Vicia faba cv. Minden was precision planted at densities of 12–100 plants/m2 in 1977 and 30–60 plants/m2 in 1978 with and without seed-bed applications of aldicarb (10 kg/ha).

Nitrogenase activity per plant decreased significantly with increased plant density but this was compensated for on an area basis by increased numbers of plants. When expressed on the basis of area, nitrogenase activity was higher with closely, than with widely spaced plants both early and late in the season. Irrespective of planting density nitrogenase activity reached a peak during vegetative growth of the plant and a second peak during rapid pod and seed development. In 1977 the second peak was interrupted by very dry soil conditions but later activity increased following rain.

Aldicarb consistently increased nitrogenase activity at all harvests after Sitona damage to the nodules was evident. Over this period plots treated with aldicarb had twice the nitrogenase activity of untreated plots in 1977 and 55% more in 1978.

Carcasses of 129 steers from ten different sire breeds including dairy breeds, traditional British beef breeds and continental breeds were classified according to the shape of the tuber ischii-tuber calcis profiles of their hindquarter using a 7·point conformation scale. Conformation class was found to be related to both commercial and dissected carcass composition as well as the dimensions of seven hindquarter muscles. At the same carcass weight and fatness the muscle content of the hindquarter increased by 0·56 kg and the bone decreased by 0·13 kg linearly per unit increase in conformation class; the corresponding increase in the muscle-to-bone ratio was 0·07. The general trend for muscle dimensions was that the convex carcasses had shorter and thicker muscles than concave carcasses. A simple method of assessing carcass conformation based on three fundamental profiles of the hindquarter, from which the seven conformation classes were derived, permitted the grouping of carcasses according to their composition. Nevertheless the accuracy of the method may be improved with further investigation.

In tubers of ten potato varieties the incidence of internal rust spot lesions increased and the calcium concentration decreased when the concentration of calcium chloride supplied to the plants fell from 9 to 1 mM. A simple linear model relating the probit transformation of internal rust spot incidence to tuber calcium concentration for each variety showed that there were substantial differences in varietal susceptibility to internal rust spot which were not related to tuber calcium concentration.

Silage, dried-grass wafers and dried-grass pellets all prepared from a single crop of perennial ryegrass were given ad libitum as sole diets to six rumen-fistulated wether sheep.

Feed intake, intake of digestible nutrients and the concentration of volatile fatty acids (VTA) in the rumen were lowest with silage, highest with pellets and intermediate with wafers. Conversely, digestibility, eating and ruminating time per kg D.M. consumed, rumen pH, the rate of D.M. and cellulose digestion in the rumen and the mean retention time of digesta in the alimentary tract were highest for silage, intermediate for wafers and lowest for pellets. The pattern of rumen fermentation differed significantly between silage and the dried-grass treatments. The rumen fluid contained higher proportions of acetic, iso-butyric, n-valeric and iso-valeric acids, but lower proportions of propionic and n-butyric acids with silage than with dried grass. Differences in rumen. VFA between the two forms of dried grass were small. Nitrogen retention was lowest for the silage treatment and this was associated with a high concentration of ammonia in the rumen.

Low nitrogen status with silage could have limited voluntary intake, whereas the difference in intake between the wafer and pellet treatments probably arose from differences in the retention time of digesta in the alimentary tract.

A study was made in the unusually dry 1975–6 season of the distribution of extractable phosphorus and potassium, and of roots, in the top soil in the second year of direct drilling on a Denchworth series clay (with winter wheat), and in the fourth consecutive year of direct drilling on an Evesham series clay (with spring barley). With both soils there were greater accumulations of phosphorus and potassium in the upper 5 cm with direct drilling compared with ploughing. In the Denchworth soil there were smaller concentrations of phosphorus at all depths below 5 cm with direct drilling and in the Evesham soil this depleted zone was located between 10 and 15 cm depth. There was little extractable phosphorus at depths below 20–30 cm.

Measurements of the overall change in concentration of extractable nutrients at each depth between the beginning and end of the season suggested that there may have been contrasting patterns of depletion with cultivation treatments. Depletion was greater between 2·5 and 5·0 cm with direct drilling, and for spring barley on Evesham soil this coincided with the zone in which roots were most abundant. For potassium, there was an increase in the concentration in the 0–2·5 cm zone, apparently due to potassium loss from the maturing crops. At harvest, the total depletion of phosphorus from all zones between 0 and 50 cm depth was appreciably less than data (Cannell & Graham, 1979) on the content of phosphorus in the crop per unit land area, indicating that release from non-extractable reserves in the soil had occurred.

Despite the exceptionally dry summer of 1976, crop growth and yield were not adversely affected by the tendency for extractable phosphorus and potassium, as well as roots, to concentrate in the upper layers where desiccation could occur most readily. Possible reasons for this, as well as factors that may contribute to the observed patterns of distribution of nutrients and roots, are discussed.

The paper reports a laboratory study on miscible displacement of reactive solutes during leaching a highly saline-sodic soil rich in soluble sodium carbonate with solutions of calcium chloride. The effect of varying flow velocities, initial soil moisture content and concentration of calcium in the leaching water on the extent of carbonate precipitation and replacement of sodium by calcium from the exchange positions was studied in soil columns. The results showed that precipitation of soluble carbonates in the soil increased with increasing flow velocity, initial soil moisture content and concentration of calcium in the leaching solution. The results further showed that the calcium exchange capacity of the soil was reduced significantly and nearly proportionally with decrease in the degree of water saturation as a consequence of decreased water application rate and initial soil moisture content. In view of the results obtained, a simple model to describe calcium-sodium exchange under unsaturated flow conditions in saline-sodic soils under consideration has been proposed. Possible implications of the results in actual field situations is discussed.

The regrowth of Aberystwyth S. 23 perennial ryegrass, S. 24 perennial ryegrass, S. 59 red fescue and S. 170 tall fescue was studied in field swards, comparing four levels of applied nitrogen, for 8 weeks following a clearing cut. The clearing cuts were in mid-October, mid-February and mid-March in each of 3 years, different plots being used on each occasion.

Grass yield was more closely related to solar radiation receipt than to temperature. When radiation during the 3 or 4 weeks before a period of study was added to radiation during the 8-week period, to incorporate some allowance for temperature, the amount of additional yield per unit of additional radiation comparing the first spring period with the autumn period was about the same as that comparing the second with the first spring period. Where no N was applied, there was little or no increase in yield above ground level or above 4 cm from week 1 to about week 6 in the autumn and first spring period, whereas where N was applied yield increased steadily, though rather slowly, during those 5-week periods. Response to N, measured as kg dry matter above 4 cm/kg N applied, was about twice as great in the second as in the first spring period; on the other hand response to N measured as number of days saved in reaching a given yield was greater in the first than the second spring period. The positive effect of applied N on relative growth rate occurred mainly in the rather early stages of regrowth, which seems to be typical of any time of year.

Applied N increased the N and nitrate-N content of herbage and reduced the watersoluble carbohydrate content. Applied N increased the number of tillers and the proportion of yield above 4 cm. Yield below 4 cm was not much affected by N or by stage of regrowth. The ‘earliness’ in spring of S. 24, S. 59 and S. 170 compared with S. 23 was associated with greater height and a higher proportion of yield above 4 cm and not with higher above-ground yield. The ryegrasses responded more to N than the fescues in respect of yield above 4 cm and number of tillers. In 2 years in which the number of tillers was relatively low at the beginning of the spring periods of study, the number increased during those periods and there was a large positive effect of applied N, whereas, in a year in which the number was high initially, there was no increase during the periods of study and little response to N.

Grass silage (21.0 % D.M.) was given ad libitum to sheep together with supplements of rolled barley, dried-grass pellets or dried-grass wafers at 12 and 25 g organic matter (OM)/kg0·75.

Intake of silage was greater with supplement at 12 g/kg0·75 but total intake of OM and digestible organic matter (DOM) increased with increasing supplement. Intake of OM was higher with the pellet supplement than with other supplements. Intake of DOM, however, did not differ between the pellet and barley treatments, but was lower with wafers.

Concentrations of ammonia and total volatile fatty acids and the molar proportions of butyric and higher volatile fatty acids were higher when silage was supplemented with barley than with dried grass. Mean rumen retention times of silage and of supplement were highest in the barley-supplemented treatments. Dried-grass wafers were retained longer than dried-grass pellets. Supplement treatments did not differ significantly for eating and ruminating times, rumen fluid volume and pH, digestion rate in the rumen and nitrogen retention.

At the low supplement rate silage consumption may have been controlled by factors associated directly with the silage, whereas at the high rate intake was limited either by physical factors or by the potential energy demand of the animals.

Two experiments were made, each with 35 autumn-calving cows fed on complete diets containing 40–70% hay and 60–30% concentrates. In both experiments, cows fed to appetite on a diet containing 11 MJ metabolizable energy/kg D.M. for weeks 7–24 of lactation ate about 20% more than cows rationed according to yield, but produced only about 3% more milk. The cows fed to appetite gained more in live weight, but lost their weight advantage during the subsequent grazing season.

In Expt 1, a further group of cows were fed to appetite on diets progressively reduced in metabolizable energy content from 11·0 to 9·2 MJ/kg. Dry-matter intake decreased by about 1·2 kg/day per 1 MJ reduction in energy content. The lower dry-matter and energy intakes of cows on this treatment did not significantly reduce their milk yield, but their response when turned out to grass suggested under-nutrition in late winter. In Expt 2, increasing the energy content of the diet in early lactation (weeks 7–12) and reducing it thereafter had no significant effect on milk yield.

Within each treatment group there were reasonably close relationships between energy intake and energy requirement. Nevertheless, it seems likely that the efficiency of feed utilization of cows fed on complete diets will be low unless intake is controlled by energy dilution.

In previous studies of the reactions of groundnut varieties to infection with Cercospora arachidicola Hori and Cercosporidium personatum (Berk. & Curt.) Deighton, the existence of disease resistance has been demonstrated. However, these investigations have not resulted in the production of high yielding, disease resistant, varieties and it has been suggested that disease resistance is physiologically linked to low seed yield. In the present study, two aspects of the host–pathogen interaction were investigated: these were varietal response to chemical disease control, and the effect of plant sterility on host and pathogen development. It was found that a general score of resistance to leaf spot did not always relate to the varietal response to disease control and reasons for this were proposed. The prevention of pod production did not affect pathogen development, but vegetative growth of the treated plants was increased. It was concluded that host and pathogen development could be confounded during the assessment of disease resistance. In future varietal screening trials, the use of single branch comparisons should prevent this confusion.

The regrowth of Aberystwyth S. 23 perennial ryegrass, S. 24 perennial ryegrass, S. 59 red fescue and S. 170 tall fescue was studied in field swards, comparing four levels of applied nitrogen, for 8 weeks following a clearing cut. The clearing cuts were in mid-October, mid-February and mid-March in each of 3 years, different plots being used on each occasion.

The application of N increased the number of leaf primordia, the number of un-emerged leaves, the rate of leaf emergence and death, leaf blade length, width and weight, sheath length, number of leaves per unit area of ground and proportion of green tissue in total yield. The application of N had little effect on the number of leaves per tiller and tended to reduce weight per unit area of leaf blade. The increase in size, weight and number of leaf blades appeared to be major reasons for the positive effect of applied N on yield, previously reported; and the increase in sheath length contributed to the increase in proportion of yield above 4 cm. Rate of leaf extension was not closely related to yield and was more sensitive to temperature than was yield. Changes during regrowth in blade and sheath length helped to explain changes in weight per tiller, previously reported. The effects of improving weather conditions in late winter/early spring were similar to the effects of applied N: larger, heavier leaf blades, longer sheaths, a taller canopy, a lower proportion of dead material, younger leaves. The length of shoot apex per leaf primordium was relatively constant. Leaves continued to emerge, at a slow rate, in the period December–February. S. 170 had the biggest leaves, particularly in May, and the slowest rate of leaf turnover. Rate of leaf extension was increased by applied N more, on average, in the ryegrasses than in the fescues.

Urea is not efficiently utilized by ruminants mainly because of its more rapid (about 4 times) rate of hydrolysis than the corresponding uptake of ammonia by the rumen microbes (Bloomfield, Garner & Muhrer, 1960). A number of attempts have been made to slow down the release of ammonia either through the production of urease immunity (Sidhu, Jones & Tillman, 1968) or by complexing urea with starch (Deyoe et al. 1968) or with molasses (Chopra et al. 1974). The present communication reports the method of preparation and in vitro breakdown of urea-hemicellulose complex.

An experiment was carried out to study the effects of underfeeding during late pregnancy and early lactation on the structure and chemistry of liver and muscle of dairy cows. Two groups of cattle were fed at 60 and 40% of estimated requirements for maintenance and pregnancy or lactation for 13 weeks before and 13 weeks after calving, and one group was fed at maintenance level only for the same period. A control group was fed at 100% of estimated requirements for the same period. All groups were subsequently fed at the control level for a further 24 weeks.

Underfeeding resulted in significant changes in muscle and liver of dairy cows. In particular, there was a decrease in liver cell volume in the underfed groups and a persistence of post-parturient fat in the moderately underfed cows. Muscle fibre diameter was reduced and there was a loss of fast twitch oxidative glycolytic fibres in the underfed cows.

In two field experiments with winter wheat varieties, the grain yields per unit area calculated from entire plots 4·2 × 1·18 m were 25% greater than the yields of the centre row. This occurred mainly because the outer rows in the plots yielded 62% more than the centre row. When the yields were calculated on the basis of a plot width of 1·53 m (the distance from path centre to path centre across the long axis of a plot), it was estimated that they were 4% less than the yields of the centre rows. In the most extreme case when a short variety in a plot of this size was bordered by neighbours 70 cm taller, its yield, relative to that of the tall variety, was underestimated by 10–12%.

A separate experiment showed that the greater yield from plants at the edges of plots was associated mainly with more ears.

This experiment was made to determine the possible reason for deficiency symptoms seen on fenugreek (Trigonella foenum-graecum) in field trials during the dry summer of 1976. Using rockwool cubes for root support, it was shown that symptoms seen in the field plants resulted from boron deficiency.

The symptoms of boron deficiency in fenugreek are described and illustrated. The main symptoms were failure offloweringor fertilization, decreased apical growth, small crisped leaves in a terminal rosette and a gradual yellowing of the lower leaves. In combination with low nitrogen, the boron-deficient plants had yellow, succulent leaves at a very early stage. High calcium and high nitrogen increased the demand for boron.

Inoculation with Rhizobium meliloti of plants with a low nitrogen supply was performed with success. The bacteria formed healthy, pink nodules on the roots inside the rockwool cubes.

The lowest content of boron in whole plants showing boron deficiency symptoms (no pods formed) was 13 μg/g and in this respect fenugreek is very similar to lucerne (Medicago sativa), a plant known to have a high boron requirement. Fenugreek has a high tolerance of excess boron.

The magnitude of response to fertilizer-N and fertilizer-P decreased with increasing amounts of total soil-N and available soil-P, respectively. Attempts have been made to group the soils into N- and P-fertility classes based on the magnitude of response to applied fertilizers on soils of different fertility with respect to these two nutrient elements.

The efficiency of digestion and absorption is dependent upon the rate at which digesta moves through the gastrointestinal tract. The following report describes the gastrointestinal transit for digesta markers given to ten species of mammals fed the same diet.

In a field trial performed within a winter-bean crop (cv. Throws MS) during 1975, Benlate, Bavistin, Cercobin and BAS352F were shown to effect some control over a mild, non-aggressive chocolate spot attack after one foliar application. Following a second foliar application, disease incidence on the leaves was significantly reduced by all except the Cercobin treatment, and reductions in the incidence of aggressive lesions on the leaves and the degree of infection on the pods were effected by all except the BAS352F treatment, indicating this chemical to be non-systemic. A reduced rate of leaf loss was observed for plants treated with Benlate, Bavistin or Cercobin, suggesting that part of the disease control effected by these chemicals might indirectly result from a delay of leaf senescence.

The solitary larval parasite Microplitis rufiventris Kok was recorded for the first time in Egypt by El-Minshawy (1963), parasitizing the lesser cotton leafworm, Spodoptera exigua Hbn. Since it could be an effective summer parasite of the cotton leaf-worm, Spodoptera littoralis Boisd., studies on aspects of its biology by Hegazi (1976), and Hegazi, Hammad & El-Minshawy (1977) have been extended to include the effect of temperature on its development.

Three experiments were carried out over a 2-year period to study the effect of plant density and spatial arrangement and the time of lifting on yield and root size of carrots. Plant density treatments ranged from 108 to 1553 plants/m2 and plant arrangement was varied by growing the plants in 1-, 2-, 3-, 4-, 5-, 10-, 18- and 36-row systems within a 152 cm bed; there were either two or three harvests in each experiment.

Total plant fresh weight, total root yield and mean root weight were not significantly affected by plant arrangement over the range studied, but they all progressively increased with later harvests. The asymptotic relationships between these yield variables and plant density were adequately described by the equation of Shinozaki & Kira (1956), the relationships being significantly different for each harvest.

Yields of canning-size roots (20–30 mm diameter) were influenced by time of harvest, plant density and the interactions between these two variables. The yield of canning-size roots increased with plant density to a maximum and then declined, the maximum yield being achieved at a higher density with later harvests. In two out of the three experiments there was no effect of spatial arrangement on canning root yields but in the third experiment there was a significant row system × density × harvest interaction.

The numbers of roots harvested per metre of row did not differ significantly between the ‘outer’ and ‘other’ rows for any row system treatment. The mean root weight, however, was consistently greater from the outer rows of systems with three or more rows and this ‘edge’ effect became larger with later harvests.

The results are discussed in relation to other published data and to carrot production. It is concluded that any of the tested row systems are equally satisfactory for carrot production and the choice can be based on such considerations as the availability of suitable harvesting equipment.