The growth of kernels at selected positions along the spike of barley was studied using three models: segmented, logistic and Gompertz. The segmented model divides the growth period into three segments: an initial constant stage, a middle period of ‘linear growth’, and a final constant stage. The identification of a period during which growth is approximately linear - the ‘linear phase’ - was estimated from the curvilinear functions by imposing some criterion to determine the period of ‘linear growth’ in order that the results were similar to those from the segmented model. From this a model of final growth, growth rate and duration of growth as a function of kernel position was developed and fitted to data from four different thinning treatments at five sowing dates. The model of final growth and growth rate was shown to have a family of gamma functions. The analysis of these models showed that there were marked interactions between sowing and thinning treatments for growth rate, less so for grain yield, but there was no substantial interaction for duration.

The indices of susceptibility of five new varieties of maize: TZE 3 (3·01), TZE 4 (6·69), TZSR (5·58) developed at the International Institute of Tropical Agriculture, Ibadan, and MSRB-W (9·53) and MSC-opaque (5·0) at the National Cereals Research Institute, Ibadan, showed that the yellow variety, TZE 3, is the most resistant to post-harvest infestation by Sitophilus zeamais Motsch and Sitophilus oryzae (L.), the latterbeing the more abundant species.

Emerging F1 generation adults of either species of Sitophilusdeveloped longer, and were more numerous in soaked maize seeds without testa than in unsoaked, intactmaize seeds. Seed germinability declined as the number of holes per maize seed caused by adult insect emergence increased.

The utility of spraying some Na-fixing micro-organisms on rice (cv. Masuri and IR-26) and wheat (cv. Sonalika) leaves grown both in N2-less sand culture and under field conditions was examined. All the growth variables studied, including dry weight, chlorophyll content and N content of plants, were enhanced appreciably in N-less sand culture and under field conditions. The yield of rice cv. IR-26 per unit area was more than doubled or nearly so with Pseudomonas azotocolUgans, Ps. azotogensis, Klebsiella pneumoniae KUPBR2, K. pneumoniae KUP4, KUP6D, KUP7D, Azospirillum brasilense, Xanthobacter fiavus and K. rubiacearum. When rice cv. Masuri was used the grain weight was doubled by A. brasilense, Ps. azotocolUgans, Ps. azotogensis, KUPBR2, and KUP6D. Grain N content was increased appreciably in mostcases. The organisms also reduced acetylene to ethylene in the phyllosphere. In wheat cv. Sonalika grown in N-less sand culture, KUP4, KUPBR2, Ps. azotocolligans, A. brasilense, X. flavus, and KUP6D each doubled the N content of plants. Under field conditions Ps. azotocolligans gave the highest grain yield although grain yield was doubled by a large number of strains. N content of grains was also increased appreciably, the best result being given by KUP4.

A telemetry system based on calibrated radio transmitters implanted in the right sublumbar fossa of cattle is described. It was evaluated in different situations. Rectal temperature was used as a standard measure of body temperature. Implant temperatures were on average 0·2 °C higher than rectal temperatures. The magnitude of changes in the two temperatures in response to environmental stimuli were very similar but the implants changed faster in response to heat stress, feeding and exercise. When cattle were confined in unshaded yards the repeatability (within-animal correlation) of implant temperatures measured at different times of the day was 0·41 ± 0·05, compared with 0·30 ± 0·05 for rectal temperatures. It was concluded that there was less extraneous variation associated with telemetric measurement.

The telemetry system proved effective for monitoring the body temperature of grazing cattle within a range of 300 m. The repeatabilities of individual daily maximum and minimum temperatures were 0·43 ± 0·12 and 0·43 ± 0·11 respectively. Observations confirmed that cattle in part regulate their body temperatures by behaviours such as shading, grazing and exposure to wind. Thus body temperature whilst grazing was alone not a good index of physiological heat tolerance.

Two methods of storing pollen of the dihaploid-inducing Dutch (Wageningen) Solatum phureja clone, IVP 48, are described. Pollination results showed that the functional fertility of one type of stored pollen is similar to that of fresh pollen when used in dihaploid induction crosses on tetraploid potatoes. No obvious relationship was found between the in vitro germination of the pollen samples and their functional fertilities in dihaploid induction crosses.

A series of 24 standardized, replicated field trials comparing 47 fungicidal treatments for the control of spring barley mildew have been analysed. The joint analysis has enabled stronger conclusions to be drawn about the relative efficacy of treatments than examination of individual trials. To increase sensitivity the trials were divided into those with high or low mildew pressure. Under high mildew pressure, the treatments which gave the greatest control of mildew also gave the highest yields. However, within any given treatment the yield response appeared not to be closely related to the degree of mildew control achieved. It is concluded that effective fungicides may have a phytotonic effect as well as a mildew control effect.

The effect of moisture stress on N fertilizer needs of spring wheat (Triticum aestivum L.) was assessed using yield and meteorological data from N x P and N x P x K factorial trials, conducted on farmers' fields in a summer and a winter rainfall area in South Africa in 1979–84. Three to five rates of N fertilizer between 15 and 135 kg N/ha (plus control) and two to four replicates were used. The data were statistically analysed by a multiple regression yield model using applied N rate, N, and seasonal moisture stress, S, as the explanatory variables. A good positive correlation (r = 0.83, S.E. = 0.341 t/ha, D.F. = 48) was obtained between the estimated and the observed yields. The effects of S on Nmax and Novl (i.e. the N rates corresponding to maximum yield and an economically optimal rate, respectively), were evaluated. For 0.05 < S 7lt; 0.3, the range of S values representative of dryland cropping conditions, Nmax was largely independent of S, whereas Nopl increased sharply with decreasing S. The results indicated that N-response models which include moisture stress parameters may be used to determine the cropping areas climatically most suitable for wheat cultivation.

To investigate whether late pregnancy results in increased resistance to insulin action in ewes, a group of 18 crossbred ewes (six with twin foetuses) were given intravenous injections of glucose (0·25 g/kg) and insulin (0·25 U/kg) about 18days before full term and again during lactation, about 36 days after delivery. Before the injections, basal plasma concentrations of glucose, free fatty acids and growth hormone were lower during pregnancy than during lactation, but insulin concentrations were similar on the two occasions and cortisol concentrations were higher during pregnancy.

Rates of glucose removal and insulin secretory responses to the glucose injection were similar on the two occasions, both in ewes with single lambs and in those with twins. Insulin injection also resulted in similar decreases in glucose concentration on the two occasions in all ewes. Recovery from hypoglycaemia was somewhat delayed during pregnancy whencompared with lactation, but less so than in wether sheep given a similar injection of insulin. The plasma free fatty acid concentration decreased more slowly after glucose injection during pregnancy than in lactation. Responses of plasma cortisol concentration toinsulin-induced hypoglycaemia were similar on the 2 days, but plasma growth hormone concentration increased far more in lactating ewes after both injections.

The results did not indicate increased antagonism to insulin action in ewes during late pregnancy, but did show that changes in the counter-regulatory hormones after the disturbances to glucose homeostasis may differ markedly in the two situations and suggest that hyper-responsiveness of the system regulating growth hormone secretion contributes to the increased plasma growth hormone concentration observed in lactating animals.

Three varieties of triticale (TL-238, TL-257 and TL-319) bred by the Plant Breeding Department of Punjab Agricultural University were studied for nutrient composition and metabolizable energy (ME) content for egg-type chicks. A feeding trial was also conducted to study the suitability of triticale as a replacement for maize in conventional high- and low-cereal diets for different classes of egg-type chickens.

The crude protein contents of TL-238, TL-257 and TL-319 were respectively 13·4,14·4 and 2·1%. Corresponding values for starch content were 51·5, 49·2 and 54·3%, respectively. ME in triticale varieties closely followed the trend of starch content. Accordingly TL-319 was higher in ME (13·58 MJ/kg D.M.) than TL-238 and TL-257 (12·91 and 12·49 MJ/kg D.M. respectively). There were no significant differences in body-weight gain or in food conversion of chicks fed diets containing different varieties of triticale. The substitution of triticale for maize in a conventional high-cereal diet improved growth and food conversion of starter chicks. In a low-cereal diet, however, triticale had an adverse effect on the growth rate and food conversion of starter chicks. At the end of 18 weeks of age, the differences in body-weight gain, food conversion and efficiency of protein utilization by chicks on all the treatments were not significantly different (P > 0·05). Results of the production phase showed that egg production, egg mass, food conversion and energetic efficiency were significantly (P < 0·05) improved by feeding triticale.

1. Eighty-six bull calves (fifty-two Friesian, twenty-two Ayrshire, twelve Shorthorn) were examined at intervals, during the first year of life, by a method which allowed classification of the degree of adherence between penis and sheath into five classes.

2. Mean age and weight at which separation between penis and sheath commenced and was completed are recorded for each breed. Significant breed differences were found.

3. The rate of separation accelerates as development proceeds.

4. The relationships between age, body weight, and commencement and completion of separation in the Friesian bulls are analysed by correlation methods. These analyses suggest that both age and body weight are important in sexual development.

5. An equation is given for the linear regression of age at completion of separation on age and weight at commencement of separation and weight at 10 weeks for the Friesian bulls.

1. The effects of different levels of first-winter nutrition over 3 years were studied on the subsequent dental development of groups of North and South Country Cheviot ewe hoggs (sheep between months and 1½ years) by recording the time eruption of each of the four pairs of permanent incisors. High-plane first-winter feeding resulted earlier eruption of the first pair of permanent incisors. Later pairs were affected to a lesser extent, with low-plane/hill-wintered groups consistently the latest to erupt. Breed and year deviations from the general pattern were small and were largely due variations in growth rate both prior to and during treatment.

2. The effects of first-winter treatment were also studied on the heavy and light hoggs (i.e. those above and below average weight) prior to treatment. Although there was only a very limited difference the time of eruption of the heavy and light within each treatment group, the effects of treatment were greater in the heavy-weight class than they were the light.

3. The effects of first-winter treatment on dental efficiency and long-term persistence were also studied. There was little difference amongst treatments at 5½ years of age in the bite position, or looseness, wear, or condition of the teeth. Brokenmouth, i.e. the loss of one or more permanent incisors, did not appear in significant proportions until 7½ years of age, when considerable treatment, breed, and year differences were present. The incidence of broken-mouth was lowest in the high-plane and hill-wintered groups and highest in the lowplane and mid-plane/away-wintered.

1. Two experiments are described in which the effects of grazing a lucerne/cocksfoot ley at various intervals throughout the season were examined, together with the effects of a June hay cut and an autumn rest period. The results are discussed.

2. In the year of treatment: (a) The wet year 1954 favoured the grass fraction and the dry year 1955 favoured the lucerne fraction but, in general, the proportion of lucerne in the sward decreased as frequency of defoliation increased. (b) The largest yields of lucerne dry matter were obtained from treatments that included a June hay cut and the largest yields of grass dry matter came from those treatments that included an autumn rest period, (c) Within the chosen programmes of defoliation, there was a tendency for greater yield of dry matter from those treatments defoliated four times when compared with one cut three times, but yields from treatments defoliated more frequently tended to be smaller, with a marked reduction from seven grazings.

3. In subsequent years: (a) Treatments in the wet year had a greater effect on subsequent lucerne vigour than treatments in the dry year, (b) Yields of lucerne dry matter from three hay cuts in the first residual year were reduced by all the grazing treatments, the greatest difference occurring at the first cut. Lucerne yield decreased with increasing frequency of treatment defoliation. There was a tendency for the autumn rest period to increase lucerne yield and for the June hay cut to reduce it. (c) Total grass dry matter yield was greatly increased by grazing treatments, the majority of this difference occurring at the first cut, and it also increased with increasing frequency of treatment defoliation. (d) The proportion of cocksfoot in the grass fraction of the sward was reduced by treatments that included defoliation during the period September–October, and it was further reduced by treatments that included a June hay cut. (e) In the second year following treatment the effect of grazing on the grass fraction had disappeared but reductions in lucerne vigour from too frequent defoliation were still evident, though reduced.

4. Grazing a lucerne/cocksfoot ley reduced the subsequent vigour of the lucerne more than would have been expected from cutting it a similar number of times. This reduction is attributed to increased competition from the grass arising from its response to nutrients in the excreta of the grazing animals. In a wet year four grazings caused a permanent reduction in lucerne vigour and more frequent grazing almost eliminated the lucerne, but in a dry year four grazings caused only a temporary reduction in lucerne vigour and had no lasting effect.

5. The interval between defoliation and the subsequent onset of flowering in the lucerne was very much less in the hot dry year than in the cooler wet year. There appeared to be a relationship between the onset of flowering and the ability of the lucerne to recover from defoliation.

Progenies of randomly chosen plants from spaced plant populations of four American and one African variety of Gossypium hirsutum L. were grown in replicated single-plant plots at Kimberley Research Station in 1967–68 (all varieties) and 1968–9 (two varieties only) to estimate intra-varietal parameters of genetic variability.

Estimates of broad-sense heritability were usually similar when derived from components of variance on either a one- or two-season analysis basis or by parentprogeny regression Heritabilities were in general lowest for lint yield and boll number and highest for lint percentage. Mean value of heritability for lint yield and boll number, considered consistent enough on a varietal and seasonal basis to allow averaging, was about 0·15. Components of variance estimates of heritability on a single environment basis for other attributes ranged as follows: boll weight from 0·05 to 0·56, lint percentage from 0·29 to 0·80, mature height from 0·00 to 0·51, micronaire value from 0·20 to 0·63 and Pressley strength index from 0·05 to 0·56.

Genetic coefficients of variation showed an opposite trend to that for heritability: lint yield and boll-number values were large and lint percentage, micronaire value, and Pressley strength indices small. Expected responses to selection for the top 2·5 % of the population for lint yield and boll number at around 10% were usually higher than for other attributes.

Genotypic and phenotypic correlations were mostly similar but correlations often deviated widely between varieties. Positive lint yield correlations with micronaire value and negative lint yield correlations with Pressley strength index were recorded; these are often undesirable associations for breeding.

The association between the period of maintenance under Ord conditions and variability shown phenotypically in the original populations was not evident from the quantitative inheritance studies. Residual variability following breeding was considered as accounting for the larger portion of the genetic variability.

In 4 consecutive years, 1948 to 1952, combined varietal and manurial trials were carried out to obtain information on the yields of marrow-stem kale, thousand-head kale and cattle cabbage in the presence and absence of sulphate of ammonia applied as a top-dressing at the rate of 6 cwt./acre.

Yield and composition of all crops were apparently affected by differences in weather conditions. In most years, and particularly for cabbage, the yield declined with successive harvests.

Increased green crop, dry matter and crude protein yields resulted from the application of nitrogenous fertilizer in 3 years, but in the other year, a very dry season, the response to the top-dressing was negligible.

Marrow-stem kale both with and without the additional fertilizer, yielded more, in terms of fresh crop, dry matter and crude protein, than thousandhead kale with the same manurial treatment. Cabbage yields often approached those of marrowstem kale at the first harvest, but were nearer to those of thousand-head by the last harvest of each year.

In a field experiment in the north-west region of Tasmania, poppies (Papaver somniferum L.) were harvested at weekly intervals beginning 10 days after full bloom and continuing until 4 weeks after the dry commercial harvest stage. At each harvest the plants were cut off at ground level and partitioned into terminal capsules, lateral capsules, seed and the combined stem plus leaf component.

The dry-matter yield of total plant and of all the components except seed achieved maximum values 2–3 weeks after full bloom and then progressively declined. For the total plant this decrease between maximum dry weight and that at the time of commercial harvest (8 weeks after full bloom) amounted to 26% while for terminal capsules it was 37% for lateral capsules 15% and for stem plus leaves 39%. In contrast, the dry-matter yield of total seed rose to a maximum by 4 weeks after full bloom and then remained constant for the duration of the experiment.

The morphine concentration of both terminal and lateral capsules reached a maximum value of 1·1% 6 weeks after full bloom and then decreased by about 10% at the dry harvest stage. The morphine concentration of stem and leaves also reached a maximum of 0·1% about the same time as capsules but decreased rapidly and had halved by dry commercial harvest. The mutually compensating factors of decreasing dry-matter yield and increasing morphine concentration gave similar total plant morphine yields at any time of harvest from 2 to 7 weeks after full bloom. The morphine extracted from the whole plant at these times of harvest was about 50% greater than that derived from capsules alone at the time of dry commercial harvest.

An experiment was conducted over a 2-year period at two sites in the central rainlands of Sudan under rainfed conditions at one location and under supplementary irrigation at the other to investigate the effects of cultivars and spacing on yield and yield components of sunflower. Row spacing had no significant effect on grain yield under either system of production. Under rainfed conditions, the late maturing cultivar Manchurian performed better under wider row spacing than Hungarian-A which is a medium late maturing variety. Size and number of seeds weie significantly affected by row width. It is argued that the choice of a row spacing for sunflower production on a commercial scale in dry regions should be evaluated in association with machine efficiency which is affected by plant height, stem circumference, head diameter and lodging, all of which were significantly affected by row width. Also the number of plants established per unit area of land differed between systems of farming.

1. Studies on the mineralization of the skeletons Scottish Blackface wethers and breeding ewes have been carried out on three widely scattered and differing Scottish hill farms using field radiography and bone-ash analysis.

2. Regular small autumnal improvements in the density of the ewes' skeletons were detected by in vivo radiography using the right radii although, in general, the radii of the ewes were at all times considered to be in good condition (for Scottish Blackface sheep on the hill) and underwent no marked resorption (as judged from in vivo radiographs) during pregnancy and lactation. This was contrary to what was expected in view of the results of previously reported laboratory experiments (Benzie et al. 1955, 1956, 1959) and also in view of commonly held beliefs that hill pastures are, in general, deficient in calcium or phosphorus, or both of these dietary factors.

3. There were few significant flock differences (both ewes and wethers) for the values assigned to the radiographs or for the results of skeletal ash determinations even though the flocks were maintained in widely separated and differing locations and husbandry systems.

4. It is suggested that further field work along these lines may be of great value to the obtaining of a clearer understanding of the ewe: hill pasture relationship.

Adult Merino wethers were fed for 16 weeks on diets of oat straw mixed with urea and pelleted (A); oat straw pellets, with access to a salt block (B); oat straw pellets, with access to a salt-urea block (C); Phalaris straw mixed with urea and pelleted (D); and Phalaris straw pellets (E). A commercial mineral supplement was given during the first 8 weeks, and a laboratory-prepared complete mineral supplement supplied during the second 8 weeks. During the fifth to eighth weeks (period I), and the thirteenth to sixteenth weeks (period II), digestibility and balance studies were conducted on sheep from each treatment.

Digestibilities of organic matter (O.M.) and cellulose were generally increased by the addition of urea, but only in one comparison, between diets A and B, was the difference significant. Urea did not significantly affect water intake in relation to food intake.

Urea increased nitrogen (N) intake, faecal and urinary N excretion, and N balance, these effects being more pronounced in period II. All sheep were in negative N status in period I; five of the 12 urea-fed sheep were in positive N status in period II. In diets B and C water intake and urine output were positively related to salt intake, but in no diet was there a significant relation between urinary N excretion and total output of urine.

Sulphur balances (excluding wool) were generally positive and did not improve significantly in period II despite higher sulphur intakes. However, a corresponding increase in the intake of phosphorus, from 0·5 g/day to about 2·0 g/day, brought nearly all sheep from negative to positive phosphorus balance. With the urea diets there was a significant, negative relation between urinary N excretion and phosphorus balance.

Intakes of sodium, potassium, calcium and magnesium appeared to be sufficient in both periods.

It seems likely that the improved response to urea which occurred during the experiment was due to the change in mineral supplementation rather than to adaptation to urea.

Two greenhouse pot experiments were conducted to evaluate labelled concentrated superphosphate (CSP) and labelled dicalcium phosphate (DCP) alone and in mixtures for maize grown on soils low, high and very high in available P. On the low P soil yield of dry forage, total uptake of P and uptake of fertilizer P increased linearly with 0, 20, 40 and 80 ppm of P applied as the various fine and granular sources varying widely in P water solubility. Hence, all of these criteria were highly correlated and suitable for evaluating effectiveness of the P on the low P soil. On the soil high and very high in P, only uptake of fertilizer P, which also increased linearly with rate of application, was suitable for evaluating the sources. Total uptake of fertilizer P decreased with increase in soil P level, but relative differences among granular sources were similar at the three soil P levels. Effectiveness of the P fertilizers decreased markedly with decreasing water solubility of the granular sources on all soils; the same trend was true for the fine sources at high soil P levels.

Actual uptake of fertilizer P or percentage recovery of labelled P applied was a better basis for source evaluation at high soil P levels than were calculated A values. There was little advantage in this study of labelling with 32P for P source evaluation at the low soil P level over use of multiple rates of the unlabelled fertilizers. However, labelling was essential at the higher soil P levels.

1. Seven experiments on spring barley and five on spring wheat carried out in 1955–7 compared dressings of ammonium sulphate and calcium nitrate applied to the seedbeds at 0·3 and 0·6 cwt. N/acre. The fertilizers were tested both when broadcast and when drilled with the seed.

2. Consistently higher yields of barley were produced by drilling than by broadcasting ammonium sulphate. Drilling calcium nitrate at 0·3 cwt. N/acre was superior to broadcasting for barley but when applied with the seed at 0·6 cwt. N/acre this fertilizer retarded germination and early growth and gave smaller yields than were obtained by broadcasting. Broadcast dressings of both fertilizers gave higher yields of wheat than combine-drilled dressings. There is a considerable risk of fertilizer ‘scorch’ when compound fertilizers containing all their nitrogen in nitrate form are combine-drilled at rates sufficient for maximum yield. This risk may be discounted when adequate rain follows drilling but the check to germination may be sufficient to reduce yields in dry springs, on light soils, and on badly prepared seedbeds. Fertilizers containing all their nitrogen in ammonium form appear to be quite safe at the rates of dressing tested in this work.

3. Calcium nitrate and ammonium sulphate gave similar yields and nitrogen contents of both crops when the fertilizers were broadcast on the seedbed. Nitrates applied at sowing-time to cereals grown in the drier parts of the country do not appear to be leached out of the root-zone before they can be taken up by crops.