The phytotoxicity of the herbicides bromoxynil, pyridate, imazethapyr and a bromoxynil + diflufenican mixture on subterranean clover and lucerne seedlings

1999 ◽  
Vol 39 (7) ◽  
pp. 839 ◽  
Author(s):  
B. S. Dear ◽  
G. A. Sandral
Keyword(s):  
Soil Water ◽  
Seed Yield ◽  
Field Experiments ◽  
Seed Set ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Weed Suppression ◽  
Positive Effects ◽  
Clover Seed ◽  
High Level

Summary. The effect of the herbicides pyridate, imazethapyr and a bromoxynil + diflufenican mixture on subterranean clover (Trifolium subterraneum L.) (cvv. Trikkala and Karridale) and lucerne (Medicago sativa L.) (cv. Aurora) seedlings was examined in randomised plot field experiments in 2 successive years. Responses were compared against an unsprayed control and a standard bromoxynil application. The herbicides and the rates of product applied were: bromoxynil + diflufenican (0.5, 1.0 L/ha), imazethapyr (0.18, 0.3 L/ha), pyridate (1.0, 3.0 L/ha), and bromoxynil (1.4 L/ha). Weeds were removed by hand from the subterranean clover experiments but not the lucerne experiments. Pyridate and imazethapyr were the least phytotoxic of the herbicides applied on both subterranean clover and lucerne. The bromoxynil + diflufenican mixture was the most phytotoxic, causing severe leaf burn and a depression in herbage biomass in both species. Despite the high level of phytotoxicity by some treatments, none of the herbicides reduced lucerne seedling numbers. Lucerne herbage yields in late spring were higher in most sprayed plots compared with the unsprayed control due to the removal of weed competition. Seed yield responses in subterranean clover due to herbicide application ranged from negative responses up to –21% with pyridate to positive responses up to 92% with the bromoxynil + diflufenican treatment relative to the weed-free, unsprayed control. The positive responses were attributed to increased availability of soil water during seed set in treatments in which herbicides suppressed legume biomass. There was a good correlation in both 1992 (R2 = 0.85–0.89) and 1993 (R2 = 0.63–0.73) between the depression in herbage yield in spring and the increase in seed set relative to the control. Soil water under the subterranean clover cultivar Karridale in spring was highest in the bromoxynil and imazethapyr treatments, which produced a large reduction in biomass, and lowest in the control and pyridate treatments, which had showed the least depression in biomass 60 days after treatment application. Although some herbicides cause a high level of phytotoxicity, their use in weedy subterranean clover–lucerne mixtures is justified in view of the small negative, and potentially large positive, effects on subterranean clover seed yield and the increased lucerne yields later in the season due to weed suppression.

Effect of phalaris (Phalaris aquatica L.) and lucerne (Medicago sativa L.) density on seed yield and regeneration of subterranean clover (Trifolium subterraneum L.)

2000 ◽  
Vol 51 (2) ◽  
pp. 267 ◽  
Author(s):  
B. S. Dear ◽  
P. S. Cocks ◽  
A. D. Swan ◽  
E. C. Wolfe ◽  
L. M. Ayre
Keyword(s):  
Medicago Sativa ◽  
Seed Yield ◽  
Seed Bank ◽  
Seed Set ◽  
Basal Area ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Phalaris Aquatica ◽  
Medicago Sativa L ◽  
Clover Seed

A mixture of 3 subterranean clover (Trifolium subterraneum L.) cultivars (cvv. Goulburn, Seaton Park, and Dalkeith) was grown with 5–40 plants/m2 of phalaris (Phalaris aquatica L.) or lucerne (Medicago sativa L.) for 3 years at Wagga Wagga, NSW (147°21´E, 35°03´S). Clover seed yield was assessed each year, the number of regenerating clover seedlings was counted, herbage yield of clover and the perennials was measured, and the change in perennial density recorded. The influence of perennials on water availability in spring and light during clover seed set was also examined. The impact of perennial density on clover was assessed using regression analyses. In each of the 3 years, subterranean clover seed yield was negatively related to perennial density, but phalaris suppressed clover seed yield more than equivalent densities of lucerne in 2 of the years. Clover seed yield was positively related (R2 = 0.30–0.85) to clover biomass in spring in all 3 years (except for subterranean clover in phalaris in 1994) and to the proportion of total photosynthetically active radiation reaching the clover canopy beneath the perennial (R2 = 0.33–0.83) in 2 of the 3 years. There was a positive relationship between clover seedling regeneration in autumn and size of the summer seed bank in both years in lucerne (R2 = 0.40–0.76) and in 1 year in phalaris (R2 = 0.76) and a negative association between perennial density and clover seedling regeneration. The rate at which the surface profile (0–37 cm) dried in spring was independent of phalaris and lucerne density over the 3 years and did not differ from that of pure clover. The late season clover cultivar, Goulburn, constituted between 57% and 79% of the seed bank following seed set, substantially more than the earlier flowering cultivars, Seaton Park and Dalkeith. Neither perennial density nor species changed the relative competitiveness of the 3 cultivars. The high seed yield of Goulburn and the lack of a perennial-induced change in surface soil water in spring suggest that growing perennials in association with subterranean clover does not increase the level of moisture stress during clover seed set. The good performance of Goulburn is attributed to superior competitive ability for light in late spring. The basal area occupied by lucerne and phalaris increased with perennial density in each of the first 2 years. However, in the third year, phalaris basal area was similar at all densities. The findings suggest that sowing low densities of lucerne should assist in promoting seed yield and regeneration of subterranean clover. Management of phalaris, which has the capacity to substantially increase plant size at low densities, may require additional strategies such as more frequent grazing in spring.

Application of non-selective herbicides during flowering of pasture legumes can reduce seed yield and alter seed characteristics

1998 ◽  
Vol 38 (6) ◽  
pp. 583 ◽  
Author(s):  
A. Wallace ◽  
R. A. Lancaster ◽  
N. L. Hill
Keyword(s):  
Seed Yield ◽  
Seed Set ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Farming Systems ◽  
Early Summer ◽  
Hard Seed ◽  
Time Of Application ◽  
Pasture Legumes ◽  
Clover Seed

Summary. Spraytopping, the application of a low rate of non-selective herbicide (usually glyphosate or paraquat) to annual grass seed heads in the spring or early summer for seed set control is widely practised throughout Australia. While grasses are the targets of the spray treatment, annual pasture legumes may also be damaged by spraytopping, particularly if the legumes are flowering at the time of application. The effect of applying glyphosate (90, 112 or 162 g a.i./ha), paraquat (100 g a.i./ha) and glyphosate plus MCPA (90 + 150 g a.i./ha) to subterranean clover (Trifolium subterraneum L. cv. Dalkeith) and annual medic (Medicago polymorpha L. cvv. Serena, Santiago and Circle Valley) pastures at various times during flowering was investigated during the spring of 1993 and 1994. Experiments were located at Tincurrin and Tenindewa, Western Australia. Subterranean clover seed yield was most affected by applications of glyphosate (90 and 162 g a.i./ha) and glyphosate plus MCPA (90 + 150 g a.i./ha) during early–mid flowering. Seed yield was reduced by as much as 88% following application of glyphosate plus MCPA when 20% of the subterranean clover plants were flowering. Treatment with paraquat (100 g a.i./ha) during mid–late flowering reduced seed yield of subterranean clover by 25–50% in experiment 1 only. Medic seed yield was reduced up to 90% depending on cultivar when glyphosate (112 g a.i./ha) was applied during early–mid flowering. In addition to seed yield, the level of hard seed was assessed. Treatment of subterranean clover during early–mid flowering with glyphosate (90 and 162 g a.i./ha) significantly reduced the quantity of hard seed produced. Thirty–forty percent of subterranean clover seed was germinable soon after seed set, compared with 7–17% germinable for the seed from untreated plants. Treatment with glyphosate (112 g a.i./ha) reduced the proportion of hard seed in the medics when applied during mid flowering. Treatment with paraquat had little effect on the proportion of hard seed formed. This work demonstrates that using a spraytopping technique for control of seed set in annual grasses may dramatically reduce seed yield in pasture legumes. Spraytopping can further reduce the ability of legumes to persist in cropping rotations by reducing the amount of hard seed formed. Implications for practical farming systems are outlined.

Effect of companion perennial grasses and lucerne on seed yield and regeneration of subterranean clover in two wheatbelt environments

2001 ◽  
Vol 52 (10) ◽  
pp. 973 ◽  
Author(s):  
B. S. Dear ◽  
J. M. Virgona ◽  
G. A. Sandral ◽  
A. D. Swan ◽  
B. A. Orchard
Keyword(s):  
Seed Production ◽  
Seed Yield ◽  
Seed Bank ◽  
Seed Set ◽  
Subterranean Clover ◽  
Seedling Regeneration ◽  
Early Autumn ◽  
Background Population ◽  
Seed Reserves ◽  
Clover Seed

Seed production of subterranean clover (Trifolium subterraneum L.) in mixtures with lovegrass (Eragrostis curvula (Schrader) Nees cv. Consol), cocksfoot (Dactylis glomerata L. cv. Currie), phalaris (Phalaris aquatica L. cv. Sirolan), danthonia (Austrodanthonia richardsonii (Cashm.) H.P. Linder, cv. Taranna), and lucerne (Medicago sativa L. cv. Aquarius) was compared with pure and degraded (invaded by annual volunteers) annual subterranean clover pasture at 2 sites (Junee and Kamarah) in the southern wheatbelt of New South Wales. Seed yields, clover seedlings in winter, and the change in the proportion of 3 subterranean clover cultivars (Dalkeith, Seaton Park, Goulburn) when grown with and without perennials were assessed. The effect of thinning the perennials to 10 plants/m2 on clover seed set was examined at the drier site. Seed production of subterranean clover in the mixtures was depressed by up to 50% compared with the pure and degraded annual swards. Initial clover seed poduction in the mixtures was at least 60 kg/ha even in the drought year at the wetter site (Junee), and >85 kg/ha at Kamarah, the drier site (seedling establishment at Kamarah failed in the drought year). Clover seed reserves in the following 2 years progressively increased to >300 kg/ha in the perennial swards at Junee but were <100 kg/ha by the end of the third year at Kamarah. In comparison, seed reserves in the pure clover and degraded annual swards were >650 kg/ha at Junee and >350 kg/ha at Kamarah. Reducing perennial density to 10 plants/m2 at the drier site increased clover seed yield about 3-fold in the first year compared with unthinned perennial swards. The increased seed yield was due to increased numbers of burrs set and increased seeds per burr and, in all perennial pasture treatments except lucerne, increased seed size. Clover seedling regeneration in 3rd and 4th year after sowing was substantially lower in the perennial-based mixtures than annual plots, with a significant (P < 0.05) positive correlation at both sites between clover seedling regeneration and seed bank size (1996, r2 = 0.46–0.64; 1997, r2 = 0.64–0.85). Following false breaks in early autumn, clover seedling populations were substantially higher in the pure and degraded clover treatments than in most perennial treatments. The proportion of the 3 cultivars present in the seed bank at the end of the pasture phase differed between sites but the sward type only influenced the proportion at the drier site. At the medium rainfall site, the later maturing cultivar Goulburn constituted 27–54% of the seed bank and the early flowering Dalkeith 25–46%, with unsown cultivars being insignificant ( <1%). At the low rainfall site, Dalkeith was the major component (33–52%) of the seed bank but the background population of unsown cultivars constituted 11–48%, the lowest proportion being in swards without a perennial component. The proportion of Goulburn was highest (23%) in the pure sward and lowest (10%) in lucerne and phalaris. It was concluded that subterranean clover could form relatively stable mixtures with perennials in medium rainfall environments, with clover populations increasing with time. In lower rainfall environments, clover seedling populations in perennial swards may be low due to reduced seed set and decreased seedling survival following early autumn rains. In these environments earlier maturing, hard-seeded cultivars are more likely to persist in mixtures and there is more potential for unsown cultivars to constitute a greater proportion of the sward. Decreasing perennial density offers scope for improving clover seed set and survival in these environments.

Lucerne, phalaris, and wallaby grass in short-term pasture phases in two eastern Australian wheatbelt environments. 2. Effect of perennial density and species on subterranean clover populations and the relative success of 3 clover cultivars of different maturity

2007 ◽  
Vol 58 (2) ◽  
pp. 123 ◽  
Author(s):  
B. S. Dear ◽  
G. A. Sandral ◽  
J. M. Virgona ◽  
A. D. Swan ◽  
B. A. Orchard ◽  
...  
Keyword(s):  
Seed Yield ◽  
Seed Bank ◽  
Seedling Survival ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Climatic Conditions ◽  
Perennial Species ◽  
Growing Season Length ◽  
Herbage Yield ◽  
Clover Seed

The effect of the density of 3 perennial species, phalaris (Phalaris aquatica L.), wallaby grass (Austrodanthonia richardsonii Kunth), and lucerne (Medicago sativa L.), on seed set, regeneration, and the relative competitiveness of 3 cultivars of subterranean clover (Trifolium subterraneum L.) was examined in 2 environments in the south-eastern Australian wheatbelt. Seed yields of subterranean clover were inversely related to perennial density at both sites over the first 2 years, the relationship varying with perennial species. Phalaris depressed the seed yield of clover more than lucerne and wallaby grass in the second and third year at equivalent densities. Clover seed yield was positively related to clover herbage yield in late spring at both sites, and inversely related to perennial herbage yield. Clover seed yield displayed an increasing linear relationship with the proportion of light reaching the clover understorey in spring, which in turn was inversely related to perennial density and perennial herbage yield. Clover seedling regeneration in mixed swards in autumn was positively related to the size of the summer seed bank, but negatively related to perennial density. Clover seedling survival following a premature germination at Kamarah was inversely correlated to the density of phalaris and lucerne in the sward. The relative competitiveness of the 3 subterranean clover cultivars varied between sites, with climatic conditions (rainfall and growing-season length) having a greater effect on the relative cultivar performance than companion perennial species or density. The later maturing subterranean clover cv. Goulburn became the dominant cultivar at the wetter site, constituting 72% of the seed bank, but declined to only 3–8% of the seed bank at the drier site. The proportion of the early flowering cultivar Dalkeith in the seed bank increased over time at the drier site and was highest (53%) in plots with the highest perennial density. We concluded that although perennial pasture species will depress clover seed yield and subsequent regeneration, these effects could be minimised by reducing perennial densities and exploiting variations in competitiveness between perennial species as identified in this study. Sowing earlier maturing subterranean clover cultivars would only be an advantage in increasing clover content in low-rainfall environments. The findings suggest that clover seed reserves and regeneration could also be increased by using grazing management to reduce the level of shading of clover by perennials, a factor associated with reduced clover seed yield.

Increased seed production of subterranean clover pastures in response to fertilizers supplying calcium

1974 ◽  
Vol 14 (71) ◽  
pp. 749 ◽  
Author(s):  
PG Ozanne ◽  
KMW Howes
Keyword(s):  
Seed Production ◽  
Calcium Concentration ◽  
Field Experiments ◽  
Seed Set ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Unit Weight ◽  
Gypsum Plaster ◽  
Total Seed ◽  
Seed Yields

The effects of four common fertilizers containing calcium on seed production in subterranean clover (Trifolium subterraneum) were measured at six locations over five years in a total of fifteen field experiments. Calcium as a sulphate, carbonate or phosphate salt was applied to subterranean clover pastures either at the start of the growing season (autumn) or at flowering (spring). Gypsum, plaster of Paris, or lime gave large increases in seed yield per unit area and also per unit weight of tops. Spring applications of superphosphate increased seed yields in only two out of four experiments. Gypsum applied in spring at 200-500 kg ha-1 was as effective as 2,000 kg ha-1 of lime applied in autumn. Applications of lime in spring were much less effective. Increased seed yields were due to increases in burr yield, seed number per burr, and mean weight per seed. They were usually accompanied by increases in calcium concentration in the seed. Responses in seed production to calcium applications were obtained in all three sub-species of Trifolium subterraneum. In two experiments, newly sown on a soil type on which subterranean clover regeneration and persistence is commonly very poor, applied calcium doubled or quadrupled seed set. In 13 experiments using soils on which subterranean clover had persisted as the major component of the pasture for several years, calcium in the year of application increased the total seed bank by 6 to 31 per cent, and the current seed set by a greater amount.

Effect of timing of forage conservation on forage yield and quality, seed yield and seedling regeneration of four subterranean clover (Trifolium subterraneum) cultivars

2008 ◽  
Vol 48 (8) ◽  
pp. 1133 ◽  
Author(s):  
B. S. Dear ◽  
B. F. Hackney ◽  
G. M. Dyce ◽  
C. A. Rodham
Keyword(s):  
Seed Yield ◽  
Seed Set ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Forage Yield ◽  
Seedling Regeneration ◽  
Yield And Quality ◽  
Cutting Height ◽  
Seed Yields ◽  
Forage Yields

Swards of four cultivars of subterranean clover (Trifolium subterraneum L.) were cut at three different times to determine the effect on forage yield and quality, seed set and seedling regeneration in two successive seasons in southern New South Wales. The four cultivars of subterranean clover (Seaton Park LF, Junee, Goulburn and Clare) were cut on 23–25 September (early cut), 8–10 October (mid cut) or 22–23 October (late cut), to simulate an early silage, late silage or hay cut. Additional treatments imposed included either grazing or leaving the regrowth after cutting and raising the cutting height from 3 to 6 cm. Forage yields ranged from 3.5 to 9.3 t dry matter (DM)/ha in the first year and from 2.0 to 5.9 t DM/ha in the second year. Herbage yield was influenced by both cultivar and harvest time with the highest yields achieved with the mid cut. Lower forage yields at the later cut were attributed to losses due to respiration and decay under dense leaf canopies. Changes in forage quality were consistent across both years, with in vivo DM digestibility declining from 76–79% to 69–70% as cutting time was delayed. Crude protein fell from 22–24% to 14–17% over the same period, depending on cultivar. Seed yields in both years were influenced by both cutting time and cultivar with a positive relationship (R2 = 0.45–0.61) between herbage present in late spring after a period of regrowth and subsequent seed yield. The early flowering cultivar Seaton Park LF had the highest seed yield in both years and the more erect cultivar Clare had the lowest. Seed yields declined with later cutting time but increased by an average of 39% when the cutting height was raised from 3 to 6 cm. Seedling regeneration reflected seed yield responses with the largest seedling regeneration occurring in treatments cut early. The study found that forage conservation in early October is likely to yield more and be of higher quality than swards cut later in the season. Seed set is greatly reduced by all cutting strategies to levels unprofitable for seed harvesting but may be adequate for pasture regeneration.

Studies on nodulation responses to pelleting of subterranean clover seed.

1961 ◽  
Vol 12 (4) ◽  
pp. 578 ◽  
Author(s):  
JA Thompson
Keyword(s):  
Seed Coat ◽  
Field Experiments ◽  
Chemical Constituents ◽  
Chemical Properties ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Coating Materials ◽  
Physical Separation ◽  
Clover Seed

In a series of field experiments on seven soils of pH 6.0 or higher, nodulation of subterranean clover (Trifolium subterraneum L. var. Tallarook) was improved by pelleting the seed with various glues and coating materials, prior to inoculation with dry peat inoculum. On these soils the responses were not related to the chemical properties of the pellet materials. The beneficial effect was apparently the result of physical separation of the seed coat and inoculum. It is postulated that pelleting of seed protects the inoculum from an antibiotic, whlch has been found in subterranean clover seed coats, and which is active against Rhizobium in culture. On a soil of pH 5.1 a nodulation response to two types of pelleting materials was apparently related to the chemical constituents of the coating materials. In this soil there was less evidence of the importance of physical separation of the inoculum from the seed coat. It seems likely that soils may differ considerably in their ability to inactivate the antibiotic. Nodulation was not improved by in situ fumigation, prior to sowing, of two soils of pH 6.0 and 6.6, which indicated that antagonism by soil microorganisms was not the cause of poor nodulation in these soils. Significant nodulation responses to pelleting were obtained in sowings in these fumigated soils.

Influence of cultivar and season on the response of Trifolium subterraneum to simazine

1992 ◽  
Vol 32 (8) ◽  
pp. 1095 ◽  
Author(s):  
BS Dear ◽  
DJ Conlan ◽  
MF Richards ◽  
NE Coombes
Keyword(s):  
Seed Set ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Yield Response ◽  
Yield Losses ◽  
Lolium Rigidum ◽  
Herbage Yield ◽  
Annual Grasses ◽  
Clover Seed ◽  
Seed Yields

The tolerance of 6 cultivars of Trifolium subterraneum (subterranean clover) to simazine applied at 0.63 and 1.25 kg a.i./ha was determined under weedfree conditions in the field by measuring herbage and seed yields. Large herbage yield losses occurred as a result of the simazine in spring in the 2 years of the experiments. In 1989, spring herbage yield losses of the cultivars at the 0.63 and 1.25 kg/ha simazine rates averaged 56 and 82%, respectively. In 1990 the spring herbage yield losses were 27 and 51%. Significant variation in tolerance was observed between cultivars in both years, with Trikkala being the most tolerant and Karridale the most susceptible cultivar. Rate of herbicide had the greatest effect on herbage yield, with cultivar having a smaller effect. In 1989, with relatively favourable spring conditions, clover seed yields were depressed by simazine, but in 1990 when drier conditions prevailed during flowering and seed set, seed yields were unaffected or slightly increased by simazine in all cultivars except the early-flowering cultivar Dalkeith. Seed yields of simazine-treated swards were 196-1480 kg/ha in 1989 and 359-686 kg/ha in 1990. The seed yield response in 1990 suggests that herbicides which retard growth in winter help to conserve soil water and, therefore, may benefit seed filling later in the season. The presence of Lolium rigidum at spraying did not reduce the effect of the herbicide on clover herbage yield and had no effect on seed set. Although simazine may reduce herbage yields and, in some cases, seed yields, its use may be justified for the control of annual grasses when other factors such as disease control, pasture quality, and level of weed competition are considered.

The effect of boron supply on the growth and seed production of subterranean clover (Trifolium subterraneum L.)

1987 ◽  
Vol 38 (3) ◽  
pp. 537 ◽  
Author(s):  
BS Dear ◽  
J Lipsett
Keyword(s):  
Seed Yield ◽  
Seed Set ◽  
Acid Soils ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Seed Formation ◽  
The Past ◽  
Foliar Symptoms ◽  
Buried Seed ◽  
Seed Yields

There has been little research on the boron (B) status of subterranean clover, despite strong indications of deficiency of B in southern Australia where clover decline has been reported. This paper describes glasshouse experiments to vary the level of B supply to clover grown on soils low in B. On a soil farmed in a cereal clover rotation, herbage yields of clover increased by 25% with applied B, but seed yields, negligible without B, increased 21-fold. On two other acid soils, from pastures, there were also large responses to B in seed yield (1.5- and 5.1-fold respectively); liming increased the responses (8- and 55.2-fold). However, herbage production was less responsive to B (25% and 1.7-fold with liming); on the unlimed soils, application of B depressed yield (- 1 and -21%). This is attributed to there being enough B to sustain herbage growth, but inadequate for seed formation. These results show that herbage yield, conventionally employed in the past, is not a satisfactory index of B status for total performance in subterranean clover. The response to B in seed yield was associated with increases in: numbers of seed set (75% to 22.6-fold, depending on the particular combination of soil and liming); size of seed (10% to 1.2-fold); proportion of buried seed (20%-70%). It is suggested that these favour establishment and persistence of clover and that clover decline may well involve deficiency of B. It was shown that concentration of B in the plant does not necessarily relate predictably to yield of herbage and that reduction in seed yield may not be heralded by foliar symptoms, since seed requirement exceeds that of herbage.

Seeding rate, time of sowing and fertilizers for subterranean clover seed production

1973 ◽  
Vol 13 (65) ◽  
pp. 681 ◽  
Author(s):  
BJ Quinlivan ◽  
AC Devitt ◽  
CM Francis
Keyword(s):  
Seed Production ◽  
Seed Set ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Major Effect ◽  
Seeding Rate ◽  
Sowing Time ◽  
Commercial Crop ◽  
Clover Seed ◽  
High Phosphate

In two experiments in successive years on a sandy soil in Western Australia, seed production of subterranean clover (Trifolium subterraneum) when sown as a commercial crop was greatly influenced by time of sowing, phosphate rates and seeding rate. Early (April) sowing, high phosphate (up to 600 kg ha-1) and higher seeding rates (up to 24 kg ha-1) all increased seed set but the major effect was that of earliness of sowing. Time of sowing interacted with phosphate rates, the time of sowing differences being only fully expressed at high phosphate rates. Artificial nitrogen applied had a significant effect on seed yield in one of the trial years.

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