days. Using this technique higher seed yields were obtained in ryegrass and timothy than when seed was direct-harvested. In prairie grass similar yields were obtained whether the erop was direct-harvested or threshed following drying in the swath for 10 days. The use of ‘drying curves’ for the prediction of correct cutting time of seed crops is suggested for ryegrass, timothy and prairie grass.