Quality Of Regrowth Research Articles

The impact of sward height, forage quality and competitive conditions on foraging behaviour of free-ranging rabbits (Oryctolagus cuniculus L.)

The habitat choice of the small hindgut fermenter, the European rabbit (Oryctolagus cuniculus L.), was studied in relation to sward height, forage quality, population size fluctuations and spatial distribution of burrows in a temperate grassland. In a multi-phase differential clipping experiment with alternating short and tall vegetation strips, rabbits tended to graze near the closest burrows in situations of equal vegetation heights, while a clear preference for short swards was found during summer (July). In this period, general crude protein content was significantly lower than in spring (April) and autumn (September), apparently leading to a potential forage quality deficit. The summer behavioural pattern with short sward preference coincided with the relatively higher crude protein content of short swards as compared to tall swards in this period, and with higher intraspecific competition, due to significantly larger numbers of animals present in summer. In autumn, rabbit densities decreased, while crude protein content of both short and tall vegetation increased to a higher, though not significantly different level, comparable with spring crude protein content. In those conditions, significant preference for low vegetation height could no longer be detected. Data suggest that selection for nutritive quality appears when intraspecific competition is high and nutritive quality remains under a certain threshold value. When, in autumn, competition decreases and nutritive quality increases again, short sward preference disappears. We conclude that short sward preference is primarily caused by the better forage quality of re-growth in periods of forage quality limitation, while this preference disappears when forage quality limitation no longer occurs.

Registration of ‘HighWest’ meadow bromegrass

AbstractThe USDA‐ARS announces the release of the meadow bromegrass [Bromus biebersteinii Roem. & Schult. (excluded)] cultivar ‘HighWest’ (Reg. no. CV‐25, PI 698169) for use on irrigated and semi‐irrigated pastures as a rapidly establishing forage grass with excellent dry matter yield (DMY) on sites receiving 350 mm of either annual precipitation or irrigation. Selection emphasis in HighWest meadow bromegrass was on crude protein (CP), DMY regrowth, quality, and seedling emergence from a deep planting depth under irrigation. HighWest has been evaluated in Utah comparing it to meadow bromegrass cultivars ‘Cache’, ‘Arsenal’, ‘Regar’, ‘Admiral’, and ‘Armada’. Genotyping by sequencing demonstrated that HighWest is significantly different genetically from Cache (P < .043), Arsenal (P < .003), Regar (P < .040), Admiral (P < .001), and Armada (P < .028) and grouped closest to Cache and Arsenal, consistent with its breeding pedigree. HighWest had greater (P < .05) percentage seedling emergence frequency at Millville, UT, compared with Arsenal, Regar, Armada, and Admiral. Based on a selection index that combined percentage seedling emergence frequency, DMY, and CP values, HighWest had a greater index value at 2.8 compared with Cache (1.7), Arsenal (−0.6), Regar (−3.2), Armada (−1.5), and Admiral (−1.0). Dry matter yield regardless of harvest date was similar to Cache, Arsenal, Regar, Admiral, and Armada. Forage regrowth of HighWest had CP values 6% greater than Cache. Water‐soluble carbohydrates were 22% greater in HighWest (87.0 g kg−1) than Cache. HighWest provides ranchers with additional plant material that maintains DMY and improves forage regrowth quality over the cultivar Cache.

Fire and forage quality: Postfire regrowth quality and pyric herbivory in subtropical grasslands of Nepal.

Fire is rampant throughout subtropical South and Southeast Asian grasslands. However, very little is known about the role of fire and pyric herbivory on the functioning of highly productive subtropical monsoon grasslands lying within the Cwa climatic region. We assessed the temporal effect of fire on postfire regrowth quality and associated pyric‐herbivory in the subtropical monsoon grasslands of Bardia National Park, Nepal. Every year, grasslands are burned as a management intervention in the park, especially between March and May. Within a week after fire, at the end of March 2020, we established 60 m × 60 m plots within patches of burned grassland in the core area of the Park. We collected grass samples from the plots and determined physical and chemical properties of the vegetation at regular 30‐day intervals from April to July 2020, starting from 30 days after fire to assess postfire regrowth forage quality. We counted pellet groups of cervids that are abundant in the area for the same four months from 2 m × 2 m quadrats that were permanently marked with pegs along the diagonal of each 60 m × 60 m plot to estimate intensity of use by deer to the progression of postfire regrowth. We observed strong and significant reductions in crude protein (mean value 9.1 to 4.1 [55% decrease]) and phosphorus (mean value 0.2 to 0.11 [45% decrease]) in forage collected during different time intervals, that is, from 30 days to 120 days after fire. Deer utilized the burned areas extensively for a short period, that is, up to two months after fire when the burned areas contained short grasses with a higher level of crude protein and phosphorus. The level of use of postfire regrowth by chital (Axis axis) differed significantly over time since fire, with higher intensity of use at 30 days after fire. The level of use of postfire regrowth by swamp deer (Rucervus duvaucelii) did not differ significantly until 90 days after fire, however, decreased significantly after 90 days since fire. Large‐scale single event fires, thus, may not fulfil nutritional requirements of all species in the deer assemblage in these subtropical monsoon grasslands. This is likely because the nutritional requirements of herbivores differ due to differences in body size and physiological needs—maintenance, reproduction, and lactation. We recommend a spatiotemporal manipulation of fire to reinforce grazing feedback and to yield forage of high quality for the longest possible period for a sustainable high number of deer to maintain a viable tiger population within the park.

Supplying nitrate before bud break induces pronounced changes in nitrogen nutrition and growth of young poplars.

Tree nutrient research concentrated on endogenous C and N remobilisation in spring has neglected to acknowledge the possibilities of significant effects of N uptake before bud break, especially on the quality of regrowth and N reserve remobilisation. To investigate this subject, experimental studies were performed on young poplars (Populus tremula×Populus alba, clone INRA 717-1B4) grown with a controlled nutrient supply: (i) without N, 'control'; (ii) N supplied throughout the course of the experiment, 'N-supply'; and (iii) N supplied only before bud break, 'N-pulse'. Results confirm the hypothesis that poplar scions can significantly take up nitrate before bud break, amounting to ~34% of the total N stored the previous year. After bud break, emerging leaves restart the sap flow, which increased nitrate uptake to support the regrowth. N-pulse and N-supply treatments were found to have significant effects shortly after a growth period, i.e. by increasing N content of all tissues (e.g. 37 and 81% in new shoots respectively), leaf area (18 and 29%) and specific leaf area (20 and 35%). Therefore, results confirm the hypothesis that early N supply plays a significant role in the N status and N remobilisation involved in the spring regrowth of young trees.

Effect of Overwintering Environment on the Survival of 30 Species of Herbaceous Perennials

Abstract There is increased interest in overwintering containerized perennials. However, there is little information available on overwintering success. The objective of this research was to determine overwinter survival and regrowth quality of 30 perennial species hardy in USDA zones 3, 4, or 5. Three overwintering treatments were used for each species: unprotected containers outside, containers in an unheated building, or in the ground. On April 16, 2004, and May 17, 2004, following overwintering, plant quality, plant height and flowering time were evaluated. Twenty-one species were successfully overwintered in an unheated building and 13 of those had quality ratings equal to or higher than those overwintered in-ground. Ceratostigma plumbaginoides, Kniphofia Pfitzer's Hybrid, Leucanthemum ×superbum ‘Snowcap’, and Stokesia laevis ‘Honeysong Purple’ rated significantly higher when overwintered in containers stored inside than in the ground. Flowering time and height measurement differences were not significant. Coreopsis ‘Limerock Ruby’, Diascia integerrima CoralCanyon™ and Gaura lindheimeri ‘Siskiyou Pink’ did not survive in any treatment. None of the species tested, with the exception of Sedum ‘Matrona’, survived when overwintered unprotected outside. Overwintering certain species of containerized perennials inside an unheated building such as a garage is a viable option for homeowners to improve survival.

Harvest Management of Switchgrass for Biomass Feedstock and Forage Production

AbstractSwitchgrass (Panicum virgatum L.), a warm‐season perennial grass native to North America, has potential as a biomass energy crop. Our objective was to develop harvest management recommendations for biomass feedstock and forage production. ‘Alamo’ switchgrass was established in 1992 at Stephenville and Dallas, TX. Four harvest frequencies (one to four cuts per year) and three final autumn harvests (Sept., Oct., or Nov.) were imposed from 1993 to 1996. Tiller densities were counted each spring. Neutral detergent fiber (NDF) and crude protein (CP) concentrations were measured in 1993 and 1994. Concentrations of NDF were lowest (avg. = 640 g kg−1) and of CP (avg. = 110 g kg−1) were highest in May‐harvested biomass. Forage quality of regrowth decreased with age, reaching NDF concentrations of 790 g kg−1 and CP of <20 g kg−1. Total seasonal yields decreased as harvest frequency increased; however, a severe drought reversed this trend at Dallas in 1996. The highest yields (15–20 Mg ha−1) occurred with a single harvest in mid‐September. Delaying the final harvest until November reduced yields. Harvest date and frequency did not affect tiller density, although tiller density decreased from 900 to 650 and 630 to 310 m−2 at Dallas and Stephenville, respectively, during 1994 to 1997. Thus, a single mid‐September harvest should maximize biomass yields in the south‐central USA. A two‐cut (spring‐autumn) system may allow a farmer to use initial growth as forage and the regrowth for biomass, but total yields would be reduced. More frequent harvests would reduce yields further.

Influence of Freeze Acclimation Procedure on Survival and Regrowth of Container-grown Campanula takesimana Nakai.

Crown divisions of Campanula takesimana were potted 1 Sept. 1994 and were grown under natural conditions until 19 Nov., when they were moved into a 3 °C greenhouse. On 15 Feb. 1995, 10 plants were randomly assigned to each of four temperature treatments (−5, −8, −11, and −14 °C), using each of four freeze acclimation procedures designated A through D: group A plants were held at treatment temperatures for 30 minutes; group B plants were first subjected to three alternating freeze-thaw cycles (−3 °C for 24 hours, 3 °C for 24 hours), then held at treatment temperatures for 30 min; plants in group C were held at −1 °C for 14 days and subsequently were exposed to treatment temperatures for 30 minutes; group D plants were held at treatment temperatures for 48 hours. A control group was held at 3 °C for the duration of the study. Following 6 weeks regrowth at 15 °C, plants were rated for survival and regrowth quality relative to unfrozen controls. At treatment temperatures of −8 °C and less, acclimation procedure significantly influenced survival and regrowth quality. Plants exposed to three freeze-thaw cycles had the highest regrowth ratings at treatment temperatures less than −5 °C, with no loss in marketability following exposure to −11 °C. In addition, all plants exposed to freeze-thaw cycles thrived following controlled freezing, whereas those in each of the other groups displayed a decline in survival with decreasing treatment temperatures. Holding plants for 14 d at −1 °C had no beneficial effect on survival or regrowth quality relative to plants held at constant above-freezing temperatures. Increasing exposure duration from 30 minutes to 48 hours significantly reduced regrowth quality at treatment temperatures of −8 °C and −11 °C.

Freezing Date and Duration Effects on Regrowth of Three Species of Container—grown Herbaceous Perennials

Abstract Three species of herbaceous perennials were transplanted from 400 cell-size plugs to 400-ml containers and grown in a glasshouse at 25C day/20C night (78/68F) ± 2C (4F) until October 10. At that time glasshouses were programmed for ambient outdoor temperatures, but maintained above 3C (38F) ± 2C at night. Plants were exposed in controlled programmable freezers to four freezing temperatures [−5,−5,−11 and −14C (23, 18,12,7F)] on November 15,1995, and January 1, 1996. Plants were allowed to remain at each temperature for either 30 or 120 minutes. Plants were then returned to the glasshouse, and rated for survival and salability following 6 weeks regrowth at 15C (59F). The rating scale was subjective and ranged from 1 to 5 (1 = worst, 5 = best, 3 and above considered salable). Regrowth means of all three species declined as treatment temperatures decreased. Although freezing date had a significant influence on regrowth quality of Aquilegia and Dianthus, only freezing duration influenced Dianthus regrowth. Neither factor significantly influenced regrowth quality of Lavandula. Treatment temperature and its interaction with freezing date or duration was statistically significant for all three species. All plants remained marketable following exposure to −11C (12F).

Seasonal Cold-acclimation Patterns of Sedum spectabile × telephium L. `Autumn Joy' and Sedum spectabile Boreau. `Brilliant'

Electrolyte leakage and regrowth were measured from September through January to determine cold hardiness of Sedum spectabile × telephium L. `Autumn Joy' and Sedum spectabile Boreau. `Brilliant' plants grown outdoors in central Iowa. Crowns were subjected to 0, –3, –6, –9, –12, –15, –18, –21, –24, or –27C. Regrowth tests were performed on whole crowns and electrolyte leakage was determined on excised tuberous root and crown tissue. Both cultivars were killed at –3C in September, but they acclimated gradually through January. Maximum hardiness was achieved in January, with killing temperatures of –27C for `Autumn Joy' and –21C for `Brilliant'. Regrowth quality ratings were significantly correlated with crown and tuberous root electrolyte leakage measurements, although the relationship was stronger for `Autumn Joy'.

Yield and Quality of RS-2, a Quackgrass X Bluebunch Wheatgrass Hybrid

Understanding the effect of defoliation frequency and N fertilization on plant growth, forage yield, and quality of RS-2, a quackgrass [Elytrigia repens (L.) Nevski.] x bluebunch wheat grass [Pseudoroegneria spicata (Pursh.) Love] hybrid, will help promote efficient use of this hybrid in livestock production systems. Plants were fertilized with 0, 112, or 224 kg N ha-1 in spring 1988 and 1989, or with a 112 + 112 kg N ha-1 split in spring and summer. One set of plants was unmowed or mowed to a 5cm stubble height once in July or August in 1988 and another set was mowed initially in May, June, July, August, September, or October 1989 and monthly thereafter through October. Peak standing crop of unmowed plants was 3,470 kg ha-1 in 1988 and 5,850 kg ha-1 in 1989. In 1989 yields of fertilized plants exceeded those of unfertilized plants by 1,000 kg ha-1. In 1988, crude protein exceeded 12% in unmowed forage and in 1989 varied from 20% in May to 8% in August. After fertilization, crude protein was increased by 2 to 4 percentage units in 1988 and by 2 percentage units in 1989, but fertilization had no effect on in vitro digestible organic matter. Regrowth contained more crude protein (15-22%) and digestible organic matter (29-40%) than unmowed forage. Sequential harvesting enhanced quality of regrowth, but standing crops did not exceed 350 kg ha-1; except in June 1989. Sixty percent of the accumulated yield was harvested with the first mowing during May through August. Plots harvested initially in September and October were only harvested once. Our findings indicate an increase in forage yield potential and forage quality of RS-2 after harvesting and fertilizing the RS-2 hybrid.

Epitaxial growth of Fe-doped sapphire thin films from amorphous Al oxide layers deposited on sapphire substrates

Thin films of amorphous Al2O3, about 280 nm thick, with Fe-cation concentrations of 0–4 at. % were deposited onto alpha-alumina [0001] substrates. Epitaxial regrowth of the thin films was found to occur during a postannealing process at temperatures of 950 and 1400 °C. The regrowth quality was determined by Rutherford backscattering spectrometry and ion channeling measurements. Perfect regrowth was found in the undoped samples after annealing at 1400 °C with a minimum backscattering yield of 2% in the Al sublattice. Furthermore, ion channeling angular scans revealed that Fe dopants occupied the substitutional sites of Al sublattice upon thermal anneal. This simple method of incorporating dopants into single-crystal alumina has potential in the fabrications of thin-film planar optical waveguides.

390 USE OF HARDENING TEMPERATURES ON SEVERAL SPECIES OF SEED-PROPAGATED HERBACEOUS PERENNIAL PLUGS PRIOR TO FREEZING

Storage of perennial plugs at subfreezing temperatures could be a valuable production tool since plants could be removed over relatively long periods for forcing. Several species of seed-propagated perennial plugs were pretreated at 0 and 5C under continuous 50 μmol·s-1m-2 PPF for 0, 2, 4, or 8 weeks. After each pretreatment period, plugs were placed into 4-mil polyethylene bags that were then sealed and placed at -2.5C for 0, 2, or 6 weeks. Plugs were then removed from the bags and placed into a 24C greenhouse for two weeks under ambient light levels and daylength, after which time they were rated for percent survival and general regrowth quality. Regrowth was not influenced by pretreatment temperature. Regrowth of Limonium dumosumtatarica, and Campanula carpatica `Blue Clips' following -2.5C storage was excellent with or without a pretreatment. Regrowth of Achillea filipendulina `Cloth of Gold,' Gaillardia grandiflora `Goblin,' and Iberis sempervirens `Snowflake' was improved on plugs given the 0 or 5C pretreatment. Hibiscus × hybrida `Disco Belle Mixed' regrowth was poor, regardless of pretreatment.

Optimization of selective area epitaxy for fabrication of circular grating distributed-Bragg-reflector surface-emitting lasers

The factors affecting the quality of regrowth of semi-insulating λ = 1.1 μm InGaAsP around circular mesas for the fabrication of circular grating distributed-Bragg-reflector surface-emitting lasers were investigated. Reactive ion etching of the mesas avoids the exposure of no growth planes on the mesa sidewalls, which results in good regrowth morphology around the entire mesa at a growth pressure of 50 mbar. High resolution scanning photoluminescence of the regrown quaternary material reveals a minimal 4 nm wavelength shift to longer wavelengths as the mesa edge is approached. A map of the photoluminescence intensity indicates that the quality of the regrown material is uniform around the periphery of the mesas. Fe doping of λ = 1.1 μm InGaAsP increases linearly with reactor gas pressure for fixed dopant and total gas flows, so the dopant flow must be adjusted for regrowth at a different reactor pressure if the same doping is desired. Activation of Fe in λ = 1.1 μm InGaAsP is independent of hydride concentration in the reactor in the range of (2–9)x10 -5 mol/l, and is virtually complete.

Determining Cold Hardiness of Heuchera sanguinea Engelm. `Chatterbox' Using Dormant Crowns

Dormant, intact crowns were used to determine the cold hardiness of the herbaceous perennial Heuchera sanguinea `Chatterbox'. Crowns were placed in moist cheesecloth, wrapped in aluminum foil, and subjected to -4,-6,-8,-10,-12,-14, -16, or -18C in a programmable freezer. Regrowth quality ratings and dry-mass measurement decreased linearly with temperature. No regrowth was evident from any crown exposed to -12C or lower temperatures. Freezing dormant plant crowns proved an efficient and reliable technique for estimating cold hardiness of Heuchera `Chatterbox'.

Storage Molds of Herbaceous Perennials

Abstract Fungi were subcultured and identified to genera from 24 species of bare-root herbaceous perennials held in commercial cold storage chambers. Ten genera dominated the cultures. Although no pathogenicity tests were conducted, most genera were usually considered to be saprophytes or opportunistic pathogens which often infect previously damaged tissue. Other species of perrennials were harvested from commercial fields and given a Benlate dip fungicide treatment prior to storage. After six months, crowns were removed, rated for mold development, potted, and evaluated for quality of regrowth. Surface molds were generally suppressed by Benlate (Benomyl 50WP), but regrowth was rarely improved and often reduced. Use of fungicides to improve cosmetic appearance of stored herbaceous perennials is not recommended on the basis of these results.

Effect of crown rust on regrowth, competitive ability and nutritional quality of perennial and Italian ryegrasses

Infection of susceptible cultivars of perennial (Lolium perenne) and Italian (Lolium multiflorum) ryegrasses with crown rust (Puccinia coronata) reduced yield measured 6 weeks after infection and at two regrowth cuts. In perennial, but not Italian, ryegrass, rust infection of mixed swards of a resistant and a susceptible cultivar reduced the contribution to yield made by the susceptible cultivar and increased that of the resistant cultivar. This effect persisted for three regrowth cuts. The trend in effect on the number of tillers, but not plant height, was similar.Infection increased leaf protein in susceptible perennial ryegrass but had little effect in Italian ryegrass. In both species, rust reduced water‐soluble carbohydrate and the predicted digestibility of susceptible and resistant cultivars, but had no effect on quality of regrowth.

Selection for in Vitro Dry Matter Disappearance in Switchgrass Regrowth1

The potential for genetic progress from selection for in vitro dry matter disappearance (IVDMD) of switchgrass (Panicum virgahm L.) regrowth forage has not been determined by breeders. Improved regrowth quality is needed to increase average daily gain of ruminants in mid‐ to late‐summer. In this study, 33 half‐sib families of switchgrass were evaluated over 2 yr for initial growth dry weight, IVDMD, and N concentration, and for regrowth IVDMD. The regrowth IVDMD was measured from plant samples taken in July (IVDMDl) and August (IVDMD2). Genetic variance estimates were obtained to predict direct selection responses and correlated responses using the modified ear‐to‐row procedure. Selection indices were also constructed to predict responses to multiple‐trait selection. Expected gains from direct selection for dry weight (1.19 kg plant−1), IVDMDl (666 g kg−1), and IVDMD2 (498 g kg−1) were 0.24 kg plant−1, and 50 and 35 g kg−1, respectively, while maximum gains from correlated responses were 0.02 kg plant−1, and 40 and 36 g kg−1, for the respective traits. An estimated index consisting of initial growth dry weight, IVDMD, N, and regrowth IVDMD2 provided simultaneous expected gains of 0.04 kg plant−1 for dry weight and 42 g kg−1 for IVDMD2. Switchgrass regrowth IVDMD may be improved without greatly altering dry matter yield per plant and should receive greater priority in cultivar development.

Control of anthracnose in the tropical pasture legumeStylosanthes capitataby burning

Abstract Although the value of burning in improving forage quality and productivity is well known, there are few reports on effects of fire on diseases of pasture plants. Burning is a broad‐spectrum control against fungi, reducing above‐ground pathogenic inoculum. Stylosanthes capitata Vog., a woody perennial legume, is well‐adapted to acid infertile soils, it regenerates after burning and has great forage potential. Many ecotypes, however, are susceptible to anthracnose, a damaging forage disease. Many disease control measures are impractical and selection and breeding for resistance may take years. The effect of burning on anthracnose of S. capitata was therefore evaluated as a temporary control measure. At the CIAT Research Station, Carimagua, Colombia, severely anthracnosed stands of S. capitata CIAT 1097 were cut and burnt in March 1979. Cut unburnt plots were used as controls. Dry weight and anthracnose lesion number were recorded each month from five random 1600 cm2 samples per treatment. In March 1980, further treatments were imposed on the plots to assess the effect of annual and biennial burns. Burning, as annual and biennial burns, dramatically reduced anthracnose by 60 to 77.5% and 74.1% respectively. Soil nitrogen content and the quality of regrowth after burning were considerably higher. Burning therefore proved a potentially successful temporary control measure of anthracnose for the particular plant‐pathogen combination.

Effects of N, P, and K Fertilization on Yield and Quality of Tall Fescue Forage in Winter1

AbstractUse of tall fescue (Festuca arundinacea Schreb.) regrowth to extend the grazing season into late fall and winter is becoming increasingly popular in middle‐latitude regions of the USA. Few studies have been reported, however, that deal with factors influencing yield and quality of regrowth forage in winter. A field study was begun in October of 1971 to measure the effects of N, P, and K fertilization on yield and quality of tall fescue regrowth in late fall and winter. Eight fertility regimes were established in each of four replications. These were: 1) N applied at 60 kg/ha in spring and after each of three summer harvests, 2) P applied at 30 kg/ha in spring and in late summer, 3) K applied at 60 kg/ha in spring and in late summer, 4) to 7) the four possible combinations of the above three treatments, and 8) no fertilizer treatment. Forage from all plots was harvested in mid‐May, early July, and mid‐August and then in either mid‐December or mid‐January. In 1971 when the experiment began, all plots were harvested on 9 October rather than mid‐August and then in either mid‐December or mid‐January. Nitrogen fertilization increased yield and concentrations of in vitro digestible dry matter, total nonstructural carbohydrate, K, Mg, and N in the late fall and winter harvested forage and decreased concentrations of dry matter and Ca. Yield and concentration of quality components decreased less in N fertilized forage than in unfertilized and P and K fertilized forage as harvest was delayed from December to January. Phosphorus fertilization had little effect upon yield and quality components. Potassium fertilization decreased both Ca and Mg concentrations. Results suggest that winter forages of sufficient quality to meet most of the nutritional needs of many classes of livestock in mid‐latitude regions of the U.S. may be obtained by manipulating summer and/or fall harvest dates and fertilization rates. Supplementation of regrowth forage with Na and Mg and possibly with P during late winter months would be required.

Diallel analysis of competition between grass species

SUMMARYTimothy [S. 50], meadow fescue [S. 53], perennial ryegrass [S. 23], Italian ryegrass [S. 22] and cocksfoot [S. 143] were grown together in all possible pair combinations at two levels of fertility, in a pot experiment. Dry weight of herbage and tiller counts were determined at 136 and 198 days from sowing. The data were analysed for competitive effects by the application of the diallel analysis technique of Durrant (1965). The competitive effects were largely compensatory in type with dominant species such as Italian ryegrass and perennial ryegrass increasing in mixtures, relative to their pure stand values, more than species such as timothy and meadow fescue declined. This resulted in a tendency for the mixture means to exceed their mid-constituent values.The competitive effects on the reciprocal differences were seen to be predominantly of the alpha type; that is, there was a constant increase or decrease in one or more species when grown with others. The alpha values were found to be correlated with the unmixed species values so that ƀ, the mean effect, wasappropriately calculated from alpha. The over-all value of ƀ was –1.216, which means that for each gram difference in weight between the species when grown by themselves there was 2.452 g increase in difference between the species when grown in mixtures, the larger species increasing and/or the smaller species decreasing. There were significant differences in ƀ values between harvests, the ƀ competitive effects being approximately twice as large in the more mature plants. Although the alpha competitive effects increased in magnitude with time the species order remained relatively constant, and in terms of competitive ability the species could be placed in the ascending order, meadow fescue, timothy, cocksfoot, perennial ryegrass and Italian ryegrass.Tiller number showed a similar pattern, but the ƀ values were smaller, and not significant. Nevertheless competition had differential effects upon the plant weight/ tillering relationship and it is possible that the resultant morphological changes would influence the re-growth quality of the species.The conclusions derived from the analysis of reciprocal differences in this work is compared with earlier examples.