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Diachorella Leaf Spot of Prairie Milkvetch in Loess Plateau, China
Get PDFPrairie Milkvetch (Astragalus adsurgens), an acclimatized good sand binder, soil and water conservation legume forage plant, cultivated widely in the arid and semi-arid districts of North China, is especially suitable for the Loess Plateau, China. Unfortunately in the mid Inner Mongolia, North Shaanxi Province and the eastern part of Gansu Province, it is often infected seriously with Diachorella leaf spot (Diachorella lathyri Fckl.). The disease primarily affects leaves, but sometimes attacks petioles and stems. On infected leaflets first appear small black spots. As the spots increase, whole leaflet is blackened. Heavy infections kill leaflets and cause severe defoliation, and infected stems may die. The Diachorella species causing the leaf spot on Prairie Milkvetch is Diachorella lathyri Fckl. and it is a new record in China. The Diachorella leaf spot is also found in the natural population of Prairie Milkvetch in the same areas. Therefore, the origin of pathogen may be the wild Prairie Milkvetch plants. In order to extend cultivation of the Prairie Milkvetch crops in the above mentioned districts, it is necessary to carry out a study and research as well as prophylactic work on the Diachorella leaf spot. So, we started a preliminary investigation and study on this disease in 1987
Spanish Subclover Ecotypes: Evaluation under Grazing
Get PDFThe introduction of australian subclover varieties in the mediterranean environments of Europe has had irregular results (Olea et al., 1985). For this reason, important projects in selection and genetic improvement of subclover varieties adapted to these environments are carried out in Spain, Portugal and Sardinia. The selection program used at Badajoz (Spain) has originated ecotypes which have been described by Gomez Pitera (1985) and Gonzalez et al. (1986). These ecotypes have short cycles, high level of hardseedness, high seed production and long flowering period. The final stage in the selection of pasture plants must include the evaluation under grazing. Subclover has a high natural capacity of seed burial and a perfect adaptation to high stocking rates and continuous grazing by its morphological and physiological characteristics (Morley et al., 1965 ; Rossiter, 1966; Katznelson, 1974). The objective of this study was to evaluate the new ecotypes and varieties of subclover under real grazing conditions
Morphological and Physiological Growth Aspects of Three Tropical Grasses
Get PDFForage plants differ considerably regarding their ability to recover from grazing. Forage regrowth is determined by shoot apex survival (Sheard and Winch, 1966); leaf area (Ward and Blaser, 1961) ; non-structural carbohydrate content (Ward and Blaser, 1961 ; Brown and Blaser, 1965) and tillering potential (Paulsen and Smith, 1969). Little is known about these concepts regarding tropical grasses
Etude des Deux de la Nutrition Azotee du Trefle Blanc (Trifolium repens L.): Activite de la Nitrogenase et de la Nitrate Reductase
Get PDFL\u27importance des deux voies de la nutrition azotee (assimilation de l\u27azote combine et moleculaire) du trefle blanc n\u27a ete etudiee qu\u27en terme de bilans 15N (Haystead et Lowe, 1977). L\u27objet de cette etude est de suivre la cinetique des activites de la nitrate reductase et de la nitrogenase au cours du cycle de developpement en presence de differentes concentrations en nitrates
The Effect of Nitrogen Deficiency on Carbon Partitioning in a Tall Fescue Sward
Get PDFIntercepted photosynthetically active radiation (PAR), lightuse efficiency and assimilate partitioning are three major determinants of crop growth (Charles-Edwards, 1982). Gastal and Lemaire (1988) reported that the amount of intercepted PAR partly explained the differences in aerial DM yield obtained with contrasting N regimes applied to a tall fescue sward. They also indicated that light-use efficiency and assimilate partitioning were involved in this N effect on DM yield but they could not differentiate between these two growth determinants. Very few field studies of the effect of a N deficiency on assimilate partitioning in forage grasses have been reported. Most studies conducted under controlled conditions or on fieldgrown spaced plants have shown that a N deficiency resulted in an increase in assimilate partitioning to the roots (Powell and Ryle, 1978; Gastal and Saugier, 1986). Colvill and Marshall (1981) reported that the assimilate supply to the roots was less in plants grown in a sward than in spaced plants. This field study was initiated to investigate the effect of N deficiency on C partitioning in a vegetative tall fescue sward
Etude de la Croissance des Repousses de Printemps du Ray-grass Anglais Apres Divers Stades D’Exploitation du Premier Cycle
Get PDFL\u27etablissement de modeles agroclimatiques de croissance des prairies contribue a !\u27elaboration de references fiables de production fourragere. Des modeles statistiques simples entre la production du I er cycle de printemps et le cumul des temperatures (Lemaire et Salette, 1981; Raphalen et Le Bris, 1985) et entre la production estivale et l\u27alimentation en eau (Raphalen et Le Bris, 1985) ont pu etre formules. Par contre, la modelisation de la croissance des repousses de printemps est plus complexe. La structure des repousses du 2e cycle est evolutive et la morphologie du couvert vegetal est tres differente selon le stade d\u27exploitation !ors du 1er cycle, ce qui n\u27est pas sans consequences sur le potentiel de production. L\u27etude presentee ici a pour objet !\u27analyse de la croissance des 2e cycles en fonction du stade d\u27interruption du 1 er cycle
Etude Des Relations Entre le Deficit Hydrique et la Fixation D’azote Chez le Trefle Blanc
Get PDFL\u27alimentation hydrique est un facteur limitant important de la fixation symbiotique chez Jes legumineuses (Pankhurst et Sprent, 1975; Sprent, 1976; Albrecht et al., 1984). Le trefle blanc, ne possedant pas de systeme racinaire puissant, subit des phases de deficit en eau !ors des secheresses estivales. Cette note rapporte le role du facteur varietal dans la tolerance au deficit hydrique du trefle blanc
Regrowth Sites of Sulla (Hedysarum coronarium L.) after Defoliation
Get PDFSulla is a semi-perennial herbaceous forage legume which has rarely been used for grazing. Field studies were undertaken to determine the relative importance of regrowth sites on sulla so that guidelines for grazing management could be refined. Regrowth was predominantly from the crown and most stems remaining after grazing subsequently died. It is concluded that grazing management should be severe and infrequent but, because regrowth is from the crown, treading damage needs to be avoided
Some Changes in Biological Soil Characteristics of Grassland Ecosystem Under Different Management Intensity
Get PDFThe papers which are in our country engaged in problems of soil biological processes under treated seminatural grassland are orientated mainly on the determination of quantitative and qualitative extents of changes originated especially under influence of application of increasing level of nitrogen fertilizers in relation to possible negative phenomenons in environments (Kopcanova et al., 1985, Tesafova and Gordienko, 1988). Our paper deals also with those problems. Its aim is to give a short information about some important changes in biological soil properties under long time differently managed grassland
Contribution a L’etude des Especes Spontenees du Genre Medicago L. en Algerie, Variabilite au Niveau des Graines et des Gousses Chez Sept Populations de M. Scutellata; Relation Avec les Conditions du Milieu D’Origine
Get PDFDans le but de resorber la jachere, de proteger les sols contre l\u27erosion, d\u27ameliorer la production des parcours et dans un souci de valorisation des ressources phytogenetiques locales d\u27interet fourrager, plusieurs travaux ont ete menes sur !es luzernes annuelles (Abdelguerfi, 1978 ; Abdelguerfi et al., 1988a et 19886). L\u27un des interets majeurs des especes annuelles du genre Medicago reside dans leur utilisation au niveau des jacheres. Grace a leurs graines dures, elles entrent facilement en rotation avec !es cereales. Mais la longevite du systeme ble/Medicago est conditionnee par la connaissance des elements se rapportant a la production de graines par la legumineuse. C\u27est dans ce sens, et pour une meilleure caracterisation du materiel vegetal local, qu\u27une etude a ete realisee sur M. scutellata (L.) Miller. Les relations entre !es caracteres poids des gausses et de mille graines, nombre de graines par gousse et rapport graines/gousses et les conditions d\u27origine (pluviometrie et altitude) des populations, sont abordees