SUMMARY Germination of Gliricidia maculata seed was not affected by scarification, or by temperature between 20°C and 32°C. Percentage germination declined above 32°C and became zero at 40°C. Gliricidia maculata seems well adapted to low calcium soils. When grown on podzolic soils (pH 5.6.) in S.E. Queensland, height, growth and dry matter yield were significantly reduced by addition of lime at 500 kg ha-1 but leaf number and survival over winter were not affected. Plants lost all their leaves as night-time temperatures declined to below 15°C in May. Gliricidia maculata must therefore be grazed from March to May and therefore has no value during winter as a Standover legume forage in a sub-tropical environment. The major use of this species is in the humid tropics.

SummaryA 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.

An early-maturing, photoperiod-insensitive cultivar of pigeonpea, Cajanus cajan (cv. QPL4), was grown in two experiments. In the first experiment, grazing began at different times by goats with a mean weight of 14 kg. On different plots grazing started 24 days (before flowering), 57 days (flowering), 98 days (50% pod fill) and 141 days (after harvest) after plant emergence. The crop was then allowed to grow unchecked to pod maturity at 139 or 154 days after emergence and was harvested on 5 April 1982 to compare the effects of time of grazing on phenology, growth and yield. Ratoons were harvested on 9 August 1982. Grain yields of main crop plus ratoons were: the ungrazed control 1920 plus 403 kg/ha, pre-flowering 8 15 plus 107 kg/ha; 50% flowering 1210 plus 3 kg/ha, pod fill 0 plus 428 kg/ha and post-harvest grazing 1250 plus 24 kg/ha. In the second experiment, young feral doe goats (mean weight 16 kg) grazed pigeonpea at 25, 50, 75 and 100 goats/ha. Grazing commenced when 50% of plants were in flower (11 January 1982). Mean daily liveweight gains per animal (over 42 days) were: 25 goats/ha, 68 g; 50 goats/ha, 49 g; 75 goats/ha, 58 g; 100 goats/ha, 35 g. Grain harvested on 14 May 1982 was 1085, 530,80, and 0 kg/ha for goat stocking rates of 25, 50,75, and 100 goats/ha. Compared with the ungrazed control, grazing in both experiments had marked effects on plant populations and dry matter yields and reduced grain yields. Pigeonpea does not seem to be a good forage, perhaps because of its low energy content; therefore, there seems little point in grazing the crop during growth because of the marked reduction in yield of grain.

SummaryPastures 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.

A grazing trial with beef cattle was conducted on three grasses, Paspalum plicatulum cv. Rodd's Bay, Brachiaria decumbens cv. Basilisk (signal grass) and Panicum maximum cv. Hamil, in the first year. P. maximum was replaced by Digitaria decumbens (pangola grass) in the second and third years. There were three stocking rates (3.0, 3.75, and 5.0 steers/ha), plots were fertilized with 300 kg N/ha, in two replicates. Animal liveweight gain was low; maximum values were 650 kg/ha for pangola grass, 640 kg/ha for signal grass and 400 kg/ha for P. plicatulum. Liveweight gain was only poorly correlated with rainfall, because low winter temperatures retarded pasture growth. Correlations between liveweight gain and individual green leaf percentage in each species were high, particularly for P. plicatulum, which had only 2% green leaf in winter. Weight loss on plicatulum was therefore high in winter, and overall performance poor, even though this species had the highest percentage of green leaf in summer. Signal grass showed a higher tolerance to grazing at 5.0 steers/ ha than the other grasses. Over most of the year, except in winter when only small amounts of green leaves were available, plicatulum had the lowest phosphorus percentage, sometimes below the 0.12% suggested as the critical dietary phosphorus percentage for cattle. Over all grasses, nitrogen and phosphorus concentrations were linearly related (r = 0.98). From this experiment, P. plicatulum was shown to be a poor grass for beef production and, for this grass and the other two species at this site, beef production using 300 N kg/ha could not be financially viable.

The yields of eight grass species, Axonopus compressus, Brachiaria decumbens, B. humidicola, B. miliiformis, Dicanthium caricosum, Ischaemum aristatum, Paspalum conjugatum and Stenotaphrum secundatum, were compared at five sites under different coconut densities giving variations in shade. Light transmission (LT) values were approximimately 100 (adjacent open area), 70, 50, 40 and 20% of full sunlight. Soils were fertile, red-brown clays developed on uplifted coral limestone (typic arguidoll), with marginal K status. Brachiaria spp. yielded most in full sunlight, with B. decumbens giving 28 t ha−1 year−1. I. aristatum was less sensitive to shade than the Brachiaria spp., at least down to 40% LT. S. secundatum, although poor yielding at 100 and 70% LT, gave the best yield of all species at 20% LT. Shaded plants had thinner leaves and larger nitrogen concentrations than unshaded ones. B. decumbens and B. humidicola are recommended for open plantations (LT > 70%), I. aristatum for moderate shade (LT 45–70%) and S. secundatum for deeper shade (30–50%) on poor fertility soils.

SUMMARYFourteen smallholder coconut plantations, subdivided into 27 uniform sub-units, were surveyed in an area around Dala, in Western Malaita, Solomon Islands. Most units (17 out of 27) had densities of 160–200 palms ha−1 with a median light transmission of 50–55%. Palm growth was poor due to low soil K, and copra yields averaged only 540 kg ha−1 year−1 Batiki (Ischaemum aristatum) was the most important sown grass, and its productivity was significantly related to stocking rate and weed control, but not directly with light transmission. Farmers should thin dense palm stands, adjust stocking rates in relation to actual areas of pasture available, and institute careful and adequate weed control.

SummaryAnimal production was compared on three pastures, Brachiaria mutica (para), B. decumbens (signal) and Panicum maximum cv. Hamil (hamil) each sown with a common legume mixture of Centrosemapubescens (centro), Macroptilium atropurpureum cv. Siratro, and Stylosanthes guianensis cv. Endeavour (stylo), at four stocking rates, 1·8, 21·87, 31·86, and 41·85 animals/ha, over 4 years on the GuadalcanalPlains, Solomon Islands.Mean live-weight gain per head over the four stocking rates and 4 years on para pastures was 01·847, on signal pastures 01·838, and on hamil pastures 01·828 kg/head/day. Mean production per hectare at the optimum stocking rates were: para at 3.6 animals/ha, 607 kg; signal at 31·86 animals/ha, 442 kg; hamil at 21·87 animals/ha, 362 kg/ha/year.The high stocking rates of 31·86 and 41·85 animals/ha caused the hamil pastures to decline to the stage where they were destocked in the 4th year of grazing.Superior production on para pastures was not simply related to green dry matter (GDM) on offer. In the 1st year of grazing, GDM was highest in hamil pastures, but in the 2nd year highest in para, and in the 3rd year mean yields were similar in all pastures, but were very low at the 31·86 and 41·85 animals/ha stocking rate in the hamil pastures.Para pastures maintained highest legume contents. The quadratic relationship between live-weight gain/head and legume content was significant over all pastures and stocking rates. Live-weight gain (LWG) per head increased up to 15% legume content, after which there was little change. Yield of green leaf, percentage green leaf, and sward bulk density did not appear to be related to LWG/head. Para pastures had lower values for all these components than the other pastures.Chemical factors contributed to the higher animal production from para pastures. Para leaf maintained consistently higher in vitro dry-matter digestibility values. Na content of para averaged 01·812%, whereas other species were 01·801 to 01·802%, and below the critical level (01·805%) for animal intake. N and S in leaf material, and Cu in total tops were also consistently higher in para grass.Results of this grazing trial suggest that selection of grass species on the basis of quality including dry-matter digestibility and mineral content, on ability to persist with increasing stocking rate, on compatibility with legumes, and on growth habit are more important than selection for dry-matter yield.

A newly selected short-statured, early flowering, photoperiod insensitive line of pigeon pea was planted in February 1979 at four densities, viz. 2 × 105, 3 × 105, 5 × 105 and 1 × 106 plants ha−1. Maximum values of relative growth rate (RGR) (0.17 g g−1 day−1), net assimilation rate (NAR) (85 g m−2 week−1) and leaf area ratio (LAR) (1.6 dm2 g−1) were achieved by 25 days from planting at the lower densities. Maximum NAR and RGR at 1 × 106 density was delayed until day 36. By day 45 this density had almost complete light interception, and all densities had complete interception by day 85. This variety had a low extinction coefficient (0.3) suggesting that canopy structure was efficient in allowing light penetration. Since crop growth rate and leaf area index (LAI) were linearly related, highest dry matter yields were at the highest density. Highest seed yield per hectare (1300 kg) was at the 5 × 105 density, but overall, yields were not significantly different. Pod number per plant was the main determinant of yield. From the relationship of pod number per plant and density, an optimum density of 7.5 × 105 plants ha−1 was predicted. It was concluded on the basis of growth and leaf area data that this new material could support a higher photosynthetic demand if the objectives of a breeding program to increase seed size and/or seeds per pod could be achieved.

SUMMARY A grazing study, comparing a naturalized and a sown pasture at three stocking rates, was conducted under a uniform stand of 65-year-old coconuts on a fertile soil in the Russell Islands. In a plot trial on this site there was no significant response to application of up to 400 kg N/ha/year over 2 years to Brachiaria decumbens . Average daily transmission of photosynthetically active radiation through the coconut canopy was 60% of full sunlight. The sown pasture consisted initially of para ( Brachiaria mutica ), signal ( B. decumbens ) and koronivia ( B. humidicola ) with the legumes Centrosema pubescens, Pueraria phaseoloides and Stylosanthes guianensis . The main species in the naturalized pasture were Axonopus compressus, Mimosa pudica, C. pubescens and Colopogonium mucunoides . Pastures were set stocked in two replicates over 3 years at 1·5, 2·5 and 3·5 animals/ha. There was no significant difference in live-weight gain between pastures in any year. Live-weight gain per head declined linearly with increasing stocking rate. Highest live-weight gain was 437 kg/ha/year in the 1st year at 3·5 animals/ha. The planted grasses declined from 60% at the start of grazing to 6% 8 months later. A. compressus increased from 2 to 24% over 3 years in the sown pasture, and from 12 to 34% of yield in the natural pasture. M. pudica increased from 27 to 44% in the sown, and remained approximately constant at 37% in the natural pasture. G. pubescens increased at 2·5 animals/ha, but was replaced by P. phaseoloides at 1·5 animals/ha and by A. compressus and M. pudica at 3·5 animals/ha. There were no significant effects of pasture treatments or stocking rate on copra yields. Where there is a cover of naturalized grasses and legumes under coconuts, cultivation and planting of exotic species cannot be recommended. Major improvement will come from thorough weed control and maintaining stocking rates between 1·5 and 2·5 animals/ha.

SummaryThe Guadalcanal Plains encompass approximately 460 km2 with both forest and grassland phases. Mean annual rainfall is 2160 mm, with a drier season from June to October, but soil moisture deficits seldom occur. Soils are freely to imperfectly drained brown loam to clays (Ustropepts). Soil analyses show available P concentrations of 15–17 μg/g, adequate K, Cu, Zn and Mn, and high Ca and Mg, but sulphate sulphur is low. A nutrient omission trial gave significant negative responses to the omission of P, K, S and Mo. However, responses to P applications were not obtained in the field with Centrosema pubescens, but significant responses to K and S were found under a cut and remove system. Yield response in the grasses Brachiaria decumbens and B. mutica to applied N was markedly limited in the absence of applied S, even though B. mutica was able to maintain S concentrations in herbage at 2–3 times those of B. decumbens. Without applied S, S contents and N:S ratios in B. decumbens were inadequate for beef cattle, but adequate in B. mutica except at high N inputs (300 kg/ha/year). Application of 40 kg S/ha to the legume C. pubescens increased yields by approximately 50%, reduced incidence of Cercospera leaf spot, and gave increased N concentrations. For establishment of sown mixed pastures on the Guadalcanal Plains we recommend the basal application of 20 kg P/ha, 50 kg K/ha, 30 kg S/ha and 0·15 kg Mo/ha, with 30 kg S/ha applied every 2 years.