Factors influencing the proportion of natural hybrids between Lolium perenne L. and Festuca pratensis Huds. in permanent pastures

Hybrids between ryegrass and meadow fescue form rarely but occur widely in old pastures. In one experiment six different hybrid genotypes were able to compete, on equal terms, with members of their parental species. In two others the proportion of the total yield due to one hybrid genotype was increased by added fertilizer or by reduced water supply.     

The Effect of Afforestation on Water Runoff in the Woodburn Catchment Area

Weekly runoff and rainfall records for 1960–71 are analysedin this paper for two catchments: a forest area, planted between1958 and 1960, of 111.5 ha and a grass area kept permanentlyfor grazing of 26.5 ha. Analysis of the data failed to detectany significant changes in the water yield from the forestedcatchment. The experiment has demonstrated the difficultiesof making precise measurements and comparisons from data collectedin areas of rolling topography where soils among other factorsdiffer.     

Measured and computed concentration patterns of propyzamide in field soils

The persistence of propyzamide in soil was studied by analysing soil samples taken at intervals two or three times after application in the spring to experimental fields. Single samples were taken from other fields. 8 to 12 months after autumn application. The concentrations were measured by electron-capture gas chromatography. Persistence is expressed in first-order dissipation rate constants and half-life values. Data were measured and collected on the adsorption of propyzamide on soils, the soil characteristics and the weather conditions. Computations of the mobility of propyzamide in soil were carried out for simplified systems. Results of measurements and computations are compared.     

Photosynthetic inhibition in Phaseolus vulgaris II. The influence of light on herbicidal action

The influence of pre-treatment and post-treatment illumination upon the herbicidal effect produced in Phaseolus vulgaris L. cv. Berna by simeton, diuron, diquat and ioxynil was examined. The increased effect noted at lower pre-treatment and higher post-treatment levels of illumination was correlated with increased inhibition of net photosynthesis. This increased effect was ascribed to enhanced photo-oxidation.     

Aperçu économique de la protection phytosanitaire des vergers français soumis à la lutte intégrée 1)

La mise en place d'une vaste demonstration de lutte intégrée en vergers dans le sud-est de la France bénéficie de l'appui financier du Ministère de l'Agriculture depuis 1967. Les structures organiques de cette action sont décrites. L'activité des techniciens spécialisés qui fournissent un appui logistique au second degré auprès des conseillers agricoles et des producteurs de fruits, tout en restant en liaison constante avec les centres de recherches et les services d'applkation, est indispensable pour assurer le développement de l'entreprise. Elle a notam-ment stimulé diverses études immédiatement utilisables dans la pratique. Des résultats probants sont obtenus en vergers de pommiers et de pêchers par l'application d'une lutte dite dirigée, qui constitue la phase de transition entre la lutte traditionnelle et la lutte intégrée. lis se traduisent par une diminution de l'ordre de 50 % du nombre des interventions insecticides et acaricides. Les données économiques correspondantes sont présentées et discutées. Outre l'aspect strictement économique, les utilisateurs apprécient la maîtrise que leur confèrent les connaissances écologiques.