In research into competition between individual cultivars of one perennial grass species sown in mixtures, fixed matrix designs have been widely used because of difficulties in identifying the components inanatural sward.Extrapolation of results from such fixed designs to the sward situation is often difficult in any but the short-term context.

This paper describes the principles, requirements and use of an electrophoretic technique together with a mathematical concept which can be used to distinguish certain perennial ryegrass cultivars when sown in mixtures. Such methods have useful implications for the study of sward composition and competitive ability of ryegrass cultivars sown in mixtures. The number of samples required to study selected 2-way cultivar mixtures using this method is indicated.

The nutritive value of diets predominantly of dried cassava (Manihot esculenta Crantz.) tubers supplemented with protein concentrates, and roughage were measured in three experiments using steers.

In Expt 1 the digestibility of diets of dried, chipped cassava tubers and tops (80:20) or rolled sorghum grain and cotton seed hulls (80:20), supplemented with 4 or 8% groundnut meal and urea, was determined. The apparent digestibility coefficients of organic matter (OM) of the cassava diets with 4 or 8 % groundnut meal (0·77 and 0·80, respectively) were significantly (P < 0·01) higher than grain diets with 4 or 8% groundnut meal (both 0·74). The digestibility of starch in the cassava diets was significantly (P < 0·01) higher than in the grain diets (1·00, 0·99, 0·94 and 0·93, respectively). There were no significant differences in the digestibility of the N component (0·62 and 0·61 v. 0·58 and 0·59, respectively). The N retained (g/day) was lower (P > 0·05) with cassava (7·8 and 6·8 v. 11·1 and 10·5, respectively) and was utilized (g/100 g apparently absorbed N) less efficiently (P > 0·05) (18 and IS v.28 and 27, respectively).

The high apparent digestibility of the cassava diet suggests that cassava could replace cereal grain in intensive finishing diets. The N retention data suggest that groundnut meal is no better than urea as a N source.

In Expt 2, 15 steers with a mean initial weight of 173 kg were individually fed pelleted diets of sorghum grain, cassava plus urea or cassava plus meat and bone meal (90 concentrate: 10 roughage). The cattle fed the grain diet ate significantly (P < 0·01) more OM (4·3 v. 3·4 kg/day), grew faster (P < 0·01) (1·21 v. 0·85 kg/day) and slightly more efficiently (P > 0·05) (3·6 v. 3·8 kg/kg) than cattle fed cassava with urea. Cattle fed cassava with meat and bone meal were intermediate between the two treatments for intake and daily gain (3·7 and 1·06 kg/day, respectively) but had the best feed conversion (3·5 kg/kg). The acetic/propionic acid ratio was similar on all three diets (1·2, 1·6 and 1·4:1, respectively), but the ratio of propionic/butyric was significantly (P < 0·01) different (5·8, 2·7 and 2·7:1, respectively).

In Expt 3, 15 other steers with mean initial weight of 195 kg were individually fed pelleted cassava diets with 0, 5 or 10% fishmeal (82 cassava: 18 roughage). The intake of OM (4·2, 4·5 and 4·7 kg/day, respectively), daily live-weight gain (0·98, 1·27 and 1·32 kg/day, respectively) and feed conversion (4·3, 3·7 and 3·7 kg/kg, respectively) were all better in cattle fed cassava with fishmeal. The proportions of volatile fatty acids in the rumen fluid were similar to that recorded in cassava fed cattle in the earlier trial.

It is concluded that cattle fed high energy diets based on dried cassava tubers can perform well. Although feed intake and daily gain of cattle fed cassava may be lower than for cattle fed grain diets, the conversion of food to live-weight gain should be similar or better.

Leaching in a salt-affected, permeable, sandy loam soil was evaluated under continuous and intermittent ponding conditions in 2 × 2 m (S1), 4 × 4 m (S2) and 6 × 6 m (S3) plots. The soil contained large amounts of soluble salts throughout the profile to the water table, chiefly chlorides and sulphates of sodium, calcium and magnesium. The leaching curves did not differ significantly between Slf Sa and S3 plots under continuous ponding but did under intermittent ponding. The leaching efficiency decreased sharply with increased plot size. The leaching efficiency in Sj plots was significantly greater with intermittent than with continuous ponding, but the reverse was true in S3 plots. The displacement of the resident soil solution in S1 plots under intermittent ponding was nearly piston-like. With increased plot size, it tended to deviate from this behaviour. The leaching curves from S3 plots (this size being reasonable in farmers' fields) were compared with those obtained from numerical solution of a simplified steady-state salt transport model. The model also included a source term, solubility rate constant, for the slightly soluble salts present in the experimental soil. The pore water velocity was estimated from field capacity and time-averaged infiltration rate. The effective dispersion coefficient and solubility rate constant were estimated by a least-squares minimization technique. A reasonably good agreement was obtained between simulated and experimental leaching curves. For practical purposes, this simple model may be adequate to predict leaching in salt-affected soils similar to the one under consideration.

Two trials were conducted to study the seasonal variation in oestrous activity over the year in Suffolk (S) or mutton Merino (M) temperate breeds, and their crosses with the local Ossimi (O) sheep under the prevailing subtropical conditions. In the first trial, groups of S, 75% S, 50% S, and O were used and the second trial involved groups of M, ¾M, ½M, ½M and O. The incidence of oestrus was measured by teasing with vasectomized rams. Suffolk ewes had a restricted period of oestrous activity (August–January) whereas M had a longer breeding season (August–March) with high incidence of long and double cycles. Local O showed irregular oestrous activity almost around the year, with particular decline in April. In both trials, all crosses had better oestrous activity than the pure parents, with the 50% S and the ½M having the best performance in the two trials, respectively. The period from September to February seemed to be the period of normal cycling activity in all breed groups, whereas the period from March to May was associated with marked breed-group variation in oestrous activity. Normal cycle length of the S was significantly (P < 0·01) shorter than the local O (16·0 v.17·7 days) and was more consistent than other breed groups. In the two trials, normal cycle length of the cross-breds was ranked between the two purebred parents.

Experiments were conducted between 1978 and 1981 to investigate the effect of autumn and spring sowing on emergence, winter survival, growth and yield of combining peas (varieties ‘Frimas’, ‘Filby’ and ‘Vedette’). Effects of growth regulator PP 333 (Paclobutrazol, ICI pic) application and defoliation on winter survival of Filby were also investigated. Field emergence of autumn-sown Frimas (winter hardy) was less than Vedette or Filby but percentage winter survival was greater. PP 333 application, but not defoliation, increased percentage winter survival of Filby sown in September. Total dry-matter production and photosynthetic area of autumn- compared with spring-sown crops varied considerably between seasons. Yield data indicated that autumn-sown crops produce similar seed yields to spring sowings when winter survival is adequate. November sowings matured 2–4 weeks before March-sown crops, depending on variety and season. Optimum sowing dates were mid-November and early March. Large seed-yield reductions occurred when sowing was delayed until mid-April.

Pure and mixed swards of Centrosema pubescens (centro), Pueraria phaseoloides (puero) and Brachiaria mutica (para grass) established under a 12-year-old mango plantation were sampled at 6-week intervals for 2 years to determine crude-protein (CP) content, dry-matter (D.M.) and CP yields and apparent digestible energy and apparent digestible crude-protein (DCP) contents. Daily dry-matter intake (DMI) and apparent digestible energy and digestible crude-protein intakes (DEI and DCPI), as well as live-weight gain (LWG) by 11·5 kg penned West African cross-bred weaner lambs, were also determined.

The pure legumes were better than the mixed swards in respect of CP (mean: 22·1, 18·8, 14·4 and 13·8% for centro, puero, centro-para grass and puero-para grass respectively) and DCP (mean: 16·2, 13·4, 10·4 and 10·0% respectively) contents, and daily DMI (mean: 50·8, 49·7, 41·8 and 41·3 g/kg W0·75 respectively), DEI (mean: 562, 531, 418 and 410 kj/kg W075 respectively) and DCPI (mean: 8·09, 6·55, 4·04 and 3·94 g/kg W0·75 respectively). On the other hand the legume-grass mixed swards, especially puero-para grass, were superior to the corresponding pure-legume swards with regard to D.M. yield (mean: 11·90, 7·69, 7·13 and 4·54 t/hafor puero-para grass, centro-para grass, puero and centro respectively) and CP yield(mean: 1·62,1·09, 1·32 and 0·99 t/ha respectively). The pure-legume stands gave the highest LWG per lamb (mean: 45·7, 3·89, 2·63 and 25·3 g/day for centro, puero, centro–para grass and puero-para grass respectively) but it was estimated that the legume-grass mixed swards would give higher returns in terms of lamb LWG on forages harvested per unit sward area than the corresponding pure-legume cover.

It was concluded that legume-grass covers would be preferred to all-legume covers if livestock were to be integrated into tree crop farming systems. However, the choice of companion grass would have to be given proper consideration as shade-intolerant grass species, such as para grass, would detract from profit maximization.

Several introduced high-yielding varieties of grain sorghum were screened for natural infestation of shootfly Atherigona yorki Deeming, and stem borers, Sesamia cretica Led. and Chilo partellus (Swinhoe), at different sowing dates in 1980–1 and 1981–2 sowing seasons in People's Democratic Republic of Yemen (PDR Yemen).

The recently introduced high-yielding variety Dwarf White Milo (DWM) was found to be more prone to infestation by shootfly and stem borers than the local variety ‘Baini’ although it gave higher yield. All varieties tested gave higher yields when sown in March, August, September than when sown in April, May, October or November; 26 August and 16 September sowings gave the highest yields. B815, W823 and 8454 gave higher yields than the recently recommended high-yielding variety DWM, in response to lower infestation with the shootfly and stem borers; B815 and 8454 gave higher yields when sown on 26 August than when sown on 16 September. On the contrary, W823 gave higher yield when sown on 16 September than when sown on 26 August. This information could be used in formulating insect pest management programmes for sorghum pests in PDR Yemen.

A field experiment was conducted for 2 years during the crop seasons of 1980–2 to study the effect of diverse plant spacings and rates of nitrogen application on the yields of herb and essential oil of palmarosa (Cymbopogon martini Stapf. var. motia). The results indicated that at closer plant spacings of 30 × 30 cm (110 000 plants/ha) and 45 × 30 cm (74000 plants/ha), palmarosa responded to higher amounts of N fertilizer (240 kg N/ha/year). It was suggested that a plant spacing of 30 × 30 and 45 × 30 cm and application of 240 kg N/ha/year result in high essential oil yield of palmarosa.

The accurate prediction of the performance of individual lots of sugar-beet seed in the field is critical when constituting blends of seed for commercial use. Previous studies indicated a need for ‘vigour tests’ to supplement the standard germination test. In many of the studies emphasis was placed on evaluation of tests in the laboratory, whereas in this study equal emphasis was placed on the determination of the values to be predicted. The performance of 20 seed lots with a range of germination between 75 and 95% was assessed in field and laboratory studies in 1981. Further investigations of ten seed lots were made in 1982 and in 1983.

The results in 1981 showed little evidence of agronomically important differences in the relative performance of seed lots with respect to establishment in the field at different sites. Similarly, most seed lots showed consistent differences over a range of tests under controlled conditions. However, use of the experiment mean as a measure of stress revealed marked differences in the range of performance between the best and poorest lota in both the field and laboratory. There were clear indications that performance in the field could be modified by non-random factors that tended to reduce the magnitude of differences among seed lots. In 1982 grazing of seedlings by birds was identified as a factor that could cause greater reduction in the establishment of seed lots with high viability relative to those with low viability. Thus, under some circumstances, a single count of seedlings in non-protected field experiments can give misleading estimates of the differences among seed lots (and probably among other treatments which affect the rate of emergence). Correlation coefficients (γ) were about 0·88 for relationships between establishment from pelleted seed in plots protected from birds and germination or emergence under controlled conditions. These results reduced the need for additional vigour tests. However, the studies emphasized that small differences in germination percentage are important as they can be associated with much larger differences in establishment, particularly under adverse seed-bed conditions. The average standard error for the mean viability of individual seed lots was ±1·89 in germination tests with four replicates of 100 seeds at each of six centres. Although inincreased accuracy may not be possible without much greater replication, we found that the distinction between normal and abnormal seedlings was an important source of experimental error. A less subjective measurement, based on hypocotyl height, warrants further study.

Two experiments were conducted to provide information on the precision of herbage sampling, the degree of replication and the logistics of managing rotational and continuous grazing experiments. In a third experiment the possibility of estimating herbage growth, during the rotational grazing of paddocks for 4 days, by linear extrapolation of measured growth estimates made during the interval between grazings was investigated. A fourth experiment was then conducted to investigate animal and herbage production responses to nitrogen applied at five levels over the range 80–900 kg N/ha with three replicates per treatment.

Results from Expts 1 and 2 showed that similar precision could be obtained under both rotational and continuous systems of grazing with the same number of replicates and samples of herbage. There was little advantage in having more than three replicates and four samples per paddock or two replicates and eight samples per paddock. Under continuous grazing a 3-weekly sampling and movement of exclosure cages was indicated. It was also found, from Expt 3 that, under rotational grazing, linear extrapolation of growth from 0–24 days did not reflect growth to 28 days in a consistent manner. Six animals per treatment, permanently in the paddocks, proved adequate for the estimation of live-weight gain.

Experiment 4 confirmed that response curves could be fitted with an acceptable degree of precision if there was one low, one very high, and two intermediate levels of nitrogen. Adjustment of the number of animals to maintain sward height at between 5 and 7 cm ensured similar sward conditions and rates of live-weight gain across all treatments.

The problems associated with the measurement of herbage production under grazing are discussed.

In a 2-year study, sunflower oultivar EC 69874 produced greater leaf area than EC 68415, but gave similar grain yields. The former was superior in leaf area, head size and yield per plant but was inferior in 100-seed weight. The leaf area was greater at lower plant density (5·5 plants/m2), which resulted in higher 100-seed weight, number of seeds per plant and yield per plant than higher plant density (11·1 plants/m2). Plant density had no influence on the percentage of filled seeds or oil content. Application of nitrogen improved the leaf area, flowerhead size, percentage of filled seeds, 100-seed weight, yield per plant and grain yield up to 60 kg/ha but decreased the oil content.

Field investigations conducted at Ludhiana (India) showed that the foliar application of 2-chloroethyltrimethyl-ammonium chloride (CCC) (50% a.i.) at 300,600 and 900 ml/ha about 5 weeks after planting did not depress plant height. The dose of 600 ml CCC/ha was most effective and increased seed yield by 1·31 and 0·74 t/ha over the control (water spray) in 1978–9 and 1979–80, respectively. The corresponding increases in total yield were 1·37 and 0·86 t/ha. However, in 1980–1 when CCC was applied 3 weeks after planting even the lower dose of 300 ml/ha depressed the plant height. Then the treatment of CCC increased significantly the number of tubers of seed size and seed yield by decreasing the ‘ware’ yield but did not influence the total yield. The yields of potatoes were not affected signifioantly by the application of N-dimethyl amino succinamic acid (B 9) and succinic acid (SA).

In an experiment where the interaction of nitrogen and CCC was studied both factors not only increased the seed yield but also increased the total yield. However, there was no interaction between nitrogen and CCC.

Local soil erosion has long been a problem on very fine sandy and silty soils in south Somerset. Some 40 fields in arable use were chosen randomly and monitored monthly for erosion in the winter of 1982–3. Erosion was measured along fixed traverses and then compared with soil attributes, site factors and cultivation practices. Winter cereals were worst affected with a third of the fields having soil losses in excess of 4 m3/ha. There was least erosion on bare ploughed ground and moderate losses on cash root crops. Soil type, organic-carbon content, clay content, drill direction, wheeling density and slope all affected soil loss in winter cereal fields.

Erosion did not assume serious proportions until a combination of soil surface conditions and soil wetness allowed run-off to form rills. Only moderate falls of rain were then needed for widespread removal of soil. Preventative measures include grassing slope convexities, more grass in the rotation to improve soil organic matter and structure, avoiding wheelings, drilling across the slope and keeping headland widths to a minimum.

Statistics are presented to illustrate the influence of growing season and location on the accuracy of NIR testing of hard red spring wheat for protein. The influence of season was greater than that of growing location, and highly significant errors are likely to occur if protein is predicted in samples from one growing season using a calibration based on samples from another season. The same was true to a lesser extent if samples from one growing location were analysed using calibrations based on samples drawn from different areas. There was evidence that some growing areas were less susceptible than others to the seasonal influence, whereas certain seasons (e.g. 1976) exerted more influence than others. Errors in predicting protein were considerably greater than errors in predicting moisture. The development and use of universal constants incorporating samples from a wide range of location and several seasons effectively counteracted the influences of both season and location, and universal constants have been developed for use in the NIR instruments of leading manufacturers, for hard red spring and durum wheats, and barley. The concept and principle of 2·point calibration using normalized mathematical treatment of the log 1/R signal is discussed and its efficiency in providing a stable calibration for the prediction of protein in hard red spring wheat has been demonstrated.

Physical measurements were made on the soil of a long-term cultivation experiment comparing direct drilling, tine cultivation and mouldboard ploughing for spring barley to investigate possible reasons for differences in yield. The soil was a typical argillio brown earth, approximately 90 cm of sandy clay loam topsoil and clay loam subsoil overlying magnesian limestone. For the three periods 1971–4, 1975–7 and 1978–80 the mean grain yields were marginally lower after direct drilling than after shallow cultivation or ploughing. There was an average decline in yield of 1·33 t/ha from the first to the last period, the decline being greater for direct drilling than the other two tillage systems. Although the surface horizon (0–5 cm) of direct-drilled soil had a higher content of organic matter than the ploughed, this did not increase the stability of the aggregates. Slaking tests had shown the soil to be inherently unstable and likely to suffer from structural problems. After the first 3 years bulk density of direct-drilled soil (0–15 cm) increased markedly to ca. l·5 g/cm8 and then remained relatively stable. In the ploughed soil, density increased steadily over the period to an average value of co. 1·45 g/cm8. Tine cultivation to 7–8 cm reduced cone resistance values in the surface compared with direct-drilled soil but below 15 cm there were no significant differences. Ploughing gave significantly lower values than direct drilling to a depth of 30 cm. Measurements of pore sizes in direct-drilled and ploughed soil were highly variable with few significant differences. Mean air capacity values (1978–80) tended to be lower in direct-drilled than in ploughed topsoil particularly for plots direct drilled after 7 years of deep tine cultivation. A limited number of root measurements in 1978 and 1980 showed that the length of root per unit of ground area was much less after direct drilling than after ploughing. Shallow cultivation, surprisingly, gave most root with a greater proportion of the root system below 20 cm than in the other two treatments. The classification of this soil according to its suitability for direct drilling cereals is discussed.

Multi-factorial experiments on winter wheat cv. Hustler in autumn 1979 and 1980 sown on a clay loam soil following potatoes tested the effects of combinations of the following eight factors, each at two levels: sowing date; amount of nitrogen; division of nitrogen; timing of nitrogen; irrigation; autumn pesticide (aldicarb); summer aphicide (pirimicarb); and fungicide (carbendazim, tridemorph, maneb and captafol).

The mean grain yields of all plots in 1980 and 1981 were respectively 9·6 and 8·3 t/ha; the best eight-plot means were 11·2 and 9·9 t/ha. Fungicides had the largest effect on grain yield, increasing it by 0·8 and 1·7 t/ha in 1980 and 1981, mainly by increasing grain size. Effects were greater with earlier sowing and the larger amount of nitrogen. Benefits from fungicide were well related to the control of leaf diseases, mainly Septoria spp., which became severe after anthesis. Fungicide temporarily decreased the number of saprophytic fungi on the developing ears. Aphids that appeared in autumn on plots sown in mid-September were controlled by autumn pesticide, which also prevented the spread of barley yellow dwarf virus that occurred only in 1981. Consequently, yield of early-sown plots in 1981 was increased by autumn pesticide, but only when the severe infection with leaf diseases was controlled by fungicide. Autumn pesticide decreased nematode populations. Aphid populations in summer were small and yield was unaffected by the decrease in numbers that followed application of an aphicide.

Sowing on 20 or 15 September, as compared with 19 or 30 October, caused faster growth and development and greater uptake of N from the soil early in the season. Effects were smaller after April: earlier sowing increased total dry weight by 2·5–3·0 t/ha and, when leaf diseases and barley yellow dwarf virus were controlled, increased yield by 0·9-l·0t/ha. Increasing the amount of N applied by 70 kg/ha (from 105 or 80), increased yield only in 1980 and then only when fungicide was used. Extra N decreased yield in 1981 in the absence of fungicide. Extra N always increased N uptake and decreased grain size. Applying mostor all of the Non 4 or 19 March instead of 15 or 23 April resulted in less uptake of N from anthesis onwards and smaller yield, especially in 1980. N in three applications instead of one had negligible effect. Trickle irrigation decreased yield slightly, despite delaying leaf senescence and increasing straw weight. Attributes of wheat on best yielding plots differed little between years. Average values were: 534 ears/m2; 40·7 grains/ear; 40·4 mg/grain; 18·8 t/ha total dry matter and 214 kg N/ha uptake by grain plus straw.

The growth, development and grain yield of two low-tillering lines of wheat of Israeli origin were compared with those of two freely tillering Australian wheat cultivars (Gamenya and Egret) in field plots. The majority of individuals from the low-tillering selections were uniculms or biculms. Detailed observations were made on the main shoot of the biculms. There was no difference in the duration of primordia production by the main shoot apex between genotypes but the rate of initiation of spikelet primordia in the lowtillering lines was significantly greater than that of the tillering cultivars and this resulted in a large ear with more spikelets. The rate of leaf appearance was very similar in all genotypes but the later-appearing leaves of the biculms were very large in comparison with those of the cultivars. The majority of the biculms produced the tiller in T3 position. At maturity the main shoot and tiller of biculm individuals produced 60 and 40% respectively more dry weight than the equivalent shoots of the tillering cultivars. The total biomass per plant of the biculms was similar to that of Egret but less than that of Gamenya. The grain yield of the main shoot of the biculms was 50% greater than that for the tillering varieties and this was associated with an increase in the number of grains per ear as there was little difference in grain size. In the biculm a high proportion of the spikelets in the mid part of the main shoot ear produced five grains; grains from basal florets were significantly larger than those of upper florets mainly because they had a longer duration of growth. Overall the grain yield of the two tillering cultivars, either per plant or per metre of row length, was approximately 30% greater than that of the low-tillering selections. The greater growth of the main shoot axis in the biculms therefore did not compensate for the grain contributed by the tillers of the freely tillering cultivars.

A continuously grazed trial on natural and sown pastures under coconuts was reported by Watson & Whiteman (1981). This has been continued for another 3 years as a rotationally grazed trial. The paddocks were divided down the centre and three animals grazed for 28 days in one half and were transferred to the other half for 28days. The same three stocking rates of 1·5, 2·5 and 3·5 steers/ha were maintained. In the sown pasture paddocks Brachiaria decumbensand Brachiaria miliiformis were planted in rows from rooted cuttings, while Centrosema pubescens (centro) and Pueraria phaseoloides (puero) were sown, with seed at 4 and 3 kg/ha, respectively. Naturalized pastures were maintained by grazing at 2·5 steers/ha during the establishment of the sown pasture. Light transmission was 62 %. Sown grasses were lost after 4 months from the start of rotational grazing. In the sown pastures puero became dominant. Animal live-weight gain (LWG) on puero was poor in the first 140 days of grazing in each year, but after this time it increased. Centro was the dominant species in the natural pasture of 2·5 and 3·5 steers/ha. However, there was little difference in yearly LWG except in year 3 when the 2·5 steers/ha had higher gains in the natural (363 kg/ha) than in the sown pasture (250 kg/ha). Th9 mean live-weight gain (kg/ha) in the first 2 years of the rotationally grazed trial (315 kg/ha) was lower than in the continuously grazed trial (364 kg/ha) at 3·5 steers/ha. The time and efficiency of collecting fallen coconuts was lower at 1·5 steers/ha in both pastures, but not different between 2·5 and 3·5 steers/ha. In continuous and rotational grazing there is little point in planting Brachiaria species. Productive pastures in plantations oan be obtained by conti oiling weeds and sowing centro and puero into the naturalized Axonopus compressus and stocking at 2–5–3–0 steers/ha. Further research on other grasses such as Ischaemum aristatum and Stenotaphrumsecundatum may lead to better grass persistence.

Pastures of a mixture of Brachiaria mutica(para) and B. decumbens(signal) grown with Gentrosema pubescens(centro) and Macroptilium atropurpureumcv. Siratro and grazed at three stocking rates 1·8, 2·1 and 3·6 animals/ha for 5 and 6 years of grazing were compared with B. humidicolacv. Tully (Koronivia) oversown with centro and siratro and grazed at 3·0, 3·6 and 4·5 animals/ha and native pastures of Themedaaustralis and Pennisetum polystachyon oversown with Stylosanthes guianensis cv. Schofield after burning, and grazed at 1·3, 2·0 and 2·7 animals/ha. All pastures were given 20 kg/ha of sulphur.

The para and centro pasture gave the highest live-weight gain with 731 kg/ha/year when stocked at 3·6 animals/ha in 1979–80. and 592 kg/ha/year in 1980–1. Signal grass gave 621 and 493 kg/ha/year in 1979–80 and 1980–1 at 3·6 animals/ha. Koronivia grass gave similar production as signal: 639, 466 and 406 kg/ha/year at 3·6 animals/ha stocking rate from 1979 to 1982. On the natural pastures 1st year gains were high, 412 kg/ha/year at 2·7 animals/ha, but declined to 224 kg/ha/year at 2·0 animals/ha in year 2.

In the para pastures, centro increased up to 50%, while with signal it increased to 25% of the botanical composition, owing to a decline in grass dry matter. In koronivia pastures, centro and siratro declined, inversely with stocking rate, and M.pudica increased in the high stocking rate. In the natural pastures T. triandra declined with increasing stocking, to 1% at 2·7 animals/ha. P. polystachyon remained approximately stable. M. pudica became important as grazing increased, and weeds also increased. Para grass was high in N, P, S and Na. N was low in signal, koronivia and T. triandra while the concentration of Na (0·41%) was high in koronivia, but it was extremely low in signal and T. triandra(0·02%).

The trials suggest that landholders could commence grazing of existing natural pastures for up to 2 years at about 2·0 animals/ha in the 1st year and 1·3 animals/ha in subsequent years to obtain 350 kg LWG/ha in year 1 and the 200 kg LWG/ha thereafter. With cultivated pastures much higher yield can be obtained using para plus centro on the low-lying aieas, and signal plus centro plus siratro on non-flooded areas. Koronivia can be used in occasionally intensively stocked areas. All pastures require S fertilizer every 2 years.

Stylosanthes humilis cv. Lawson, S. hamatacv. Verano, S. guianensis cv. Endeavour and Macroptilium atropurpureum cv. Siratro were oversown into native grassland dominated by Arundinaria ciliata and grazed by cattle at 2·5, 3·5, 4·5, 5·5 and 6·5 animal units/ha per half-year during the wet season for 4 years.

Siratro was the most persistent of the legumes but its susceptibility to heavy grazing pressure limited its contribution at the higher stocking rates. At the start of grazing its mean yield was 1420 kg/ha representing 40 % of total pasture yield while at the end of 4 years in the lowest stocking rate treatment it comprised 18% of total yield at 460 kg/ha.

The long-term productivity of the three Stylosanthes species was poor and their percentage contribution to the pastures was either zero or very low by the end of 4 years. Yield of Verano, the most successful of the three, declined from 5000 kg/ha in 1977 to 20 kg/ha in 1980. The main factor contributing to the poor performance of these species was the strongly competitive nature of A. ciliata. Percentage composition, height and yield of this tall, rhizomatous grass increased with time independent of stocking rate, and the illuminance of the Verano canopy was reduced to 0·38–0·65 full sunlight. Cattle showed negative selection for bamboo grass and consumed leaf but not stem; leaf to stem ratio was negatively (and unusually) related to stocking rate.

Stocking rate effects were reduced by the intervening dry season resting periods and the over-riding influence of other factors such as the prevailing climatic conditions, disease occurrence and plant interference.