The effects of sowing date and cutting stage on grain yield, biomass and leaf area were analysed in three spring triticale genotypes (× Triticosecale Wittmack) grown at three different sites in Spain during 1990/91. Results indicated that the most appropriate sowing date for grain yield in these environments seemed to be from the last 10 days in November to mid-December. Cutting reduced grain yield, biomass and leaf area at anthesis, and these decreases were greater in a drier environment (the only exception being cutting at Zadoks growth stage (GS)31 at Lleida), and when the cutting was done at GS31 rather than GS30. The significant relationships found between the percentage loss in grain yield and biomass and leaf area at anthesis after cutting suggest that genotypes intended for grain and forage production need to be able to regenerate leaf area rapidly after cutting.

Experiments on spring barley at Rothamsted over the years 1974–81 were used to study how sources of powdery mildew inoculum affected responses to fungicide sprays applied at different times. Reinfection of early-sprayed plots was generally faster where they were close to a potent source of inoculum than where they were not. Conversely, effects of sources on yield, although not always significant, occurred mainly in the later-sprayed plots. Sources thus had their most important effects before these later sprays were applied, and probably during the very early stages of the epidemic. This implies that if experiments are to approximate to fields, they should, initially, be part of a large, uniformly-susceptible area of crop.

Regression analyses showed that delaying the application of fungicide sprays after the optimum date caused smaller yield losses in plots near minimal sources of inoculum than in plots near more potent sources. There was no conclusive evidence for effects of inoculum sources on the optimum date to apply a fungicide spray but the tendency was for the optimum to become later as inoculum pressure increased.

Separating fungicide-treated plots with mildew-resistant barley resulted in larger treatment effects and smaller residual mean squares than where there was no separation. Judged by residual mean squares alone, precision was approximately doubled by separation.

In order to understand better the relationship between plant physical structure and rate of intake, twelve plant species were compared: Trifolium repens L., Medicago sativa L., Onobrychis viciifolia Scop., Desmodium intortum (Mill.) Urb., Brassica napus L., Spergula arvensis L., Lolium perenne L., Lolium multifiorum Lam., Festuca arundinacea Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and Zea mays L. The effects of early as opposed to late harvesting were compared. Plants were grown in a heated glasshouse in each of 2 years, examined for morphology, anatomy, neutral detergent fibre and digestibility, and fed to sheep for 1-min test periods to record rate of intake.

Rate of intake was in the order tropical grasses < temperate grasses < broad-leaved species < S. arvensis. The range was wide: from 4·6 g dry matter/min with C. gayana to 15·6 g with S. arvensis. The lowest rate of intake was associated with the possession of a large number of veins, close together, in parallel lines (tropical grasses); a rather higher rate was associated with fewer veins, further apart, in parallel lines (temperate grasses); the next to the highest rate was associated with broad leaves, which had a network of veins; the highest rate was associated with thin stems containing thin vascular bundles. L. perenne, L. multifiorum, C. gayana and C. ciliaris were similar in the thickness of large and small leaf blade veins and leaf sheath veins. F. arundinacea and Z. mays had rather thicker veins. T. repens, 0. viciifolia. D. intortum and B. napus were similar in the thickness of petiole vascular bundles. Neutral detergent fibre was lowest in B. napus and highest in C. gayana and C. ciliaris. In vitro digestibility was highest in B. napus and lowest in D. intortum.

The effectiveness of chewing by sheep during eating in breaking a forage diet into particles was studied in twelve plant species over 2 years and related to the physical structure of the plants and their rate of intake. The twelve species were: Trifolium repens L., Medicago sativa L., Onobrychis viciifolia Scop., Desmodium intortum (Mill.) Urb., Brassica napus L., Spergula arvensis L., Lolium perenne L., Lolium multiflorum Lam., Festuca arundinacea Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and Zea mays L. In each case early harvesting was compared with later harvesting. The plants were grown in a heated glasshouse.

L. perenne and L. multiflorum were broken into a large number of particles per g dry matter; the particles were rather long and thin. F. arundinacea was broken into heavier, slightly shorter and slightly wider particles. C. gayana and C. ciliaris were broken into particles which were smaller, heavier and contained more vascular bundles than those of Lolium, reflecting the lower rate of intake, greater weight per unit area of leaf blade and greater proximity of bundles of the tropical grasses. Z. mays leaf blades broke into shorter, wider particles than the leaf blades of the other grasses, reflecting the much wider blades of Z. mays.

The leaflets of the four leguminous species and the leaf blades of B. napus were broken into particles with an average length:width ratio of c. 2:1, compared with an average ratio of c. 7:1 for particles derived from grass leaf blades other than those of Z. mays. The legume leaf petioles were broken into particles with an average length: width ratio of c. 13:1; many of the legume petioles were not split longitudinally during chewing. The stems of M. saliva and D. intortum were broken into particles similar in length and width to those from the stems of the tropical grasses, although the rate of intake of the legume diets was at least twice that of the tropical grass diets. The average length: width ratio of particles from B. napus petioles and stems was 5:1. A high proportion of particles from the B. napus and D. intortum diets had a rough surface. 5. arvensis was broken into more particles per g dry matter than the legumes and B. napus, despite its very high rate of intake. Many pieces of stem of S. arvensis were not split longitudinally during chewing.

The impact of white clover on seasonal yield and nutritive value traits in perennial ryegrass was investigated using six ryegrass varieties which expressed contrasting levels of water soluble carbohydrate (WSC). These were sown in an upland environment at Syfydrin, near Aberystwyth, in mixtures with white clover and in monocultures. Plots were grazed by sheep and sampled during 1991–93. Grass yields in mixtures and monocultures were similar except during mid to late summer when clover contents were high. White clover had a considerably lower WSC content but a much higher crude protein (CP) content than the ryegrasses. The WSC content of grasses in mixed swards was consistently lower than in monocultures and markedly so during mid to late summer. Use of ryegrass varieties with a relatively high WSC content can compensate for this depletion. Consequently high WSC grasses may reduce the amounts of nitrogen excreted by ruminants grazing mixed swards by increasing the efficiency of protein use from clover.

Lucerne (Medicago sativa L.) sowing rates were evaluated to determine how environmental conditions affect seedling establishment and plant survival. Lucerne (cv. Peace) was sown during 1988 at rates ranging from 2·8 to 11·2 kg ha-1 at one irrigated and two dryland sites (a forest and a mid-elevation grassland site) near Kamloops, British Columbia, Canada. Dry matter (DM) yield was measured for 3 years, and plants were counted to estimate seedling establishment and plant survival. Sowing year DM yield increased linearly with sowing rate at the irrigated and forest sites, but at the mid-elevation grassland site it decreased at sowing rates > 5·6 kg ha-1. In the first full-production year, DM yield levelled off at sowing rates > 8·4 kg ha-1 at the irrigated site and was not affected by sowing rate at the forest site. At the grassland site, first full-production year DM yield decreased at sowing rates > 2·8 kg ha-1. In the second full-production year, there was a linear effect of sowing rate on DM yield at the irrigated site, but it did not affect DM yield at the two dryland sites. At all sites, the percentage of seedlings that survived to the end of the second growing season decreased curvilinearly as seedling density increased. Survival was less at the irrigated site than at the dryland sites. Higher sowing rates are required at irrigated sites than at dryland sites to obtain maximum yield or a required plant population density.

Stands of bambara groundnut (Vigna subterranea (L.) Verde.) were grown in five controlledenvironment glasshouses at the Tropical Crops Research Unit, University of Nottingham, Sutton Bonington Campus, in 1990. Five soil moisture regimes were imposed (one per house), from fully irrigated each week (treatment A), to no irrigation after crop establishment at 35 days after sowing (DAS) (treatment E). Decreasing the amount of water applied resulted in a decline in total dry matter production and harvest index, and a reduction in pod yield from 412 (treatment B) to 0·041 ha-1 (treatment E) at 125 DAS. A maximum leaf area index of 5–4 was achieved by treatments B and C at 90 DAS, resulting in a fractional interception of c. 0·8 of incoming radiation. Total accumulated radiation interception values were 749, 693, 688, 618 and 554 MJ m-2 for treatments A, B, C, D and E, respectively. The efficiency of conversion of the radiation intercepted into dry matter was reduced from 1·41 to 0·50 g MJ-1 by drought.

The pollination requirements of cashew (Anacardium occidentale L.), an andromonoecious tree, were studied in NE Brazil, where cashew is indigenous. It was shown through the use of bagging and caging experiments, controlled hand-pollination and emasculation of flowers, that the wind plays little role in cashew pollination and that cashew is self-fertile, although only pollen from the large stamen, either male or hermaphrodite-derived, can effect pollination. Insects appear to be the major pollinators of cashew, in agreement with the pollination syndrome suggested by the morphology of its flowers. Direct observations of insects visiting flowers and counts of pollen grains adhering to such insects suggest that the honey bee (Apis mellifera L.), although a non-native insect, is the major pollinator of commercially grown cashew in NE Brazil.

The effect of water stress on nitrogen fixation in seven common bean (Phaseolus vulgaris L.) genotypes was investigated in Celaya, Gto., Mexico, in 1991. Beans were grown under four moisture regimes: (1) well-irrigated, control, (2) with water stress during the vegetative stage, (3) with water stress during the reproductive stage and (4) with water stress during the whole growing cycle. Biological nitrogen fixation was measured by 15N-isotope dilution using sorghum as a reference crop. Nodulation and N2-fixation data showed genotypic differences in response to water stress. Under non-stressed conditions, cv. Bayocel fixed the most nitrogen (85 kg/ha) and cultivar Flor de Mayo Baji'o the least (33 kg/ha). Under water stress at the reproductive stage, these cultivars fixed 9 and 6 kg N/ha, respectively. Water stress during the reproductive stage reduced nodulation by an average of 43% with no recovery after rewatering. Water stress during the reproductive stage had a greater effect on N2-fixation than on grain yield; in comparison to the control, N2-fixation was reduced to one sixth while grain yield was only reduced by 50%.

Among lentil-growing regions, it is only in West Asia that both large-seeded, yellow cotyledon and small-seeded, red cotyledon lentil (Lens culinaris Medikus) are grown by farmers. This study examined the adaptation to temperature and rainfall of the two seed-size groups in West Asia; first in germplasm evaluated in Syria in the 1978/79 and 1979/80 seasons and assessed for cold susceptibility in Turkey in the 1979/80 season, and second in breeding lines over the decade 1984–93 at three sites in West Asia.

Large-seeded material consistently had a longer reproductive growth period than the small-seeded group by 2·8 days, an extended period being required to fill its greater seed mass per pod. In the breeding material, the large-seeded group consistently produced taller plants and more straw than the smaller seeded-group. Germplasm with large seeds was less susceptible to winter cold than that with small seeds. Additionally, in the breeding material there was an advantage in seed yield of the largeseeded group over the small seeds in average temperatures < 10 °C from January to April, with the converse true at higher temperatures. In the breeding material, the large-seeded group showed an advantage in seed yield over their small-seeded counterparts at the two wetter sites, whereas the smallseeded group was better adapted to dry environments. Based on this adaptation, the potential of some regions currently growing exclusively large-seeded lentil for producing the other seed type is emphasised.

Sewage sludge applications were made to two freely draining grassland sites of contrasting rainfall in SW England in 1991/92 and 1992/93. Applications were made in autumn, winter and spring (following first silage cut), with raw sludge applied by injection and digested sludge both as a surface application and injection at application rates of 140 m3/ha and 125 m3/ha for raw and digested sludge respectively. A tine-only treatment and an untreated control were also included. Nitrate leaching was measured following autumn and winter applications using porous ceramic cups. Average NO3--N concentrations in drainage water exceeded the EC limit for potable water of ll·3 mg/l following autumn injection of digested sludge at one site for both years. Average concentrations in drainage water for all other sludge treatments were below this limit. Up to 24, 11 and 6% of the applied total N was leached from injected digested, surface-applied digested and injected raw sludge respectively. Autumn applications resulted in greater leaching losses than winter application. Leaching losses were greater from digested than from raw sludge when both were applied by deep injection. Injection of digested sludge as compared to surface application exacerbated nitrate leaching losses. Herbage yields and N recoveries were better from later sludge applications, with the exception of injection treatments, where spring sludge injection during a prolonged dry period resulted in yield reductions as compared to autumn injection.

A grazing experiment was conducted for 8 weeks in the spring/summer of 1993 at Palmerston North, New Zealand, to study the effects of condensed tannins (CT) in Lotus corniculatus (birdsfoot trefoil cv. Grasslands Goldie) upon the lactation performance of ewes rearing twin lambs. Effects of CT were evaluated by studying the responses of ewes to twice daily oral supplementation with polyethylene glycol (PEG; MW 3500), which binds and inactivates CT. A rotational grazing system with restricted feed allowance was used. Measurements were made of pre- and post-grazing herbage mass, the composition of the feed on offer and diet selected, voluntary feed intake (VF1), milk yield and composition, liveweight gain and wool production. The concentration of metabolites in rumen fluid and in blood plasma was also measured. Lotus contained 35–5 g total nitrogen and 44–5 g total CT/kg dry matter in the diet selected, with an in vitro digestibility of 73%. At peak lactation (weeks 3 and 4) milk yield and composition were similar for control (CT-acting) and PEG-supplemented (CTinactivated) ewes but, as lactation progressed, the decline in milk production and in the secretion rates of protein and lactose were less for control than for PEG-supplemented ewes. In mid and late lactation (weeks 6–11), control ewes secreted more milk (21 %), more milk protein (14%) and more lactose (12%) than PEG-supplemented ewes. Milk fat percentage was lower for control than for PEG-supplemented ewes, but secretion rates of fat were similar for the two groups. VFI, liveweight gain and wool growth were similar for both groups. Plasma urea and glucose concentrations were lower for control than for PEG-supplemented ewes, but concentrations of non-esterified fatty acids (NEFA), growth hormone and insulin were similar for the two groups. The concentrations of ammonia and molar proportions of iso-butyric, iso-and n-valeric acids in rumen fluid were lower for control than for PEG-supplemented ewes; molar proportions of acetic, propionic and H-butyric acids were similar for the two groups. It was concluded that for ewes rearing twin lambs grazing L. corniculatus, the action of CT increased milk yield and the secretion rates of protein and lactose without affecting VFI, thereby increasing the efficiency of milk production. The increased milk production did not appear to be mediated by effects on plasma concentrations of growth hormone or insulin.

The pre-natal and post-natal development of wool follicles in sheep of five genotypes with contrasting wool types was examined to provide data on which to base studies of physiological factors affecting wool type via follicle development. This study was conducted following Autumn mating in 1992 at Palmerston North, New Zealand (40° S, 176° E). The rate and timing of follicle development in midside skin samples from Romney, Merino, Merino × Romney (M × R), Drysdale and Wiltshire foetuses and lambs collected at weekly intervals from days 76 to 143 of gestation and 1, 3, 7, 12 and 32 weeks after birth were examined.

Primary (P) follicle density had a similar pattern of development in each of the genotypes, although the Merino had a significantly greater density of P follicles than the other genotypes. There was a difference in the rate of P follicle maturation between genotypes with the Drysdale, Wiltshire and M × R completing P follicle maturation before the other two genotypes. However, the majority of P follicles in all genotypes were producing fibres by 111 days of gestation. It was concluded that the small differences in the density and time of development of the P follicles could not cause the differences in wool type between genotypes.

The pattern of development of the secondary (S) follicle population was examined by comparing S: P ratios. The initiation of S follicles began at similar ages in the five genotypes, but initiation was completed earlier in the Romney, Drysdale and Wiltshire than in the Merino and M × R, as indicated by a significant genotype by age interaction (P < 0·001). There was no difference between genotypes in S:P ratio from 90 to 104 days of gestation. The S:P ratio of the Romney, Drysdale and Wiltshire did not change significantly from 104 days of gestation until the end of the study, indicating that few S follicles were initiated in these genotypes after 104 days of gestation. The M × R data showed a significant increase in S:P ratio until 119 days of gestation and the Merino S:P ratio increased until 126 days of gestation.

The period between days 90 and 125 of gestation was identified as being the critical period for the development of different follicle populations in Merino and non-Merino genotypes and it is this period which should be the focus for studies to determine physiological factors controlling secondary follicle development.