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).     

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

An experiment was conducted in two successire years to measure the effect of two levels of fertilizer N, 50 and 300 kg/ha (45 and 270 Ib/ac) on the productivity of pastures grazed by young beef cattle. Two stocking rates were imposed at the lower N level and 4 at the higher level. The responses per kg fertilizer N were approximately 1 kg liveweight gain, 20–24 Meal ME and 8–9 kg DM. Maximal yields of about 1000 kg gain/ha (890 Ib/ac) and 19,000 Meal ME/ha (7700 Mcal ME/acre) were recorded. Animal performance was similar on the low and the high N pastures. There was evidence that the chemical quality of pasture was lower on the low N pasture in the first year, but there was no difference in the second year. The numbers of dung pats per ha and the refusal of herbage due to fouling were reduced by Increasing the stocking rate.     

THE EFFECT OF NITROGENOUS FERTILIZER ON THE RATE OF GROWTH OF ITALIAN RYEGRASS

In an experiment described earlier (13), the N content of Italian ryegrass in spring reached a high value one or two weeks after applying N and then fell quickly at first and then more slowly. After 10 weeks average N content (in DM) was 0.6% from an application of 25 lh N/ac (28 kg/ha), 0.9% from 75 lb N (84 kg/ha), and 12% from 125 lb N (140 kgJha). Nitrate-N content fell more abruptly and tben remained fairly constant. Percentage nitrate–N (in DM) fell below 0.10% during the second week after an application of 25 lb NJac, during the third week after 75 lb N, and during the fifth week after recciriag 125 lb N. The yield of N increased during the first 5 or 6 weeks, remained fairly constant for 3–5 weeks, and then hegan to fall. During the ninth and tenth weeks, the crop lost an average of 9 lb N/ac per week (10 kg/ha) after an application of 75 Ib N/ac and 12 lb N/ac per week (13 kg/ha) after 125 Ib N.     

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.     

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 EFFECT OF THE TIME AND LEVEL OF INJECTION OF ANHYDROUS AMMONIA ON THE PRODUCTIVITY OF GRASSLAND

Four levels of nitrogen, 188, 285, 358 and 392 kgJ.ha (150, 225, 285 and 350 units/ac) supplied as anhydrous ammonia were injected on each of four occasions, 18 Dec, 5 Feb., 12 Mar. and 16 Apr. DM and CP yields were estimated at each of three harvests taken on 4 June, 19 July and 28 Sept Total DM yields showed only a 10% difference between the highest yielding injection date, 12 Mar., which yielded 12270 kg/ha (10946 Ib/ac) and the lowest, 16 Apr., which yielded 11169 kgJ.ha (9963 Ib/ac). Early injection of ammonia promoted growth during the late spring and later injections resulted in increased yields at the two later harvests. The responses per kg fertilizer N were 11.9 kg DM (10.8 lb/unit) and 3.6 kg CP (3–3 Ib/unit). It was concluded that ammonia should be applied to grassland before April and, preferably, during March, for maximum yields of DM and CP.     

THE EFFECTS OF CUTTING AND FERTILIZER TREATMENTS ON THE YIELD AND BOTANICAL COMPOSITION OF CHALK TURF

Annual factorial applications of N and K fertilizers, with or without mowing, to Festuca rubra turf on a chalk rendzina at Swyncombe, Oxon, had large effects on yield and botanical composition over a period of 10 years. The yield of herbage was increased markedly hy N, and less by K, but the N × K interaction was significant. Mean yields of herbage DM for tbe 10-year period were: no N or K, 730 kg/ha per year; N, 1967; K, 1013; N+K, 2794 kg/ha per year (651, 1755, 904 and 2492 lb/ac per year). N caused an increase in DM production by F. rubra; the NxK interaction was a result of increased growth of species other tban F. rubra. Unmown plots became extremely matted, and undecomposed litter of F. rubra leaves and stems accumulated, especially if N, or N and K together, were given. F. rubra turf seems to he unusually stable, apparently because it forms a mat in which other more demanding species cannot establish themselves.     

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     

RED CLOVER SILAGE FOR MILK PRODUCTION

Nine wilted silages made from tetraploid red clover were fed in four winter-feeding experiments to 32 Ayrshire cows. The DM content of the silages averaged 23±5% (range 15±8–27±1) and contained an average of 19±6% crude protein, 14±2% digestible crude protein and 52±0% digestible organic matter. The pH values varied from 4±0–6±2, depending on the DM content and mechanical treatment of the crop, and the rate of application of formic add. The silages were fed ad lib.with supplementary concentrates and the average daily intakes of silage DM ranged from 16±0–24±0 Ib/cow (7±3–10±9 kg). The highest daily intakes were obtained with double-chopped silage containing 24–26% DM with a pH of 4±0. Although the red-clover silage had a high content of N and apparently provided a balanced ration with the addition of barley, yields of milk were increased significantly by substituting 1 Ib (0±4 kg) groundnut cake for 1 Ib barley in the daily ration of the cow. The silage contained oestrogenic compounds but the breeding pattern and fertility of the cows were not affected adversely. The tetraploid red clover produced approximately 9000 Ib DM/ac (10 100 kg/ha) in the 1st-harvest year and it is concluded that a safe and highly palatable silage with high intake characteristics can be made if the clover is wilted to about 24% DM, double chopped, and formic acid is applied at the rate of 0±5 gal/ton.     

THE EFFECT OF NITROGENOUS FERTILIZER ON THE RATE OF GROWTH OF ITALIAN RYEGRASS.

Residual response to an initial application of nitrogen was measured in 3 years and was found to be quite large, e.g. a response of 8 Ib DM per extra Ib N at the first harvest, when applying 125 Ib N/ac (140 kg/ha) rather than‘75 Ib (84 kg/ha) and allowing 6 weeks' growth, was increased to 21 Ib DM when yield from residual cuts was taken into account. Response was large in relation to the amount of N estimated to have been left behind after the first harvest. Marginal recovery of N, already quite high at the first harvest, was increased to a little over 90% when yield from residual cuts was taken into account Recovery, however, was lower than this when 10 weeks' growth was allowed before the first harvest, and it seems that, in this case, some N may have been lost from the system. A supplementary experiment suggested that the residual effect of N on DM yield could be obscured to some extent by fresh applications of N.     

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

Two successive grazing experiments were conducted over 12 weeks on perennial ryegrass pastures with 50 and 44 young cattle to study the effect of N fertilizer when applied at a daily rate of 1 or 3 kg N/ha. At each level of N two stocking rates differing hy 20% were imposed. At the liigher N level and stocking rate, three frequencies of grazing were imposed. At the stocking rates imposed N tended to reduce the daily liveweight gain per head, but increased the total liveweight gain per ha by from 0.79 to 1.58 kg/kg N. A 20% increase in stocking rate depressed gain per head in both years. In the first year it did not improve gain/ha, hut in the second year gain/ha was increased by 12–17%. There was a tendency for performance per animal and per ha to increase as the grazing cycle was lengthened. In 1969 the highest yield in the whole season was 1880 grazing days and 1260 kg gain/ha. The overall response to N fertilizer was similar to that recorded in other reports, but it is possible that a lack of K had limited pasture growth.     

NITROGEN AND ITALIAN RYEGRASS

This paper describes the regrowth of Italian ryegrass, following a cut in late April, measured by recording DM yields at weekly intervals up to 14 weeks. There were 4 levels of applied N: 25, 75, 125 and 175 Ib/ac (28, 84, 140 and 196 kg/ha). Rate of growth up to 10 weeks was compared with that recorded in similar experiments in Cambridge in earlier years and was found to be generally similar. The highest yields of DM and digestible organic matter were recorded after 11 weeks; beyond this stage there was a fall in yield. There was a large response to 75 Ib N compared with 25, a moderate response to 125 Ib compared with 75 (greater during the last 7 weeks than during the first 7 weeks), and little response to 175 Ib compared with 125. The time-saving value of N is noted. DM content was appreciably lower than in Cambridge, apparently because of both surface and internal moisture, but showed similar trends. In some of the early weeks, especially at high N, the crop appeared to be supplying water well in excess of livestock needs. In vitro digestibility was much affected by stage of growth and little affected by level of N.     

‘MaxClover’ grazing experiment: I. Annual yields,botanical composition and growth rates of six dryland pastures over nine years

Six dryland pastures were established at Lincoln University, Canterbury, New Zealand, in February 2002. Production and persistence of cocksfoot pastures established with subterranean, balansa, white or Caucasian clovers, and a perennial ryegrass‐white clover control and a lucerne monoculture were monitored for nine years. Total annual dry‐matter (10.0–18·5 t DM ha^?1) and sown legume yields from the lucerne monoculture exceeded those from the grass‐based pastures in all but one year. The lowest lucerne yield (10 t ha^?1 yr^?1) occurred in Year 4, when spring snow caused ungrazed lucerne to lodge and senesce. Cocksfoot with subterranean clover was the most productive grass‐based pasture. Yields were 8·7–13·0 t DM ha^?1 annually. Subterranean clover yields were 2·4–3·7 t ha^?1 in six of the nine years which represented 26–32% of total annual production. In all cocksfoot‐based pastures, the contribution of sown pasture components decreased at a rate equivalent to 3·3 ± 0·05% per year (R² = 0·83) and sown components accounted for 65% of total yield in Year 9. In contrast, sown components represented only 13% of total yield in the ryegrass‐white clover pastures in Year 9, and their contribution declined at 10·1 ± 0·9% per year (R² = 0·94). By Year 9, 79% of the 6.6 t ha^?1 produced from the ryegrass‐white clover pasture was from unsown species and 7% was dead material. For maximum production and persistence, dryland farmers on 450–780 mm yr^?1 rainfall should grow lucerne or cocksfoot‐subterranean clover pastures in preference to ryegrass and white clover. Inclusion of white clover as a secondary legume component to sub clover would offer opportunities to respond to unpredictable summer rainfall after sub clover has set seed.     

Lime and major nutrient fertilizers required to establish a perennial ryegrass/white clover pasture on a non-calcareous gley in the Scottish uplands

A field experiment with mixed swards of perennial ryegrass and while clover carded out in 1982–83 using small cut plots is described. With perennial ryegrass, lime slightly decreased annual dry matter (DM) production in 1982 (the sowing year) but increased it in 1983 (the first harvest year) by about 1 t ha^-1. Applications of N and P produced small increases in DM in 1982 and greater increases in 1983. In the latter season annual DM production varied from an average of 3·5 to about 10 t ha^-1 with 0 or 480 kg N ha^-1 applied in three equal-sized dressings throughout the growing season. Application of 40 kg P ha^-1 in 1982 increased DM production by about 2·5 t ha^-1 in 1983 but higher rates had little effect. Fifteen mg extractable P kg^-1 soil seemed sufficient to support levels of production normally expected from ryegrass pastures in upland Scotland, Applications of K did not affect DM production. N increased tiller weight and sward height of ryegrass; lime and P tended to increase tiller weight but this effect was not statistically significant. Leaf appearance and tiller number were not affected by treatments.
The white clover content of the pasture was decreased 10-fold by application of N and increased by lime and P (1·45 and 1·46-fold. respectively). The DM response to P was most apparent in limed soil and was also affected by the siting of the plots in the experimental area. Effects of lime and P on growth of white clover were to increase the number of stolon growing points and root nodule numbers per unit area.
The results emphasize the importance of lime and P fertilizer for establishment and growth of pasture in this soil and the differences between white clover and ryegrass in their responses to these.     

The role of the legume in the nitrogen cycle of productive and sustainable pastures

The role of the legume in the nitrogen (N) cycle was examined in grazed pastures receiving no N fertilizer of both temperate and tropical regions by simulating the fluxes of N through different processes of the cycle. The amounts of legume-fixed N required to balance the cycle without invoking a drain on soil organic N reserves (i.e. no net N mineralization) was estimated to vary from 38 to 53% of the above-ground herbage N or from 20 to 31% on a dry matter (DM) basis for tropical pasture systems with a range of pasture utilization of 10–40%. At higher pasture utilization levels of 50-70%, more typical of intensively grazed temperate pastures, the N input requirement in the absence of fertilizer N would be 57-67% of the aboveground herbage N or 35-45% DM. An examination of the role of each contributory process of recycling (viz. excreta returns, internal cycling or remobilization from senescing tissues, litter decomposition) suggests that variations in the amounts of internally cycled N would have the greatest impact on the requirement for biologically fixed N at low levels of pasture utilization (10-40%), while at high pasture utilization levels of 70%, variations in the recovery of excreta-N would have a major effect on the requirement for fixed-N to balance the cycle. The amounts of biologically fixed N required to sustain a range of herbage DM yields of 3-22 t DM ha ^?1 yr^?1 would range from 15 to 158 kg N ha^?1 yr^?1 for tropical pastures. For intensively managed temperate pastures producing 6-15 t DM ha^?1 yr^?1 with a N content of 3·5%, a range of fixation of 120-352 kg N ha^?1 yr^?1 is required. These simulations indicate how legume contents of 20-45% of herbage DM could contribute to productive and sustainable (in terms of N) pasture systems of both temperate and tropical regions     

The long-term effects of a range of pasture treatments applied to three semi-natural hill grassland communities. 1. Pasture production and botanical composition

Five pasture treatments: (1) controlled grazing, (2) controlled grazing + lime, (3) controlled grazing + lime + phosphate, (4) controlled grazing + lime + phosphate + oversown white clover and (5) controlled grazing + lime + phosphate + oversown white clover + oversown perennial ryegrass were applied to three semi-natural hill grassland communities. The communities were those dominated by Agrostis/Festuca, Molinia and Nardus. The proportion of Nardus at the Nardus-dominant site was substantially reduced by herbicide before treatments were applied. All treatments were grazed simultaneously by mature wether sheep on three occasions each year. There were two grazing periods each of 4 weeks duration between mid-May and mid-August with a further grazing period of 3 weeks starting mid-October. During each grazing period stock numbers were set so that a residual herbage mass of 560 kg DM ha ^?1 remained at the end of the grazing period. Measurements of net herbage accumulation (NHA) were made annually over a period of 13 years at each site. The green:dead ratio of grasses, species composition of the pasture and the pH of the soil were measured at intervals during the experiment. Estimates of mean annual NHA ranged from 3860 kg DM ha^?1 for treatment 1 (controlled grazing) to 5170 kg DM ha^?1 for treatment 5 (oversown white clover and perennial ryegrass). The application of lime and phosphate increased annual NHA by 300–350 kg DM ha^?1 with a further increase of around 400 kg DM ha^?1 when white clover was sown. Increases in NHA between year 1 and year 13 ranged from 30% for treatment 1 to around 55% for treatment 5. Although there was no difference in the mean NHA between sites, the herbage from the Agrostis/Festuca site contained a higher proportion of green grass and white clover than that from the other sites. The highest levels of green grass and white clover were found on the oversown treatments at each site. The grazing pressure exerted produced relatively little change in the botanical composition at the Agrostis/Festuca site. At the Molinia-dominant site the Molinia was largely replaced by Nardus during the first 6 years and Nardus also increased in cover at the Nardus site. Application of lime and phosphate generally increased the proportion of Poa pratensis, Festuca rubra and Agrotis tenuis but did not halt the spread of Nardus at the Molinia and Nardus sites. White clover and perennial ryegrass were successfully introduced by oversowing and proportions remained high throughout the 13 years. The cover by bryophyte spp. increased at all sites with the greatest increases occurring in each case on the less comprehensive pasture treatments. These results suggest that on Agrostis/Festuca-dominant pastures herbage biomass production can be increased with relatively low-cost pasture treatments while maintaining Species diversity. However, Nardus and Molinia dominant pastures are likely to require more comprehensive pasture treatments involving sown grasses and white clover to provide herbage of acceptable quality and avoid an increase in Nardus and bryophytes in the sward. With a regime of episodic summer grazing and the addition of fertilizers oversown pastures can be maintained over long periods of time.     

MINERALIZATION OF NITROGEN AND PHOSPHORUS FROM ORGANIC MATERIALS OF PLANT AND ANIMAL ORIGIN AND ITS SIGNIFICANCE IN THE NUTRIENT CYCLE IN GRAZED UPLAND AND HILL SOILS

Plant DM production from natural Nardus and Festuca–Agrostis pastures under two cutting regimes ranged from 1023 to 2265 kg/ha. The amounts of mineral N and P produced during the incubation of these plant materials, and from sheep faeces derived from them, were measured under a range of temperature and moisture conditions. These amounts, together with the N liberated in urine, and the increase in inorganic P concentration which resulted from the conversion of feed to faeces, were used to calculate the range in ‘potentially available’ plant nutrients derived from decomposition pathways in the presence and absence of sheep. Factors which infiuence the actual availability of nutrients for plant growth are considered and the results discussed in relation to the role of the grazing animal in the soil-plant–aaimal nutrieut cycle.     

POTENTIAL PRODUCTIVITY OF RED CLOVER VARIETIES IN S.W. SCOTLAND

A reassessment of the potential productivity of 37 varieties of red eiover suggests that DM productivity is equivalent to grass given fertilizer N at 252 kg/ha for the 1st year, 209 kg/ha for 2nd year and 144 kg/ha for 3rd year of production. Corresponding equivalents for CP productivity of the red clover swards were 298, 228 and 206 kg N/ha. Varietal differences in productivity were significant Average yields of total herbage DM in the 1st, 2nd and 3rd harvesting years were 10.9, 8.7 and 8.2 t/ha, containing 6.5, 5.9 and 6.0 t/ha red clover, respectively. For two harvesting years, the most productive varieties were Essi, Kuhn, Hungaropoly, Robina, Tilo Daehnfeldt, Redhead and Corona Otofte. Rea 4N and a few other tetraploid varieties were very productive in the 3rd year. Hungaropoly, although showing a decline in the 3rd year, was the most productive over 3 years, with an average yield of 11.5 t/ha per year total herbage DM containing 10.2 t/ha per year red clover DM. Such high potential DM production warrants further investigation into the persistence of red clover, its conservation and the problems of its utilization by livestock.     

PRODUCTIVITY OF TROPICAL PASTURES

A 50-animal herd of dairy cows was pastured throughout one year on fertilized Pangola grass pastures in the humid tropical environment of Turrialba, Costa Rica. Information was collected on monthly grazing pressure, forage consumption and digestibility and milk production. The average number of animal units (375 kg) over the year was 2.57/ha. Total milk produced was 6014 kg/ha. Forage consumption varied from 1.81–3.60 kg DM per 100 kg liveweight, with two periods of low consumption coinciding with the flowering period of Pangola grass and with a drier season. Digestibility fluctuated from 50.3–65.7% and followed the same pattern. Calculations were made of the efficiency of DM conversion, which was around 12%, with two higher values for the periods of stress, interpreted as utilization of body reserves. Calculations of the nitrogen balance of Pangola pastures are also presented.     

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.