JASP 3 -- 1985.pdf - International Herbage Seed Group

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10 JOURNAL OF APPLIED SEED PRODUCTION, VOL. 3, 1985abnormal seeds (Figure 2). These speeds also gave the highestEsvalues (Bilsland et al., 1984).Severity of scarification is extremely important in producingnormal germinating seeds. Increasing the number ofpasses through the rubber concaves increased impaction andlowered normal germinating seed percentages. Grant (1979)also found that increasing the number of passes in a similarFerrell Scarifier with rubber concaves lowered germinationof Stylosanthes guianensis var. intermedia cv. Oxley. Theuse of carborundum concaves is often too abrasive on herbagelegumes, producing too many abnormal seedlings(Grant, 1979). Preliminary tests before experiments on Makulotus began showed that at any speed, too many split andcracked seeds were produced when carborundum concaveswere used.Forcing seed through the mesh screen on the WestrupPolisher bruised and damaged seed, resulting in abnormalgerminating seedlings. However, smaller size grid meshscreens can be fitted and the bottom of the screen blocked offso that all seed travels through to the end of the cylinder.Operating speed of scarification equipment is important.Jones (1971) found that a speed of 17 50 rpm was the optimumspeed in a hammer mill to scarify Cotalaria ochroleucaseed; 1700 rpm was the optimum speed to scarify Oxley finestem stylo in a Ferrell Scarifier with rubber concaves (Grant,1979). With Maku lotus in a similar scarifier, 800-1000 rpmwere the optimum scarifying speeds.The mechanical scarification treatments were evaluatedusing the formula developed by Bilsland et al., (1984). Inthis formula the overall effectiveness of scarification (E 5)will range from 1.00 to -1.00; 1.00 indicates optimum scarification,0 indicates no net improvement from scarificationand negative values indicate seed damage. In these experimentsthe highest Es value was 0. 70 from the Westrup Polisherwith one pass through to the end of the cylinder. Thehighest Es value for the Eddy-Giant Scarifier was 0.61 fromthe speed of 900 rpm and 0.60 from 800 rpm. These valueswere lower than the optimum values for M. sativa (Es =0.77) and T. vesiculosum (Es = 0.82) that Bilsland et al.,(1984) achieved. The lower values for Maku lotus werebecause of the high numbers of abnormal germinating seedsproduced. With the highest normal germinating seed percentage(78. 8) and the highest Es value (0. 70), scarification bythe Westrup Polisher was the most effective.About half the seedlots of Maku lotus have normal seedgerminations less than 80% (Official Seed Testing Station,MAP, pers. comm.) because of high hard seed content. Theproportion of hard seed depends on climate during seedmaturation and harvest (Hare and Lucas, 1984) and scarificationduring mowing and threshing (Clifford and McCartin,1985). There is a difficulty in commercially scarifying seedlotswith high hard seed content to achieve normal germinationsabove 80%, as was found in this experiment. Thisillustrates the importance of buying seed with purity andgermination certificates provided. Farmers wishing to oversowpastures may prefer having a high hard seed content tospread the period of germination; whereas those sowing seedfor seed production which needs a rapid, even establishment,especially when spraying for weed control is necessary, willprefer seed with the highest normal seed germination.CONCLUSIONLarge seedlots of Maku lotus can be scarified effectively ina Westrup Polisher. Scarfication can be carried out in anEddy-Giant Huller and Scarifier if rubber concaves are usedat speeds of approximately 800-900 rpm. Sulphuric acidscarification can still be effectively used on small seedlots ofMaku lotus.ACKNOWLEDGEMENTSMr. George Hill, Plant Science Department, Lincoln College,Canterbury, for suggesting the initial experiments; theMAP Official Seed Testing Station, Palmerston North forgermination tests and seed data; Mr. Kenyon Moore ofGrasslands Division, DSIR, for technical assistance.REFERENCES1. Bilsland, D.M., N.R. Brandenburg, and A.G. Berlage. 1984.A procedure for evaluating scarification processes. J. of Appl.Seed Prod. 2:45-49.2. Clifford, P.T.P., and J. McCartin. 1985. Effects of pre-harvesttreatment and header types on seed loss and hard seed content atmowing, recovery, and separation when harvesting a whiteclover seed crop. N.Z. J. of Exp. Agric. 13: 307-316.3. Grant, P.J. 1979. Mechanical scarification of Stylosanthes guianensiscv. Oxley seed. Proc. Grassl. Soc. Southern Africa.14:137-141.4. Hare, M.D., and R.J. Lucas. 1984. Maku lotus (Lotus pedunculatusCav.) seed production. 1. Development of Makulotus seed and the determination of time of harvest for maximumseed yields. J. of Appl. Seed Prod. 2:58-64.5. Hyde, E.O.C. 1954. The function of the hilum in some papilionaceaein relation to the ripening of the seed and the permeabilityof the testa. Ann. of Bot. 18:241-256.6. Jones, M.E. 1971. Seed scarification. Rhodesia Agric. J.68:25-31.7. Kowithayakorn, L., and M.J. Hill. 1982. A study of lucerneseed development and some aspects of hard seed content. SeedSci. and Technol. 10:179-186.8. McKeon, G.M., and J.J. Mott. 1982. The effect of temperatureon the field softening of hard seed of Stywsanthes humilis and S.hamata in a dry monsoonal climate. Aust. J. Agric. Res.33:75-85.9. Mott, J.J., G.M. McKeon, C.J. Gardener, andL. 'tMannetje.1981. Geographic variation in the reduction of hard seed contentof Stylosanthes seeds in the tropics and subtropics of NorthernAustralia. Aust. J. Agric. Res. 22:861-869.10. Purl, K.P., and A.S. Laidlaw. 1984. The effect of temperatureon components of seed yield and on hard seededness in threecultivars of red clover (Trifolium pratense L.). J. of Appl. SeedProd. 2:18-23.11. Porter, R.H. 1949. Recent developments in seed technology.Bot. Rev. (Lancaster) 15:221-344.12. Quinlivan, B. J. 1965. The influence of the growing season andthe following dry season on the hardseededness of subterraneanclover in different environments. Aust. J. of Agric. Res.16:277-291.13. Quinlivan, B.J. 1971. Seed coat impermeability in legumes. J.Aust. Inst. of Agric. Sci. 37:283-295.
JOURNAL OF APPLIED SEED PRODUCTION, VOL. 3, 1985 1114. Rolston, M.P. 1978. Water impermeable seed dormancy. Bot.Rev. 44:365-396.15. Scott, D.J., and J.G. Hampton. 1985. Aspects of seed quality.pp. 43-52. In M.D. Hare and J.L. Brock (eds.) Producingherbage seeds. Grasslands Research and Practice Series No. 2,N .z. Grassland Assoc., Palmerston North.16. Suckling, F.E. T., and J.F.L. Charlton. 1978. A review of thesignificance of buried legume seeds with particular reference toNew Zealand agriculture. N.Z. J. of Exp. Agric. 6:211-215.17. Taylor, G.B., and M.J. Palmer. 1979. The effect of someenvironmental conditions on seed development and hardseedednessin subterranean clover (Trifolium subterraneum L.).Aust. J. of Agric. Res. 12:227-238.18. Tran, V.N., and A.K. Cavanagh. 1984. Structural aspects ofdormancy. pp. l-44 In D.R. Murray (ed.). Seed physiology.vol. 2., Germination and reserve mobilization. Academic Press,Sydney.19. Win Pe. 1978. A study of seed development, seed coat and seedlongevity in 'Grasslands Pawera' red clover (Trifolium pratenseL.). Ph.D. thesis, Massey University, Palmerston North, N.Z.Seed Yield Response to Fungicide Application in PaclobutrazolTreated Perennial RyegrasstJ.G. Hampton3 and P.D. HebblethwaitezABSTRACTFungicide application (triadimefon plus carbendazim pluscaptafol) at monthly intervals from tillering (February) untilharvest (July) to perennial ryegrass cv. S24 treated with thegrowth retardant paclobutrazol (PP333) at spikelet initiation(March), increased seed yield in 1981 and 1982 by increasing thenumber of seeds per spikelet. Seed yield responses to fungicideapplication in these non-lodged crops were not as great as thosepreviously reported for lodged crops.The incidence of leaf pathogens in both years was low. Fungicideapplication increased leaf area duration by delaying thesenescence of photosynthetic tissue. The importance of sourcesize and duration in the perennial ryegrass seed crop isdissussed.Additional index words: Lolium perenne L., seed production,seeds per spikelet, leaf senescence, leaf area duration.INTRODUCTIONSeed yields in the perennial rye grass (Latium perenne L.)seed crop are usually around one-tenth of the theoretical!Contribution from Department of A_griculture and Horticulture,School of Agriculture, University of Nottingham, Sutton Bonington,Loughborough, Leics., U.K. Received for publication 28 June1985.2Qraduate Research Fellow and Reader in Agronomy respectively,University of Nottingham School of Agriculture, Sutton Bonington,Loughborough, Leics., U.K ..3Present address: Official Seed Testing Station, Ministry of Agricultureand Fisheries, P.O. Box 609, Palmerston North, NewZealand.potential because of poor seed site utilization (Hampton andHebblethwaite, 1983). Recent experiments with chemicalmanipulation of the crop have shown that both growth retardantand fungicide application can significantly increase seedyield (Hebblethwaite et al., 1982; Hampton andHebblethwaite 1984; 1985a).Poor seed site utilization resulting from seed abortion hasbeen associated with lodging of the crop (Hebblethwaite etal., 1980). Hampton and Hebblethwaite (1985a) suggestedthat seed abortion occurred because of assimilate shortage,due to competition from the elongating stem (Clemence andHebblethwaite, 1984) and from vegetative tillers (Hampton,1983), as well as from a loss of photosynthetic tissue in alodged canopy.Fungicide application to lodged crops increased seed yieldby increasing the number of seeds per spikelet. Hampton andHebbethwaite (1984) showed that these increases were associatedwith an increased leaf area duration brought aboutby delays in senescence of photosynthetic tissue. Seed yieldincreases in response to growth retardant application havealso been associated with increased numbers of seeds perspikelet (Hebblethwaite et al., 1980; 1982), although recentexperiments with paclobutrazol (PP333) have demonstratedthat increased fertile tiller production also contributed to seedyield increases (Hampton and Hebblethwaite, 1985a).Paclobutrazol has fungicidal properties (Froggatt et al.,1982), and Hampton and Hebblethwaite (1985a) showed thatone effect of its application was to increase leaf area duration.However, the effects of the fungicidal properties of thechemical and the delay in leaf tissue death because of theabsence of lodging could not be differentiated. Trials in 1981and 1982 examined whether the substantial seed yield increasesobtained from paclobutrazol application could befurther increased by fungicide application.
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