JASP 3 -- 1985.pdf - International Herbage Seed Group
Share Embed Flag
Download ePaper

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

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

ihsg.org
11.07.2015 Views

Seed Dormancy and Germination of Switchgrass from Different Row Spacingsand Nitrogen Levels1R.E. Mullen, P.C. Kassel, T.B. Bailey, and A.D. Knapp2ABSTRACTVarious levels of seed dormancy in switchgrass (Panicumvirgatum L.) influence germination results. However, mostgermination data in switchgrass seed production managementstudies have not considered seed dormancy. The purpose of thisstudy was to determine whether seed dormancy varies withmanagement practices. Seed dormancy and germination responseof three switchgrass cultivars to different row spacingand nitrogen (N) treatments on 2- and 3-year-old stands wereexamined. Field experiments were conducted in 1979 and 1980on a predominantly Webster loam (Typic Haplaquoll) soil nearAmes, Iowa. Blackwell, Cave-in-Rock, and Pathfinder cultivarswere seeded in a clean-tilled seedbed on 18 May 1978 at arate of 230 seeds mt of row in 20-, 60-, and 100-cm rows andfertilized with 0, 90, and 180 kg ha-t ofN. Prechill germination(PG), short-term dormancy (STD), long-term dormancy (LTD),and viable seed did not appreciably differ among cultivars atdifferent row spacings. Prechill germination and STD valuesincreased with additions of N fertilizer to 180 kg ha-t forCave-in-Rock, but N fertilizer decreased these values forBlackwell and Pathfinder. Seed dormancy and germinationamong cultivars significantly varied between years. Prechillgermination values averaged 37, 48, and 44% in 1979 and 16,40, and 38% in 1980 for Cave-in-Rock, Blackwell, and Pathfinder,respectively. Short-term dormancy among cultivars wasgreatest for Cave-in-Rock in 1979 but least in 1980. Long-termdormancy was greater for all cultivars in 1980 than in 1979 andinfluenced pure live-seed yields. Results indicated that for 2-and 3-year-old stands of cultivated switchgrass, germinationand seed dormancy can vary among cultivars, years, andN-levels. The 2-week prechilling treatment commonly used instandard switchgrass germination procedures may not uniformlybreak seed dormancy for different cultivars.Additional index words: native grasses Panicum vergatum L.,prechill germination, pure live-seed yield, seed quality, tetrazoliumtest, viable seed, warm germination test, warm-seasongrasses.IJoumal Paper No. J-11996 of the Iowa Agric. and Home Econ.Exp. Stn., Ames, IA 50011. Project 2470. Received for publication30 September 1985.2Associate professor, Dept. of Agronomy; extension crop productionspecialist, Spencer, IA (formerly graduate research assistant);professor, Dept. of Statistics, and associate professor, Dept. ofPlant Pathology, Seed and Weed Sciences, Iowa State Univ.,Ames, IA 500 II, respectively.INTRODUCTIONSeed dormancy frequently has been observed in switchgrass(Panicum virgatum L.) and other warm-season grasses(Blake, 1935; Robockeret al., 1953; Sautter, 1962; Shaidaeeet al., 1969). The degree and length of dormancy and treatmentsnecessary to overcome seed dormancy in native grassesvary with species and locations of production. Variable seeddormancy and the resultant variable germination have complicatedresults of seed-quality experiments in switchgrass.Switchgrass germination has been improved by exposingseeds to freezing (Blake, 1935) or to a chilling temperature of10 C (Sautter, 1962; Norris and Decker, 1943). Norris andDecker (1943) suggested that switchgrass germinates best at17/30 C, or 20/30 C for 16/8 h cycles. Seedlings can becounted at 7, 14, 21 , and if needed, 28 days after planting.New seed should be prechilled for 2 weeks at 10 C. Thisgermination procedure was similar to the procedure of theAssociation of Official Seed Analysts (A.O.S.A.) (Anon.,1978). Combine-harvested and recleaned switchgrass, cv.Pathfinder, seed germinated 84 and 94%, respectively, whena30-dayprechill period at5 C was used (T.N. Shiflet, 1970).Unpublished studies of germination and seedling growth ofswitchgrass. Dept. of Agronomy, Univ. of Nebraska, LincolnNE). Germination values were 30 and 35% less, respectively,when prechilling was not used. Shiflet concluded thatprechilling increased the germination percentage of switchgrassseed that was less than 1 year old and increased thegermination rate of switchgrass seed stored over 1 year.Improved germination has been observed for native grassseed stored after harvest. Robocker et al. ( 1953) reported thatgermination percentages were greatest 2 years after seedharvest for big bluestem (Andropogon gerardi Vitman) andswitchgrass and 1 year after seed harvest for indiangrass(Sorghastrum nutans (L.) Nash). Hoover et al. (1947) andWheeler and Hill (1957) reported that switchgrass had 30%germination the year after seed harvest and that germinationpercentage may double if seeds are stored more than 1 year.Shaidaee et al. (1969) found that 'Grenville' switchgrassseed, 7 years after harvest, had greater field emergence thanyounger seed. It seems that seed of switchgrass in dry storagefor several years may exhibit less dormancy and may becapable of producing better stands in the field.Cultural practices and other factors have influenced seedquality of switchgrass and other native grasses. Smika andNewell (1968) found that side-oats grama (Bouteloua curtipendulaMichx.) produced heavier caryopsis weight whengrown in 101-cm rows than in solid stands. Kneebone and28

JOURNAL OF APPLIED SEED PRODUCTION, VOL. 3, 1985 29Cremer (1955) studied the relationship of seed size to seedlingvigor in several native grasses, including buffalograss(Buchloe dactyloides Nutt.), indiangrass, side-oats grama,and switch grass. Switchgrass showed pronounced differencesin germination percentages in response to seed size, but otherspecies showed no response. 'Blackwell' switchgrass seedsized on 1.27-, 1.15-, and 1.06-mm screens emerged 82, 64,and 31% respectively, in sphagnum moss. Smaller switchgrassseed also required 7 days longer to germinate thanlarger seed.The effect of nitrogen management on seed quality varieswith species of native grasses. Austenson and Peabody (1964)found no differences in seed germination tests or purity testsamong row spacing or N level treatments in several coolseasonspecies grown for seed. Cosper et al. (1967) thatgermination of western wheatgrass (Agropyron smithii Rydb.)slightly increased as N level increased up to 88 kg ha-l,although the trend was not statistically significant. Smikaand Newell (1966) found that seed weight of western wheatgrasswas not influenced by N level but that seed weight wasincreased by irrigation at growth initiation and heading stagesof growth. Smika and Newell (1965) also showed that seedweight of side-oats grama was increased by N applications upto 88 kg ha-l.It is evident from the literature that seed dormancy associatedwith native grasses can influence germination responseand complicate interpretations of treatment effects on seedquality. Primary emphasis of experiments measuring effectsof cultural management on seed quality of switchgrass havecentered on germination without regard to seed dormancy.Row spacing and nitrogen fertilization are important managementconsiderations for seed production of switchgrass,but little or no information is available on row-spacing ornitrogen-level effects on switchgrass seed dormancy andsubsequent germination capability. This study was conductedto compare seed dormancy and germination response of threeswitchgrass cultivars to three N levels and three row spacingson 2-, and 3-year-old stands.MATERIALS AND METHODSField experiments were conducted in 1979 and 1980 on apredominately Webster Loam (Typic Haplaquoll) soil at theAgronomy and Agricultural Engineering Research Centerlocated near Ames, Iowa. The study site contained someNicollet loam (Aquic Hapludoll) soil and was blocked accordinglyin experimental layout. Blackwell (B), Cave-in­Rock (C), and Pathfinder (P) cultivars of switchgrass wereused in the experiment. Cave-in-Rock switchgrass is a bottomlandecotype and was developed by the Soil ConservationService in Elsberry, Missouri. Selections were initially fromsouthern Illinois. Cave-in-Rock was the tallest cultivar studied,having coarse stems and leaves. Pathfinder switchgrass, asynthetic cultivar and upland ecotype, was developed inNebraska. It has fine leaves and stems. Blackwell switchgrassis an upland ecotype and was collected in northernOklahoma on fine-textured soils. It was further developed inKansas and has vegetative characteristics similar to those ofPathfinder.Cultivars were seeded in a clean-tilled seedbed on 18 May1978 at a rate of230 seeds m-1 of row in 20-, 60-, and 100-cmrows, which corresponds to seedling rates of 13.5, 4.5, and2.7 kg ha-l, respectively. Four-row plots were used in the20-cm row seedings, and 3-row plots were used in the 60-and 100-cm row seedings. Each plot was 3.7 min length.After seeding, the soil was firmed with a roller packer, andno fertilizer was applied. Atrazine (2 chloro-4-ethylamino-6-isopropyl amino-1, 3-5-triazine) was applied to plots at a rateof 3.36 kg ha-l active ingredient was a preemergence treatmentin 1978 and as a postemergence treatment during springgrowth initiation in subsequent years. Hand hoeing was usedeach year as an additional weed control measure and tomaintain row-spacing treatments. Plots were fertilized withurea in May 1979 and 1980 at rates ofO, 90, and 180 kg ha-lofN.The experimental design consisted of three whole plotsreplicated three times. Row spacing treatments were randomlyassigned to each of the whole plots. Nitrogen treatmentswere applied in random strips across each whole plot,and cultivars were assigned in random strips perpendicular toN treatments for each whole plot.Seeds were hand-harvested during 22 to 29 September1979 and 20 to 27 September 1980. Cave-in-Rock maturedapproximately 1 week later than Blackwell and Pathfindercultivars. Harvest was initiated when seed from the top of thepanicle had begun to shatter and the seed from lower paniclebranches was hard and brown. Seed was harvested from a 3.2m length of one row in the center of each plot. Harvestedinflorescences were dried in a 38 Cheated-air oven for 7 daysand stored at 10 C until threshed. Inflorescences were threshedwith a hammer mill at 850 rpm with a 4.8-mm screen. Seedwas cleaned with a Clipper bench-type seed cleaner with aNo. 8 (3 .0 mm) screen for preliminary cleaning and a No. 6(2.3 mm) screen for additional cleaning. A 1-mm screen wasused as a lower screen in all cleanings. Unthreshed seedswere separated from remaining trash with a 1. 8-mm screen,hand threshed, cleaned, and returned to the sample. Seedsubsamples were threshed by hand rubbing to remove glumes,sifted in a 1.8-mm screen, and cleaned in an air-columnseparator.Standard germination tests, with prechill (PG) and without(WG) prechill, were conducted on units of 100 seeds(A.O.S.A. Anon., 1978). Seeds were planted on blotterpaper moistened with 0.2% KN0 3• Seeds were prechilled at5 C for 2 weeks. The germination test was conducted ingrowth chambers set at 15/30 C temperatures for 16/8 hcycles for 28 days with light during the warm cycle, accordingto A.O.S.A. (Anon., 1978) specifications. Germinationwas counted at 7, 14, 21, and 28 days after planting. Seedgermination was defined according to A.O.S.A. (Anon.,1978). Ungerminated firm seeds from the prechill test werecut in half and stained with 0.1% tetrazolium to determineviability. Seed viability (V) was expressed by the equation,V = c + t, in which c = germinated seeds (prechill test) per100 seeds, and t = ungerminated firm seeds per 1 00 seedsthat were alive based on the tetrazolium test. Seed dormancywas divided into short-term (STD) and long-term (LTD)dormancy in which STD = prechill test % - warm test % and

<strong>Seed</strong> Dormancy and Germination of Switchgrass from Different Row Spacingsand Nitrogen Levels1R.E. Mullen, P.C. Kassel, T.B. Bailey, and A.D. Knapp2ABSTRACTVarious levels of seed dormancy in switchgrass (Panicumvirgatum L.) influence germination results. However, mostgermination data in switchgrass seed production managementstudies have not considered seed dormancy. The purpose of thisstudy was to determine whether seed dormancy varies withmanagement practices. <strong>Seed</strong> dormancy and germination responseof three switchgrass cultivars to different row spacingand nitrogen (N) treatments on 2- and 3-year-old stands wereexamined. Field experiments were conducted in 1979 and 1980on a predominantly Webster loam (Typic Haplaquoll) soil nearAmes, Iowa. Blackwell, Cave-in-Rock, and Pathfinder cultivarswere seeded in a clean-tilled seedbed on 18 May 1978 at arate of 230 seeds mt of row in 20-, 60-, and 100-cm rows andfertilized with 0, 90, and 180 kg ha-t ofN. Prechill germination(PG), short-term dormancy (STD), long-term dormancy (LTD),and viable seed did not appreciably differ among cultivars atdifferent row spacings. Prechill germination and STD valuesincreased with additions of N fertilizer to 180 kg ha-t forCave-in-Rock, but N fertilizer decreased these values forBlackwell and Pathfinder. <strong>Seed</strong> dormancy and germinationamong cultivars significantly varied between years. Prechillgermination values averaged 37, 48, and 44% in 1979 and 16,40, and 38% in 1980 for Cave-in-Rock, Blackwell, and Pathfinder,respectively. Short-term dormancy among cultivars wasgreatest for Cave-in-Rock in 1979 but least in 1980. Long-termdormancy was greater for all cultivars in 1980 than in 1979 andinfluenced pure live-seed yields. Results indicated that for 2-and 3-year-old stands of cultivated switchgrass, germinationand seed dormancy can vary among cultivars, years, andN-levels. The 2-week prechilling treatment commonly used instandard switchgrass germination procedures may not uniformlybreak seed dormancy for different cultivars.Additional index words: native grasses Panicum vergatum L.,prechill germination, pure live-seed yield, seed quality, tetrazoliumtest, viable seed, warm germination test, warm-seasongrasses.IJoumal Paper No. J-11996 of the Iowa Agric. and Home Econ.Exp. Stn., Ames, IA 50011. Project 2470. Received for publication30 September 1985.2Associate professor, Dept. of Agronomy; extension crop productionspecialist, Spencer, IA (formerly graduate research assistant);professor, Dept. of Statistics, and associate professor, Dept. ofPlant Pathology, <strong>Seed</strong> and Weed Sciences, Iowa State Univ.,Ames, IA 500 II, respectively.INTRODUCTION<strong>Seed</strong> dormancy frequently has been observed in switchgrass(Panicum virgatum L.) and other warm-season grasses(Blake, 1935; Robockeret al., 1953; Sautter, 1962; Shaidaeeet al., 1969). The degree and length of dormancy and treatmentsnecessary to overcome seed dormancy in native grassesvary with species and locations of production. Variable seeddormancy and the resultant variable germination have complicatedresults of seed-quality experiments in switchgrass.Switchgrass germination has been improved by exposingseeds to freezing (Blake, 1935) or to a chilling temperature of10 C (Sautter, 1962; Norris and Decker, 1943). Norris andDecker (1943) suggested that switchgrass germinates best at17/30 C, or 20/30 C for 16/8 h cycles. <strong>Seed</strong>lings can becounted at 7, 14, 21 , and if needed, 28 days after planting.New seed should be prechilled for 2 weeks at 10 C. Thisgermination procedure was similar to the procedure of theAssociation of Official <strong>Seed</strong> Analysts (A.O.S.A.) (Anon.,1978). Combine-harvested and recleaned switchgrass, cv.Pathfinder, seed germinated 84 and 94%, respectively, whena30-dayprechill period at5 C was used (T.N. Shiflet, 1970).Unpublished studies of germination and seedling growth ofswitchgrass. Dept. of Agronomy, Univ. of Nebraska, LincolnNE). Germination values were 30 and 35% less, respectively,when prechilling was not used. Shiflet concluded thatprechilling increased the germination percentage of switchgrassseed that was less than 1 year old and increased thegermination rate of switchgrass seed stored over 1 year.Improved germination has been observed for native grassseed stored after harvest. Robocker et al. ( 1953) reported thatgermination percentages were greatest 2 years after seedharvest for big bluestem (Andropogon gerardi Vitman) andswitchgrass and 1 year after seed harvest for indiangrass(Sorghastrum nutans (L.) Nash). Hoover et al. (1947) andWheeler and Hill (1957) reported that switchgrass had 30%germination the year after seed harvest and that germinationpercentage may double if seeds are stored more than 1 year.Shaidaee et al. (1969) found that 'Grenville' switchgrassseed, 7 years after harvest, had greater field emergence thanyounger seed. It seems that seed of switchgrass in dry storagefor several years may exhibit less dormancy and may becapable of producing better stands in the field.Cultural practices and other factors have influenced seedquality of switchgrass and other native grasses. Smika andNewell (1968) found that side-oats grama (Bouteloua curtipendulaMichx.) produced heavier caryopsis weight whengrown in 101-cm rows than in solid stands. Kneebone and28

logo

products

Resources

Company

Terms of service
Privacy policy
Cookie policy
Cookie settings
Imprint
Change language
Made with love in Switzerland
© 2024 Yumpu.com all rights reserved

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!