The application of chemical desiccants to lucerne and red clover after cutting is studied from the standpoint of increasing the drying rate in relation to pan evaporation. Significant increases in the evaporation-based drying constant are found on both first and second cuttings of these crops, but the savings of a full day's drying time is expected only for second-cut lucerne in the north-eastern U.S. climate. The effect of crop density on drying rate is also studied. In conjunction with a theoretical analysis, it is determined that the drying constant varies as γ-0.65, where γ is the areal density. The evaporation-based drying constant is then related to crop yield and the ratio of cutting width to windrow width.

Two field experiments examined the influence of soil nitrogen on grain yield, wateruse efficiency and residual nitrate accumulation of four winter grain legumes in a legume–fallow–wheat rotation. In the first experiment, conducted on a clay soil with a high total soil nitrogen content (0·194%), the three legumes Cicer arietinum, Vicia faba and Pisum sativum gave similar yields, with Lupinus angustifolius showing poor yields. Water-use efficiencies followed similar trends to the grain yields. Wheat yields and concentration of nitrogen in the grain, following a fallow after the legume crops, showed no differences from a full 2-year fallow. In the second experiment on a low fertility soil (0·081 % total soil nitrogen), Cicer arietinum gave the highest yield and the greatest water-use efficiency. All legumes and long fallow resulted in a similar increase in wheat yield when compared with a wheat-fallow-wheat rotation. The legume crops generally increased soil nitrate status between their sowing and the sowing of a wheat crop 2 years later; such increases were greatest with Pisum sativum at the high fertility site, with a suggestion of the reverse occurring at the low fertility site.

The isotope dilution technique was used to measure endogenous faecal excretion and absorption of dietary Ca and P by growing lambs. Groups of four lambs were given 0·8 or 1·2 kg/day of a pelleted barley and soya-bean diet containing 4·2 g P/kg D.M. and supplemented to contain 1·79, 3·52 or 4·67 g Ca/kg D.M.

At the lowest dietary concentration of Ca, absorption of Ca was insufficient to meet the Ca required for deposition in the newly formed bone matrix of the skeleton; retention was 0·39, 1·16 and 1·12 g/day with increasing dietary Ca concentration. The proportion of dietary Ca absorbed decreased (P < 0·001) with increasing Ca intake, ranging from 0·85 to 0·44. Endogenous faecal excretion of Ca was independent of the absorption of dietary Ca, but increased (P < 0·05) from 17·2 at the lower to 21·1 mg/kg live weight/day at the higher D.M. intake. Plasma concentration of Ca was higher for the female (2·51) than the male (2·33 mmol/1) lambs and increased linearly (P < 0·001) with dietary concentration of Ca from 2·31 to 2·52 mmol/l.

The retention of P increased with Ca and D.M. intake. On the other hand, the proportion of dietary P absorbed (0·85) was independent of Ca intake and hence of P retention. Increases in P retention were reflected by decreases in urinary P, but not in endogenous faecal excretion. Endogenous faecal excretion of P increased with D.M. or P intake from 17·9 at the lower to 33·5 mg/kg live weight/day at the higher intake.

The results are discussed in relation to dietary allowances of Ca and the mechanism of P homoeostasis.

Fertilizer nitrogen recovery under fallow and under a wheat crop (Triticum aestivum L., cv. Miriam) grown on a deep loessial silty loam (Calcixerollic Xerochrept), was studied with 15N labelled KNO3. The labelled nitrogen was applied (at a rate of 180kg/ha) to 30 cm diameter microplots enclosed in hard plastic tubes that protruded 5 cm above the soil surface. In the 1st year of the experiment there was a long dry spell during the main part of the growing season and plant dry-matter yields were low. The 2nd year was wet, with heavy rain early in the season. About one-third of the fertilizer N applied to the fallow was lost from the top 60 cm layer in the 1st year. Most of the fertilizer N remaining in the soil as mineral N at the end of the first season was lost in the 2nd year. The possible reasons for such low N-conservation efficiency are discussed.

Comparisons were made of the tuber yield and leaf morphology of three dihaploids, their chromosome-doubled derivatives and tetraploid parthenogenetic parents grown in a glasshouse at low, medium and high fertilizer levels. Differences in yield between the dihaploids and doubled dihaploids were not significant (P > 0·05) and responses to increases in fertilizer were similar. Leaf complexity showed generally large (usually significant, P< 0·05) increases when the fertilizer level was increased from medium to high. For the heterozygous tetraploid parents the tuber yield increased more than leaf complexity. Probably the dihaploids and doubled dihaploids utilized the additional fertilizer to increase foliage growth rather than tuber yield whereas the converse was the case for the tetraploid parents. There was no evidence that chromosome doubling resulted in changes in the response of dihaploid genotypes to changes in the fertilizer level.

The honeybee alarm pheromones 2·heptanone and isopentyl acetate were repellent to honeybee foragers when applied to plots of oil-seed rape and field beans and to sunflower heads. Their possible use to repel bees from crops before insecticide application is discussed.

Azospirillum brasilense was treated with nitrosoguanidine and five antibiotic-resistant mutant strains isolated. Variations in growth, N2-fixation, ultraviolet-dark survival and level of antibiotic resistance were found between the mutant strains. Mutant strains STR 112 and KR 2051 showed maximum nitrogenase activity, glutamine synthetase activity and hydrogenase activity (H2 uptake) at 32 °C and 40 °C respectively. Inoculation of cheena genotypes with A. brasilense and its mutants led to significant increase in associative nitrogen fixation, dry weight of roots and grain yield compared with the uninoculated control, with significant strains × genotypes interactions in calcareous soil. It was also noted that under laboratory conditions Azospirillum inoculation may have produced its response by hormonal means and/or associative N2-fixation.

Mature sheep fitted with rumen and duodenal cannulae, and fed a pelleted hay diet, were given supplementary phosphorus by continuous infusion into the rumen and the effects on salivary phosphorus secretion, net intestinal phosphorus absorption and faecal endogenous phosphorus excretion were studied. In control periods little phosphorus was excreted in the urine and little increase was seen in response to supplementation, the faeces being the major pathway for excretion. Increasing phosphorus intake led to an increase in net intestinal phosphorus absorption, a rise in plasma phosphate concentration, an increase in salivary phosphorus secretion and an increase in faecal endogenous phosphorus excretion. Overall net intestinal absorptive efficiency for phosphorus did, however, decrease as intake rose so that changes in faecal endogenous phosphorus excretion were in part due to increased salivary phosphorus secretion and in part to a reduction in overall absorptive efficiency. The significance of these changes in relation to the control of phosphorus balance in ruminants is discussed.

Cell wall preparations from stems of four mature grass species, pangola grass, setaria, sugar cane and barley straw were incubated in nylon bags in sheep fitted with rumen cannulae and fed chopped pangola grass at hourly intervals. After varying incubation times D.M. loss, and incorporation of 35S into microbial cystine on the fibres, were measured. Pangola and barley straw were digested to a much greater extent (ca. 48 and 44%) than sugar cane and setaria (ca. 29 and 23% respectively) and digestion was still continuing after 60 h. With the exception of setaria, microbial colonization of the cell wall preparations peaked after 24 h incubation and then declined. In setaria only a small amount of [35S]cystine was measured, the level of which did not change appreciably after 18 h.

After 24 h incubation, microbial colonization on pangola fibre was about three times that on barley straw and sugar cane. Only on pangola fibre did cystine accumulation, and its subsequent rapid decline, coincide with the development and detachment of fungal sporangia. There was no relationship between the extent of microbial colonization and D.M. loss from the fibres. Sulphur concentrations, both in the plant fibres and rumen fluid, could not explain the greater fungal growth on the pangola cell walls in preference to the other species.

Random inbred lines produced by doubled haploidy and single seed descent have been used to estimate the number of genes or more correctly effective factors (k) controlling quantitative characters in barley. Estimates of k obtained by various biometrical methods are generally an underestimate since the effective factor may be considered a unit only in a temporary sense. In the past, estimates of k have been used to predict the range of inbreds extractable from a cross. Alternative and efficient methods are now available to predict the number of inbreds expected to exceed any given standard. Under these circumstances the need to estimate the number of genes is questionable.

All 53 lettuce cultivars inoculated with cucumber mosaic virus became infected. Leaf mosaic symptoms were generally mild and unreliable for distinguishing degrees of resistance between cultivars. Yield reduction was the most satisfactory criterion for evaluating resistance, with reductions in individual cultivars ranging from 8 to 50%.

An account is given of vegetational and yield changes occurring in sown swards of Lolium perenne L. to which four alternative management treatments were applied for 8 years.

With infrequent cutting (four cuts per year), and a fertilizer nitrogen rate of 188 kg/ha per year, there was a substantial invasion by Agrostis spp. At 376 kg N/ha under cutting the main invader was Agropyron repens (L.) Beauv. with a lower proportion of Agrostis. After cutting at 752 kg N/ha, the swards became dominated by A. repens. With rotational sheep grazing, at 376 kg N/ha, the main invader was Poa annua L., although the proportion was low and L. perenne remained the dominant species. The plant successions which occurred with each type of management as the swards became older had little influence on the yield or quality of herbage under grazing or cutting.

Because sward age is confounded with the influence of year-to-year environmental variation, the experiment was designed to enable independent assessments of these factors to be made. Sequential sowings were made to produce an array of swards between 1 and 7 years old. Year-to-year fluctuations in the pattern of herbage production were quantified after allowing for the progressive increase in sward age. Similarly, the influence of age was investigated by adjusting yields for year effects, and comparing swards of different ages in the same year.

Year-to-year variation in the total yield of dry matter was much greater than variation attributable to sward age. There was similarly more variation due to year than to age in the yield of D.M. at any one season. In the most extreme comparison, the D.M. yield at an individual defoliation in one year was 2·8 times the lowest yield at the same season in a different year, whereas the yield at the same season varied by a factor of up to 1·5 between swards of different ages.

The influence of age on quality was quantified for cut swards only. There was an age effect only at the first cut, when the percentage of digestible organic matter (DOM) declined with age, and herbage nitrogen concentration increased, at the lowest level of fertilizer N, but these changes did not occur at higher N levels. Annual yields of DOM declined significantly with age, but only at the highest N level, and there were no significant changes in the annual yield of herbage N.

Comparisons were made of the cumulative D.M. yields for several years of young swards, resown every 3 years, and undisturbed swards, up to 7 years old. Young swards gave a higher yield during the first two years after sowing, but the advantage was lost in the period of ploughing and establishment, during which time the undisturbed swards achieved a small advantage in cumulative yield. Cumulative yields of DOM and N from young swards were not sufficiently different from those of older swards to suggest that there would be an advantage from regular resowing. A theoretical analysis was made to predict the long-term yields of D.M. and DOM from different renovation strategies at yearly steps from 2 to 7 years. This suggested that ploughing and resowing gave little or no advantage in productivity over swards which were not renovated before age 7, and resowing too frequently gave a loss of yield.

The paper contains an appendix by A. Smith and R. E. Deriaz describing a method used for the correction of analytical results obtained for variable contamination of herbage samples by extraneous materials.

The improvement of milk production by the establishment of four specialized lines and subsequent within-line selection over a 7-year period under grazing conditions at Kraim station in mid-Syria is described. The specialized line showed a substantially higher total milk production amounting to a mean 25% superiority over the control line in 1979–81.

The heritability of total milk yield as estimated from paternal half sib analyses was 0·53 ± 0·169 for 2-year-old ewes and the genetic correlation of a single maximum daily yield record (+ 0·93) with total yield indicates the possibility of simplified selection procedures for this trait.

The effect of several other factors (for example, ewe age and season of lambing) on various aspects of lactation in Awassi ewes is reported.

Differential growth from 1 to 20 weeks of age was studied on 320 rabbits from two lines (New Zealand White and California) and both sexes by means of the allometric equation log y = log a + b log x. Regression lines were fitted to the evolution of organs (blood, skin, thymus, heart–lungs, liver, kidneys and alimentary tract), carcass, tissues (bone, lean and fat) and anatomic components (head, breast and ribs, loin, abdominal wall, fore and hind legs) relative to empty body weight; stomach, caecum and intestines relative to alimentary tract; bone and lean groups relative to total bone and lean and fat depots relative to total fat.

The convenience for a correct description of relative growth of determining both the quantitative growth, in order to apply the allometric equation only to the real growth period of each component, and the possible existence of allometric changes, is discussed.

The results for each component are presented and discussed. There were no significant differences due to line, and sex had a significant influence (P < 0·001) only on the relative growths of total fat, lean content in the loin and hypodermic fat. All the components, with the exception only of thymus, presented a change in their allometric coefficients. These changes for most components, except fat depots, were concentrated in a small interval of time (4–8 weeks of age) between weaning and the inflexion point of the body weight growth curve.

Cobalt, as cobalt sulphate and cobalt-EDTA, was applied to pastures at 15 sites in south-east Scotland. Herbage cobalt and extractable soil cobalt concentrations were monitored at these sites over the period 1978–81. Although the sites were located in a generally cobalt-deficient area, considerable variation between sites was observed both in the concentration of cobalt present in untreated pasture and in the response to cobalt additions. There was no significant correlation between herbage cobalt concentrations and soil cobalt status as determined by acetic acid extraction. Application of cobalt sulphate (6 kg/ha) increased herbage cobalt concentrations at all sites but at several sites the response was short-lived. In general, cobalt-EDTA was less effective than cobalt sulphate in increasing herbage cobalt concentrations.

Extractable soil cobalt concentrations of the control areas showed some variability between samplings, but the variability was much greater for the cobalt-treated plots. Cobalt applied to pastures was found to accumulate in the top 0–4 cm layer of soil and penetrated deeper only in soils of low pH. Overall, only a third of the cobalt applied to pastures as cobalt sulphate was recovered by acetic acid extraction of the soil and less than 20% of the cobalt applied as cobalt-EDTA.

Untreated and paclobutrazol-treated field-grown plants of winter oil-seed rape cv. Jet Neuf were exposed to 14CO2 at anthesis. Redistribution of labelled assimilate was followed in sequential harvests between exposure and maturity.

Labelled assimilates moved progressively from the leaves into the stem and reproductive parts. At maturity 9% of 14C fixed at anthesis had been mobilized into reproductive organs. Paclobutrazol increased the proportion of 14C translocated to the uppermost branches especially the terminal raceme.

It is suggested that stem reserves are valuable for yields commonly achieved in U.K. commercial practice.

Adult Finn-cross ewes, pregnant from September matings, were kept under natural (control) or artificial photoperiod (experimental). The artificial photoperiod consisted of an abrupt increase in daylength to 18 h for 30 days in November, followed by a step wise decrease of 30 min every 10 days until May.

The ewes of the two groups were either exposed daily to rams after lambing in January-February or after weaning in March, or were kept isolated from the males until mating in April. Time of mating in the latter animals was determined by measuring the intra-vaginal electrical impedance. Hormone treatment for oestrus induction was given after weaning to a portion of the control and experimental ewes. The ovarian activity of the animals was determined by examining their plasma progesterone changes.

Daily teasing of the ewes from lambing to weaning and/or treatment with artificially decreasing daylength did not influence the ovarian activity during this period. All the ewes which were examined for ovulation, from both the control and experimental groups, ovulated 40–60 days after lambing, and 96% of the animals of the two groups which were not treated with hormones for oestrus induction exhibited spontaneous oestrus in March–May.

The lambing–first ovulation and the lambing–first spontaneous oestrus intervals were longer in the light-treated than in the control ewes, and in the animals kept isolated from the rams until mating than in those exposed to the males after lambing or weaning.

A conception rate of 70–100% and a high rate of cycle activity were obtained during the two consecutive years of the experiment in both control and experimental animals, treated or not with hormones and exposed or not to rams. In view of these results, no conclusions could be drawn about the effectiveness of the artificial photoperiod, ram effect and hormone treatment, alone or in combination, in inducing cycling activity and to increase the fertility of Finn-cross ewes during the seasonal anoestrus in Israel.

The yield results are reported for an experiment in which 21 rates of nitrogen fertilizer were applied on pure-sown swards of four grasses, S. 24 and Barvestra perennial ryegrass, S. 37 cocksfoot and S. 53 meadow fescue. Growth curves fitted to the herbage yield data for each grass in each year are presented. On average the total dry-matter yield curves for the two ryegrasses were similar to one another, but showed a slightly smaller response to nitrogen rates below 300 kg/ha than did S. 23 ryegrass in an earlier experiment, and a more rapid decrease in response at higher rates. S. 37 cocksfoot had a similar dry-matter yield response to the ryegrasses at the low nitrogen rates, but the response decreased more rapidly at nitrogen rates over 250 kg/ha. The dry-matter yield response of S. 53 fescue decreased even more rapidly with nitrogen rates over 200 kg/ha. The mean estimates of the optimal nitrogen rate for each of the four grasses, i.e. the nitrogen rate at which the dry-matter response had decreased to 10 kg/kg N, was 380, 372, 357 and 327 kg N/ha for S. 24, Barvestra, S. 37 and S. 53 respectively, compared with 409 kg/ha for S. 23 ryegrass in the earlier experiment.

An experiment comparing continuous winter wheat with the two wheat crops in a rotation of beans, oats, wheat, wheat, with four rates of application of N fertilizer, is described and the results discussed.

The wheat following wheat in the rotation consistently outyielded the wheat following oats, but the continuous wheat yielded on average less. Response to N fertilizer was not affected by sequence of cropping and since there was practically no response to the highest increment of N, it is clear that additional N could not have brought the yield of the continuous wheat up to the level of the wheat in rotation.

A study was made of growth and N concentrations of field-grown crops of spring barley (Hordeum vulgare L. cv. Georgie or Triumph). Nitrogen concentrations were calculated on the basis of both dry matter and tissue water because previous research had indicated that K concentrations expressed on the basis of tissue water were better for assessing the K status of crops. The aim was to see whether this was also the case for N.

When supplies of P and K were adequate, the addition of N fertilizer stimulated growth in all crops except when sufficient N was already supplied as farmyard manure. Percentage N in dry matter declined as plants grew and was higher in plants given N than in plants grown without N, although the difference diminished with time. Nitrogen concentrations calculated on the basis of tissue water were very similar for both N-sufficient and N-deficient crops despite large differences in growth rates. Nitrogen concentrations in tissue water also declined but only until anthesis, thereafter they increased. This pre-anthesis decline was due to the increase in the amount of stem tissue which had lower N concentrations in tissue water than leaves. Similarly the post-anthesis increase in N concentrations was due to the development of the ears which had high concentrations of N in tissue water.

The effects of deficiencies of P or K or water on N concentrations in tissue water of the cultivars Georgie or Julia were studied also in field experiments at Rothamsted. Lack of P and K inhibited growth of crops given 144 kg N/ha. Crops grown without N grew more slowly than those given N but their growth was not further inhibited by lack of P or K. Deficiencies of either P or K increased N concentrations calculated on the basis of tissue water in crops given 144 kg N/ha but not in crops grown without N. The increase in concentration was not due to changes in the proportions of leaves and stems but to real increases in N concentrations in leaves, stems and ears. Drought decreased growth and also resulted in higher N concentrations in tissue water.

In the absence of other limiting factors, N concentrations expressed on the basis of tissue water were very similar for both N-sufficient and N-deficient crops. They increased only when growth was limited by factors other than N. The implications of this for the control of N concentrations by crops is discussed.

It is concluded that N concentrations expressed on the basis of tissue water are unlikely to be useful for determining the N requirements of barley. Percentage N in dry matter might be more useful for this purpose.