The effect of lodging on 14C-assimilate distribution after anthesis in Lolium perenne, CV. S24, grown for seed

Field experiments in 1981 and 1981 examined assimilate distribution in lodged and non-lodged plots of perennial ryegrass ( Lolium perenne) , cv. S24, grown for seed. Lodging was prevented either mechanically (1982 only) or chemically, by application of paclobutrazol (PP333) at 2 0 kg a.i. ha^-1. For each treatment, main-tiller ears, stems and leaves and subtending vegetative tillers were fed with ¹⁴CO₂ at 24 and 17 days after anthesis in 1981 and 1982, respectively, and the pattern of ¹⁴C-assimilate export from each fed part was determined.
Prevention of lodging increased assimilate movement to the ear from the flag leaf, although movement from main-tiller leaves was primarily downwards to vegetative tillers. Assimilate movement to the stem was also increased because the cessation of stem elongation was delayed, especially where lodging was prevented by PP333. Both increases were at the expense of the tillers, although their number was not reduced in non-lodged plots. Possible reasons for these changes in assimilate distribution are discussed.     

A comparison of seed harvesting methods for perennial ryegrass treated with the growth retardant paclobutrazol

Methods of harvesting seed of perennial ryegrass cv. S24 treated with the growth retardant paclobutrazol applied at spikelet initiation at a rate of 2.0 kg active ingredient ha⁻¹ were examined in 1982. The greatest seed yield (2202 kg ha⁻¹) was obtained from swathing the crop at 35% seed moisture content and combining 2 days later, but this was not significantly different from that obtained from swathing at 48% seed moisture content or double direct combining at 35% seed moisture content. Seed yields from a single direct combining at either 35% or 25% seed moisture content were significantly lower than those of other treatments.     

The use of growth regulator RSW0411 in seed crops of Lolium perenne L.

Field trials were conducted in 1985 and 1986 to assess the effects of the growth regulator RSW0411 on a Lolium perenne L. (perennial ryegrass) seed crop. Applications were made at spikelet and floret initiation, and at 1, 2, 3 and 4 kg active ingredient ha⁻¹.
Seed yield increases in 1985 were associated with increased reproductive tiller numbers and seed numbers, but in 1986 there were no seed yield responses.
Lodging was less severe in 1986, and there was less secondary filtering during seed maturation. In 1985, fertile tiller numbers were lower in control plots at harvest. These results are discussed in relation to the seasonal disparity in seed yield response.
RSW0411 application significantly decreased culm lengths by shortening the basal internodes, and this effect was greater with higher application rates. Stem width was increased in 1985 at the base and middle of the stem, and earlier applications increased the basal width by more than later applications.
Germination was not affected by RSW0411 treatment, except when applied at 4 kg active ingredient ha⁻¹ in 1985, when there was a small decrease. This was related to a low 1000-seed weight, and is discussed in relation to seed maturity at harvest.     

Nitrogen studies in Lolium perenne grown for seed. IV. Response of amenity types and influence of a growth regulator

In field trials in 1979–81, perennial ryegrass cultivars Royal and Majestic (amenity) and Morenne (agricultural) produced maximum seed yields at levels of applied N ranging from 40 kg ha⁻¹ to 160 kg ha⁻¹. Available soil N levels were estimated at 55 kg ha⁻¹; hence maximum seed yields were obtained at total nitrogen levels of 95–135 kg ha⁻¹ in Royal, 95–215 kg ha⁻¹ in Morenne, and 175–215 kg ha⁻¹ in Majestic.
Applied N at rates above 120 kg ha⁻¹ either reduced or did not significantly increase seed yield, decreased seed numbers per unit area and decreased spikelets per tiller and seeds per spikelet.
The use of a growth regulator increased seed yields by preventing lodging, but did so irrespective of nitrogen application rate. It is suggested that failure to increase seed yield at high N rates is a result not of poor pollination because of lodging, but seed abortion as a consequence of competition for assimilate supply by secondary vegetative tillers.     

Effects of interval between harvests and application of fertilizer N in spring on the growth of perennial ryegrass in a grass/white clover sward

A perennial ryegrass/white clover sward, which had been grazed for over 2 years, was cut at 1-, 2-, 3- or 6-week intervals from 18 April to 28 November 1986. Two rates of fertilizer N application in spring, 0 and 66 kg N ha⁻¹, were compared. Perennial ryegrass growth was studied in three 6-week periods, beginning on 18 April, 18 July and 17 October. Clover growth was studied in the same three periods and described by Fisher and Wilman (1995) Grass and Forage Science , 50 , 162–171.
Applied N increased the number of ryegrass tillers m⁻², the rate of leaf extension and the weight of new leaf produced tiller⁻¹ and m⁻²per week. Increasing the interval between cuts reduced the number of ryegrass tillers m⁻² and increased the rate of leaf extension, weight tiller⁻¹and the weight of new leaf produced tiller⁻¹week⁻¹. Increasing the interval between cuts increased the weight of new ryegrass leaf produced m⁻² where N had recently been applied, but otherwise had little effect on the weight of new leaf produced m⁻². Applying N favoured the grass in competition with the clover in every respect, whereas increasing the interval between cuts only favoured the grass, compared with clover, where N had recently been applied; where N had not been applied, the ratio of ryegrass tillers to clover growing points in the sward was very little affected by the interval between cuts.     

The effects of regrowth and maintenance height on a grass sward with a high density of tillers

A perennial ryegrass sward was grazed by sheep in April 1993 to a target sward surface height (SSH) of 3 cm to create a high density of grass tillers. From 3 May, the sheep were removed and small plots were established on the sward, when the average tiller density (± s.e.) was 35 900 ± 420 live tillers m⁻². Different regrowth treatments were then imposed by allowing plots to regrow to target SSHs of 6 cm (18 g dry matter (DM) M⁻²), 9 cm (78 g DM m⁻²), 12 cm (132 g DM m⁻²) or 15 cm (197 g DM m⁻²). The plots were then maintained by cutting at either 6 or 9 cm SSH until the end of the experiment on 30 September. Live tiller density was reduced by regrowth beyond 8.9 cm (78 g DM m⁻², P <0.001) and leaf-stem ratio and in vitro organic matter digestibility were reduced by regrowth beyond 6.1 cm (18 g DM m⁻², P < 0.05). The effect on live tiller density was sustained through the remainder of the season. From the beginning of June to the end of September, maintenance of SSH at an average of 9.1 cm compared with 6.4 cm also resulted in lower live tiller density, live-dead tiller ratio and leaf-stem ratio and higher herbage mass (at least P < 0. 05). There were significant interactions between regrowth SSH and maintenance SSH, so that leaf-stem ratio, live-dead tiller ratio and live tiller density were reduced by regrowth to a SSH of 16–4 cm followed by maintenance at 9.1 cm, compared with regrowth to 6.1 cm and maintenance at 6.4 cm.     

Yield response of improved upland pasture to the control of leatherjackets under increasing rates of nitrogen

In each year from 1984-5 to 1987-8 the effect of leatherjackets on yield of improved upland pasture was assessed at Redesdale Experimental Husbandry Farm in Northumberland. Chlor-pyrifos at 0.72 kg ha⁻¹ was applied in November or December to half the plots; these and the untreated plots received one of four fertilizer rates (0, 40, 80, 120 kg N ha⁻¹). All rates increased yield by a mean of about 24 kg DM kg N⁻¹.
There was a significant correlation (Y (t DM ha⁻¹) = 0-21 + 0-00168 ×, r = 0-99 ( P = 0.001)) between yield response to chlorpyrifos and leatherjacket numbers m⁻² in November/ December. Treatment thresholds for leatherjacket numbers are given.     

The influence of selected agronomic factors on the yield of forage peas

Five trials were carried out in 1979 to assess the influence of cultivar, seed rate, fertilizer application and the inclusion of oats as a companion crop on the dry matter (DM) yield of forage peas grown in the west of Scotland. Despite the season being abnormally cold the crop consistently produced between 6 and 8 t DM ha^-1. There was little difference between cultivars in the yield of forage produced but there were considerable differences in the time taken to reach maturity. All cultivars lodged. There was no yield response to seed rate of between 80 and 280 kg ha^-1 nor to fertilizer N and K applications. The inclusion of oats in the seeds mixture greatly reduced lodging and had no marked effect on DM yield but the organic matter digestibility and crude protein concentration were lower than recorded for peas grown alone in previous years.     

The influence of sowing date, harvest date and seed rate on the yield of forage peas

A series of preliminary trials is described to assess the potential and some of the cultural requirements of new cultivars of forage peas grown as pure stands in the west of Scotland. Optimum sowing date was late March for harvesting 15 weeks later to leave sufficient of the growing season for a catch crop or the establishment of a grass sward. Yield of dry matter (DM) at harvest was approximately 6 t ha^-1 but DM concentration varied greatly with season. The digestibility of the organic matter was of the order of 0·700 and the crude protein concentration in the DM 170 g kg^-1. DM yield increased with increasing seed rate up to 200 kg ha^-1 the maximum rate tested.     

The impact of low numbers of leatherjackets on grass yield

Experiments were carried out on seven sites in Fermanagh to investigate the yield loss caused by leatherjackets in grassland. Populations on the sites ranged from 65,000 to 865,000 ha⁻¹ and significant damage was recorded from all sites except the least populated. Greater yield increases were obtained by controlling leatherjackets in September when compared with control in March. Regression models were fitted and it was found that 125,000 leatherjackets ha⁻¹ in March caused a yield loss of 50 kg herbage dry matter (DM) ha⁻¹ by mid-May. Based on these figures the average yield loss to leatherjackets in Northern Ireland, from 1965 to 1982, was 208 kg DM ha⁻¹. Controlling leatherjackets in September, rather than March, increased the potential avoidable yield loss by a factor of 2.72. The average yield loss at first silage cut is therefore 566 kg DM ha⁻¹. On average, 100,000 ha grassland in Northern Ireland may be suffering an annual loss of 1t herbage DM ha⁻¹.     

The influence of seed rate and pesticides on the establishment and growth of white clover slot-seeded into a permanent pasture

The establishment and growth of white clover (cv. Grasslands Huia) was investigated in two experiments with seeds sown in slots cut in old permanent pasture in early May 1982. In the first experiment, fully protected from pests and diseases, either 50 (low), 100 (medium) or 200 (high) seeds were sown evenly per metre length of slot; 100 seeds were also sown in a clumped pattern unevenly. In the second experiment, the effects of various combinations of molluscicide, insecticide and fungicide were investigated.
Nine weeks after sowing there were 27, 37, 34 and 62 seedlings m⁻¹ on the low, medium even, medium uneven and high seed-rate treatments, representing percentage establishments of 54, 37, 34 and 31 respectively. By September, however, there were no significant differences between the dry weights m^−l of any of the treatments. In the second experiment, damage by slugs occurred early in treatments without molluscicide and caused a mean reduction of 70% in seedling establishment. As a result significantly smaller dry weights m⁻¹ of clover were recorded in September in these than in other treatments. Failure to protect against insects resulted in smaller seedlings.
The results indicated that variations in seed rate within the range investigated were not critical but that failure to protect against pests decreased percentage establishment and subsequent growth.     

Herbage production and nitrogen recovery from slurry injection and fertilizer nitrogen application

An experiment was carried out during 1986 and 1987 to examine the effects of mid-season slurry injection and fertilizer-nitrogen (N) application on herbage dry matter (DM) yield and N recovery. Cattle and pig slurry were injected at 56 and 112 m³ ha⁻¹ into an established sward. Five rates of fertilizer-N, as calcium ammonium nitrate, ranging from 0 to 120 kg ha⁻¹ in 30-kg increments, were superimposed on these treatments, and in both years DM yield was measured in one cut after 70 d regrowth. Slurry treatments increased herbage DM yields significantly ( P < 0-001). The efficiency of slurry total N compared with calcium ammonium nitrate-N averaged 53% in 1986 and 86% in 1987. The mean apparent recovery of slurry total N in herbage was 55% in 1986 and 40% in 1987. Fertilizer-N application increased ( P < 0.001) the mean yields of herbage in both years but when combined with some of the slurry treatments, DM yields over the five N-levels did not differ significantly, giving rise to interactions in 1986 ( P < 0-001) and 1987 ( P < 001). It is concluded that mid-season injection of slurry can be an effective means of utilizing slurry-N in terms of herbage DM production and consequent N use.     

Response to late season nitrogen of upland swards in Wales

During 1984 and 1985, trials at sixteen sites throughout Wales measured the yield response in upland swards from applying 40 and 80 kg N ha⁻¹ at three dates, 20 August, 4 September and 18 September. All sites were between 230 m and 345 m above sea level. Grass yields were measured by cutting plots during October and November.
Nitrogen increased the herbage dry-matter (DM) yield at all sites in both years. The yield response per kg N applied varied between sites. Mean yield response for the two years declined from 16·2 kg DM kg N⁻¹ with 40 kg N ha⁻¹ applied on 20 August to 8·9 kg DM kg N⁻¹ with 80 kg N ha⁻¹ applied on 18 September. In general there was a decline in response to N with increased rate and delay in time of application. The results indicate that responses above an optimum of 9 kg DM kg N⁻¹ can be obtained well into September. A general rule that 1 kg N can be economically applied per 4 summed day degrees air temperature >6 °C remaining in the autumn up to 30 November is suggested.
Delay in application and increasing N rate increased crude protein in the herbage but had only small effects on modified acid detergent (MAD) fibre and sugar. Generally, grass quality was good. Sward density assessed during the spring after nitrogen had been applied appeared to have been unaffected by the treatments.     

Lime and major nutrient fertilizers required to establish a perennial ryegrass/white clover pasture on a non-calcareous gley in the Scottish uplands

A field experiment with mixed swards of perennial ryegrass and while clover carded out in 1982–83 using small cut plots is described. With perennial ryegrass, lime slightly decreased annual dry matter (DM) production in 1982 (the sowing year) but increased it in 1983 (the first harvest year) by about 1 t ha^-1. Applications of N and P produced small increases in DM in 1982 and greater increases in 1983. In the latter season annual DM production varied from an average of 3·5 to about 10 t ha^-1 with 0 or 480 kg N ha^-1 applied in three equal-sized dressings throughout the growing season. Application of 40 kg P ha^-1 in 1982 increased DM production by about 2·5 t ha^-1 in 1983 but higher rates had little effect. Fifteen mg extractable P kg^-1 soil seemed sufficient to support levels of production normally expected from ryegrass pastures in upland Scotland, Applications of K did not affect DM production. N increased tiller weight and sward height of ryegrass; lime and P tended to increase tiller weight but this effect was not statistically significant. Leaf appearance and tiller number were not affected by treatments.
The white clover content of the pasture was decreased 10-fold by application of N and increased by lime and P (1·45 and 1·46-fold. respectively). The DM response to P was most apparent in limed soil and was also affected by the siting of the plots in the experimental area. Effects of lime and P on growth of white clover were to increase the number of stolon growing points and root nodule numbers per unit area.
The results emphasize the importance of lime and P fertilizer for establishment and growth of pasture in this soil and the differences between white clover and ryegrass in their responses to these.     

Seed production of an Arrhenatherion elatioris hay-meadow in the eastern Italian Alps

Due to agricultural intensification, semi-natural Arrhenatherion elatioris meadows are becoming rare in central Europe. Despite the increasing importance of their biodiversity value, little information is available on seed production which could be used to enlarge their regional presence. To contribute to this knowledge, the seed production of the major grass species were analysed for the spring growths of an Arrhenatherion elatioris meadow in 2003 and 2004. In the first study year, fertile culms of Anthoxanthum odoratum , Arrhenatherum elatius , Avenula pubescens , Dactylis glomerata, Holcus lanatus and Trisetum flavescens were collected on different dates and analysed for their reproductive efficiency. Floret site utilization was greater than 0·60 for all species and seed viability was above 80%, except for A. odoratum . Seed dormancy was present to a small extent only in A. odoratum and A. pubescens . With regard to the whole meadow, the density of fertile stems amounted to 850 m⁻² (811 m⁻² of which were grasses) and standing seed yield at seed maturity of the six grasses was about 33 100 seeds m⁻². As a consequence of the increase in viability occurring during seed development, the maximum standing viable seed yield was reached later. The total number of seeds produced throughout the spring growth period was 2·8 times that of the maximum standing seed yield. The quality and quantity of the seed production from spring growth make it suitable for establishing species-rich semi-natural grassland provided that seed obtained from the second cut is included to increase the presence of legumes and forbs.     

Effects of soil disturbance, seed rate, nitrogen fertilizer and subsequent cutting treatment on establishment of Bromus inermis seedlings on degraded steppe grassland in China

Establishment of seedlings of Bromus inermis , a native grass species of China, into a degraded steppe grassland was studied in an experiment with a factorial combination of different soil disturbance (control and harrowing), cutting post-sowing (control and cutting), nitrogen (N) fertilizer application (0 and 100 kg KNO₃ hm⁻²) and seed rate (400, 800 and 1200 seeds m⁻²) treatments. Seedling emergence and survival rates, and plant performance, were followed over 2 years. Seedling emergence was increased by soil disturbance (harrowing). Cutting post-sowing and N fertilizer application did not increase seedling emergence. Seedling survival rates at the end of first growing season were strongly influenced by harrowing and the use of higher seed rates. Seedling height was higher in the harrowing and the N fertilizer application treatments and at the higher seed rates. Seedling survival rates in the second growing season were low but much higher with harrowing than the other treatments. Soil disturbance by harrowing may have increased contact between seed and soil, and reduced competition from established plants. It is concluded that, for the restoration of degraded semi-arid grassland in China by re-seeding, soil surface disturbance is necessary for successful seedling establishment, and modest seeding rates should be used to control costs.     

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.     

Herbage growth and utilized output from grassland on dairy farms in southwest England: case studies of five farms, 1982 and 1983. I. Herhage growth

Herbage growth was measured in two contrasting years on five farms representing a range of soil types. On fields cut for conservation in 1982 DM production varied between farms from 12.3 tha^-1 to 14.1 tha^-1 in line with fertilizer N levels, which ranged from 220 to 333 kg ha^-1. In 1983 production was from 10.3 tha^-1 to 12.3 tha^-1; this again corresponded with fertilizer N, except on farm B which had the shallowest soils. On fields used for grazing all farmers used rotational management. Herbage accumulation was measured by trimming to 25 mm and harvesting after 4 weeks. As on conservation fields, herbage accumulation was generally greater on farms using more N, at least up to 300 kg ha-1.
In 1982 growth consistently exceeded predictions based on plot experiments. In 1983 growth was on average less than predicted on grazing fields but slightly more than predicted on cutting fields-We conclude that such predictions of annual production are a valuable aid to farm planning, and need not be reduced to allow for on-farm conditions, although they are least good at low levels of N. Predictions of individual cuts were not satisfactory, with a strong tendency to overestimate first cut and underestimate second cut.
There was no indication that annual herbage production was less on badly drained than on well drained soils. Indeed, in the dry summer of 1983 badly drained land appeared to have an advantage, despite considerable poaching damage in the spring. Furthermore, there was no evidence that production was deficient on swards dominated by Holcus and Agrostis spp.     

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

Annually sown cool-season small-grain cereal species can provide a valuable source of cool-season herbage for livestock in the southern Great Plains of the USA but limited access to field equipment for cultivation and sowing is an obstacle to their use. Italian ryegrass ( Lolium multiflorum Lam.) (IRG) can persist through self-seeding and may offer an alternative source of cool-season herbage. The effects of cutting dates in mid-April, early May or mid- to late May following sowing in the previous September, and of removing 0·57, 0·73 or 1·00 of the herbage mass at this time, on subsequent seed deposition, seedling re-establishment and herbage production of IRG were measured. Later cutting dates reduced seed production, seed deposition, 1000-seed weight and eventual re-establishment of IRG seedlings. Removing different proportions of the herbage mass did not compensate for reduced seed deposition arising from later cutting dates. Numbers of seed heads and seed required to achieve a self-seeded target population of 500 established seedlings m⁻² ranged from 885 to 5650 seed heads m⁻² and 3360 to 5850 deposited viable seeds m⁻². Re-establishment of IRG through self-seeding showed a 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 its rate of re-establishment.     

Fertilizer requirements for maintenance of a perennial ryegrass (Lolium perenne L.)/white clover (Trifolium repens L.) pasture growing on a humus iron podzol in N.E. Scotland

Ryegrass/white clover pastures were reseeded on heather moor in north-cast Scotland in 1978/79. By 1981, despite moderate fertilizer applications, the pastures had deteriorated and dry matter (DM) production was low. After preliminary soil and herbage analysis an omission trial was carried out in 1982/83 at two sites (A and B) to identify the factors which limited production.
At site A depressions in growth occurred in the absence of N, P and K. Perennial ryegrass was severely N deficient with concentrations in leaves of less than 22 g N kg⁻¹ in spring and summer even after application of 120 kg N ha⁻¹ annually. Rates of nitrogen fixation were high in spring but rapidly declined in June and July as the soil moisture tension increased. Application of N fertilizer also reduced the N₂ fixation rate. Deficiencies of F and K occurred despite apparently high levels of extractable F in the soil. Uptake of these nutrients was inhibited in the dry soil during the summer. White clover was more susceptible to drought than perennial ryegrass, probably because it rooted at a shallower depth.
Growth at site B was limited by acidity and lack of N and K. The soil pH was 4 8 (s.d. = 0middot;75) at 1-5 cm depth. Application of 2 5 t lime ha⁻¹ in spring 1982 had not altered the pH by autumn 1983.
It was concluded that methods of incorporating lime into the soil, together with ways of increasing the rates of N₂ fixation by white clover and transfer to grass, should be investigated further. Regular small applications of N and K may be necessary to sustain DM production at the level required by the farming system.