Vicia faba cv. Minden was planted at densities ranging from 6 to 98 plants/m2. Nitrogen was applied to the soil as split dressings or as a foliar spray. CO2 concentration in the canopy was increased in some plots to 0·22% for 3 weeks during the early pod-filling stage.

Yield and number of seeds per plant varied inversely with plant spacing between 9 and 98 plants/m2. Mean seed weight increased up to 13 plants/m2 and then remained constant between 13 and 98 plants/m2. Yield/ha was unaffected by plant density above 18 plants/m2.

Application of 200 kg N/ha as ‘Nitro-Chalk’ (mixture of NH4NO3 and CaCO3) to the soil as split dressings did not affect yield or its components but 80 kg N/ha as urea applied in four foliar sprays increased yield by 361 kg/ha (8·6%). Recovery of the labelled nitrogen in the grain varied from 28% when applied during vegetative growth to 8% when applied in the reproductive phase and 15% in the foliar spray.

The highest yield (5·12 t/ha) was obtained by supplementary CO2. The results suggest that there is no advantage in applying fertilizer nitrogen to well-nodulated spring beans.

Crosses and reciprocal crosses were made between English material of Vicia faba major × Vicia faba equina and minor.

Half the major type plants had the stem apex removed before pollinations commenced. Apical dominance affected the success of crosses between major × equina, minor. On higher nodes and, on lower nodes when the apex was removed, there was no evidence of unilateral incompatibility. All crosses produced seed.

A Kenya Highland maize was planted at three altitudes, 1268, 1890 and 2250 m. Development rate, dry-matter accumulation and leaf area production were recorded during vegetative growth, together with grain formation and dry-matter accumulation in the primary cob. Rainfall, insolation, soil and air temperatures were continuously recorded at all sites. Maize developed faster at low warm altitudes, the rate being dependent on soil and air temperature. During vegetative growth, this relationship could be satisfactorily explained by an integrated temperature, but during the reproductive phase, some allowance had to be made for over optimal temperatures at low warm altitudes. Altitude had little effect on crop leaf area at any particular development stage, but leaf area production rates were closely related to leaf emergence rates. Before establishment of complete ground cover, large differences in dry-matter accumulation rates were observed which appeared related to rate of leaf area production. Once full ground cover was established, crop growth rates became much more similar. Potential number of grains per embryonic primary cob was greatest at low altitudes, but the final number of grains per cob at harvest was greatest at high altitudes. Rate of increase of grain weight was constant and very similar at all sites until growth stopped abruptly at 69, 83 and 96 days after tasselling at low, medium and high altitudes respectively. Rate of accumulation and partition of total dry matter in the primary cobs was similar at all sites, but owing to greater duration of development at high altitudes, dry matter per cob increased with altitude. Large yield differences were found at harvest, yield decreasing with decreasing altitude. Yield differences were mainly due to variations in number of grains per plant, although grain size also contributed. In this and other trials it was shown that the number of grains per plant at harvest was closely related to the mean thermal growth rate (expressed in units of g/plant/growing degree day) during the grain site initiation period.

Mouldboard ploughing, deep and shallow tined cultivation followed by conventional seed-bed preparation, and direct drilling were compared from 1972 to 1976 on a calcareous clay soil in two experiments, one on winter wheat and the other on spring barley.

At sowing the moisture content, bulk density and resistance to penetration in the surface layer of soil of uncultivated land were all greater than in soil that had been ploughed or cultivated deeply. Below 10 cm moisture content was less and root penetration was greater in the uncultivated soil. In all years winter wheat established and yielded well following direct drilling and shallow cultivation. In two dry autumns wheat establishment following ploughing was slower and less complete than with direct drilling, and in 1 year the yield was less. Spring barley established and yielded well without consistent differences in all years with all treatments.

In a preliminary laboratory experiment in Iran, not reported here, 5 out of 30 plant materials incorporated into a highly calcareous soil had a positive effect on increasing the DTPA- (diethylenetriaminepentaacetic acid)-extractable Fe and all except one significantly increased the vegetative growth of sorghum. The plant materials included Lawsonia inermis L., Malva silvestris L., Zyzyphus nummularia Wak. and Lavandula carnopifolia L. A glasshouse study was repeated with two California soils pretreated with 0·5% Fe2O3 to determine if these organic materials have practical value in making Fe available to plants. A calcareous, Fe-deficient Hacienda (fine-loamy, mixed, thermic aquic natrargid) and a non-calcareous Yolo (fine-silty, mixed, non-acid, thermic typic xerothents). The previously mentioned organic materials and Laminaria saccharina L. (Lamour) were incorporated into the soils at two rates, 15000 and 20000μg/g, as air dry and in ash form. An adequate supply of major and micronutrients other than Fe was ensured. Other treatments included 5 μg Fe/g as FeSO4, Fe-138 chelate and control. All of the plant materials with the exception of L. carnopifolia significantly increased dry-matter yield and Fe, Zn, Cu and Mn uptake by sorghum in the Hacienda soil. In the Yolo soil the above were not significant. Thin-layer chromatography of the extracts of the plant materials revealed the presence of significant quantities of phenolic substances.

The relationships between the number of stems per tuber and tuber characters measured before planting were studied using a wide range of tuber weights of the varieties Désirée and Maris Piper. The effects of the storage temperature of the seed tubers and the site of growth on these relationships were then investigated over 3 years.

Linear relationships between the numbers of stems per tuber and tuber weight accounted for more of the variation in numbers of stems than linear relationships established using tuber shape or sprout measurements. The linear relationships had positive slopes and intercepts, showing that small seed tubers produce more stems per unit weight than large seed tubers. There was little evidence of non-linear effects.

On average over all treatments, using ten plant samples, single linear relationships between above-ground stems and tuber weight accounted for 64 % of the variation in above-ground stems with D6sire'e and 58 % with Maris Piper. When separate regression lines were fitted for each treatment the best models in each variety accounted for about 86 % of the variation in above-ground stems. The best model with Désirée had parallel lines showing that the advantage, in terms of stem production, of small seed over large seed increases in environments favouring stem development. The relationships for each treatment are used to show how the stem density established can vary when planting tubers at the recommended spacing.

Seed tubers of comparable weight, planted at different sites, gave different numbers of stems suggesting that the optimum spacing may vary from one site to another.

It is suggested that breeding varieties for yield stability might be aided by selectingfor low variation in the relationship between the number of stems per tuber and tuber weight.

Six experiments are reported which examined the effects of various seed cutting treatments on numbers of tubers and tuber yields of several maincrop potato varieties. Using conventional potato ridges, the cutting of seed tubers into 12 mm cubes or the use of potato peel reduced early growth and yields compared with whole tubers in some experiments but in two others had little effect on tuber yields. In Majestic, seed cutting produced large increases in number of stems and tubers and increases in yields of small sized tubers. In Pentland Crown and King Edward, the effects of seed cutting were small. In King Edward no differences in growth and yield were found between individual eyes and in this variety and Pentland Crown, 56g whole tubers produced similar yields to halves of 112 g seed tubers planted at the same seed rate. The implications of cutting for use in commercial production are discussed.

Samples of soya-bean meal, groundnut meal, sunflower meal and fish meal were incubated in nylon bags in the rumens of sheep receiving either whole barley or dried grass. For the vegetable sources of protein the rate of disappearance of protein was greater when they were incubated in the rumens of sheep receiving dried grass than in sheep receiving whole barley. The rate of disappearance of fish meal did not vary between sheep fed whole barley or dried grass.

Rate of outflow of protein particles from the rumen was determined by rendering the protein supplement totally indigestible by a treatment with sodium dichromate. The rate of outflow was greatest with sheep receiving dried grass and increased with increasing feeding level.

The mathematical expressions of degradation rate and outflow rate were combined to give the total amount of protein degraded in the rumen for the grass and barley diets at two levels of feeding.

The amino acid composition of residues left in the nylon bags after 9 h of incubation were shown to be almost identical to the amino acid composition of the original protein supplement, indicating that the composition of the amino acid in the undegraded protein entering the abomasum essentially resembled that of the supplements.

Varietal differences in resistance to non-aggressive chocolate spot infection were detected in the field, although complete resistance was not observed. Following artificial inoculation under growth-room conditions, a parent–offspring regression of disease scores for the heterogeneous stock Chivers was estimated as 0·51 ± 0·24, and although this cannot be regarded as a reliable heritability estimate, it demonstrates a degree of additive genetic control. An F2 diallel cross, under field conditions, indicated resistance to be controlled mainly by dominant alleles within a system of partial dominance. Detached-leaf tests indicated that within virtually complete dominance systems, dominant alleles facilitate fungal penetration and induce a hypersensitive response within the leaf. Control of further lesion development was indicated to be effected by a virtually complete additive system.

Resistance to bean common mosaic virus in the cultivars Seafarer and Aurora from the U.S.A. is controlled by the dominant gene I originally found in the cv. Corbett Refugee.

The associations between yield, nitrogen and soluble-carbohydrate concentration within S. 23 perennial ryegrass were investigated at three levels of nitrogen application. Controlled growth room conditions were used.

The simple correlation between yield and nitrogen concentration was negative at the low rate of nitrogen application, not present at the intermediate rate of nitrogen and positive though not significant at the high rate of nitrogen. Yield and soluble-carbohydrate concentration were only correlated (positively) at the low nitrogen rate.

At low nitrogen there were ‘efficient’ genotypes with relatively high yield and low nitrogen concentration. ‘Inefficient’ genotypes had relatively low yields and high nitrogen concentration. The majority of genotypes were neither markedly efficient or inefficient. The efficient genotypes at low nitrogen maintained their yield advantage at higher nitrogen levels with average nitrogen concentration and high numbers of tillers. Inefficient genotypes remained relatively stable in yield, numbers of tillers and nitrogen concentration.

Partial correlation indicated an underlying high degree of dependence between yield, nitrogen and soluble-carbohydrate concentration at all nitrogen levels. The association of yield and nitrogen concentration showed a similar trend over nitrogen levels to that obtained using simple correlation. Yield and soluble-carbohydrate concentration were positively related, and nitrogen and soluble-carbohydrate concentration inversely related, when the effects of the remaining attribute were eliminated.

Data extracted from Lee et al. (1977) confirmed that yield and nitrogen concentration for varieties under field conditions varied with level of nitrogen application in a similar manner to genotypes in the controlled growth room. The variety (Melle) could be characterized as being particularly efficient.

Both sets of results indicate that selection for high yield of nitrogen in herbage can best be achieved through selection for yield alone.

Two experiments with growing pigs grouped in pens and three with growing pigs kept in metabolism crates were undertaken in order to determine young growing pigs'dietary requirement for phosphorus of vegetable origin, the relative potency and true digestibility of that source and the effect of dietary Ca concentration on its utilization. Much of the P was contained in wheat offal, and of this 900 g/kg total P was phytin-P.

In the first two experiments the responses to vegetable P were measured by pig live-weight gain, gain: feed ratio, several conventional carcass measurements and the weight, length and density, and the ash, Ca and P contents of the fourth left metacarpal, and also by the alkaline phosphatase activity of blood serum. No significant differences were found between treatments in terms of body-weight gain, gain: feed ratio, or the commercially important carcass characteristics. The requirement of pork pigs for P was measured by bone and serum enzyme characteristics when all the dietary P was of plant origin, apart from 0·3 g P/kg from casein. Under the conditions of this experiment this P requirement appeared to be met when the diet contained 5–6 g P/kg. The potency of vegetable P in Expts 1 and 2 and of wheat offal P in Expt 3 relative to feed grade dicalcium phosphate was 0·77, equivalent to a net retention of 0·4–0·5 as a proportion of that consumed estimated from growth and digestibility measurements. A true digestibility coefficient of 0·53±0·01 for wheat offal P was obtained in Expts 4 and 5. The effect of variation in dietary N and energy, associated with variation in dietary offal concentration, on the reliability of the potency estimates is discussed.

Increasing dietary Ca concentration caused a slight decrease in the digestion of wheat offal-P. The soaking of wheat offal in water for an average of 11 h before feeding increased P digestion in one of two experiments. In vitro evidence indicated that soaking initiated the hydrolysis of insoluble P compounds.

Three field experiments at the University of Nottingham, in 1976, 1977 and 1978, examined whether a growth retardant chemical, ancymidol, could be used to restrict stem extension, delay the onset of lodging and thereby increase the seed yield of S. 24 perennial ryegrass. Applications of ancymidol increased seed yield by up to 60% by increasing number of seeds per unit area, although this was associated with a delay in the onset of lodging in 1977 and 1978 only. Application of ancymidol increased the percentage of the total above-ground crop dry matter harvested as seed, but it was not possible to relate this to the growth of the crop between anthesis and harvest.

The DTPA-extractable Zn in 28 Tarai soils was found to be significantly correlated with Bray's ‘percent yield’ values for rice and wheat. The critical limit of ‘available’ Zn, below which responses of both crops to applied Zn may be expected, was 0–53 mg Zn/kg soil. On the basis of this critical limit, it may be inferred that in the 16 Zn deficient soils, rice and wheat yields would respond markedly to zinc application. The magnitude of crop response in these soils was greater in rice (39–244%; mean value 117%) than in wheat (33–101%; mean value 60%).

Under experimentally controlled nutritional levels, using Hereford, Hereford x Dairy Shorthorn, Dairy Shorthorn and Friesian breed-types, 288 animals were studied for age of eruption of the four pairs of front permanent teeth. Standard deviations are similar to those of other reports on Bos taunts. Breed differences were negligible and there is no evidence of heterosis. Lower nutritional levels delayed and higher levels advanced eruption. This effect had a maximum difference of 72 days if the differential nutrition was applied in calfhood. Differential nutrition later produced a smaller effect. It is concluded that in practice, the age of teeth eruption cannot be used to determine accurately the previous nutritional status of individual animals.

Dilute formalin was used to sample earthworm populations after the second (1969) and sixth (1973) harvests from a continuous barley experiment in which the cultivation treatments include deep (30 cm), normal ploughing (20 cm) and tined (three passes to 20 cm) cultivations and no tillage (direct drilling), at four nitrogen rates: 0, 50, 100 and 150 kgN/ha. Eight species of Lumbricidae were found, with Allolobophora chlorotica and A. longa co-dominant in both years, joined by A. caliginosa in 1973.

In 1969, Lumbricus spp., particularly large Lumbricus terreslris, tended to be more numerous in the untilled plots.

In 1973, the total populations had increased by 170%, with 50–100% more earthworms in untilled than ploughed plots, one third more with 50 and 100 kg N/ha fertilizer than with no nitrogen, and one-third more in the slightly heavier sandy clay loam soil than the lighter loam.

Most earthworm species reacted in the same way, and the reasons for any unusual reactions are discussed.

Seven hundred and fifty purebred Angoni, Barotse and Boran cattle and their crosses sired by Friesian and Hereford bulls were compared for live-weight and carcass characters in Zambia. The cattle were born between September and December in three consecutive years and were reared on unimproved veld. In the first year all females and a random half of the males received supplementary feed in winter and the males were slaughtered at 2·5 years of age. The remaining males received the same total amount of winter supplementary feed prior to slaughter at 3·0 years of age. The males born in the second year were pen fed for a period prior to slaughter at 3·0 years of age. Males born in the third year were slaughtered at 3·5 years of age and received no supplementary feed.

Genotype differences were important at all live weights and there were year of birth x genotype interactions at the 0·5, 1·0 and 1·5 year weights and a genotype × feed treatment interaction at the 2×0 year weight. Boran purebreds were heavier than the Angoni and Barotse purebreds; at 3·0 years the differences were +42·3 kg ( + 12·9%) and + 25·2 kg (+ 7·7 %) respectively. Cross-breds had heavier live weights than their corresponding purebreds with Boran crosses consistently heavier than the Angoni and Barotse crosses. The Friesian and Hereford sired Boran cross-breds were + 51·0 kg (+13·5 %) and + 43·0 kg (+ 11·6 %) heavier respectively than the purebred Borans at 3·0 years of age.

There were large differences between the genotypes for all carcass characters with Borans having heavier carcasses than the Angonis and Barotses by + 20·3 kg (+ 10·6 %) and + 19·1 kg ( + 10·0%) respectively. The average carcass weight advantages of Friesian and Hereford crosses with the Angoni, Barotse and Boran breeds over the corresponding purebreds were + 40·3 kg ( + 19·0%), + 33·6 kg ( + 16·2%) and + 31·0 kg ( + 14·0%) respectively. There were few important carcass differences between the corresponding Friesian and Hereford crosses.

The mortality rate during the experiment was 8·2% with only small differences between genotypes.

The interactions found in the experiment indicated that breed comparisons should be conducted over a number of years and at various management levels. For growth and carcass production under the conditions of the experiment the use of exotic crossbreds is clearly advantageous.

In northern areas of maize production in Europe and America, increasing use is being made of the association between accumulated temperature and stage of crop development. Temperature is accumulated either in terms of day-degrees above a given base temperature, taken to be 10 °CC in the U.K., or in terms of developmental units (‘Ontario Units’). Formulae for obtaining the daily contribution from recorded maximum and minimum air temperatures are available for compiling accumulated temperature totals for each of these methods, but the processing of long series of data is tedious, even with the assistance of computer programs. Results are presented from several locations in the central lowlands of England to suggest that very close approximations to the true monthly or seasonal totals can be obtained from the regression relations with corresponding mean monthly or seasonal temperatures.

For the sites considered the regression equations were sufficiently close to make joint, ‘regional’, regression equations appropriate. It is believed that the results will be applicable to other areas of England, and that the methods suggested might provide a suitable basis for supplementing the information available on accumulated temperatures elsewhere in northern Europe.

Experiments testing the effects on leafless peas of aldicarb, triazophos and a mixture of benomyl with zineb, were made on clay-with-flints soil at Rothamsted and on sandy loam at Woburn in 1977 and 1978.

The crop was shown to be susceptible to a wide range of pests and pathogens including the pea and bean weevil Sitona lineatus, the migratory nematode genera Pratylenchus, Tylenchorhynchus and Tylenchus, the pea moth Cydia nigricana, the aphids Acyrihosiphon pisum and Macrosiphum euphorbiae, the bean leaf roll and pea enation mosaic viruses and the powdery mildew fungus Erysiphe polygoni.

The mean yield of the four experiments when none of the treatments was applied was 3·6 t grain/ha, increased to 4·3 t/ha when all were applied. Aldicarb had the largest effect and increased mean yield at Rothamsted by 0·3 t/ha, attributed mainly to control of S. lineatus, and by 0·8 t/ha at Woburn attributed to control of S. lineatus and perhaps also to migratory nematodes, particularly Tylenchorhynchus. Triazophos and benomyl plus zineb did not individually increase yield but at Woburn when both aldicarb and triazophos were applied benomyl plus zineb increased mean yield by 0·7 t/ha.

All crops lodged severely, irrespective of treatment but perhaps because of experimental conditions. We suggest that susceptibility to lodging under field-scale conditions requires further study.

Four experiments were carried out over a 2-year period to investigate the effect of plant density and spatial arrangement and the time of lifting on yield and root size of carrots. Plant arrangement was varied by growing the plants in 1-, 2-, 3-, 4-, 5- and 10-row systems in beds with rows 12–5 and 37–5 cm apart. With each row arrangement crops were grown at target densities of 108, 323 and 537 plants/ma. There were three times of harvest. Total root yield was not significantly affected by plant arrangement or, in three out of the four experiments, by plant density but yields progressively increased with later harvests at all density levels. Yields of canning-size roots (20–30 mm diameter) were influenced by plant density and time of harvest and there were highly significant interactions between these variables on canning root yields. Highest absolute yields were obtained from the latest harvests from the medium and high plant density treatments; with the lowest density treatments the highest yields of canners were obtained from the earliest harvests. Mean root weight was significantly affected by plant density and harvest time. Row system effects on mean root weight were shown to be largely accounted for by differences in percentage seedling emergence and hence the plant density obtained under the different row system treatments and a possible reason for this effect is discussed. The relationship between mean root weight and plant density was not affected by the pattern of plant arrangement in these experiments. Total root yields were shown to be related to cumulative potential evapotranspiration from sowing rather than to chronological time. It is concluded that with the range of row systems used in these experiments, row spacing had little effect on root yield but confirmed previous work that plant density and time of harvest were the most important variables controlling mean root size and hence the yield of roots of any particular size grade.