The influence of four seeding times on herbage dry matter (DM) yields and clover content of white clover (Trifolium repens L.)/orchardgrass (Dactylis glomerata L.) mixtures was evaluated at Truro, Nova Scotia and Charlottetown, Prince Edward Island from 1985 to 1988. Sacramento, Sonja and Milkanova white clover/orchardgrass mixtures were assessed under simulated grazing (four or five harvests per year) over two production years at each location.

Delaying seeding from May to August reduced total herbage DM yields significantly in the first production year, from 8·1 to 3·3 t/ha in Truro and from 11·0 to 7·2 t/ha in Charlottetown. Late seeding significantly reduced clover content in the herbage of the first two harvests in the first production year but, by the mid to late-season harvests, white clover content had increased to levels similar to those of the May seeding. Estimated white clover DM yields were highest in June, and dropped in the second production year at both locations. Sonja and Milkanova white clovers consistently outyielded Sacramento in herbage DM yields and clover content in both locations irrespective of seeding dates.

Seed is often stored in warehouses where the temperature may drop below freezing or increase to 40°C depending on the time of year. Survival of rhizobia on lime-coated alsike clover (Trifolium hybridum L.) seed stored in polypropylene bags was monitored under various temperature regimes ranging from –10 to 35 °C at Agriculture Canada Range Research Station, Kamloops, British Columbia, Canada during 1990 and 1991. Rhizobia were applied ata range of initial concentrations. Seed was inoculated with a peat-based clover inoculant (‘B’ inoculant, Nitragin Ltd, Milwaukee, Wisconsin, USA), and then given a commercial polymer-based lime coat (GNR™, Grow Tec Ltd, Nisku, Alberta, Canada). Rhizobia died continuously at all temperatures within the range —10 to 35°C. The dependence of Iog10(number of viable rhizobia/seed) on storage time was best described by a linear equation: Iog10(viable rhizobia/seed) = a + b (time). Coefficient a providedan estimate of the initial concentration of rhizobia. Coefficient b provided a measure of how rapidly rhizobia died. The death rate of rhizobia was the same during storage at 5 or 20 °C, but increased at a storage temperature of 35 °C. Storage at freezing temperatures did not increase the rate of rhizobial death but repeated freezing and thawing resulted in an increase. As the rate of rhizobial death was similar at constant temperatures from — 10 to 20 °C, temperature requirements are not stringent. Nevertheless, some temperature control is required to maximize the legal storage life of preinoculated coated seed, which in this study was estimated to be 96 days.

Almond trees (Amygdalus communis L. cvs Garrigues and Ramillete) were grown in the field under non-irrigated conditions in Murcia, Spain. Seasonal variations in leaf water potential components were studied in 1989. Predawn leaf water potential showed high values in both cultivars, due to the absence of soil water stress. Pressure-volume curve analysis indicated that the leaf osmotic potential at full saturation (Ψo(sat)) for cv. Garrigues remained fairly constant throughout the season. Bulk modulus of elasticity (E) showed, in both cultivars, a tendency to decrease as the season progressed. E values were higher in Ramillete than in Garrigues. The relative water content at the turgor loss point (RWCtlp) seemed to be controlled by E values. The larger relative apoplastic water content (RWCa found in Ramillete might have allowed it to retain more water at low leaf water potentials than Garrigues. These facts would support the suggestion that Ramillete is a more drought-resistant cultivar than Garrigues.

Thirteen experiments conducted near Tenby, Dyfed, between 1973 and 1980, examined the effects of seed-tuber weight and within-row spacing on tuber yields of seven potato varieties grown for early production. These data have been used in an attempt to develop an approach to the determination of optimum tuber planting densities in early crops which will provide agronomists with logically applicable principles. Tuber planting densities, which maximized the net crop return (ware value minus seed cost), were estimated for eight ratios of seed cost to ware value ranging from 0·25 to 8·0. Optimum tuber planting densities decreased with the use of higher ratios of seed cost: ware value and heavier seed, except for ratios of 0·25 and 0·50 applied to yields of tubers > 25 mm harvested in June. In general, later harvesting together with the use of larger riddle sizes give a lower optimum density with ratios < 2·2·0. Optimum densities for Red Craigs Royal, Ulster Sceptre and Vanessa were higher than for the other varieties.

The results provide an illustration of how to approach the problem of selecting tuber planting densities in order to maximize net crop returns in early potato varieties.

Yields of dry matter, nitrogen, phosphorus and potassium in herbage and cereals from fields representing different stages of the rotation were recorded on two organic farms in 2 years. Amounts of N, P and K purchased and sold were also recorded on these farms.

Some additional data was obtained from three other organic farms. Herbage production was very satisfactory, whether fields were grazed or cut. The proportion of clover in sown swards was, in most cases, satisfactory to high, but the clover content was very low in a few fields. The yields of cereals were about equal to or below the average obtained on farms using fertilizer and other agrochemical inputs. Manure was normally applied to the leys, which were the fertility-building part of the rotation, rather than to the cereal crops. Leaching of K from manure heaps was considerable.

Purchases of N, P and K (mainly in manure) seemed excessive on one of the farms. On one of the farms studied in less detail, less P and K were purchased than were sold. More attention could be given to the balance between purchases and sales of N, P and K and to the efficient conversion of N into saleable produce.

Clones from the potato species Solanum phureja and 2x and 4x hybrids between S. phureja and S. tuberosum were tested for the culinary quality of their tubers following steaming, frying and baking. The quality of S. phureja tubers was high but material from the F 1 hybrids showed more disintegration or blackening after cooking than either parental species. Tetraploids produced by backcrossing 4x Fl hybrids toS. tuberosum cultivars showed less of these defects.

Fourteen S. phureja and 2x F1 hybrid clones selected for their unusual tuber skin pigmentation or shape were found to have a variety of baked flesh colours from orange-yellow to cream with red marbling. Their cooked flesh texture was generally floury and often crumbly. It is suggested that S. phureja material could be exploited as a novel food source for specialized use in North European countries.

The flowering response of a late-flowering mutant of Sesbania rostrata was compared with that of the parent plants by sowing it on ten different dates, from December 1990 to September 1991, in India. Flowering response was also studied following exposure to an 8-h photoperiod at four different stages of growth. The parent flowered at different times of the year depending on the time of sowing, while the mutant flowered only during October–November irrespective of sowing date. The parent was sensitive to a short-day photoperiod as early as 15 days after sowing, but the mutant became sensitive to the critical photoperiod only after 60 days of vegetative growth. The mutant, by virtue of its longer vegetative phase, had the potential to produce adequate phytomass irrespective of the time of sowing.

Bambara groundnut (Vigna subterranea (L.) Verde.) is grown throughout southern and western Africa, primarily as a subsistence crop, but agronomic information is scarce. The rates of emergence, flowering and pod production were assessed for 20 weekly sowings between 16 October 1990 and 26 February 1991 at Sebele, Gaborone, Botswana. Daylength during this period changed from 12·7 h to 13·7 h and back to 12·6 h. Mean time to 50% emergence was 111 days while mean time to 50% flowering was 47·5 days. The thermal time to first pod production varied with daylength, decreasing as daylength decreased, to an approximately constant value when daylength after flowering was less than about 12 h. Consequently, the plant size at which pods were produced also varied. The practical implications for date of sowing and plant spacing are discussed.

On two organic farms, nitrate-N and ammonium-N in the surface layers of the soil of representative fields were recorded for 2 years. Nitrate-N was also determined in different soil layers down to 120 cm at the beginning, middle and end of two winters and at intervals after ploughing three fields, to seek evidence of leaching.

Nitrate-N and ammonium-N were both consistently low in the surface layers of fields in ley. Nitrate-N accumulated in arable soils on some occasions when there was little or no crop uptake of N, after ploughing, and after very heavy applications of manure.

There was some evidence of nitrate leaching in all five fields which were deep-sampled. In four cases, the loss by leaching appeared to be < 25 kg N/ha per winter. In the other case, in which a 4-year ley was ploughed on 5 October, the loss by leaching appeared to be c. 70 kg N/ha. Ploughing in winter, rather than early autumn, might have reduced the nitrate leached, but the drilling of the next crop might have been delayed.

The nitrate concentration of water draining from recently ploughed sandy soil in Shropshire was high, but it would have been diluted by water draining from unploughed fields.

The response of low glucosinolate, low erucic acid (double low) cultivars of oilseed rape to spring nitrogen application was examined at Cockle Park, Northumberland in three successive seasons (1987–90). Seed yield and protein content increased in response to increasing nitrogen application. In each season over 85% of the maximum recorded yield was obtained with an application of 150 kg N/ha. In the absence of spring nitrogen, seed yield varied considerably over the three seasons. The variation in seed yield and protein content between 1987/88 and 1988/89 can partly be explained by differences in the availability of soil nitrogen in the different seasons. Seed glucosinolate concentration was significantly increased withnitrogen applications between 0 and 150 kg/ha. Increasing nitrogen beyond 150 kg/ha hadlittle or no effect on seed glucosinolate concentration. The results are examined with reference to the varying effects of increasing nitrogen application rates on seed glucosinolate concentrations reported previously.

The duration of flowering was investigated in 14 accessions of indeterminate faba (field) beans (Vicia faba L.) planted near Adelaide, South Australia in 1986 and 1987. All flowers and young pods were removed from plants at 4–7 day intervals. Plants of ‘Mediterranean’ origin produced 20–30 flowering nodes while those of European ‘spring bean’ type produced up to 50. Terminal inflorescences were eventually produced in all accessions. In control plants, the number of days between anthesis at successive nodes was partly dependent on nocturnal minimum temperature and varied very little between genotypes. It should be possible to make best use of the growing season by optimizing the potential production of nodes, but there is little opportunity for manipulating the rate of their appearance.

Measurements of foetal head diameter (HD) and trunk diameter (TD) were made using ultrasonic scanning of 11 pregnant llamas (Lama glama). Each llama was scanned fortnightly to obtain measurements of HD and TD from c. 84–271 and 65–168 days since mating respectively. There were approximate linear relationships between TD and days after mating and between HD and the logarithm of days after mating.

Calibration equations for predicting the number of days after mating (d) from foetal measurements constructed using (i) the inverse method in which d is regressed on HD or TD and (ii) the classical method in which HD or TD are regressed on d. These calibration methods were assessed by crossvalidation, treating each animal in turn as the individual for which predictions were required. Analysis of the prediction errors showed bias in the classical method, which consistently underestimated d at low values. A components of variance analysis indicated substantial variation between individuals which must be taken into account in calculating standard errors of prediction (S.E.P.) and confidence intervals. S.E.P. of d from TD can be reduced from 12·5 to 10·4 days by increasing the number of observations on an individual from one to four at fortnightly intervals. For prediction from HD, the equivalent figures are size dependent: examples are from 8·3 to 5·6 days, and from 26 to 18 days, for HDs of 2 and 6 cm respectively. The effect of small positive correlations between residuals of successive fortnightly measurements on the same llamas had a negligible effect on S.E.P.S, increasing them by c. 0·2 days. Ultrasonic scanning is suitable for determination of stage of pregnancy of llamas providing S.E.P.S which are small in relation to their long gestation period (335–360 days).

Effects of diseases on growth and yield of linseed (cv. Antares) were assessed by controlling diseases with fungicide treatments in field experiments at Rothamsted from 1988 to 1990. Fungicide seed treatments decreased the incidence of Alternaria lesions on cotyledons and stem bases of emerging seedlings in 1989 but decreased emergence in 1990. The incidenceof leaf browning, associated with Alternaria spp. and Botrytis cinerea, was less in 1989 and 1990 than in 1988 when the period, in July, between flowering and harvest was wet, but the incidence of powdery mildew was greater in 1989 and 1990 than in 1988. Fungicide spraysdecreased leaf browning in 1988 and powdery mildew in 1990. In 1988 there were more capsules per plant and the crop was taller than in either 1990 or 1989, when July and August were hot withperiods of dry weather. The incidence of plants with dark brown stems, associated with Verticillhun dahliae, was greater in 1989 and 1990 than in 1988, but was not greatly affected byfungicide treatments. The incidence of Alternaria linicola on sepals, capsule cases and seed from capsules sampled before harvest was decreased by fungicide treatments. Other fungi isolated from these tissues included A. alternata, A. infectoria, B. cinerea, Fusarium spp. and V. dahliae. Yields of grain and oil were increased by fungicide treatments in all three years, but the yield increases were greatest in 1988 when fungicide treatments also increased 1000-grain weight. The incidence of fungi on the harvested seed was not greatly affected by fungicide treatments.

Stages in the diagnosis of an interveinal leaf chlorosis in bean in the Usambara Mountains of northern Tanzania are described. Leaf tissue analysis, soil analysis, a 25 factorial trial with treatments of nitrogen, phosphorus, potassium, the trace elements copper and zinc and lime at one location and data from a series of 43 factorial trials of N, P and K demonstrated the leaf condition to be due to potassium deficiency. Large growth and yield responses to N, P and K were recorded. The responses were accompanied by greater numbers of pods and seeds/pod. The application of N and K increased leaf concentrations of the respective elements but depressed the concentrations of other major and minor elements in leaves. There were no effects of trace elements or lime.

The mineralization and nitrification processes in pig slurry were investigated in Spain in 1990 in three calcareous soils, differing mainly in content and type of clay, two classified as Typic Calciorthids and one as a Xerollic Calciorthid. Two different amounts of slurry were mixed with the soils, one equivalent to 273 mg N/kg soil and the other equivalent to 546 mg N/kg soil. The mixtures of soil and slurry were aerobically incubated for 16 weeks at 28 °C. A mean initial immobilization of 22·19% of the total-N added was detected in soils treated with the lower rate of slurry. The amount of mineralized N after 112 days of incubation was between 36 and 47% of the total-N added with the lower slurry application to the three soils. The net amount of N mineralized throughout the experiment was therefore within the range 14–23% of the total-N added. The nitrification of the NH4-N added to the soil began after 7 days of incubation, and followed a first-order kinetic model. The mean values of potential nitrate formation were 61 and 51% of the total-N added in soils amended with 273 and 546 mg N as pig slurry per kg soil respectively. The rate constants were higher in the treatments with the lower slurry application (0·043–0·083 per day). Therefore, in these treatments, the nitrification process was faster and total nitrate levels were higher than in soils receiving double that amount of slurry. The NO3-N evolution was parallel to the total-N evolution from the 14th day of incubation onwards. The N-mineralization process was limited by the transformation of the organic-N into ammonium (ammonification).

Sixty-four multiparous Friesian cows were given one of eight diets from weeks 4–20 of lactation at the former National Institute for Research in Dairying, Shinfield, Reading in 1983–84. The diets consisted of 13·5 kg/day of experimental concentrates plus hay at 4·5 kg/day (fixed) or ad libitum. Concentrates were high-starch (S) based on cereal grains and cassava, high-fibre (F) based on highquality by-products, and two intermediate types containing 2:1 (SF) and 1:2 (FS) starch:fibre, all with a crude protein concentration of c. 180 g/kg DM. The diets were designed to provide similar intakes of digestible energy and crude protein at fixed hay intakes.

With ad libitum feeding, hay intake was lowest on S concentrates. With increasing fibre in the concentrates, the yields of milk, protein and lactose fell but fat concentration and yield were increased. These changes were linear and were unaffected by hay intake. Increasing hay intake to ad libitum had no effect on milk yield but increased the concentrations and yields of fat and protein. It also changed a net liveweight loss on fixed intakes to a gain on ad libitum intakes.

Diet digestibility was measured using sheep at about maintenance and cows at production intakes. Digestibility was higher in the sheep, probably because of the difference in level of intake. In the cows, increasing fibre in the concentrates reduced the digestibility of dry matter, organic matter, energy and nitrogen but increased the digestibility of fibre fractions and ether extract. Level of hay intake had variable effects on mean digestibility and on the relationship with concentrate type.

Increasing the fibre in the concentrates increased the molar proportions of acetate and n-butyrate in the rumen and reduced the proportions of propionate, n-valerate and n-caproate.

It is concluded that, with mixed diets of hay and relatively high proportions of concentrates, changes in the starch:fibre ratio of the concentrates by substitution of high quality by-products for starchy ingredients can induce linear changes in the yields of milk and the principal solids constituents and in milk fat concentration. Since changes in yields of fat and protein went in opposite directions, the optimal concentrate composition depends on the milk composition required by the market. These conclusions may not apply if poorer quality by-products are used.

Sixty-four lactating buffalo cows (24 normal cycling, 8 pregnant and 32 repeat-breeder), selected from two buffalo farms near Cairo during 1987 and 1988, were studied during thefirst 26 days after oestrus (day 0). Plasma progesterone concentrations were significantly (P < 0·01) higher in pregnant than in cyclic (between days 3 and 5) and repeat-breeder (between days 0 and 8) animals. Concentrations of total unconjugated oestrogens were also highest (P < 0·01) in the pregnant group between days 6 and 16. Cyclic and pregnant cows had higher (P < 0·01) concentrations of plasma calcium between days 3 and 7, inorganic phosphorus at all times and glucose between days 2 and 8 than repeat-breeders. Plasma protein concentrations were greater at all times, except between days 6 and 8, in the first two groups. Analysis of the uterine fluid collected from cyclic and repeat-breeder buffalo cows revealed that concentrations of all biochemical components, except for calcium, were significantly (P < 0·01) higher in flushings from the uterus of cyclic animals than from repeat-breeders at alltimes for inorganic phosphorus, between days 6 and 12 for glucose and on day 2 as well as between days 8 and 12 for protein. Large differences were found in calcium levels, especially on day12 when flushings from repeat-breeder cows contained more than six times the concentrations of this metabolite in uterine flushings from cyclic animals. The results suggested that reduced luteal function, related to atypical profiles of plasma biochemical components, during the oestrous cycle in repeat-breeder buffalo cows might provide the basis for altered syntheses and secretions of uterine calcium, phosphorus, glucose and proteins which are needed for embryo development.

Voluntary intakes of a medium-quality grass hay were measured in winter (early January) and in spring (late April) near Edinburgh for two separate groups of six red deer, together with digestibility and mean retention times of the particulate-phase marker, 103Ru-phenanthroline. The deer were then slaughtered and the weights of digesta and the dimensions of the alimentary tract were measured. Voluntary intakes of dry matter were significantly higher in spring than in winter, but there was no difference in digestibility or mean retention time of 103Ru-phenanthroline. There were no significant differences in any of the organ weights or the dimensions of the intestines between the groups slaughtered in winter and spring. Dry matter proportions of digesta in the rumen, abomasum, small intestine and caecum, the wet and dry weights of rumen digesta and the water-filled capacity of the rumen were significantly greater in spring.

The study investigated the effects of chronic elevation or suppression of circulating prolactin levels on seasonal wool growth in Romney sheep. Ewes (n = 10/group) were housed indoors under natural lighting (latitude 34 °S) and received either 50 mg bromocriptine i.m./ewe/28 days (Group B), 1 mg spiperone s.c./ewe/day (Group S) or no treatment (Group C) commencing in summer. Wool growth and liveweight were measured every 4 weeks and venous blood samples were collected for prolactin determination. Plasma prolactin levels (mean±s.E.) in Group C exhibited a gradual seasonal decline from 121±29 ng/ml to 35±9 ng/ml. Bromocriptine suppressed prolactin levels rapidly from a pretreatment value of 118±2 ng/ml to below 12±7 ng/ml for the duration of the study. Prolactin levels in Group S were not significantly higher than Group C, with the exception of the first 14 days following the initial treatment. A seasonal reduction in wool growth of c. 25% was observed in all groups; however, no significant treatment effect was evident. Mean liveweight of all animals increased from 50·4±0·8 to 56·8±0·7 kg during the study. These results indicate that perturbation of the annual cyclic secretion of prolactin does not affect wool growth in the Romney ewe.

Silages were prepared from the tropical grasses, pangola grass (Digitaria decumbens) and setaria (Setaria sphacelata), with the addition of molasses (4% w/w) and/or leaves (33%) from the leguminous trees leucaena (Leucaena leucocephala) and gliricidia (Gliricidia sepium). All forages were grown at the University of Queensland farm in south eastern Queensland during 1985. These silages, together with hays made from these grasses and sorghum silage (13 diets) were fed to sheep to assess their nutritive value. All silages were well preserved, as indicated by low pH (3·5–4·4), low ammonia N (26–57 g/kg total N) and high lactic acid (73–95% total acids) contents. The addition of legumes increased both the dry matter (DM) and total N (TN) contents of silages to the same extent as the addition of both legumes and molasses at ensiling. Sheep given silages prepared from pangola grass and legumes (±molasses) consumed similar DM intakes (22·9–25·4 g/kg0·75 per day) as sheep given pangola grass hay (23·9 g/kg0'75 per day). Silage made from pangola grass + molasses was of low palatability (16·1 g/kg0·75 per day). The digestibilities of silage DM (DMD) and its fibrous components were significantly (P<0·05) lower (DMD 53·3–60·6%) than that of pangola hay (DMD 64·7%). Silages and hay made from setaria, and sorghum silage, were of lower nutritive value than those from pangola grass. The addition of leucaena and molasses increased silage DM intakes (21·1 g/kg0·75 per day) above those for setaria hay and setaria + molasses silage (16·7 and 19·0 g/kg0·75 per day respectively). The intakes of silages made from gliricidia (17·1 g/kg0·75 per day) were significantly (P <0·05) improved when molasses was included at ensiling (21·8 g/kg0·75 per day). The digestibilities of silage DM were significantly (P<0·05) higher (DMD 53·6–60·4%) than that of setaria hay (DMD 40·6). Liveweight change in sheep was significantly (P<0·05) correlated with intakes of digestible DM (r2= 0·74) and with N intake (r2= 0·82). The inclusion of legumes in the silages increased N retention and, for setaria silages, also increased rumen ammonia concentration. It was concluded that tropical grasses can be effectively ensiled by the addition of legumes alone and, with the exception of setaria/gliricidia silages, the resultant silages were of sufficiently high quality to merit their use in tropical animal production systems.