Field experiments were conducted for three seasons, 1971–2, 1972–3 and 1973–4 to study the effects of nitrogen fertilizer and seed rate and their interactions on grain yield and its components and attributes of growth of two wheat varieties, Giza 155 and Mexipak. The semi-dwarf Mexipak was found to be more responsive to nitrogen application than the taller Giza 155 in a number of aspects, namely, grain yield per unit area of land, the number and weight of grains per ear, the dry weight per ear and dry weight of ears/m2. The numbers of spikelets and grains per ear of both varieties decreased linearly with an increase in seed rate. The 1000-grain weight was not affected in both varieties by either seed rate or N fertilizer.

Variety × nitrogen, variety × seed rate and nitrogen × seed rate interactions were significant; the variety × nitrogen × seed rate interactions were not significant. Mexipak was found to have a definite optimum seed rate of 192 kg/ha at an optimum N level of 129kgN/ha for maximum grain yield. Giza 155 was less responsive to changes in seed rate and therefore its optimum seed rate was not as definite as that for Mexipak. Evidence presented here suggests that wheat varieties of different growth habits grown in the Sudan should receive differential treatments when the policies of setting optimum seed rates and nitrogen fertilizer rates are considered.

Grain yield of both varieties was positively correlated with total dry weight of shoot at heading.

A field experiment was made with pigeon pea (Cajanus cajan (L.) Millsp.) at the Indian Agricultural Research Institute, New Delhi, during the rainy seasons of 1975 and 1976 to study the effects of plant type, plant population density and the application of phosphate fertilizer on growth and yield of pigeon pea. Cultivars BS-1 and UPAS-120 produced significantly more grain with 100 × 103 plants/ha, whereas the cultivar Prabhat produced most when 200 × 103 plants/ha were grown. Application of 13 kg P/ha increased most growth and yield attributes and increased the grain yield significantly over the control to which no P was given; however, no additional increase was obtained when 26 kg P/ha was given. The highest-yielding cultivar BS-1 benefited most from phosphate fertilizer.

Some applications of near infra-red reflectance (NIR) analysis in plant breeding have been tested. Prediction of the nitrogen content of cereals, kale and beans, and nitrogen and oil in rapeseed was sufficiently accurate for screening purposes although wheat straw gave a less accurate result. The prediction of nitrogen content of wheat grain could be supplemented by the simultaneous estimation of grinding resistance and bran cleanliness, characters of importance for bread-making quality. Hagberg falling number, sodium dodecyl sulphate (SDS) sedimentation volume and loaf volume could not be accurately predicted by NIR. Encouraging results were obtained for predicting malting quality of barley and the digestibility of kale samples.

The pattern, production and survival of tillers was studied in two spring wheat varieties in field and pot experiments for two seasons.

The time-trend of tillering was such that tiller production reached a peak well before ear emergence, then death reduced the number of vegetative shoots to a level determined by seed rate (in the field) and nitrogen level (in field and pot experiments), and thereafter the number of live shoots remained more or less constant. In field experiments plants grown at high seed rates and low rates of N application attained their maximum numbers of shoots at an earlier date. Number of shoots perm2 increased with an increase in seed rate and N level. However, the number of fertile shoots per plant at harvest decreased with an increase in seed rate and were composed mostly of main shoots. The high mortality rate of shoots was attributed to the high temperatures prevailing in this country during the growth period. Mortality of shoots started earlier at high seed rates and low rates of N application.

In pot experiments, giving the N fertilizer in doses throughout the growth period reduced the rate of mortality of tillers rather than increasing their rate of initiation. A lower dose of N, given in portions over a long period, resulted in a higher number of live tillers than a dose double this amount given once at sowing. Numbers of spikelets and grains increased to a greater extent as a result of split application of N than did grain weight per ear of main shoots and of primary + secondary tillers. Mexipak had fewer spikelets per ear than Giza 155 and yet its number of grains was greater, particularly in ears of primary and secondary tillers.

Crops of potatoes grown on 0·2–0·3 ha in each of the years 1971–8 at Stockbridge House Experimental Horticulture Station achieved total tuber yields of 70–94 t/ha. Yield was determined by the period and rate of tuber growth. The observed period of growth varied from 96 to 132 days and the rate from 0·55 to 0·90 t/ha/day. Rate of growth had the greater influence on variability of yield between the years. The number of tubers produced per unit area had little influence on their total weight, but had marked effect on their size. Adequate water supply was essential for very high yields. Experiments indicated that current recommendations for potash fertilizer can be adequate but that nitrogen and phosphate fertilizer use may need to be enhanced for very high yields. For high yields, the number of seeds planted per hectare may need to be higher than normally recommended in order to avoid the production of large tubers unsuitable for the ware market.

Field studies were made for 2 years on a sandy loam soil under dryland conditions of north-west India with three pigeon-pea varieties in relation to plant density and the application of phosphate fertilizer. Varieties Pusa Ageti and P4785 with better developed root system and profuse nodulation had higher grain and stalk yield, and higher N and P yield than Prabhat. Root and shoot growth and root nodulation were adversely affected with increasing plant densities in the range 50 × 103 and 150 × 103 plants/ha. Stalk and total N and P yield increased with increasing plant density. Plant density of 117 × 103 plants/ha produced maximum grain yield of 1·53 t/ha. Phosphorus fertilizer promoted root and shoot growth, intensity and volume of nodulation and increased grain, stalk, N and P yield. The effect of plant density on grain yield was more pronounced in the presence of phosphate fertilizer. The economic optimum rate of P ranged between 22·1 and 23·1 kg/ha under different plant densities.

A series of glasshouse and growth-cabinet experiments were carried out to investigate aspects of flower and pod production in Phaseolus vulgaris L. (French bean). Abscission of flowers and immature pods varied between 45 and 80% in the seven cultivars tested, with flowers which opened first being most likely to produce mature pods. Seed yield was only slightly reduced and sometimes increased by the removal of opened flowers for periods of up to 15 days from the start of anthesis depending on the conditions under which plants are grown. It was demonstrated that plants compensated for flower removal by setting pods from flowers which opened later. Similarly, when opened flowers were removed from alternate nodes plants compensated by setting pods from flowers which opened on nodes not being deflowered.

The physiological basis for premature abscission of reproductive structures in grain legumes is discussed.

Three experiments were conducted to assess the effects of different protein and energy levels on turkeys during the periods 12–16 weeks, 16–20 weeks and 20–24 weeks. Compared with 20 and 22% protein, 18% significantly depressed weight gain and feed efficiency during the 12–16 weeks period, while 14 and 16% protein, compared with 18%, significantly depressed weight gain and feed efficiency during the 16–20 weeks period but gave similar weight gain and feed efficiency as the 18% protein during the 20–24 weeks period.

During all periods between 12 and 24 weeks, the two energy levels tested (11·72 and 12·56 MJ/kg) did not significantly affect weight gain and feed efficiency whereas feed consumption was significantly higher on the lower energy level.

The present studies suggest that 20, 18 and 16% protein, all with metabolizable energy of 11·72 MJ/kg, may be recommended for turkeys aged 12–16 weeks, 16–20 weeks and 20–24 weeks respectively.

Six horses were fed Setaria sphacelata var. sericea cv. Narok hay in a mineral balance experiment and were in negative calcium balance. This should have ensured maximum efficiency of calcium absorption. Only 6·3% of calcium from a single dose of 1·32 kg calcium oxalate was retained by the horses, which supports the suggestion that horses cannot utilize calcium in tropical grasses if it is present as calcium oxalate crystals.

The growth and development of two new maize hybrids (FARZ 27 and FARZ 23) were studied in density experiments located at two contiguous ecological zones in Nigeria. The range of planting density used was from 2·6 to 6·6 plants/m2. Within this range, the relationship between dry-matter yield and density was asymptotic at final harvest. At the forest location of Jago (7·3 °N, 4·2 °E), both varieties attained optimum grain yield at planting density of 4·4 plants/m2, while at the derived savannah location of Alagunmu (7·8 °N, 4 °E), FARZ 23 attained optimum grain yield at 4·4 plants/m2 and FARZ 27 attained its optimum grain yield at 6·6 plants/ma2. This response of the new maize varieties to density treatments indicates that they could be planted at higher densities than are now used in the country.

Differences between varieties did not quite reach statistical significance but, at both locations, FARZ 27 produced more dry matter and grain per unit area than FARZ 23. FARZ 27 gave its higher grain yield mainly by producing more seeds per unit area than FARZ 23. Physiological measurements like net assimilation rate, crop growth rate and leaf area index were also higher for FARZ 27, although there were no significant differences between the varieties at most sampling dates. The partition of dry matter was identical in both varieties, although FARZ 27 showed a slightly better balance by partitioning more assimilates to the grain. Also, there was an indication of remobilization of stored assimilates from the stem to the grain in both varieties. Both varieties produced more dry matter and grain at the derived savannah location of Alagunmu than at the forest location of Jago. Physiological measurements were also higher at the derived savannah location.

The true and apparent metabolizable energy (TME and AME) of a range of indigenous feedingstuffs and finished feeds were determined by rooster bioassay techniques adapted to suit a small nutrition laboratory.

The AME and TME of some common feedingstuffs were similar to the values published elsewhere. The AME of two finished feeds were similar to their zero-N corrected metabolizable energy values determined by the conventional total collection method. The mean ±S.E. endogenous and metabolic excreta energy per bird for 24 h was 70·4 ± 2·94 kJ.

The winter-heading cauliflower varieties St Thomas, St Gwithian, St Agnes, Janavon, St Hilary, St Buryan, BB74605, St David and St Keverne were grown at Trefloyne, Tenby for 3 years from 1977 to 1980. Plants of all varieties were sampled periodically to determine the rate of curd expansion, the final number of leaves, the time of curd initiation, and the distribution of dry matter within the plant.

The patterns of development of leaf area were similar in all varieties. Dry-matter distribution was similar for all varieties except for root growth; later-maturing varieties had a greater dry weight of root and a higher proportion of the total dry matter as root, than early varieties. Early rates of curd growth declined with later-maturing varieties and it is suggested that there may be a relationship between the time of curd initiation, root growth and the rate of curd growth.

The mean total number of leaves formed before curd initiation varied from 49 to 102 depending on the variety and year. The earliest varieties St Thomas and St Gwithian took co. 120 days to reach 50% curd initiation and matured in 6–7 months from sowing while the late variety St Keverne took over 200 days to reach 50% initiation and more than 11 months to mature. The time interval between 50% initiation and 50% maturity increased with later-maturing varieties but on the basis of accumulated day degrees > 6 °C it declined with later varieties. The latter also matured more uniformly than earlier varieties when using an accumulated day-degree scale > 6 °C as a time scale.

The results suggest that the low temperature threshold below which curd induction occurs may vary with variety. There was also evidence that the base temperature for curd growth is lower with later-maturing varieties.

A study is reported of the effect of initial potential for milk production of individual cows on the change in milk output consequent upon a change in amount of feed allowed per day. In this study equal initial rations and equal changes in ration were imposed on all cows. The main conclusion was that the greater the initial yield of milk, of milk fat, of solids-not-fat (SNF) or the SNF content of the milk of a cow the greater was the effect of a change in feed allowance on that attribute. It is argued that the effects are large enough to warrant consideration in practical feeding systems.

Field experiments were made at the Punjab Agricultural University, Ludhiana, during 1974–5 to 1978–9 to study the possibility of improving wheat yield by more efficient use of radiant energy through modification of the shape of the canopy under varying levels of fertilizers, irrigation and seed rates. The results showed substantial yield increase by sowing half the seed and fertilizers in one direction and half in rows at right angles, giving a spacing of 22·5 × 22·5 cm, thereby intercepting more light, which showed a significant direct relationship with yield, but there were negative correlations with soil temperature. The increase in row spacing decreased the yield. With 33% extra fertilizer than the local recommendation, sowing the crop in two directions gave 0·96 t/ha (33·4%) higher yield, whereas none of the other sowing methods showed significant increase. Mixing varieties to form a prismatic canopy gave higher yield than the mean of the varieties sown alone. Irrigating the crop more than thrice did not prove beneficial. North-south row direction tended to improve yield compared with east-west rows. Seed rates varying from 50 to 200 kg/ha showed neither significant effect, nor interaction with canopy shape except in 1978–9 when 150 kg seed/ha showed yield improvement over 100 kg/ha.

Plasma progesterone concentrations were monitored in 69 lactating Friesland dairy cows during the post-partum period. Cyclic ovarian activity resumed in most cows within 40 days of calving. Forty-eight per cent of cows remained pregnant to their first insemination, 41% returned to oestrus before day 30 after insemination, and a further 11% returned to oestrus between days 30 and 88 after insemination.

The mean of progesterone values on days 11 to 4 before insemination tended to be higher in cows that conceived than in cows that did not conceive. These differences were signficant on day –8 (P <0·05) and on days –8, –7, –6 and –5 combined (P <0·01). Cows in which the concentration of progesterone in plasma did not rise above 4·5 ng/ml during this period did not conceive. After insemination, mean progesterone concentrations between pregnant and non-pregnant cows diverged after day +8. Relatively low concentrations of plasma progesterone (< 1 ng/ml) up to day +8 after insemination did not preclude conception. There was no indication that embryo loss between days +30 and +88 after insemination was related to an insufficiency of ovarian progesterone during early pregnancy.

In four experiments in different years, plants of four winter-heading cauliflower varieties with mean numbers of leaves and leaf initials varying from 9·5 to 16·5 were stored for periods of 14–24 days at different temperatures from 0 to 5 °C. Cold treatment tended to delay the time from sowing to 50% maturity but did not reduce the spread in the time of maturity of individual plants within a population. The reasons for this are discussed.

The nutritive value of a new forage pea (Pisum arvense), commercially available as ‘Rosakrone’, was assessed by feeding the seeds in ground form to laying hens as a supplementary source of protein in diets based on mixed cereals. Like other pulse seeds they were found to be relatively deficient in methionine. The effect of this on egg production was overcome by adding synthetic methionine to the diet.

However, there was also present an anti-nutritive factor, similar in action to that found in other pulse seeds, which caused live-weight loss and reduced the rate of lay to about 0·85 of normal in 20 weeks with 40% pea meal in the diet. This anti-nutritive factor appeared to be heat stable.

Field experiments on spatial arrangements in intercropping systems were conducted under rainfed conditions in north-western India during 1975 and 1976. In these experiments sorghum yield increased by 21·6, 20·3, 29·2, 36·5 and 14·;2% when grown in association with the legumes greengrarn, blackgram, grain and fodder cow peas and groundnut respectively when compared with sorghum alone. Spatial arrangements had only marginal effect on sorghum yield but the yields of all the intercrops were appreciably affected. Paired rows with two rows of intercrop in 90 cm spacing resulted in maximum yield of all the intercrops. The land equivalent ratio (LER) was also influenced considerably by different intercrops and spatial arrangements. Planting of sorghum in paired rows having two rows of grain cow pea within 90 cm spacing gave maximum LER in both the years; however, net returns were maximum with fodder cow pea in same spatial arrangement.

Lures containing the synthetic pheromone components (E)- and (Z)-citrals, geraniol and nerolic and geranic acids made new hives, not previously occupied by honeybee colonies, more attractive to caged honeybee swarms than unbaited hives (20 out of 20 tests). The lure also made old hives, previously occupied by colonies, more attractive to caged swarms (19 out of 20 tests) and to swarms in natural conditions (12 occupied compared with none without the lure). Adding (E)-9-oxo-2-decenoic acid (part of the queen's mandibular gland pheromone) to the lure increased its attractiveness to caged swarms (20 out of 20 tests). Practical implications in beekeeping are discussed.

Measurements were made of changes in body water, estimated by the dilution of deuterium oxide, in six Hereford x British Friesian lactating cows in their second lactation and in four of the same animals in their third lactation. The animals were subjected to a prolonged period of underfeeding followed by a period of realimentation. Milk yields were measured twice daily whilst measurement of live weight and certain blood constituents were made at 7-day intervals during the experimental periods in both years. During underfeeding milk yield differed markedly among the cows and it appeared that the cows with a higher milk potential maintained a higher yield but in doing so they incurred a greater loss of body weight. On refeeding there was little or no response in milk yield. Weight losses during the second lactation consisted mainly of body fat (calculated by difference) but the four higher yielding cows lost appreciable amounts of body water and probably significant amounts of body protein. In the third lactation all four cows lost less body fat but more body water and probably body protein than they did in the second lactation. On refeeding all animals in both years except the two lowest yielders in the second lactation gained substantial amounts of body water and probably protein but relatively little or no body fat. Significant negative and positive correlations were obtained between plasma glucose and loss of body water and between plasma free fatty acids and loss of body fat respectively.