The impact of age on the productivity of sown pastures of green panic (Panicum maximum var. trichoglume cv. Petrie) growing on black earth soil in south-east Queensland was measured from 1976 to 1981. During winter and spring, weaner steers grazed at 2·4 animals/ha on summer-spelled pastures which, in each year, were 1, 2, 3, 4 and 5 years old. Pastures were given 58 kg N/ha as urea each year. Live-weight gain averaged 74 kg/head on 1-year-old pasture but only 35 kg/head on 5-year-old pasture, with most of the reduction in weight gain in winter (June to August) occurring up to age 3 years, and with most of the reduction in spring (September to November) occurring for pastures older than 3 years.

The decline in animal production was not caused by changes in species composition of the pasture. Rather, weight gain on older pastures was restricted by pasture quality in winter and by reduced pasture growth in spring, but not by presentation dry-matter yield. The decrease in pasture productivity seemed to be primarily due to reductions in available soil mineral N with age, since the N concentration of plant shoots decreased as a pasture aged. Tt is postulated that the immobilization of N in decomposing grass litter is a primary cause of productivity decline in ageing pastures.

An analysis of chickpea experiments carried out in northern Syria during the 1980–1 and 1981–2 growing seasons showed that both intercepted solar radiation and its rate of conversion to dry matter were variable components of dry-matter production. Among the sources of variation in the experiments, the most important factor affecting both interception and utilization of solar radiation was site. Winter planting also led to increased solar radiation interception and utilization. Used in conjunction with chickpea lines resistant to blight, winter planting seems likely to lead to increased productivity. In higher rainfall areas, where the crop is usually grown, such an increase would be of commercial significance. In drier areas, winter planting would enable the cultivation of chickpea as a subsistence crop.

Field experiments were conducted in 1983–4 to investigate the effect of precision drilling and plant density on establishment, growth, radiation interception and yield of combining peas of varying leaf phenotype (Varieties ‘Birte’, leafed; ‘Filby’, leafless; and ‘BS3’, semi-leafless). Precision drilling established a more uniform plant distribution than øyjord drilling; visual differences observed soon after emergence were not observed at flowering. Precision drilling resulted in more radiation interception early in the season for semi-leafless but not leafed peas; dry-matter production and photosynthetic area index (PAI) were not increased. Yield data indicated that precision drilling produced similar yields to øyjord drilling at similar densities. Increasing plant density increased radiation interception, dry-matter production and PAI during vegetative growth; density treatment effects were less marked post-flowering. Pea leaf phenotypes differed in their yield response to increasing density. Radiation interception was related to dry-matter production and PAI to obtain an estimate of photosynthetic efficiency (ε) and the attenuation coefficient (k), respectively, ε and k were constant irrespective of spatial arrangement, leaf phenotype and plant density. The relative importance of spatial arrangement and plant density in increasing radiation interception and PAI and influence on yield is discussed; other potential agronomic advantages of precision drilling are described.

Random F3 families from six crosses typical of those being made in a spring barley breeding programme at the Scottish Crop Research Institute were used to rank the crosses on the basis of their predicted probabilities of exceeding a given standard for a number of characters. The predicted rankings were then compared with the observed rankings of the crosses based on observations of random inbred lines from the same crosses. The agreement between predicted and observed rankings was very good for single characters and good for bivariate combinations of the characters. The agreement for the bivariate combination of height and single plant yield was exact and the combination also appeared to be capable of accurately ranking crosses on the basis of height and plot yield.

The practical considerations of using such a cross prediction technique in a cereal breeding programme are discussed. Results from this experiment suggest that single plant measurement could be replaced by measurements on progeny rows, thereby saving considerably on labour. Predictions could just be made on the most important characters in the breeder's model for the early identification of the best crosses but this is still an advance on the approach of making many crosses and assessing relatively few selections from each cross in yield trials.

Two experiments, each involving five potato cultivars, investigated the effects of date of planting and harvesting of the seed crop, and of two seed storage temperature sequences, on date of dormancy break, sprout growth and subsequent field growth. The seed storage sequences in each case involved early or late accumulation of temperature to produce a physiological age of 600 day-degrees > 4 °C.

The effects of seed crop husbandry on most variables were small, with the exception of date of dormancy break, which occurred earliest when the seed crop was planted and harvested early. Effects of temperature sequence were more pronounced, although cultivars differed significantly in degree of response. Late temperature accumulation gave a larger number of sprouts per tuber, the length of the longest sprout was increased, as was the total sprout length per tuber. Emergence was more rapid, ground cover was initially greater and the number of mainstems per plant was greater with late temperature accumulation. Secondary stem production was more prolific and the total number of stems per plant greater when temperature accumulation was early. The number of tubers per plant reflected the total number of stems, and individual tuber size generally decreased as numbers increased, with the result that storage temperature treatment affected graded yields in some varieties.

The field growth of the crops from the late temperature accumulation treatment was in many ways suggestive of greater physiological age than the early temperature accumulation treatment, although the number of day-degrees accumulated was the same in each case. It is possible that the number of day-degrees underestimates physiological age as the period of accumulation is delayed.

Desodification of a highly saline-sodic, permeable, sandy loam soil was accomplished in 2 × 2 m (S1), 4 × 4 m (S2) and 6 × 6 m (S3) plots under continuous and intermittent ponding. The soil contained large amounts of soluble salts and exchangeable sodium throughout the profile to the water table. The chief salts were chlorides and sulphates of sodium, calcium, and magnesium. The leaching curves with respect to desodification did not differ significantly between the S1, S2 and S3 plots under continuous ponding but did under intermittent ponding. With intermittent ponding, the efficiency of leaching exchangeable sodium in the S1 plots was very significantly higher than that in the S2 and S3 plots, i.e. the leaching efficiency decreased sharply with increased plot size. The leaching efficiency in the S1 plots was significantly greater with intermittent than with continuous ponding, but the reverse was true in the S2 and S3 plots. The results further indicated that there is no need to apply an amendment such as gypsum, mainly because calcium and magnesium present in such soils are adequate to replace the initially high exchangeable sodium during leaching. The displacement of exchangeable sodium in the S1 plots under intermittent ponding was nearly piston-like. With increased plot size, it tended to deviate from this behaviour. It is concluded that under practical situations in which reclamation is accomplished in large plots, the practice of leaching the saline constituents with intermittent ponding would be less effective. Thus, leaching of salts down into the soil with a single heavy irrigation would be more desirable.

The effects of the time of sowing on growth and chemical composition of carrots grown from May to November were studied during 3 years.

Delaying sowing for 1 or 2 months after the beginning of May resulted in a reduction in the growth of both roots and foliage and gave roots with lower dry-matter content and glucose/fructose ratio but higher amounts of hexoses, total nitrogen and amino nitrogen in root dry matter. Sowing date had no influence on the concentration of sucrose, phosphorus, potassium, calcium and magnesium in root dry matter up to 137 days from sowing. Carotene decreased only after the last sowing. Sucrose concentration of the roots increased throughout the periods studied irrespective of the time of sowing. The longer the growing period the higher was the sucrose concentration. The concentration of hexoses decreased from the first harvest at 70 days to reach a constant level at about 130 days from sowing.

The results did not indicate the presence of a well-defined stage of biochemical maturity in the autumn when carrot roots are expected as most suitable for harvest and subsequent long-term storage.

Two trials designed to measure progress in the yield of durum wheat cultivars released in Mexico by the Institute Nacional de Investigaciones Agrícolas over the period 1960–84 were grown in the Yaqui Valley, Sonora, Mexico, during the 1983–4 and 1984–5 cropping seasons. The trials compared grain yield, above-ground biomass, harvest index (ratio of dry grain yield to dry above-ground biomass), yield components, grain-growth rates and phenological characters for eight key cultivars and the modern advanced line, Carcomun ‘S’, when grown at a high level of agronomic inputs and management.

The grain yield of durum wheat was estimated to have risen for 25 years of breeding from 3·70 to 8·40 t/ha. The estimated average annual rates of increase in grain yield for the periods 1960–71 and 1971–85 were 251 and 121 kg/ha respectively. Grain yield improvements were based on a linear increase in the number of grains/m2 over the 25-year period, the result of more grains per spikelet. An improved above-ground biomass at maturity was a feature of the two modern genotypes, Altar 84 and Carcomun ‘S’. Harvest index increased with each new cultivar up to the release of Mexicali 75 in 1975, but thereafter the higher grain yields achieved with the modern genotypes were not associated with a higher harvest index. Thousand-grain weight remained steady for the released cultivars but fell slightly for the advanced line Carcomun ‘S’. Improvements in yield were not associated with a longer cropping cycle.

It is concluded that a breeding strategy combining selection for morphological characters thought to confer high yield potential, such as a more erect leaf posture and high number of grains per spikelet, with selection for grain yield per se has been successful in improving the grain yield of durum wheats adapted to north-west Mexico. Improvements have come not only in the size of the grain sink and the efficiency of assimilate partition to grain but also in the biomass produced above ground.

Competitive and regulatory effects of defined inflorescences on the development of other inflorescences and subsequent yield performance of field beans (Vicia faba L.) were investigated. Genotypes differing greatly in yield performance (two inbred lines and the F1 hybrid produced from the two inbred lines) were used in both field and pot experiments. Yield was manipulated by the removal of defined inflorescences at various times and positions.

In comparison with untreated control plants the removal of up to four inflorescences from basal, central or apical nodes caused a loss of yield potential of up to 65%. Nevertheless the final seed yield per plant was not reduced. This was because additional pods and seeds developed at remaining inflorescences. After the removal of inflorescences from either basal or apical regions of the plant significant overcompensation effects occurred. The effects were influenced by the growing conditions. The capacity for compensation existed at differing yielding levels regardless of different genotypes or growing conditions.

The results are discussed with respect to the utilization of the initiated yield potential and to yield reliability.

A study was made under rainfed (unirrigated) conditions in a subtropical and semi-arid region of northern India during the winter (October–March) seasons of 1980–1 and 1981–2 to evaluate the growth, resource use and seed yield performance of four intercropping systems, namely mustard alone, ⅔ mustard +⅓ chickpea, ⅓ mustard + ⅔ chickpea and chickpea alone grown at 7·5, 15·0, 22·5 and 30·0 plants/m2.

The total economic productivity of intercrop systems was greater than that of either component grown alone. The components of seed yield (number of primary and secondary branches, number of pods, seed weight per plant and weight of seed) increased in mustard where intercropped but the opposite occurred in chickpea. These growth attributes were decreased with an increase in plant population density. The two crop species needed an individual density less than their sole crop optima to form an optimum density when intercropped. A mixture of ⅓ mustard + ⅔ chickpea appeared to be the best system for the rainfed conditions in which these experiments were made and produced greatest yield advantage.

Chickpea grown in ⅓ mustard + ⅔ chickpea combination had greater nodulation with higher dry weight per nodule. A greater leaf area index (LAI) for both the crop species was noted in ⅓ mustard + ⅔ chickpea mixture than were found in other systems. The maximum LAI of mustard and chickpea was attained at 60 and 120 days after sowing respectively and this may be why a lower proportion of mustard plants in the intercrop was more advantageous.

A combination of ⅓ mustard + ⅔ chickpea removed more nitrogen from the soil, had better water use efficiency and comparatively less soil moisture depletion than the sole crop. Soil nitrogen utilization and soil moisture depletion were less at higher densities.

A new protein supplement in the form of water-washed neem (Azadirachta indica) seed kernel cake for tropical countries such as India, Pakistan, Ceylon, Burma and also for tropical regions of Australia, Africa, the Middle East and South-East Asia which could be successfully fed to cattle has been reported by Nath, Rajgopal & Garg (1983). The adverse effect of the bitter or toxic principles contained in the neem seed kernel cake could be removed by water washing. It has a potential of providing Rs.350 million worth of additional feed in India alone and if all the neem seeds produced in India could be harvested and utilized for the preparation of oil, the production of the cake could reach 7–8 times its present value.

There is currently considerable interest in the use of anabolic compounds to improve the efficiency of animal growth and to produce leaner carcasses. While the majority of work has centred on beef production, the growth performance of sheep is also improved (Galbraith & Topps, 1981). However, little is known of the effects of anabolic steroid hormone administration on wool growth. The few experiments which have been conducted indicate that exogenous oestrogens depress wool output (Slen & Connell, 1958) while exogenous testosterone has consistently enhanced both greasy and clean wool yields (Slen & Connell, 1958; Osborne, 1968; Southcott & Royal, 1971). Little is known, however, of the effects of the synthetic steroids on wool growth. Coehlo, Galbraith & Topps (1981) reported a reduction in wool per unit body weight in sheep implanted with trenbolone acetate and oestradiol-17β, suggesting lowered efficiency of wool growth. Similarly Yasin & Galbraith (1981) noted that trenbolone acetate, in combination with either oestradiol-17β or zeranol, reduced wool output per unit body weight. Neither of these trials attempted to isolate the effects of trenbolone acetate alone from those of the androgenplus-oestrogen combination.

Para-rubber (Hevea brasiliensis Muell-Arg.) is a major plantation crop in South-East Asia. In addition to its economically important latex, the para-rubber tree produces seeds that serve as a source of industrial oil. Rubber seed meal (RSM), a by-product of the oil extraction, contains moderately high amounts of crude protein and is available at lower prices than most traditional vegetable protein supplements in the region. The estimated availability of RSM in South-East Asian countries is about 1·2 million tonnes.

Recently, radiotelemetry has been widely used in the measurements of various physiological attributes, e.g. body and skin temperatures, heart rate and heat flux across the surface in unrestrained animals (Zervanos & Hadley, 1973; Moen, 1978; Mautz & Fair, 1980). The present note provides some basic information on heat flux across the skin in untethered black Marwari goats of the Rajasthan desert, measured by radiotelemetry during winter.

There is little information on rates of protein synthesis in individual muscles in ruminant animals. Skeletal muscle is the largest single tissue and, as such, has a considerable effect on nitrogen transactions in the body. Arnal (1977) found a substantial decline in synthetic rate between 1 and 16 weeks of age in lambs and also observed differences between red and white muscles. Bryant & Smith (1982a) measured synthesis in several muscles of mature sheep and they observed lower rates than Arnal (1977) with little difference between most muscles. Vastus intermedius muscle in the hind leg, however, had higher rates of synthesis than other muscles. Here we report rates of protein synthesis in individual muscles in rapidly growing lambs approximately 12 weeks of age. The major back muscle, the longissimus dorsi, and two hind leg muscles, the vastus lateralis and the vastus intermedius, were chosen for study.