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Etude des Deux de la Nutrition Azotee du Trefle Blanc (Trifolium repens L.): Activite de la Nitrogenase et de la Nitrate Reductase
Full text linkL\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
Full text linkIntercepted 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
Full text linkL\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
Full text linkL\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
Full text linkSulla 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
Full text linkThe 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
Full text linkDans 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
Evaluation of Annual Medics and Subclovers in Oklahoma
Full text linkOklahoma has a continental climate with cold winters and a late spring or early-summer rainfall peak. Kneebone (1959) found little justification for attempts to use native legumes for revegetation purposes in western Oklahoma rangelands. Denman et al. (1961) evaluated 54 genera, 216 species and 1,366 entries of legumes in Stillwater, Oklahoma between 1951 and 1959. They concluded that only alfalfa and some vetches (Vicia spp.) had any forage potential. Most clovers and medics failed to survive the winter cold.
Subclover is largely but not wholly Mediterranean in its distribution (Morley, 1961) and has been grown on limited hectarages in the southeartern US and the Texas gulf coast region. Donald (1960) pointed out that genetic variation in subclover collected from fringe areas of the Mediterranean basin broadened the area of adaptability for many cultivars but few recent studies in the Southern Great Plains have evaluated any of the many new cultivars commercially available
Basic Aspects, Objectives and Preliminary Results of a Subterranean Clover Improvement Program in Sardinia (Italy)
Full text linkThe process of extended agronomical rehabilitation of the heavily deteriorated pastures, activated in Sardinia in the 1970\u27s, has been largely supported by the introduction of subterranean clover (Trifolium subterranuem L. sensu lato) as a cultivated plant in the island. Although this annual self-reseeding species has readily become the most widely sown pasture legume in Sardinia, the broadscale use of imported varieties has not always been an unqualified success, particularly in terms of long-term persistence. Therefore, the need to define clearly the particular combination of characters contributing to adaptation in Sardinia, and to develop local varieties specifically adjusted to Sardinian climatic and edaphic conditions, has been invoked for a better exploitation of the potentialities of subterranean clover. According to these requirements, a selection program was activated in the early 1980\u27s. Some basic aspects, objectives and preliminary results of this program are summarized in this paper
Analysis of Variation in Sainfoin (Onobrychis viciifolia) by Clustering
Full text linkSainfoin (Onobrychis viciifolia) is a forage legume that attracts interest due to its feeding value to ruminants. This is based on factors such as hight voluntary intake, non-bloating and protein protection, all of which appear related to the concentration of condensed tannins in the plant tissue (Ulyatt et al., 1977). Agronomic difficulties with sainfoin such as low yield and poor persitence show a lack of consistency between experiments which seem to be due, in part, to the level of heterogeneity displayed by the available sainfoin cultivars and germplasm (Fortune and Withers, 1980; Rumball, 1982). By permitting examination of the relationships between measured variables, multivariate techniques offer a method of grouping individuals into lines (Chatfield and Collins, 1980). This is frequently a requirement of plant breeders. The objective of this work was to examine the pattern of variation in sainfoin grown under controlled environmental conditions. The numerical approach was to examine the variability, simplify the array of data collected, and to consider the effective use of the reduced data