The ability of two chemicals, Benlate and BAS352-04F, to control chocolate spot (Botrytis fabae) disease of field beans (Vicia faba) was examined in five small-plot or field experiments. The incidence of the fungus was never such as to reach the aggressive stage naturally, although severe infection was induced temporarily in certain experiments by enclosing the plots in plastic-covered boxes after inoculation with fungus. Increasing the recommended dose of BAS352-04F but not Benlate resulted in improved control and applying either chemical twice was preferable to a single application. Control by BAS352-04F was sometimes better than Benlate in the early days after infection whereas the reverse was true later. These results are in keeping with their roles as contact, and systemic and contact fungicides respectively. In these small experiments, with low levels of infection, the use of fungicides did not result in significant increases in yield or yield components.

Effects of 0, 1·7, 3·3 or 5·0 kg/day of a protected soya bean – tallow supplement, incorporated into a hay:concentrate diet (25:75) and fed ad libitumto Friesian cows, on intake and digestion of fatty acids, on output of milk fatty acids and on blood lipoprotein composition were measured.

Most of the increased intake of fatty acids, approximately 1 kg/day, was accounted for by increased intakes of C16:0, C18:0 and C18:1. At low intakes, amounts of all fatty acids apparently digested were linearly related to their respective intakes. At high intakes of C16 and C18 acids, curvilinear relationships were established.

Yield of total milk fat was related positively to dietary intakes of total fatty acid and carbohydrate and negatively to live-weight change. Yields of short and intermediate chain acids in milk, synthesized within the mammary gland, were negatively correlated and yields of C18 fatty acids positively correlated with respective dietary intakes of these acids. Decreased proportions of C4–16 and increased proportions of C18:0 and C18:1 fatty acids in milk were associated with increased protected tallow in the diet. Yields of C16:1 and C18:1 were positively related to corresponding outputs of saturated acids and negatively to weeks of lactation. The proportion of C18:1 in milk was positively related to the corresponding proportion of C18:0.

The increased intake of fatty acids resulted in increased concentrations of very low density lipoproteins (VLDL, d < 1·019 g/ml), low density lipoproteins (LDL1 + LDL2, 1·019 < d < 1·06 g/ml), high density lipoproteins (d > 1·060 g/ml) and serum free fatty acids. Most of the increase in low density lipoproteins was accounted for by a very large increase in LDL1, whose proportion increased from 17 to 75% (2 to 22% of total serum lipid). The proportion of triglyceride in the combined low density lipoprotein fraction decreased from 11 to 2% whilst phospholipids increased from 29 to 36%. These changes were attributed to the increased proportion of LDL1 present.

The proportions of VLDL and LDL triglyceride taken up by the mammary gland averaged 0·79 and 0·34 respectively. The proportion of VLDL+LDL triglyceride taken up by the gland decreased with increased amounts of fatty acid digested. Yields of C18 fatty acids in milk tended to be positively related to apparent uptakes of VLDL triglyceride and to VLDL C18 fatty acids, but negatively related to apparent uptakes of LDL triglycerides and LDL C18 fatty acids. It is suggested that the increased LDL1 resulted from the utilization of VLDL triglyceride for milk fat formation.

Protected lipid feeding increased the proportion of C14:0, C16:0 C16:1 and C18:1 and decreased the proportions of C14:1 and C18:0 fatty acids in jugular serum triglycerides. Similar changes were observed in jugular VLDL triglycerides. Differences in the compositions of VLDL and LDL triglycerides across the mammary gland were observed and attributed either to selective uptake or to interchange of fatty acids between triglycerides and free fatty acids.

Weekly blood samples were collected from 42 Friesian cows between 5 weeks before and 10 weeks after calving, and analysed for serum cholesterol, albumin, total protein, glutamate-dehydrogenase, sorbitol-dehydrogenase and ornithine-carbamyl-transferase and blood glucose.

Cholesterol concentrations increased 2½-fold during the first 8 weeks of lactation. There was also a transient decrease in glucose concentration at calving, but there was no relationship between conception rate and the concentrations of these two constituents.

Albumin concentrations decreased at calving in some but not all cows and remained low for up to 2 weeks. Average concentrations of albumin determined by two analytical methods, a HABA dye-binding and a single radial diffusion assay method, were significantly lower (P < 0·05) between 0 and 2 weeks post-partum in eight cows which required four or more services than in 32 cows which conceived after fewer services. Similarly, the average decrease in concentration over calving was greater in those cows which conceived only after four or more services (P < 0·01).

Globulin concentrations (total protein minus albumin) decreased during the 5 weeks before, and increased in the 3 weeks following calving. The net change over calving was significantly related to conception rate, and the albumin/globulin ratio was reduced (P < 0·001) in the eight cows requiring four or more services.

Activities of all three enzymes doubled after calving, but there was no correlation between these increases and the decreases in albumin concentration, suggesting that, if liver insufficiency is a factor, it is probably due to malfunction rather than tissue damage.

Height variability in spring wheat (Triticum aestivum L.) cultivars permits growing them in systematic mixed stands and such mixtures are reported to lead to better utilization of solar radiation. Studies on such wheat mixtures are limited. A field experiment was therefore conducted for two wheat seasons (1974–5 and 1975–6) at the Indian Agricultural Research Institute, New Delhi, to compare the yield potentials of the mixed and pure stands of three spring wheat cultivars varying in plant height. Two kinds of canopy stands, namely, pyramidal and columnar, were created by making appropriate row arrangements of the cultivars while seeding. Mixed stands gave significantly higher straw yields and the grain yield was also significantly higher than the highest yielding cultivar in its pure stand at a high rate of nitrogen application (120 kg N/ha).

A long-term manurial experiment on potatoes was initiated in 1970 on the acidic brown hill soil of Simla to study the effects of fertilizers supplying per hectare: 44 kg P (P44); 44 kg P and 125 K (P44K125) and 88 kg P with 125 kg (P88K125) and of farmyard manure (FYM) supplying 44 kg P/ha applied annually and biennially. The potatoes gave large responses to all the manures. The annual or biennial effects of FYM measured in years of application were as great as that of P and K fertilizer in increasing tuber yield and K uptake by tubers but FYM increased P uptake more than fertilizers did. FYM applied each year gave largest uptake of P. P88 treatment was not better than P44 treatment. The residual effects of the manures on yield were measured in years when the treatments were not applied; the residual effects of FYM were higher than those of fertilizers. Mean residual effects of the treatments on P uptake were 46% and 51% of their annual or biennial effects respectively. About 90% of P added to the soil was not taken up by the crops and was present in the forms of aluminium-bound P, iron-bound P and calcium-bound P in this descending order. The residual effects of the treatments on K uptake were about 84% of their annual or biennial effects. About 60% of K applied to the soil was not taken up by the crops and most was present in exchangeable form. Annual applications of all the manures were better than their biennial applications indicating that residual effects built up from three applications over 6 years were too small to sustain yields.

Soil analyses made 6 years after the start of the experiment showed that FYM was a better source of P than single superphosphate in increasing soil available P. FYM also increased soil exchangeable K more than the K fertilizer did. The highest increase in available P and K in soil was from annual applications of manures. Biennial applications of P as superphosphate or FYM resulted in P accumulating in the soil, while biennial K fertilizer dressings did not increase exchangeable K; however, biennial FYM did increase exchangeable K. Using P alone reduced soil available K. FYM increased pH, organic carbon and total N in soils while P and K fertilizer increased only the pH.

The nature of genetic variation in an intervarietal cross (J 34 × SS 167) of upland cotton was determined for seed cotton yield, number of bolls, weight of 100 seeds, ginning outturn and halo length. The materials consisted of six generations (P1, P2, F1, B1, B2 and F2) which were raised at two locations. In those cases where the additivedominance model was inadequate, models with different numbers of parameters were applied along with the six-parameter model. A consistent and high negative correlation was observed between [h] and [l], and [i] and [l] in all the models at two locations. Correlation between [d] and [i] was also consistent and negative, but its magnitude was low. Dominance and dominance × dominance, and additive × additive and dominance × dominance components were found to be antagonistic in effects to each other and the interactions observed were of duplicate type, i.e. [h] and [l] had opposite signs.

The dominance component fluctuated greatly over models for a particular character at a particular location. Contrary to this the additive component was observed to be important and consistent over models at a particular location for a particular character. Also this was the only significant component involved in the inheritance of all the characters at both the locations. The expression of different components of variation was highly influenced by the environmental effects.

Field experiments were made for 3 years (1975–8) on soils deficient in both available N and S to test the effects of these nutrients applied as fertilizers on yellow mustard (Brassica campestris L.) and mustard (Brassica juncea L.).

In all the 3 years, grain yield of both mustard crops significantly increased with increased N rates. The grain response to added S was not consistently significant, however; maximum yields were obtained only when high rates of N and S were applied together. N and S fertilizer significantly increased the concentration and uptake (kg/ha) of N and S in grain, and there was a significant positive N × S interaction. Adequate N/S ratio appears to be 7·5:1 or less for the grain of these mustard crops. Protein content of grain improved markedly with applied N and S. Application of 60 kg S/ha increased the oil content by 12% in yellow mustard and 16% in mustard. Although N had little effect on percentage oil, total oil production increased many fold. The combined application of N and S had the largest effect in determining the concentration and uptake of N and S, and on protein and oil content in grain. This study indicated that additions of 60 kg S/ha to mustard crops receiving adequate fertilizer N are likely to improve their yield and quality.

The N, P and K contents of leaves, straw and grain of the durum wheat Kyperounda, the aestivum wheat Pitic 62 and Athenais barley under semi-arid conditions (150–400 mm) as influenced by N and P fertilizers are reported (N rates: 0–105 kg/ha; P rates: 0–26 kg/ha).

Fertilizer N increased linearly the N content of the leaves, straw and grain as well as the K content of leaves and straw, but slightly reduced P content of the grain. Straw K content was increased relatively more in Athenais barley. Such increases of N and K content occurred beyond the N rates giving maximum grain and sheaf yields. Increased K content of the straw resulting from fertilizer N is wasteful where the straw is removed, and accelerates depletion of soil K. Durum wheat grain containing more than 2–8% N showed less than 6% yellow berry (mealy grains) but at lower N contents yellow berry could be high or low depending on location.

Fertilizer P did not significantly influence the P content of any of the components analysed even though it increased grain and straw yields, particularly in the drier years.

The adsorption of oxamyl under various conditions of time, pH, temperature, organic matter and exchangeable cations on illites and kaolinites was examined. The first order reaction indicated diffusion-controlled adsorption, maximum adsorption occurring at pH 6–5 which is near the pK value of oxamyl. Exchangeable cation in the order Na > H > Ca, organic matterand increasing temperature decreased adsorption. Adsorption isotherms and the molecular structure of oxamyl point to a reaction mechanism for oxamyl association with acid- and base-saturatedclays which involve either protonation or co-ordination of exchangeable clay cations to the carbonyl of the amide structure.

After a preliminary period in which they were all fed maize straw plus a proteinmineral supplement, 18 Merino wethers were divided into six groups and fed straw, proteins and minerals as before, plug pellets containing maize grain so that these constituted 0, 78, 156, 235, 313 and 393 g/kg of the total daily intake.

The diets provided sufficient protein so that NH3 and branched-chain volatile fatty acids were not limiting for growth of the fibre-digesting bacteria in the rumen.

The intake of straw, the digestibility of cellulose and hemicellulose, and the mass of cellulose and hemicellulose digested per day declined linearly as the proportion of pellets in the diet increased above 78 g/kg. This decline was not related to the pH of the ruminal contents which was unaffected by the feeding of up to and including 235g pellets/kg diet, and which, with one exception, was only 2–6 pH-hours below pH 6 when more grain was fed.

As the proportion of pellets in the diet increased the number of cellulolytic bacteria in the rumen declined to an extent which correlated well with the decrease in mass of cellulose digested per day. There was no change in the relative proportions of the predominant genera.

There was no decrease in the number of xylanolytic bacteria in the rumen as more pellets were fed, but there was an indication of a change in the predominant genera producing diffusible xylanases.

It is concluded that some factor, in addition to nutrient limitation and pH, may play a role in the decrease in intake and digestion of roughage when starch is fed. It is suggested that starch or sugars derived from it may per se inhibit the synthesis and/or activity of the rumen cellulases and hemicellulases.

In a field study, the effect of N, P, K and their combinations on the growth, yield and nutrient uptake pattern by mesta (Hibiscus cannabinus L.) was studied. No effect of N, P, K on growth characteristics like plant height and base diameter occurred up to 60 days. Effect of fertilizer treatments on plant growth was observed only after 90 days. The effect of N was more pronounced than P and K. Initially, growth of leaves was higher than both the bark and the wood. Nutrient concentration was at a maximum in the early stages of growth but declined with age and became steady at about 60 days. The quality of fibre obtained after 120 days of growth was assessed and the effect of nutrients on quality is discussed.

Linear relationships between both total and tuber dry-matter yields and the amount of radiation intercepted by potato crops are demonstrated. Their existence suggests that, in the absenceof disease and drought, the essential objective in the production of this crop is to maximize radiation interception. This paper critically assesses the influence of factors which the grower can control on light interception and estimates potential yields for specific environments. The implications of this analysis for growers, breeders, research and the whole industry are discussed.

The present study was carried out on 39 local Awassi ewes. After parturition, lambs were left to suckle their dams for the first month of age, after which they were separated into two suckling regimes, restricted and continuous.

The average milk yield of ewes in the continuous system was 155·7 kg during the lactation period of 167±6·1 days whereas that of the restricted system was 139·8 kg during a lactation period of 183 ± 5·7 days. However, differences were not significant. Significant differences (P < 0·01), in favour of the continuous system, occurred in the amount of milk suckled by lambs in the different suckling systems from the 8th week onwards till weaning. Measured hand milk showed no significant differences between the two regimes.

Averages of butter fat percentages were 5·63 and 6·69 in the continuous and restricted systems respectively. The total percentage suckled milk, regardless of suckling regime, was 36·7 ± 1·99; averages were 41·6 ± 0·89 and 31·7 ± 3·52 in the continuous and restricted systems respectively.

The averages of commercial milk production from the 9th week after lambing until the end of lactation were 45·9 and 61·7 kg in the continuous and restricted systems respectively (P < 0·01). Averages of butter fat quantities in the commercial milk yield were 3·25 and 5·03 kg in the continuous and restricted systems respectively (P < 0·01).

The weights of lambs in the two suckling regimes started to differ significantly from the 14th to the 46th week of age; lambs reared under the continuous system were 4 kg heavier at the yearling age than those of the restricted system.

It might be worth considering weaning and selling extra lambs at 3 months of age to make full use of the high growth rate encountered in this period. The breeder could also obtain 11·4 kg more milk from ewes from 9 to 17 weeks after lambing in the restricted system than those in the continuous one. It might be advisable to use the restricted system and wean the lambs at 12 weeks of age; the excess milk obtained will outweigh the extra gain in body weight of 1·52 kg encountered in the continuous system.

Maize and cowpea were grown at various replacement ratios (100/0, 67/33, 50/50, 33/67 and 0/100) in field experiments. The experiments were carried out during the early growing seasons of 1977 and 1978 at Ibadan in the rainforest zone of Nigeria. A maize cultivar (FARZ 17) and three cowpea cultivars (Ife brown, New Era and TVu 4557) were used.

Maize sown alone gave a greater yield than all mixtures. The yield of New Era cowpea was no less when grown in mixture with maize than when grown alone; indeed when grown in a 50/50 mixture it was significantly greater.

During the dry summer of 1976, measurements were made of the photosynthesis, transpiration, respiration, and growth of irrigated (I) and non-irrigated (NI) spring barley growing in large field plots. Using a field enclosure, the photosynthesis of the irrigated barley was measured on 19 separate days during the latter two-thirds of the growing season when the plants were large enough to have measurable gas exchanges. The response of photosynthesis to water stress was determined from 3 days' comparative measurements on the I and NI crops, using both the field enclosure and, on 2 days only, a single-leaf photosynthesis chamber.

Water stress in the NI crop caused large decreases in yield: the dry-matter yields of grain and straw were respectively reduced by 19 and 27%; number of grains (but not grain mass) was also reduced. Field enclosure measurements, which were in good agreement both with values for canopy net photosynthesis derived from the leaf chamber measurements and with estimates of dry-matter production derived from plant weighings, indicated that the net CO2 uptake per unit leaf area was little affected by water stress. Results from the plant weighings and mensurations showed that, during the growing season, the main effect of water stress, mediated by the survival of fewer tillers and the premature senescence of leaves, was a reduction of leaf area (by 40%).

Two experiments, involving a total of 112 sheep, are described, in which ewes at different reproductive states were given complete diets with a varying grain: straw ratio. In Expt 1 ewes at three reproductive states (dry, pregnant and lactating) were given diets with four levels of coarsely ground oat straw (10, 25, 40 and 55% straw). In Expt 2 ewes in five reproductive states (early pregnancy, mid pregnancy, late pregnancy, lactation and dry) were given a basal diet similar to that given in Expt 1 but with five levels of straw (15, 25, 36, 45 and 55% straw).

The results showed that the intake of ewes varied with reproductive state, the highest intakes occurring during lactation. No significant diet × reproductive state interaction was observed which suggests that in ewes the physiological state can override some of the physical limitations to intake imposed by increased dietary roughage concentration.

The leaf growth, carrying capacity and dairy production of four summer-growing pastures were measured in a subtropical area of Australia. The growing season was subdivided into ten 4-week periods and the production was estimated for each period. Carrying capacities were determined by rotationally grazing four paddocks of each pasture over the 4-week period, and varying the stocking density so that a target weight of leaf material remained on the pasture at the conclusion of each grazing.

A non-limiting rate of nitrogen fertilizer increased total leaf production of kikuyu by 97% over a control treatment without nitrogen, but the response was not evenly distributed throughout the season. It fell to 50% during autumn when growth on the nitrogen-fertilized pastures was restricted following heavy defoliation during late summer. The use of the tropical legumes, siratro and glycine, in a mixed sward with kikuyu, did not increase leaf production over a kikuyu control pasture. The legumes grew poorly and this appeared to be due to the combined effects of their poor adaptability to the krasnozem soil, a high plant mortality especially during the first winter after sowing, the 4-week grazing interval and strong grass competition.

The carrying capacity of the nitrogen-fertilized pasture was 1·3–5·3 cows/ha at the beginning (September–October) and end (April–mid June) of the growing season, and increased to a peak of 7·4–9·7 cows/ha during February-mid March. Nitrogen fertilizer increased the carrying capacity by an average of 131% over that on a kikuyu pasture without nitrogen. The carrying capacities were similar on kikuyu and on a mixed carpet grass-kikuyu pasture, both without nitrogen, but were less on a tropical legume-kikuyu pasture which was grazed at a lighter grazing intensity during autumn to aid legume persistence.

Reflecting the experimental method of adjusting the stocking density according to the pasture available, differences in dairy production per cow were small relative to differences in the carrying capacity. Consequently seasonal variation in total dairy production/ha mirrored the carrying capacity. Nitrogen fertilizer increased the average production of 4% fat-corrected milk to 13·2 t/ha/40 weeks, an increase of 133% over the control without nitrogen.

The results illustrate the marked seasonal imbalance in growth and carrying capacity for a given pasture, and emphasize the need to use mixed feeding systems to provide a uniform level of nutrition for a fixed number of cows.

Relations were developed between the carrying capacity or production of fat-corrected milk (FCM)/ha and various measures of pasture growth for six pasture treatments grown in a subtropical environment. The pasture and animal production variables were obtained from pastures grazed on a weekly rotation using stocking densities which were varied so that a target weight of leaf material remained on the pasture at the conclusion of each grazing.

Within a treatment, there was a curvilinear relation between the rate of leaf growth and carrying capacity, with the greatest efficiency of conversion at the lowest leaf growth rates. This relation generally varied between pasture treatments because of differences in grazing intensity. There was little variation in the production of FCM per cow between grazing periods within a treatment, reflecting the experimental technique of matching the stocking density to the amount of forage. Consequently FCM/ha largely mirrored the stocking density with some adjustment for differences in production per cow caused by differences in grazing intensity between treatments. Production of FCM/ha was affected more by a unit change in residue leaf yield than by a unit change in leaf yield before grazing.

Using the rate of leaf removal (intake plus grazing losses) per cow as an inverse index of grazing intensity, it was apparent that the use of variable stocking densities to obtain specified residue yields after grazing did not necessarily equalize the grazing intensity because the rate of leaf removal per cow varied according to the before-grazing leaf yield. Also soiling by dung caused differences in the acceptability of forage for grazing, resulting in differences in grazing intensity between pastures with the same yield and stocking density.

Experiments were carried out to assess the increase in yield potential of winter wheat in the U.K. due to variety improvement since the early years of this century. The effects of other genetic changes were minimized by applying fungicide to control eyespot and foliar diseases, and by using nets to prevent lodging. The experiments were carried out in 1978 at Cambridge. One, on soil of high fertility in Camp Field, received 104 kg N/ha and the other, on soil of lower fertility in Paternoster Field, received 38 kg N/ha. Twelve genotypes were tested. Eight were varieties which formed a chronological series beginning with Little Joss, introduced in 1908. The remaining genotypes were recently developed selections from the Plant Breeding Institute and a line bred by the French breeders, Benoist.

The average yield of the 12 varieties and lines tested was 3·96 t/ha in Paternoster Field and 6·40 t/ha in Camp Field. In both fields the two highest yielding entries, Hobbit and the advanced breeding line 989/10, outyielded Little Joss by close to 40%. Benoist 10483 was the only entry for which the percentage yield advantage depended on high soil fertility.

The newer, high yielding, varieties were shorter and reached anthesis earlier than the older varieties. They had lower stem weights/m2 than the older varieties but similar maximum leaf area indices and leaf weights/m2. Within each experiment the total dry-matter production of the varieties was similar, the increase in grain yield due to variety improvement being associated mainly with greater harvest index (ratio of grain yield to grain + straw yield).

It is argued that by a continuation of the trend towards reduced stem length, with no change in above-ground biomass, breeders may be able to increase harvest index, from the present value of about 50% to about 60%, achieving a genetic gain in yield of some 25%. As the limit to harvest index is approached, genetic gain in yield will depend on detecting and exploiting genetic variation in biomass production.

Pod yield of groundnut and grain yield of wheat grown in that sequence was compared as affected by date of sowing and response to direct, residual and cumulative P application over 3 years in a field experiment. Total yield of groundnut and wheat was higher when groundnut was sown on 22 June and the following wheat on 1 November than when groundnut was sown on 6 July, followed by wheat sown on 16 November. Limited P requirement of groundnut was indicated by the small and inconsistent response to applied P on soil low in available P. Wheat responded to the second increment of P and direct application to wheat proved more effective than residual effects of previous application. Differential response of wheat to direct and residual P application in the groundnut-wheat cropping sequence indicates that P applications are more effective for wheat than groundnut, and groundnut can grow well on the residual P that remained in the soil.