ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01220.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe relative uptake of P was measured in two varieties ofLolium perenneusing radioactive tracer techniques. The diploid cv. Hora and the tetraploid cv. Terhoy were sown as pure stands and as 50:50 mixtures at both high and low density. Uptake from four depths 10, 20, 30 and 40 cm was examined. The results showed that: in pure stands the diploid uptake at 10 cm exceeded that of the tetraploid although at deeper levels the uptake pattern was similar; in mixtures the uptake of the tetraploid variety increased markedly at 10 cm while that of the diploid variety decreased. The diploid compensated for its decreased uptake at 10 cm by a substantial increase in uptake at 20 cm; overall the tetraploid variety had a deeper pattern of uptake than the diploid; in general, uptake at high density was greater than that at low density; the mixture showed a greater degree of P utilization than pure stands in the upper layers of the soil; when these two varieties are grown together in 50:50 mixtures the tetraploid is relatively more efficient in taking up.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01221.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe DM digestibility (DMD) and organic matter digestibility (OMD) of 36 tropical grass samples were determined bothin vivoandin vitro. Regressions relating OMD to DMD were calculated.In vivoOMD=1·02in vivoDMD+ 0·1, r=0·99.In vitroOMD=1·05in vitroDMD—4·7, r=0.99. At the same DMD, thein vitromethod predicted OMD 2·8 to 3·4 percentage units lower than thein vivomethod. This difference was caused by the difference in mean apparent digestibility of the ash,in vitro71%,in vivo47%.In vivoDMD was correlated (r=0·92, P<0·01) within vitroDMD and the regression relating these two factors had a residual standard deviation of ±1·42 digestibility units. This deviation was reduced to ±1·9 digestibility units when OMD was determined. For both DMD and OMD significant differences were found between grass species in the relation betweenin vivoandin vitrodigestibility.To overcome biased estimates of OMD it was suggested that conversion equations should be avoided, and that thein vitromethod be standardized with samples of knownin vivoOMD as similar as possible to thos

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01222.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01223.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe duration of the juvenile phase in early‐flowering (Dorset Marl) and late‐flowering (S123) red clover is described. Neither cultivar responded to inductive conditions at the first leaf stage but Dorset Marl attained maximum sensitivity by the 3‐leaf stage. A comparable response was obtained with S123 only after the production of 12–13 leaves. The growth characteristics of the two types under continuous long or short days are described and possible explanations are advanced for the characteristic differences in tillering and stem internode

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01224.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe results are reported of the effects of fertilizer and grazing or cutting for hay over a period of 6 years on the composition of anAgrostis/Festucapermanent pasture on low‐lying land at Beghroke Hill. Applications of N up to 264 units/ac each year associated with frequent defoliation every 21 days produced only small changes in sward composition;Agrostisspp. declined andPoa trivialisincreased.Lolium perennedid not increase from a small initial presence. Records of animal performance and hay yield showed that the mean output from the experiment as a whole was 530 Ib liveweight gain/ac and 0·5 ton hay/

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01225.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTFor three weeks after emergence, micro‐swards ofLolium rigidumwere defoliated to a height and at a frequency which represented a range of set stocking rates of less than, similar to, and more than 7–8 sheep/ha as based on the results of Greenwood and Arnold (6) and referred to as D1, D2and D3respectively. The effects of these defoliation regimes on the growth and development of emergent swards were evaluated according to their effect on increments of DM from plant parts, rate of appearance of leaves and tillers, concentration of soluble carbohydrates, and on the uptake and concentration of inorganic nutrients.Defoliation began five days after emergence, when the dry weight of the shoot was 3g/m2. After 20 days of treatment, 6±7 g/m2of DM had been removed from D1, 5±5 g/m2from D2and 51 g/m2from D3; and the dry weight of shoot remaining was 13, 7 and 4±5 g/m2on D1, D2and D3respectively. The effect of defoliation on dry weight of plant parts increased in severity in the order leaf 1, stem+sheaths, leaf 2, roots, leaf 3, tiller 1, tiller 2, leaf 4. Average relative growth rate of the sward was reduced from 17% per day on D1to 13% per day on D3. There was no necrosis of root tissue. Emergence of the later leaves and of the tillers was retarded by up to three days by more frequent defoliation. Alcohol‐soluble carbohydrates in the root fell from over 6% to about 1±5% on all treatments. Uptake of N. P and K was limited by increasing intensity of defoliation and because concentrations of those elements were not greatly affected, the limitation could be ascribed mainly to the effects of defoliation on plant size.The plausibility of the technique for the experimental simulation of grazing of emergent annual grass swards in Western Australia is discussed. It is concluded that for set‐stocking rates of less than about 12 sheep/ha, grazing, while reducing DM production just after emergence, is unlikely to produce severe physiological stresses i

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01226.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTExperiments 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 exponent

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01227.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThree 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 he

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01228.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTFarm‐scale trials with Ayrshire dairy cows were conducted in South‐West Scotland over two seasons to compare set‐stocking and paddock grazing at similar stocking rates and N fertilizer rates.At a stocking rate of 1±9–2±0 cows/ac throughout the grazing season and a fertilizer N rate of about 400 units/ac, milk production per head from set‐stocked cows was equal to that from paddock‐grazed cows. No health problems arose as a result of applying fertilizer to the fields which were set‐stocked.These trials hare established that set‐stocking is a viable system for the intensive management of dairy cows on grassland in the UK, but further work is necessary to determine whether paddock‐grazing has a higher potential for milk productio

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01229.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY