Growth and digestibility trials were conducted to investigate responses of young cross-bred sheep to alkali-treated straws and supplements. Oat and wheat straws were coarsely milled, sprayed with NaOH solution and then sprayed with a solution containing N, S, P, Cu and Co, and mixed with powdered limestone. The treated straws were fed ad libitum with no supplement (0) or with 150 g/day of either cotton-seed meal (CSM) or whole barley grain (B). In a preliminary trial to study the effect of frequency of ort collection on intake of treated straw, consumption decreased (P < 0·05) when frequency of ort collection was reduced from once daily to once weekly. This was associated with an increase in the neutral detergent fibre content of the orts. During the growth trial, which lasted 105 days, intake of treated straw increased by 34%.

When no supplement was fed, digestibility of treated oat straw was higher (P < 0·05) and dry-matter intake lower (P < 0·05) than that of treated wheat straw. However, calculated intakes of metabolizable energy (ME) and measurements of growth and wool production were similar on the two straws (P > 0·05).

When supplements were fed, there was no effect on intake of the treated straws. Mean live-weight gains were 51·4, 80·2 and 77·3 g/day on treatments 0, CSM and B respectively (P < 0·01). This was associated with higher intakes of ME (P < 0·01) which accounted for 73% of the variation in live-weight gains. Mean clean wool growth was 7·6, 10·5 and 9·3 g/day on treatments 0, CSM and B respectively (P < 0·01). This effect was associated more with nitrogen (N) absorption than with ME intake (80 and 48% of the variation in wool growth respectively).

It was concluded that the treated straws provided sufficient nutrients for modest growth in young sheep, that the supplements had no effect on intake of the treated straws and that additional live-weight gain and wool growth obtained by feeding CSM and B were associated with energy intake and nitrogen absorbed respectively.

Two seed-resistant land races were crossed to a seed-susceptible cultivar to produce Fl, F2, BC1; and BC2 generations. It was observed that seed resistance was conditioned by two unlinked recessive genes and cytoplasmic factors. Similarly, generations derived from a pod-resistant, seed-susceptible cultivar with a seed-resistant, pod-susceptible land race demonstrated that seed and pod resistance are independently inherited.

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.

Beets with a coefficient of variation (c.v.) of weight of only 36–46% were produced by reducing the variation in cluster size, sowing depth, time of seedling emergence, proximity and size of neighbours to as low a value as practicable. The relative importance of these different sources of variation in plant size was examined in two experiments sown in contrasting conditions.

Variation in time of seedling emergence was a major source of variation in plant size and was partially caused by variation in the environment around the clusters. Variation in true seed size and between-plant spacing was achieved by use of clusters of different sizes, but these factors were associated with only a negligible variation in root size. Similarly, local interactions between plants, brought about by variation in plant-to-plant spacing, accounted for only a small proportion of the variation in root weight.

Although the first or second clonal cuttings of heat-treated sugar cane were widely used for seed, differences were not detected among crop years or locations in the incidence of ratoon stunting disease. Sugar-cane mosaic virus (SCMV) disease was widespread in all areas surveyed; however, the plant cane crop had a lower incidence of SCMV than the first or the second ratoon crop. The estimated cane yield was increased approximately 19·4 t/ha by heat treatment during the 2-year survey period.

The management system used to control the sugar-cane borer (SCB), Diatraea saccharalis (F.), was effective regardless of the crop year or area surveyed. Season-long SCB control was achieved by the use of two (1981) or three (1982) properly timed applications of insecticide and the use of a SCB moderately resistant variety resulting in an average of 6–9% bored sugar-cane internodes.

Poor weed management, particularly with johnsongrass (Sorghum halepense(L.) Pers.), accounted for much of the reduction in cane yield (P < 0·01); the estimated yields of the second ratoon crop were substantially altered, particularly those of farms surveyed in the Bayou Lafourche area.

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.

This study examines the effect of sodium (Na) supplementation on the intake and digestibility of Na-deficient feed by cattle, and the potential applicability of faecal analysis to the diagnosis of Na deficiency in the field. Mature cattle fitted with oesophageal fistulae were fed chaffed Setaria sphacelata cv. Nandi hay ad libitum in metabolism cages, with and without a Na supplement (10 g Na daily as NaHCO3). In the first of two experiments the hay contained 0·44 g Na/kg D.M., and in the second, 1·05 g/kg. Prior to an unsupplemented treatment the animals were rapidly depleted of Na by removal of saliva via the fistula; Na status was assessed on the basis of the ratio Na/K in saliva.

When the feed contained 0·44 g Na/kg, Na supplementation increased voluntary intake by 28% (P < 0·01) and digestibility by 12% (P < 0·05). No such responses were obtained in Expt 2, in which the feed contained 1·05 g Na/kg.

Examination of available data suggests that a diagnosis of Na deficiency in cattle is indicated if the faecal Na concentration is below 1 g/kg D.M., and the ratio Na/K in faeces is less than 0·1. Further data are required to confirm these criteria, which should prove useful in the field when samples of saliva, the diagnostic criterion of choice, are not available.

Blossom-end rot, a non-parasitic disease, was found to occur widely on some oblong varieties of watermelon, causing much damage in the southern region of Oman (Dhofar). Fruit contact with soil surface seems to be the major agent of blossom-end rot of watermelon, especially in the early stage. Incidence of watermelon blossom-end rot was apparently reduced by mulch using a mixture of dried grasses or coconut leaves.

Three sheep, equipped with cannulae in the dorsal rumen sac, abomasum and ileum, were fed a low sodium diet of artifically dried young grass. Mean daily intake of sodium was 310 mg. The sheep were given daily supplements of 0 or 2·3 g sodium by an intraruminal infusion.

The concentration of K in mixed saliva and ruminal fluid from the sheep not given sodium supplements increased and the concentration of Na decreased markedly. The changes in the ion concentrations were associated with an increase of the transmural potential difference across the ruminal epithelium.

The altered ion concentrations of Na and K in the ruminal fluid and the increased potential difference were accompanied by a decrease in Mg absorption from the forestomachs. The apparent availability of Mg from the gastrointestinal tract decreased from 34·5 (sodium supplementation) to 22·3 (low sodium intake).

It is suggested that a daily intake of Na of 310 mg did not cover the sodium requirement of these sheep and that a low sodium intake influences the absorption of Mg in a similar manner as it has been observed with a high K intake.

The results are discussed in context of grass tetany in ruminants. It is suggested that an inadequate intake of sodium is an overlooked factor of the pathogenesis of this disease.

A new tillage procedure was examined for the improvement in physical environment it might provide during the establishment of a vegetable crop, particularly in a dry spring. This procedure, of cultivating the soil mainly in autumn, was compared with the conventional method of cultivating in the spring on a sandy loam soil. The physical condition of seed beds prepared by the two methods was assessed by in situ measurements of soil temperature, water retention characteristics, hydraulic conductivity and surface roughness. Plant responses were compared by monitoring the emergence of onion seeds. Dry spring conditions were simulated by sheltering some plots from rain.

Final emergence, emergence time and rate of emergence were all superior following autumn cultivation for both dry and wet seed beds. The major factor affecting emergence was the coarseness of the seed bed which influenced the mechanical impedance to shoot growth. Differences in soil temperature between treatments were small, as were hydraulic conductivities under dry conditions. Preparing a seed bed in autumn rather than spring resulted in a good tilth with lower mechanical strength. This minimized the constraints on emergence when soil strength increased under dry conditions.

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.

In sugar cane, investigations made earlier (Singh & Gururaja Rao, 1985) have shown that high-yielding varieties have higher net assimilation rate than low-yielding types. Similarly, differences in progeny means for relative growth rate and net assimilation rate have been reported by George (1965). In other crops also, varietal differences in leaf area index and net assimilation rate have been reported (Watson, 1947). It appears that in this crop, limited attempts have been made to study all the growth characteristics. This paper describes the differences in most of the growth characteristics in six sugar-cane varieties.

The conventional Kjeldahl method which is usually employed for determination of total N in soil does not effect quantitative recovery of NO2- or NO3- (Bremner, 1965). Therefore, various modifications have been suggested (Cope, 1916; Davisson & Parson, 1919). Bremner (1965) observed that the quantitative recovery of NO2- and NO3- by any method, other than the modified Olsen's method (Bremner & Shaw, 1958), is not certain.

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.

In tropical and subtropical areas many cattle suffer from heat stress for more than half of each year. Added to the environmental heat stress is the heat production associated with lactation (Berman et al. 1985) and the resultant increased storage of heat (Araki et al. 1984). While the net effect of lactation on body temperature has been evaluated in dairy cattle (Collier et al. 1982) its effect on beef breeds in tropical and subtropical areas has not been defined. This is now possible with improved telemetry equipment, which allows body temperatures of free-ranging cattle to be monitored up to distance of 400 m.

Water stress during the period when tubers are initiated may reduce the final number of tubers (MacKerron & Jefferies, 1986) and increase the incidence of common scab (Streptomyces scabies) in susceptible cultivars (Lapwood & Hering, 1970). It is important, therefore, for the maintenance of a large number of tubers and for the limitation of scab, to be able to estimate the time of tuber initiation. Tuber initiation has been defined differently by a number of workers (e.g. Sale, 1979; Sands, Hackett & Nix, 1979; O'Brien et al. 1983; MacKerron & Jefferies, 1986) based on either the number or proportion of stolon apices that have reached a certain size (usually twice the diameter of their stolons). These are definitions of tuber growth rather than development and require destructive sampling at frequent intervals for recognition of the event. Temperature has a major influence on the rates at which plant organs develop so that the time taken to reach a given developmental stage may be related to thermal time, defined as the time-integral of temperature (Jones, 1983). In potato the physiological age of tubers (Wurr, 1978; Allen et al. 1979; O'Brien et al. 1983), sprout development and extension (MacKerron, 1984), and the initiation of leaf primordia (Kirk, Davies & Marshall, 1985) have been related to thermal time. In a model of the development and bulking of potatoes Sands et al. (1979) used a single non-linear function to describe the effects of time and temperature on several development processes including tuber initiation. That function did not adequately describe the time taken to tuber initiation and Sands et al. (1979) did not then use tuber initiation as an important stage in their model.

It is increasingly being recognized that water intake in goats is considerably lower than in sheep on the same feed (Gihad, 1976; Gihad, El-Bedawy & Mehrez, 1980; Alam, Poppi & Sykes, 1983). It is, however, difficult to judge the significance of this difference for water transactions in the digestive tract. This paper describes the comparative water consumption and flow in the digestive tract of kids and lambs.

Predatory arthropods can play an important role in the natural control of cotton pests, including bollworms (Heliothis zea Boddie and H. virescens F.). Smith & Fontenot (1942) reported that widespread use of calcium arsenate in cotton fields reduced the number of coccinellids, which resulted in increased damage by pests. Ewing & Ivy (1943) confined several predacious insects collected from cotton (individually in jelly glasses fitted with slightly moistened blotting paper) and supplied them daily with eggs deposited by insectary-reared bollworm moths. The maximum number of eggs destroyed in a day by a single adult of the convergent lady beetle (Hippodama convergent Guerin-Meneville) was 275. Adults of another species of lady beetle (Coleomegilla fuscilabris Muls.) frequently consumed all the eggs given them, an adult on average consuming 22 eggs per day. All the 12 species of predacious insects found in cotton fields survived on bollworm eggs. Whitcomb & Bell (1964) showed that the three most common lady beetles in cotton fields in Arkansas were: (1) spotted lady beetles (Coleomegilla maculata De Geer), (2) convergent lady beetles, and (3) ninespotted lady beetles (Ciccinella novemnotata Herbst). They recorded 24 species of lady beetles, all feeding on lepidopterous eggs including those of bollworms. Many of these predators were captured while feeding on small bollworm larvae. Van den Bosch & Kagen (1966) proposed guidelines for the mass releases of convergent lady beetle adults as a pest control measure in cotton. Lingren, Ridgway & Jones (1968) reported from small-container experiments that adult females of convergent lady beetles consumed an average of 129·9 bollworm eggs per day.