Flowering response of pearl millet to water stress during panicle development.

In pearl millet, severe water deficit during the period of panicle development delays flowering. The flowering response of both main shoot and tillers to water stress during panicle development was investigated using four hybrids. Panicle initiation of all tillers occurred in the three early genotypes despite water stress. In the late genotype, however, panicle initiation of tillers occurred only after the release of stress. The delay in flowering due to water stress was more pronounced in the tillers than in the main shoot. However, the proportion of tillers producing an inflorescence was increased by water stress. Grain yield losses on the main shoot by water stress were compensated by an increase in tiller grain yields. Delay in flowering and buffering by tillers provide an important adaptive mechanism to overcome a period of drought stress prior to flowering

Tropical pasture science/ Whiteman

391 hal.: ill, tab.; 21 cm

Grazing studies on the Guadalcanal Plains, Solomon Islands 3. Comparison of existing mixtures with koronivia (Brachiaria humidicola) and with natural pastures

Pastures of a mixture of Brachiaria mutica (para) and B. decumbens (signal) grown with Centrosema pubescens (centro) and Macroptilium atropurpureum cv. Siratro and grazed at three stocking rates 1.8, 2.7 and 3.6 animals/ha for 5 and 6 years of grazing were compared with B. humidicola cv. 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 areas, 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

Grazing studies on the Guadalcanal Plains, Solomon Islands 1. Climate, soils, and soil fertility assessment

The 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, 50kgK/ha, 30 kg S/ha and 0-15 kg Mo/ha, with 30 kg S/ha applied every 2 years

Effects Of Stocking Rate Of Goats And Stage Of Crop Growth When Grazed On Grain Yield And Goat Production From Pigeonpea (Cajanus Cajan)

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

Revegetation of mine wastes at Mt. Isa, Queensland. I. The nature of the material and defining the problems

Of chemical and physical analyses in the laboratory and field were undertaken on the fine crushed rock material disposed of after ore extraction as large flat tailings dams, The aim was to define those factors limiting plant growth. Analysis showed that available phosphorus was extremely low. Nitrogen levels were also low. pH was approximately neutral between 6.7 and 7.6, due to the high levels of dolomite. Soluble salts, particularly NaCI, MgSO4 and CaSO4 were high, leading to high values of conductivity, up to 0.052 m Sm-1. The particle size distribution was dominated by fine fractions. In the field high bulk density values up to 1.57 g cm-3, combined with strong surface crusting lead to low values of infiltration. Thus high salt levels are not readily leached. These factors as limitations to plant growth are discussed

Animal production from rotationally-grazed natural and sown pastures under coconuts at three stocking rates in the Solomon Islands

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 28 days. The same three stocking rates of 1.5, 2.5 and 3.5 steers/ha were maintained. In the sown pasture paddocks Brachiaria decumbens and 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 inoreased. 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). The 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 can be obtained by controiling 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 Stenotaphrum secundatum may lead to better grass persistence

Light transmission and pasture composition under smallholder coconut plantations in malaita, solomon islands

Fourteen 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

Tropical Pasture Science

--.371 hal.;ill.;24 c

A Course Manual in Tropical Pasture science

--.371 hal.;ill.;23 c