Search

The benefits of using white clover (Trifolium repens L.) as a source of nitrogen (N) and nutritious feed in pasture grazed by ruminant livestock have been widely recognized. However, clover is considered inadequate and unreliable as the main source of N input, since its abundance in pasture is patchy, low (typically <0·20) and shows great year-to-year variation. This is thought to be due to the metabolic costs of N fixation, competition with grass, the preference for clover by grazing animals and patchy dung and urine deposition. One solution suggested by a number of authors is to increase the heterogeneity within the pasture by spatially separating clover from grass. This method of pasture management, in order to sustain higher clover content in both the sward and diet of grazing animals, would remove inter-specific competition and equalize grazing pressure, allowing clover to grow unimpeded in greater abundance than previously observed. An existing spatially explicit grass–clover simulation model, developed to investigate the intrinsic spatial and temporal variability within mixed grass–clover swards, was modified and then used to examine the impact of spatial separation on the content, variability and patchiness of clover in pasture. The results show that spatial separation increases both the content and spatial aggregation of clover and reduces year-to-year variation compared with a mixed pasture that fluctuates around a lower mean. The same model was also used to examine the impact of spatial separation across a range of spatial scales, from narrow strips to complete separation, as a means of managing the concerns over disruption to the N cycle within the pasture. The present study shows the importance of the initial sowing arrangement of plant species in sustaining a high content of clover within a pasture in the short term, to at least 20 years depending on the scale of separation, and demonstrates that the spatial separation of clover from grass within a grazed pasture may overcome some of the limitations associated with the use of clover in conventional grass–clover pastures. Results are discussed in terms of benefits to both herbage dry matter production and animal performance. [ABSTRACT FROM PUBLISHER]

The benefits of white clover ( Trifolium repens L.) in pastures are widely recognized. However, white clover is perceived as being unreliable due to its typically low content and spatial and temporal variability in mixed (grass-legume) pastures. One solution to increase the clover proportion and quality of herbage available to grazing animals may be to spatially separate clover from grass within the same field. In a field experiment, perennial ryegrass ( Lolium perenne L.) and white clover were sown as a mixture and compared with alternating strips of ryegrass and clover (at 1·5 and 3 m widths), or in adjacent monocultures (strips of 18 m width within a 36-m-wide field). Pastures were stocked by ewes and lambs for three 10-month grazing periods. Over the 3 years of the experiment, spatial separation of grass and clover, compared with a grass-clover mixture, increased clover herbage production, although its proportion in the sward declined through time (0·49-0·54 vs 0·34 in the mixture in the first year, 0·28-0·33 vs 0·15 in the second year and 0·03-0·18 vs 0·01 in the third year). Total herbage production in the growing season in the spatially separated treatments decreased from 11384 kg DM ha−1 in the first year to 8150 kg DM ha−1 in the third year. Crude protein concentration of clover and grass components in the 18-m adjacent monoculture treatment was greater than the mixture treatment for both clover (310 vs 280 g kg−1 DM) and grass (200 vs 180 g kg−1 DM). There was no clear benefit in liveweight gain beyond the first year in response to spatially separating grass and clover into monocultures within the same field. [ABSTRACT FROM AUTHOR]

The benefits of using white clover in pastures have been widely recognised for many years. However, clover is perceived as being unreliable because of its typically low content, which is spatially and temporally variable, in mixed pastures. One proposed solution to increase the proportion of clover in the diet of grazing animals and composition in the pasture is to spatially separate clover from grass within the same field. In a field experiment ryegrass and white clover were grown in fine mixtures, and in pure alternating strips of ryegrass and clover of 1.5 m, 3 m or 18 m width within a field. Pastures were grazed for two grazing periods of 9 and 12 weeks, and measurements of sward surface height (SSH), herbage mass and composition and clover morphology were taken. Grazing behaviour was also observed. Results showed that spatial separation in the long term, when compared with a fine mixture, increased clover availability (18% to 30% v. 9%, based on standing dry matter) and was not grazed to extinction. Ewes maintained their preference for clover throughout the experiment (selection coefficient 2 to 5), which resulted in a reduction in the SSH of clover in monocultures to <3 cm and significant changes to the morphology of clover (smaller leaves, shorter petioles and thicker stolon), at the expense of maximising their intake. Spatial separation in the short term may therefore allow grazing animals to select their preferred diet; however, in the long term in continuously grazed pasture, their preference for clover depletes its availability. [ABSTRACT FROM PUBLISHER]

We are printing, by kind permission of the Law Commission, two sections of the report of the Law Commission on injuries to unborn children. This report was the result of a request to the Law Commission by the Lord Chancellor at the time (Lord Hailsham of Saint Marylebone) to advise on `what the nature and extent of civil liability for antenatal injury should be'. The Law Commission followed its usual practice in such circumstances of consulting various bodies and obtaining expert advice on the subject and then embodying the results in a working paper (Working Paper No. 47 - injuries to unborn children) published on 19 January 1973, which preceded their report (Cmnd 5709). Meanwhile a Royal Commission is considering much wider issues of civil liability for injury (including antenatal injury) but the terms of reference for the Law Commission were much narrower and confined to the position of children injured before birth. In the section relating to the present law the report makes it clear that it is probable that liability under the common law already exists. The Scottish Law Commission has also issued a report (Cmnd 5371). They were given different terms of reference and came to somewhat different conclusions. We are printing from this long report the paragraphs discussing the medical background and the summary of recommendations. As will be evident on reading the paragraphs on the medical background to injuries to the unborn child, events are moving very rapidly, particularly in the study of congenital defects and the effects of drugs but the problems of proof present great difficulty. Other causes of injury to the unborn child are better known to the general public: for example, those following the illness, infection and disease of the mother during pregnancy, injury caused in attempted termination of pregnancy and the risks resulting from the mother's condition. The summary of the recommendations sets out very clearly the legal position of the unborn child, as the Law Commission sees it, arising from injury before birth, the final conclusion being that `legislation is desirable'. These extracts from the report, apart from their intrinsic interest, lead on to the paper by Mr Kennedy and Dr Edwards in which they set out their criticisms of it, and provide quick references to the original document. [ABSTRACT FROM PUBLISHER]