Preliminary studies on allelopatic effect of some woody plants on seed germination of rye-grass and tall fescue

In order to investigation of allelopathic effects of some ornamental trees on seed germination of rye-grass (Lolium prenne) and tall fescue (Festuca arundinaceae), this experiment was conducted in a randomized complete block design with 3 replicates at the laboratory of Horticultural Sciences Department of Ferdowsi University of Mashhad, during 2008. In this research, we studied the effect of aqueous and hydro-alcoholic extracts of Afghanistan pine (Pinus eldarica), arizona cypress (Cupressus arizonica), black locust (Robinia psedue acacia) and box elder (Acer negundo) leaves that prepared in 1:5 ratio on seed germination percent and rate for two grasses. The results showed that all extracts decreased statistically seed germination in compared to control treatment. The highest germination percentage and germination rate of tested grass detected in control treatment. Hydro-alcoholic extracts of all woody plants (15, 30%) were completely inhibited seed germination of rye-grass and tall fescue. Also aqueous extract of arizona cypress was completely inhibited seed germination of tall fescue and had more inhibitory activity than other aqueous extracts on rye-grass. Between aqueous extracts, the highest and lowest seed germination of rye-grass was found in Afghanistan pine and arizona cypress, respectively.     

Assessment of allelopathic potential of barnyard grass (Echinochloa crus-galli) on rice (Oryza sativa L.) cultivars

Laboratory, greenhouse and field studies were conducted to assess the allelopathic potential of 44 rice cultivars (Oryza sativa L.) on barnyard grass (Echinochloa crus-galli P. Beauv. var. oryzicola Ohwi). Rice cultivars exhibited marked differences in the inhibition of barnyard grass growth and development. In the laboratory, Gin shun rice cultivar extracts exhibited the greatest activity on the weed seedling growth, reducing dry weight by 61%, while Kasarwala mundara cultivar extracts exhibited the greatest activity on seed germination, reducing germination by 23% and germination speed by 46%. In a greenhouse study of a residue mixture, the Philippine 2 cultivar showed the greatest inhibition percentage on seedling emergence (57%), total seedling length (74%) and dry weight (73%). In the field study, the Juma 10 cultivar demonstrated the most inhibitory effect by reducing barnyard grass tiller number (80%), leaf area (49%) and leaf (61%) and stem (74%) dry weight (68%). These results suggest that there are differences among the varieties for allelopathic inhibition of barnyard grass, and that the development of barnyard grass suppressive rice cultivars that have greater allelopathic potential may be possible.     

Influence of sward condition on leaf tissue turnover in tall fescue and tall wheatgrass swards under continuous grazing

Two experiments were carried out on a tall fescue sward in two periods of spring 1994 and on a tall wheatgrass sward in autumn 2001 and spring 2003 to analyse the effect of sward surface height on herbage mass, leaf area index and leaf tissue flows under continuous grazing. The experiment on tall fescue was conducted without the application of fertilizer and the experiment with tall wheatgrass received 20 kg P ha^?1 and a total of 100 kg N ha^?1 in two equal dressings applied in March (autumn) and end of July (mid‐winter). Growth and senescence rates per unit area increased with increasing sward surface height of swards of both species. Maximum estimated lamina growth rates were 28 and 23 kg DM ha^?1 d^?1 for the tall fescue in early and late spring, respectively, and 25 and 36 kg DM ha^?1 d^?1 for tall wheatgrass in autumn and spring respectively. In the tall fescue sward, predicted average proportions of the current growth that were lost to senescence in early and late spring were around 0·40 for the sward surface heights of 30–80 mm, and increased to around 0·60 for sward surface heights over 130 mm. In the tall wheatgrass sward the corresponding values during spring increased from around 0·40 to 0·70 for sward surface heights between 80 and 130 mm. During autumn, senescence losses exceeded growth at sward surface heights above 90 mm. These results show the low efficiency of extensively managed grazing systems when compared with the high‐input systems based on perennial ryegrass.     

Sowing date and nitrogen supply determine the outcome of competition between dallisgrass (Paspalum dilatatum Poir.) and tall fescue (Festuca arundinacea Schreb.) in the Pampas region of Argentina

The effects of sowing date and nitrogen (N) fertilizer on the inter‐specific competition between dallisgrass (Paspalum dilatatum Poir.) and tall fescue (Festuca arundinacea Schreb.) in the humid Pampas of Argentina were investigated in two pot experiments where a constant soil moisture content was maintained. Tall fescue and dallisgrass seeds were sown either in the spring (October 2000) or in the autumn (March 2001) in mixed and mono‐specific stands with 0 or 100 kg N ha^?1. In the spring, competition from tall fescue depressed dry‐matter (DM) yield of dallisgrass from 1·53 to 0·36 g DM per plant and tiller number from 9·4 to 3·7 tillers per plant in mixed and in mono‐specific stands, respectively, while tall fescue had 3–4 times higher DM yields in mixed stands. Leaf extension rate (LER) of tall fescue was higher (1·3 mm d^?1) than that of dallisgrass (0·53 mm d^?1). In the autumn, inter‐specific competition did not affect DM yield of dallisgrass and N fertilizer increased DM yield from 0·53 to 2·07 g DM per plant, tiller number from 6·8 to 14·2 tillers per plant and LER at the beginning of autumn from 1·2 to 2·12 mm d^?1 in both species. As temperature decreased, LER was reduced in both species to 0·31 mm d^?1 by late autumn. The number of leaves per tiller was not affected by treatment. Nitrogen fertilizer increased N concentration of above‐ground tissues of both species (18 g kg^?1 DM in autumn and 20 g kg^?1 DM in spring). It was concluded that a productive mixed pasture of dallisgrass and tall fescue can be obtained by sowing early in the autumn. The application of N fertilizer in this season is essential to ensure a high herbage yield and quality.     

刚果12号桉对4种豆科植物的化感作用

采用室内生物检测的方法研究了刚果12号桉叶片自然释放的挥发性物质、叶片水抽提物、叶片经水蒸气蒸馏所得的桉油、含挥发性水溶性物质的冷凝水和含水溶性非挥发性物质的渣汁3个组分以及桉树根际土壤水浸液对绿豆、大豆、柱花草与大翼豆4种受体植物的化感活性。结果表明：刚果12号桉叶片释放的挥发性物质对4种受体植物种子的萌发有强烈的抑制作用：桉叶水抽提物与根际土壤水浸液对绿豆、大豆、柱花草与大翼豆4种受体植物种子萌发与幼苗生长不但有一定抑制作用，而且土壤水浸液对绿豆、大豆和柱花草幼苗的根生长还有不同程度的促进作用，处理分别比对照高出13％、2％、23％。从桉油、冷凝水与渣汁3个组分的化感活性来看，渣汁的最强，桉油次之，冷凝水最低，即单位叶片中水溶性物质的化感活性比挥发性的高。这表明水溶性化感活性物质可能是刚果12号桉的主要化感作用物质。     

Forage biomass,soil cover,stability and competition in perennial grass–legume pastures with different Paspalum species

The short life span, irregular forage production and susceptibility to weed colonization of cool‐season grass–legume pastures are serious problems in grazing dairy systems in warm‐temperate regions. The inclusion of warm‐season species has the potential to mitigate these problems. In this study, we evaluated the effect of the inclusion of two warm‐season grasses with different growth habits on seasonal forage biomass, soil cover and weed colonization. Three different pasture mixtures were evaluated under grazing: conventional pasture (CP) [tall fescue (Festuca arundinacea), white clover (Trifolium repens) and birdsfoot trefoil (Lotus corniculatus)], CP with Paspalum dilatatum and CP with Paspalum notatum (CP + Pn). Forage biomass and soil cover were sampled thirteen times during a 3‐year trial, and sampling times were grouped by season for the analyses. The mixtures with Paspalum showed higher soil cover in the autumn, while in the winter CP had higher soil cover than CP + Pn. Competition with tall fescue was similar between mixtures with Paspalum, when considering biomass, but it was higher in CP + Pn when considering soil cover. The inclusion of P. notatum increased biomass during the autumn but decreased the mixture performance during winter by reducing tall fescue soil cover. The addition of a warm‐season grass species with a moderate competing ability like P. dilatatum is likely to avoid a negative impact on the cool‐season component of the pasture.     

THE USE OF MIXTURES OF GRANULAR DALAPON, BIRDSFOOT TREFOIL SEED AND FERTILIZER FOR ROUGHLAND PASTURE RENOVATION

Trials were conducted to determine the feasibility of combining granular dalapon, P fertilizer and birdsfoot trefoil seed in mixtures for renovating natural grass pastures in Ontario. The aim was to develop a 'once-over' method to facilitate the renovation of pastures characterized by rough topography, rock outcrops or surface boulders.
Dalapon at 4 lb. a.i./ac (4.4 kg/ha) controlled the growth of Canada bluegrass ( Poa compressa L.) and did not affect the germination and seedling growth of trefoil when applied simultaneously with the seed. Up to 100 lb/ac (112 kg/ha) P₂O₅ could be added to the mixture without detriment to trefoil establishment. The application of dalapon, P and seed in mixture by fixed-wing aircraft, helicopter or ground equipment gave five-to ten-fold increases in pasture productivity and proved to be a practical method of pasture renovation.     

A comparison of perennial ryegrass‐ and tall fescue‐based swards with or without a cropping component for dairy production: Animal production,herbage characteristics and financial performance from a 3‐year farmlet trial

Perennial ryegrass/white clover swards have some limitations in temperate grazed dairying systems. This study tested the hypothesis that farmlets based on alternative species would be equally or more profitable than those perennial ryegrass‐based, and would produce more herbage in summer‐dry conditions. Six farmlets were established; three with perennial ryegrass‐ and three with tall fescue‐based swards. For each grass species, one farmlet was solely based on grass‐clover swards while the other two had either chicory‐red clover or lucerne crops planted on 20%–25% of the area. Animal‐ and herbage performance‐related variables were measured for 3 years, and calculated financial performance was evaluated. Using tall fescue improved total annual herbage yield compared with perennial ryegrass, but animal production and operating profit were lower. This was likely due to the reduced yield and nutritive value of tall fescue during spring and an associated decline in daily milksolids production. The deficit in spring milksolids production was never recovered, despite greater herbage production from tall fescue during summer/autumn. Incorporating chicory‐red clover or lucerne crops reduced both annual herbage and milksolids production. This reduced farm income, while increasing operating expenses as the farmlets required crop renewal and more purchased supplementary feed to maintain feed supply. Under the conditions of this study (i.e., partial irrigation, high nitrogen supply), changing the forage base from perennial ryegrass to tall fescue did not improve animal production or profitability, nor did incorporation of crops on 20%–25% of the farmlet area.     

Water use efficiency and drought survival in Mediterranean perennial forage grasses

In Mediterranean areas, water use efficiency (WUE) is mainly increased by maximising crop growth during the rainy seasons. Perennial forage species have a number of advantages in comparison to the predominantly used annuals. They can utilize water from autumn to spring, while annuals need to be sown or to germinate from the soil seed bank. Under Mediterranean annual rainfall pattern, perennial plants must grow from autumn to spring and survive under summer aridity. Drought survival can impact water use efficiency through plant mortality and stand recovery after autumn rainfalls. In order to enhance knowledge of physiological and agronomic traits associated with WUE and persistence, a 3-year study was conducted at two Mediterranean sites, comparing a range of accessions of two perennial species, cocksfoot (Dactylis glomerata L.) and tall fescue (Lolium arundinaceum (Schreb.) Darbysh). Within the accessions of predominantly Mediterranean origin, we defined four major functional types, i.e. groups of accessions with similar response to summer drought. One type (FT1) is represented by the only cultivar of a semi-arid cocksfoot (Kasbah) that is completely summer dormant, with high persistence under the most arid situations but with low WUE. The type FT2 all cocksfoot cultivars (Currie, Delta-1, Jana, Medly, and Ottava) that are not or less summer dormant, with good perenniality and intermediate productivity at rainy seasons. The type FT3 includes the cultivars of tall fescue (Centurion, Flecha, Fraydo, and Tanit) that combine an incomplete summer dormancy, a deep rooting system and the highest WUE from autumn to spring. The type FT4 is represented by a cultivar of tall fescue (Sisa) with no summer dormancy, therefore less persistent and also less productive. Dehydration avoidance in tall fescue and cocksfoot and summer dormancy in cocksfoot were the main strategies contributing to persistence under summer drought. WUE in autumn was highly correlated with sward recovery after drought. Seasonal and total WUE were also highly correlated with biomass production over the same period and with depth and density of the root system. Parameterization of functional types of the major species of forage grasses will enhance future modelling work to test the effects of a range of environments and future climate scenarios.     

酢浆草（Oxalis corniculata）植株水浸提液对萝卜和生菜的化感效应

通过采用不同浓度的酢浆草植株水浸提液处理萝卜和生菜种子与幼苗,测定其对不同受体材料种子发芽、幼苗生长和植株保护酶系统的影响,探讨酢浆草植株水浸提液对部分模式蔬菜植物的化感作用,推测其可能的生理机制。结果表明：酢浆草植株水浸提液对萝卜和生菜的种子萌发和幼苗生长表现出较为明显的化感抑制。酢浆草植株水浸提液处理后,萝卜和生菜的种子萌发、幼苗生长均被抑制,抑制程度随处理浓度增加而增强,对胚根的抑制强度大于胚轴。酢浆草植株水浸提液对幼苗各种保护酶活性的影响表现出不同的变化规律,POD和CAT的活性均随处理浓度的增加     

A COMPARISON OF COCKSFOOT- AND TALL FESCUE-DOMINANT SWARDS FOR OUT-OF-SEASON PRODUCTION

Swards based on a mixture of SI 70 tall fescue and S215 meadow fescue were very early in spring, gave high yields for conservation in mid-season and, rested from mid-August, gave good grazing in November-December. Under this treatment, the tall fescue assumed dominance, and the swards were persistent and remained productive. The digestibility of the tall fescue swards was always higher than that of swards based on cocksfoot with which they were compared. During spring and autumn the former sward was better grazed by stock, but the position was reversed in mid-summer. Cattle grazing tall-fescue-dominant swards made better liveweight gains than those grazing cocksfoot swards during November-December.     

决明属（Chamaecrista spp）豆科牧草8个品种化感潜力的研究

研究决明属（Chamaecrista spp.）豆科牧草8个品种[圆叶决明（Chamaecrista rotundifolia）CPI86134、CPI34721、CPI86178、CPI3248、ATF2232、CPI57503和羽叶决明（Chamaecrasta nictitans）ATF2217、ATF2219]对禾本科牧草百喜草（Paspalum notatum）的化感作用,以确定该8个豆科牧草品种的化感潜力。结果表明,8个决明属豆科牧草品种具有较强的化感作用;随着浓度的逐渐降低,8个品种开花期浸提液的化感抑制作用逐渐减弱,结荚期浸提液的化感促进作用逐渐加强;同一品种,同一生长时期,不同浓度（5%、7.5%和10%）的化感作用综合效应表现不同;同一生长时期,同一浓度,不同品种的化感综合效应表现也不同。可见,决明属牧草8个品种的化感作用受浓度、生长时期和品种的影响。     

THE AGRONOMIC EVALUATION OF SYN 1 TALL FESCUE IN THE WEST OF SCOTLAND

The agronomic value of Syn 1 tall fescue, a synthetic variety derived from North African parent material, was determined in three experiments. Herbage yield, sward purity and digestibility were measured under cutting treatments for incremental sward growth during autumn/winter, and for sward regrowths during autumn/winter, spring and a complete season. Similar data were obtained for sward regrowths during autumn/winter and spring under defoliation by grazing. Syn 1 was compared with several of the north-temperate region tall fescues, e.g. S170, Rozelle and Manade, also with S143 cocksfoot Syn 1 showed yield superiority in autumn/early winter when there were comparable populations of tall fescue. Under cutting management, Syn 1 swards thinned out rapidly because of lack of winter-hardiness and yields were depressed in the second season; the effects were worst under the winter foggage-type management. Under grazing, with probably less severe defoliation, Syn 1 swards maintained yields for an additional season, but thereafter failed to persist Syn 1 swards had low spring- and annual-yields. The yield advantage of Syn 1 in autumn/early winter was not sufficient to be of great agricultural value and with its shortcomings in winter-hardiness and annual yield, it was considered unsuitable for West of Scotiand conditions. The main value of plant material such as Syn 1 may lie in ccmferring autumn/winter growth potential to winter-hardy north-temperate tall fescues in a breeding programme.     

Establishment of legumes in grass swards: effects of pesticides on slugs,insects, legume seedling numbers and forage yield and quality*

Three legumes, red clover (Trifolium pratense L.), alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.), were planted with a minimum-tillage drill into eight grass fields, three in early spring, two in late spring and three in late summer, in Pennsylvania. The objective was to use pesticides at planting time to control slugs and insects which attack legume seedlings and ascertain whether pest control prevented seedling loss and increased yields of grass and legume dry matter (DM), in vitro DM digestibility and crude protein (CP). Methiocarb bait alone or in combination with carbofuran granules or spray applied at planting sometimes controlled the slugs Derocerus reticulatum (Müller), D. laeve (Müller) and Arion fasciatus Nilsson and improved establishment of seedling red clover and alfalfa but not birdsfoot trefoil. Increased yields of DM, digestible DM, CP and legume DM after treatment was greatest in late-spring sowings. Larvae of the clover root curculio, Sitona hispidulus (F.), attacked roots of legumes in the spring following the year of sowing. Late spring and summer sowings without pesticides sustained considerable seedling losses from pests, whereas seedlings from early spring sowings in untreated areas were injured less.     

大蒜鳞茎浸提液对大豆种子萌发和幼苗生长的化感效应

为探明大蒜鳞茎浸提液对大豆种子萌发和幼苗生长的化感作用,通过对大豆种子进行不同质量浓度(0,20,40,80,100 g·L^-1)大蒜鳞茎浸提液的处理,测定不同处理的发芽率、发芽势、发芽指数、根长、下胚轴长、植株鲜重、SOD活性、POD活性、CAT活性和MDA含量,并计算化感觉效应指数以及综合化感效应,探明大蒜鳞茎浸提液对大豆的化感效应。结果表明:大蒜鳞茎浸提液对大豆种子萌发及幼苗生长呈现低浓度促进、高浓度抑制的双重化感效应。浸提液质量浓度为20~40 g·L^-1时,对大豆种子萌发及幼苗生长具有一定的促进作用,SOD和CAT活性显著上升,MDA含量变化不大;浸提液质量浓度为80~100 g·L^-1时,对大豆种子和幼苗表现出明显的抑制作用,SOD和POD活性开始下降,MDA含量显著增加。此外,大豆种子萌发及幼苗生长的各项指标对大蒜化感物质的敏感程度不同,以对根长的化感作用较为敏感,可作为衡量大蒜对大豆化感作用的评价指标。     

Nodulation and root growth of forage legumes sown into tall fescue swards

Establishing forage legumes into endophyte‐infected tall fescue (Festuca arundinacae Schreb.) pastures is problematic, especially in well‐established stands. A oversowing field experiment determined if this problem was because of poor nodulation. Four renovation techniques, clipped sward (treatment A), herbicided + rye seeding in the previous autumn (treatment B), herbicided in the autumn and spring (treatment C) and herbicided to suppress the sward (treatment D), were investigated to determine their effect on nodulation and root growth of lucerne (Medicago sativa L.), red clover (Trifolium pratense L.) and white clover (T. repens L.) at 16, 22 and 29 d after sowing the legumes. A pot experiment was also conducted under optimal growth conditions and using the same soil to determine the nodulation and root growth potentials of these legume species. At adequate rhizobial populations (>6 × 10⁴ cfu g^?1 soil), substantial nodulation of all species occurred by 29 d after sowing in treatments C and D, whereas nodulation of clovers was usually reduced in treatment A. Total root lengths for all sampling dates, species and treatments were severely restricted, especially under treatment A. A general correspondence of nodulation with root growth was observed for all species, with high correlations (r ≥ 0·85) between these variables for all legume species and treatments, suggesting that soil moisture, and possibly competition for light, were the limiting factors. These results demonstrate that weak stands of forage legumes, typically found when sown into tall fescue swards, are probably not because of inadequate nodulation. Rather, inhibition of root growth by detrimental physical/chemical conditions or allocation of limited photosynthate to shoots instead of roots is suggested.     

假臭草水浸提液化感作用研究

以小白菜(Brassica campestris L.ssp.Pekinensis(Lour.)Olsson),萝卜(Raphanus sativus L.),水稻(Oryzasativa L.),热研2号柱花草(Stylosanthes guianensis cv.Reyan No.2)作为测试植物,研究新鲜假臭草(Praxelisclematidea(Griseb.)King and Robinson)水浸提液对种子发芽,新鲜假臭草和风干假臭草水浸提液对幼苗早期生长的化感效应以及不同生长环境下的假臭草浸提液对萝卜幼苗早期生长的化感作用。结果表明:新鲜假臭草浸提液对4种测试植物的种子发芽都有抑制作用。假臭草叶和完整植株水浸提液的化感作用明显大于其它器官水浸提液化感作用,叶可能是假臭草释放化感物质的主要器官。风干和新鲜假臭草水浸提液在低浓度时抑制所有测试植物幼苗根系生长。在逆境(如干旱和养分胁迫)中,假臭草会释放更多的化感物质,从而导致其化感作用增强。     

不同秸秆及绿肥浸提液对玉米化感作用的研究

采用室内培养试验,通过测定油菜秸秆、小麦秸秆、紫云英及紫云英+油菜秸秆4种浸提液对玉米发芽、幼苗生长及干重的影响,研究不同秸秆及绿肥对玉米的化感作用。结果表明,当浸提液浓度≥10 g/L时显著降低玉米发芽率。除紫云英+油菜秸秆浸提液对幼苗生长及干重表现为较强抑制作用外,其他浸提液均表现为显著促进作用或微弱抑制作用,紫云英浸提液促进作用最强,其中,油菜秸秆、小麦秸秆、紫云英浸提液均在5 g/L时对幼苗总干重的促进作用最大,分别较对照提高10.85%、11.51%、16.71%。除紫云英+油菜秸秆外,其他秸秆及绿肥对玉米的化感作用整体上均表现为促进作用,油菜秸秆、小麦秸秆、紫云英及油菜+紫云英浸提液的综合敏感指数分别为2.64%、3.59%、10.32%、-7.33%。     

The heterotoxicity of Hordeum vulgare L. extracts in four growth stages on germination and seedlings growth of Avena ludoviciana

Phytotoxicity of barley extracts (Hordeum vulgare L.) on wild oat (Avena ludoviciana Durieu) was investigated. Water extracts five varieties of barley were bioassayed on germination and seedling growth of wild-oat to test the heterotoxicity of barley on wild-oat, study the dynamics of allelopathic potential over four growth stages and identify the most allelopathic plant part of barley in each stage. Whole barley plants were extracted at growth stage 4 (stems not developed enough), whilst for the following growth stages roots, stems, panicles and leaves were extracted separately. Seedling growth bioassays demonstrated that the wild-oat responded differently to the allelopathic potential of barley. For wild-oat radical growth and coleoptile growth were more depressed than germination, though. The allelopathic potential of barley plant parts was not stable over its life cycle for wild-oat. Leaves and stems were the most phytotoxic barley plant parts for wild-oat in the all stages. Among the varieties Eizeh appeared as the best one showing toxicity to seed germination of wild oat at its stage 4 and 8. Results suggested that the response by wild-oat varied depending on the source of allelochemicals (plant part) and the growth stage of the barley plant and kind of variety. The results leaded to conclude that Eizeh variety of barley was good to grow as it has good check on seed germination of wild oat plants as well as it also retarded the growth of root and shoot length of oat.     

南瓜根系及根部土壤水浸液化感作用研究

以黄瓜、西瓜作受体材料,研究南瓜根系及根部土壤水浸液的化感作用。结果表明,南瓜根系及根部土壤水浸液对受体种子萌发率、萌发指数、幼苗根长、苗高和苗干重存在化感促进或抑制效应。对指标进行综合效应分析,发现南瓜根系及根部土壤水浸液化感作用呈现浓度效应及受体差异性,一定浓度水浸液处理对受体种子萌发阶段、幼苗生长阶段及整体生长有促进作用,但西瓜较黄瓜对浓度敏感,0.02 g/mL南瓜根系及根部土壤水浸液对黄瓜化感促进强度最大,0.04 g/mL处理下,表现为化感促进强度降低或微弱抑制作用;0.02和0.04 g/mL南瓜根系水浸液及0.04 g/mL根部土壤水浸液对西瓜则表现为强烈抑制现象。