POTENTIAL PASTURE PRODUCTION IN THE UPLANDS OF WALES

The DM and N contribution of S184 white clover in mixed ryegrass/clover swards was recorded at Pant-y-dwr Hill Centre (305 m) for 4 years, 1967–70. By direct comparison with fertilized grass swards it was estimated that the clover N contribution on peaty gley soil averaged 100 kg N/ha per year (89 Ib N/ac) under cutting and 98 kg N/ha (87 ib/ac) under grazing with faecal return. On more fertile acid brown earth the corresponding contributions were 81 and 90 kg N/ha (72 and 80 Ib/ac). Full replacement of clover by N fertilizer would require average annual applications of 268, 229, 156 and 128 kg fertilizer N/ha, respectively (239, 204, 139 and 114 Ib N/ac).     

POTENTIAL PASTURE PRODUCTION IN THE UPLANDS OF WALES

Resown S23 perennial ryegrass pastures showed considerably greater response to the application of fertilizer N (0·1075 kg N/ha per year = 0–960 Ib N/ac) at 305 m O.D. than the native Festuca ovina/Agrostis tenuis and Molinia caerulea dominant communities on identical brown earth and peaty gley soils. Ryegrass DM production during 1967–70 increased with N application rates up to 538 kg N/ha per year (480 Ib N/ac) on the acid-brown earth, while on the extremely N-deficient gley soil yield responses were recorded up to 1075 kg N/ha (960 Ib N/ac). Percentage N recovery by ryegrass, bowever, although improved by grazing and re circulation, was less than under lowland conditions and the response to N during the growing season was also lower, exceeding 20 kg DM/kg N from applications in May, June and July only. The recovery of N by Festuca/Agrostis and Molinia in 1968–70 ranged from 3% and 2% at 938 kg N/ha to 14% and 9% at 117 kg N/ba per year, respectively. The respective maximum average DM yields recorded were 29 t/ha and 2.2 t/ha from the native communities and 70 t/ha and 62 t/ha from the corresponding resown pastures (2610, 1950, 6250 and 5520 Ib/ac). The results are discussed in relation to the strategy of land improvement in upland areas.     

POTENTIAL PASTURE PRODUCTION IN THE UPLANDS OF WALES

Detailed soil and vegetation analysis at Pant-y-dwr Hill Centre illustrated the main physical, chemical and biological factors involved in low output from rough grazing on 5 soil series, ranging from acid brown earth to undifferentiated peat, which are representative of most of upland mid-Wales. While all the soils, derived from Silurian shale, had low pH and base saturation status and high lime, phosphate and potash requirements, the principal restraint on the productivity of resown grassland, particularly on the wet peaty gleys, was low available N status.     

POTENTIAL PASTURE PRODUCTION IN THE UPLANDS OF WALES

Study of the growth of heavily fertilized swards of S23 perennial ryegrass (Lolium perenne) at a hill and a lowland centre in mid-Wales during 1968–69 demonstrated that lower productivity in the uplands could only be partially attributed to a shorter growing season and poorer summer growth conditions. Comparison of yields with potential transpiration estimates indicated that winter damage had an important bearing on production during the following year. In 1969, the adverse combination of a mild autumn and a severe winter led to a spring tiller density which was less than 25% of normal at the hill centre. With an annual fertilizer input of over 500 kg N/ha (480 lb N/ac) total DM production in 1968 and 1969 was 10.6 and 4.4 t/ha at the upland site compared with 14.8 and 10.1 t/ha in the lowlands (9450, 3920, 13,190 and 9000 lb/ac).     

THE POTENTIAL OF LOTUS spp. FOR HILL LAND IN WALES

Thirty-four introductions of Lotus corniculatus and L. uliginosus , obtained from Europe, North America and New Zealand, were grown in plots with Aberystwyth S23 ryegrass at three centres in Wales (230–400 m a. s. 1.) to assess their potential as legumes for poor acid hill soils. The control white clover varieties were generally successful in these difficult conditions, whereas all the Lotus introductions were poor in two experiments and in the third experiment gave way to volunteer white clover by the third harvest year. These results indicate that none of the numerous Lotus varieties tested would be a useful addition to pasture seeds mixtures for hill lands in Wales.     

THE EFFECT OF BURNING OF NATIVE PASTURE ON SOIL TEMPERATURE IN NORTHERN NEW SOUTH WALES

Thermocouples were used to measure temperatures at shallow depths (top 39 mm) in soils during late winter burning of hayed-off native pasture. Different intensities of burning were investigated. The maximum temperature recorded for any treatment was 75–5°C, at 1 mm below the soil surface, and marked temperature rises were recorded only in the upper 10 mm of the soil. The results suggest that the temperature rise induced by burning would have little direct effect on soil organic matter, the microbial populations, or buried seeds. The possible significance of these results in practice is discussed.     

THE EFFECT OF NITROGEN APPLICATION TO PASTURE ON BEEF PRODUCTION

Five grazing experiments each lasting 2 or 3 years were made between 1955 and 1967, all starting in the first year of ryegrass/cocksfoot/clover or ryegrass/clover leys. A high and a low rate of N, 235 and 45 Ib/ac on average (263 and 51 kg/ha) were compared for beef production. High- and low-N treatments gave mean clover contents for the grazing season of 8 and 24 % on a dry-weight basis, respectively. High N consistently gave a smaller liveweight gain/animal than low N, on average 1±92 and 2±08 Ib/day (0±87 and 0±94 kg/day), respectively. Liveweight gain/ac was 20% greater for high N than for low N, and in terms of net energy the production from high- and low-N, respectively, was 18,500 and 15,000 MJ/ac (45,700 and 37,100 MJ/ha). Data from these experiments, together with published results, were used to calculate a regression of liveweight gain response on N rate and an equation was derived from this to express the output in terms of profit. At 1971 prices profit was maximal at λ0±9/ac (λ2/ha) with 112 Ib N/ac (125 kg N/ha); it was considerably greater at 1973 prices when higher rates of N were justified.     

THE EFFECTS OF WINTER GRAZING ON SUBSEQUENT PRODUCTION FROM PASTURE

The eflFects of various systems of winter-grazing management on pasture production in the following spring and summer were studied in four trials in the Pentland Hills, Scotland. Winter grazing reduced the yield of herbage in spring, but growth in May and June was primarily influenced by the level of nitrogen application in spring, irrespective of winter-grazing treatments.     

THE DRY-MATTER PRODUCTION, BOTANICAL COMPOSITION, IN VITRO DIGESTIBILITY AND PROTEIN PERCENTAGE OF PASTURE LAYERS

Irrigated plots of a mixed sward of four grasses and white clover were cut to a height of 3 cm in either June, August, October, December or February. The plots cut at each commencement date were harvested when the height of growth of the pasture was either 10, 18, 25, 32, 40, 48 or 55 cm. At each harvest, the pasture was cut at 7 to 8 cm intervals down to a height of 3 cm. DM production, botanical composition, in vitro digestibility (DOM) and CP of each layer was determined. DM production declined from the lower to the upper layers for pastures shorter than 32 cm. For pastures taller than 32 cm, DM production declined from the lower to the middle layers, then increased in the upper layers, due mainly to the presence of seed heads. Maximum percentages of DOM and CP were observed for the middle layers of the pastures taller than 25 cm. For pastures shorter than 25 cm, DOM and CP percentages increased from the lower to the upper layers, for all commencement dates. The percentages of DOM and CP of each layer decreased as the height of growth increased. The percentage of DOM showed a positive correlation with the percentages of Lolium perenne, Bromus unioloides and Trifolium repens, and a negative correlation with the percentages of Paspalum dilatatum and chlorotic material. The percentage of CP showed a positive correlation with the percentages of Paspalum dilatatum, Dactylis glomerata and Trifolium repens and a negative correlation with the percentages of chlorotic material and the total of the four grasses within the pasture layers. The lower layers of the pasture produced large quantities of DM and, despite the lower in vitro digestibility of these layers, they produced more DOM than the other pasture layers. The DOM production of the pasture increased with increasing height of growth, but decreased as the commencement date was altered from winter through to the end of summer.     

BEEF PRODUCTION FROM PASTURE LEYS IN UGANDA*

The potential for producing beef in savanna grassland areas is discussed in relation to the results obtained from grazing trials on sown pastures at Serere Research Station, Uganda. Liveweight gains from small East African Zebu stock are used to illustrate the progress that has been made in the selection of improved pasture species and mixtures grown at various levels of fertilizer application. The utilization of herbage from selected pastures is shown to vary under different grazing management systems, grazing pressure having the greatest effect upon animal production. The need for further investigations and the integration of existing research findings into farming practice is stressed.     

THE EFFECTS OF CHANGES IN HEIGHTS OF CUTTING AND GROWTH ON THE DIGESTIBLE ORGANIC MATTER PRODUCTION AND BOTANICAL COMPOSITION OF PERENNIAL PASTURE

Irrigated plots of a mixed sward of Lolium perenne, Paspalum dilatatum, Bromus unioloides, Dactylis glomerata and Trifolium repens were used in 2 experiments during 4 years. In the first experiment, die treatments comprised factorial combinations of heights of cutting of 3, 6 and 10 cm (1.2, 2.4 and 3.9 in.) above ground level, and heights of growth of 5, 13 and 20 cm (20, 5.1 and 8.0 in.) above the height of cutting. In the second experiment, 8 combinations of dose (3 cm or 1.2 in.) or lax (10 cm or 3.9 in.) cutting were applied at various times during each year. In the first experiment, DM production for cutting heights of 3, 6 and 10 cm was 50, 44 and 43 t/ha (198,17.5 and 171 ton/ac), respectively; the DOM production was 37, 32 and 32 t/ha (147, 12.7 and 12.7 ton/ac). DM production for growth heights of 5, 13 and 20 cm was 45, 46 and 48 t/ha (17.9, 183 and 191 ton/ac), respectively. DOM production, 34 t/ha (13.5 ton/ac), was not affected by height of growth. Percentages of protein (26, 22 and 20) and DOM (76, 72 and 71) declined as the height of growth was increased; but cutting height produced no significant effects in them. As cutting height was increased the percentage of clover declined (40, 31 and 23) and that of grasses increased (52, 66 and 72); diere were smaller changes with changes in height of growth. Hie second experiment showed that the difference between close and lax cutting became significant only when lax cutting was applied for at least half of the cuts each year. DM production was similar for treatments witii the same number of close or lax cuts, regardless of the time of year at which the two heights of cutting were applied.     

COMPETITION BETWEEN WHEAT AND UNDERSOWN PASTURE IN THE YEAR OF SOWING AND THE EFFECT OF UNDERSOWING ON THE YIELD OF PASTURE IN THE FOLLOWING YEAR

Sowing pasture species with wheat caused a reduction in the growth and yield of the pasture species. This reduction was more severe with wheat drilled at 7 inch row spacing than at 14 in., and was least when the two crops were in alternate 7 in. rows. The reduction appeared to be due principally to the shade cast by the wheat. The pasture also reduced the growth and yield of wheat, but the effect of row spacing and position were opposite to and very much less marked than those of wheat on pasture. The yield of the pasture early in the following season was related to the seed yields in the year of establishment; later in the season, however, differences in yield among the various treatments disappeared.     

THE USE OF GRAZING-ANIMAL OBSERVATIONS IN THE EARLY STAGES OF PASTURE EVALUATION IN THE TROPICS

The use of grazing-time records for the estimation of grass species consumption was investigated in the context of two small-plot grazing trials. It was found that sampling errors were significantly lower than those involved in the cutting techniques used and that a high level of repeatability of results could be obtained.
The overall correlations between fresh-weight yield estimates from sample cuts and grazing records for individual plots were found to be 0·57*** and 0·72*** in the two trials. The bias that was introduced into some of the estimates of species yield appeared to be corrected through the use of palatability data.
It is concluded that the use of grazing-time records for yield estimation amongst species of broadly similar growth habit may have a definite potential in tropical Africa, but that the method requires further testing before being widely adopted.     

THE USE OF GRAZING-ANIMAL OBSERVATIONS IN THE EARLY STAGES OF PASTURE EVALUATION IN THE TROPICS

An observational technique for measuring pasture palatability is described in which a palatability index is constructed to indicate the species selected by stock under specified conditions of choice. The index differentiates these species from others that stock are prepared to eat when opportunities for selection are more limited. The potential usefulness of this index in the initial testing of tropical pasture species is discussed.
Results are reported from two 3-year experiments where the method was used. Coefficients of variationin individualgrazingsranged from 13·5 to 22·2% with experimental meansof 19·2 and 18·3%. Hyparrhenia rufa and Cenchrus ciliaris were found to be the m6st consistently palatable of the grasses offered.     

EFFECTS OF DIFFERENT GRAZING ROTATIONS ON PASTURE PRODUCTION

Different grazing treatments applied to pastures in which perennial ryegrass was dominant had little influence on DM production during the main reproductive growth period in late spring and early summer. Lax and infrequent grazing at this time did, however, reduce tiller density. During the dry summer period lax infrequent grazing increased production by 20%, while in the vegetative growth period in autumn those pastures which were alternately lax- and hard-grazed outyielded those which were hard grazed by 63%. In all treatments, initial recovery growth resulted almost exclusively from the production of leaf tissue. The rate of leaf growth declined three to five weeks after grazing, depending on treatment and season, and subsequent yield increase was dominated by sheath and stem growth.     

REMOVAL OF THE EFFECTS OF UNEVEN GRAZING IN PASTURE EXPERIMENTS

An experiment is described in which uneven grazing by sheep introduced a bias in a white clover variety trial. The data were adjusted by covariance, using as the independent variable the position of the plots within the paddocks.
Attention is drawn to the errors that may result from uneven grazing and a comparison is made with errors due to transference of fertility. Means of avoiding similar occurrences are suggested.     

THE YIELDS OF LUCERNE VARIETIES IN WEST WALES

Nine varieties of lucerne were grown at the Welsh Plant Breeding Station in broadcast plots, without a companion grass, and three cuts of each variety were taken each year for three years.
None of the newer varieties significantly outyielded the control variety Du Puits, although Alfa and G.P.R.l. produced 6% and 4% more dry matter. Cardinal gave a similar yield to the control; Omega and G.P.R.2 produced considerably less. A new late variety AF1 yielded 8% less dry matter than Du Puits but was equal to it in yield of crude protein. Vernal and Provence were very markedly inferior to all other varieties.
The average yields of the lucerne fraction were 5910, 11,850 and 10,160 Ib/acre in the first, second and third harvest years. Unsown grass contributed from one-half to one ton per acre per annum, in inverse proportion to yield of lucerne; the contribution was greatest in the first cut, but was negligible in the last two cuts.
Data were also collected on susceptibility to leaf spot ( Pseudopeziza medicaginis ) and on plant counts.     

PASTURE DEVELOPMENT IN THE BEEF CATTLE REGIONS OF ARGENTINA

An account is given of the climate, vegetation and native pastures of the beef-cattle regions of Argentina. Though some of these native pastures have a satisfactory carrying capacity, most of them are defective in quality or low in productivity; there is considerable scope for increasing production through the establishment of sown pastures. Trials have been made with a wide range of grasses and legumes, principally of African and European origin. Though the pattern of species to be used in these regions is imperfectly resolved, the authors present a map showing tentative boundaries for temperate, sub-tropical and tropical species. Work to date suggests that pasture development can probably proceed over great areas without the use of fertilizers, and this adds to the attractiveness of pasture programmes. A problem of no less importance than the technical aspects of pasture improvement is that of gaining a greater investment of capital into the development of cattle estancias.