THE EFFECT OF NITROGEN, STOCKING RATE AND GRAZING METHOD ON THE OUTPUT OF PASTURE GRAZED BY BEEF CATTLE

An experiment was conducted in 1971 and 1972 to study the effects of two levels of fertilizer N (50 and 504 kg/ha) on the productivity of pastures grazed by young beef cattle. Two stocking rates were imposed at the lower N level and three at the higher. In addition to rotational grazing, set-stocking and an integrated grazing-conservation system were included. The responses/kg N were approximately 1 kg live-weight gain, 19–24 Meal ME and 8–9 kg DM. Maximum yields of 1200–1300 kg live-weight gain/ha and 25,000–27,000 Meal ME/ha were recorded. Productivity of set-stocked pasture was similar to rotational grazing at the high N level, but lower at low N. The integrated system yielded comparable results to high-N rotational grazing. Performances and herbage intakes per animal reflected the stocking rates imposed.     

THE INFLUENCE OF SUPPLEMENTARY FEEDING ON THE HERBAGE INTAKE AND GRAZING BEHAVIOUR OF DRY COWS

The herbage intake and grazing behaviour of 4 dry cows on autumn grass receiving 2, 4, 6 or 8 kg concentrates/day, was assessed in a 4×4 Latin Square experiment. Total OM intake increased from 11±5 kg/day with 2 kg concentrates to 13±6 kg/day with 8 kg concentrates. The average supplementary effect was 0±46 kg increase in OM intake/kg OM fed as concentrates. Minutes per day spent grazing decreased from 495 with 2 kg concentrates to 359 with 8 kg. The mean decline was 22 min./kg concentrates or 28 min./kg OM in concentrates eaten. Herbage was eaten at an average rate of 47 min./kg OM.     

THE EFFECT OF CUTTING HEIGHT AND NITROGEN LEVEL ON THE YIELD, IN VITRO DIGESTIBILITY AND CHEMICAL COMPOSITION OF ITALIAN RYEGRASS SWARDS

Three cutting heights, 2±5, 7±6 and 12±7 cm (1, 2±5 and 5 in.) and three levels of fertilizer N, 168, 280 and 392 kg N/ha (150, 250 and 350 Ib N/ac) were imposed on a sward of Italian ryegrass (Lolium multiflorum) cv. Irish. Lowering the cutting height and increasing the level of applied N increased the yield of herhage DM. Increasing the level of applied N had a greater effect on the chemical composition of the herbage than altering the cutting height     

Adsorption and activity of chitinase on kaolinite

Chitinase is adsorbed on kaolinite below the isoelectric point of the enzyme, pH 6.8. Maximum adsorption is reached below pH 4.6. The amount of chitinase adsorbed to kaolinite depends on the concentration and on the ratio of enzyme to kaolinite. Adsorption results in reduction of chitinase activity. the extent of which depends on the amount of kaolinite present, on pH, and on the length of exposure time. Upon sorption of chitinase on kaolinite the optimal pH for activity is increased from pH 4.7 to 5.7.     

Fertilizing fish ponds. I — Chemistry of the waters

Fertilization experiments were carried out in the Mex fish farm using superphosphate, ammonium nitrate and organic manure as fertilizers.The water was analysed monthly for inorganic phosphates, nitrates and silicates, in addition to chlorosity and pH.The ponds fertilized with chemical fertilizers exhibited a more rapid consumption of nutrients than the pond fertilized with organic manure.Phosphates and nitrates disappeared from the ponds after about two days of addition.     

INVESTIGATIONS ON THE DRYING OF HERBAGE AT TEMPERATURES UP TO 50°C*

Experiments to determine the exposed layer drying rate of cut leaves and stems of a tetraploid (Sabel) and diploid (S23) ryegrass are described. Drying was achieved by passing air through the crop; the changes in weight were monitored continuously. Airflow was fixed throughout the experiments at 37·5 ft/min (0·190 m/s) and the temperatures were controlled in the range 25°C to 50°C. Comparisons were also made of the drying rates at different stages of maturity. Drying curves were determined and moisture content was shown to decay exponentially with time, the relationship approximating closely to a two term exponential.     

Laboratory incubation studies of chlorophenoxyacetic acids in chernozemic soils

The relative persistence of 2,4-D, MCPA and 2,4,5-T in some Saskatchewan soils was assessed under laboratory conditions. Under moist conditions, 2,4-D and MCPA showed half-life times of between 14 and 41 days but the MCPA half-life was usually 1 or 2 days longer. 2,4,5-T exhibited a half-life period over twice the length of the other chemicals. The half-life times were directly correlated to microbial plate counts, the larger numbers of soil microorganisms being associated with shorter residence times. Half-lives depended on soil moisture content and the best moisture levels for chemical loss appeared to be just less than field capacity. The use of ¹⁴C in 2,4-D incubation studies showed that the initial cleavage of the 2,4-D molecule was associated with the ether linkage and was not a decarboxylation.