THE EFFECT OF CUTTING AND NITROGEN TREATMENTS ON YIELD, PROTEIN CONTENT AND CERTAIN MORPHOLOGICAL CHARACTERISTICS OF TIMOTHY AND SMOOTH BROMEGRASS

Timothy and bromegrass were studied in pure sowings in a glasshouse, and each in a mixture with lucerne, dominated by the grass–fraction in the first crop year, in the field. In the glasshouse both species were cut 3, 5, or 6 times at a 2–in. and 6 times at a 3/4–in. stubble height. In timothy, cutting 6 times gave lower DM but higher protein yields than less frequent cutting. In bromegrass close cutting gave higher DM yields than lax cutting. The following results applied to both species: root weight decreased with increasing severity of defoliation, final tiller density was very low under close cutting, and a complete application of N at the time of sowing was superior to a split application.
In the field, the first cut was taken on 5 dates at intervals of 1 week, the second cut 6 or 8 weeks after the first cut, and the third cut 7 weeks after the second cut (for bromegrass mixture only). DM yield was generally the higher the later the first cut was taken and the longer the subsequent rest period. However, the opposite applied for best sustainment of yield. The 1 1/2–in. stubble treatments outyielded the 3 1/2–in. treatments. Generally, production of CP was influenced more by DM yield than by % content. Reduced removal of tiller primordia in the second cut led to higher third–cut yields, but at the cost of total yield. Difficulties in the control of shoot apex removal encountered in both glasshouse and field are discussed.     

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.     

Chlorophyll production and chloroplast development in norflurazon-treated plants

The chlorophyll production of wheat (Triticum vulgare L. cv. Mericopa), corn (Zea mays L. cv. Everta), and alfalfa (Medicago sativa L. cv. Saranac), treated with the herbicide 4-chloro-5-methylamino-2-(3-trifluoro-methylphenyl)pyridazin- 3-one (norflurazon) and grown under high light intensity (10 760 lux) was markedly reduced. Corn and wheat seedlings germinated and grown for 7 days in an agar medium containing 1 mg/1 norflurazon were almost completely bleached. Alfalfa was even more sensitive to norflurazon, 0.1 mg/1 causing almost complete chlorosis. Under low light intensity (10.76 lux) the influence of norflurazon on chlorophyll production was greatly reduced. It is thought that norflurazon inhibits carotenoid synthesis leaving the chlorophyll of the plant subject to photooxidation. Electron micrographs of chloroplasts from green, partially bleached, and bleached areas of corn leaves treated with norflurazon indicate that the herbicide causes progressive deterioration of the lamellar system.     

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.