Six field experiments on the effects of rate and time of application of nitrogen, three variety trials and one trial combining varieties with rates of application of nitrogen, all on winter wheat grown continuously and direct-drilled on a single farm, are described and the results discussed.

The experiments showed that worthwhile yield responses could be obtained to very high rates of N application and that percentage protein in the grain increased linearly with amount of N supplied even to the highest rate (350 kg N/ha) applied. The effects of time of application were variable but there was a suggestion that applying the nitrogen in two doses in the spring gave more yield than a single dose, in one experiment. Applying some N in the autumn gave no more yield than applying it all in the spring.

The variety trials gave results reasonably consistent with those of the National Institute of Agricultural Botany but the variety x nitrogen trial showed clear differences between varieties in response to nitrogen; the oldest variety, Maris Huntsman, showed a maximum at about 240 kg N/ha whereas none of the new varieties had reached their maximum by 270 kg N/ha.

It is argued that field trials devoted to improving crop yields for a particular farm are worthwhile if site x treatment interaction is large and season x treatment interaction is small.

Mainstem leaf appearance and leaf extension were monitored at 7-day intervals throughout the vegetative development of field-grown winter wheat plants, during two growing seasons 1977–9. Using hourly air and soil temperature records, it was found that the rate of leaf appearance was controlled by soil temperature, with the best linear relationships being obtained using accumulated soil temperature above a base temperature of 0 °C at 1 and 5 cm depth. Leaf appearance could be predicted equally well using 09.00 G.M.T. screen air temperatures although deviations from each linear relationship were found during very cold periods when slow leaf extension rates delayed leaf appearance.

Leaf extension was also found to be linearly related to temperature, with the best fit being obtained using accumulated soil temperature above 2·5 °C at 5 cm depth, suggesting a threshold of 2·5 °C for leaf extension. The response to temperature (extension per unit of accumulated temperature) was the same for all the leaves of a given plant, or sowing date; however, the fact that the rate of leaf extension increased progressively with sowing date suggests that plant response to temperature may be determined at crop emergence (possibly mediated by rate of change of day length). Leaf extension rates could be predicted satisfactorily using 09.00 G.M.T. soil temperatures (5 or 10 cm) but less so using screen air temperatures.

The prediction of plant leaf areas or crop leaf area indices using such relationships between temperature and leaf growth was found to be hampered by rapid and irregular rates of leaf senescence.

A mass-selection scheme for outbreeding diploid potatoes of the Phureja-Stenotomum Group is described; the scheme includes both seedling and ongoing tuber populations. Provision is made for higher yielding clones to contribute more true seed to ensuing generations. A computer is used to document and randomize the plantings. Selection criteria and methods are described. Results are given from an experiment to monitor progress. The use of diploid potatoes in British breeding, and the historical development of breeding methods, are reviewed in relation to the present mass-selection scheme.

The growth and feed intakes of Corriedale wether sheep when grown from 30 to 50 kg body weight by five different growth paths are described.

Group A (control) grew continuously (fed ad libitum). After reaching ca; 40 kg body weight, group B and C animals lost 21% of their initial body weight over 9 and 18 weeks and at 122 and 63 g/day, respectively, and began realimentation at 30 kg body weight. Group D and E animals were ca. 50 kg body weight when weight loss was imposed and they lost body weight at similar rates (125 and 157 g/day) respectively. Animals in group D lost 34% of their initial body weight over 18 weeks and began realimentation at 30 kg body weight (the same as groups B and C). Group E animals lost 23% of their initial body weight over 9 weeks to begin realimentation at 35 kg body weight. Except during periods of weight loss, animals were fed ad libitum. Compensatory growth was observed in all groups which had lost weight, with early recovery growth rates 1·6–1·8 times higher than control sheep of the same weight.

Rate of body-weight loss did not induce any significant differences in response to realimentation but results (groups B and C) suggest that the more rapid the loss, the more rapid will recovery be during realimentation. When sheep at different body weights lost the same proportion of their initial body weights, the heavier sheep (group E) attained final slaughter weight quicker than the lighter sheep (group B). When the proportion of body weight lost to reach a particular lower body weight was varied (groups B and D), the greater weight loss was associated with higher and more persistent growth rates during realimentation.

After weight loss, ad libitum dry-matter intake was significantly lower during the first 10 kg of gain during realimentation in all treatment groups (B, C, D, E) than in control group A. There were no differences between treatment groups in recovery of dry-matter intake.

Gross efficiency in all treatment groups was higher than in the control group A during the first 10 kg of recovery of body weight, but it then declined rapidly. This increase in gross efficiency was considered to be due to a combination of increased growth rates, reduced feed intakes and lower maintenance requirements. When the complete growth paths from 30 to 50 kg were considered, there were no significant differences in total feed consumed by the sheep following the five different growth paths.

A field experiment was conducted on a saline sodic soil at Kanpur to study the effects of sedimentary pyrites and Zn on the yield, Zn and Ca utilization by rice and wheat crops and on the amelioration of saline sodic soil. The grain yield of the first crop of rice increased from 1·55 t/ha for the ‘control’ to 3·44 and 4·01 t/ha with the 40 and 80% gypsum requirement pyrites treatments. The grain yield of succeeding wheat and rice crops also increased significantly owing to pyrites residues. The favourable effect of pyrites on crop yield was associated with an appreciable decrease in the pH, electrical conductivity and exchangeable and soluble sodium content of the soil resulting in greater utilization of Zn and Ca by the crops. Zinc applications also greatly increased grain yield and Zn uptake by the crops. The higher levels of pyrites with adequate N, P and K fertilizers but without Zn did not give yields that were obtained by adding 11 kg Zn/ha.

Significant yield responses were observed in the succeeding wheat and rice crops to Zn residues from the higher Zn treatments. The ‘pyrites+Zn’ treatment was most effective in decreasing the Na content and enhancing Ca uptake which increased the Ca/Na ratio in plants. The Zn treatment alone also decreased soil pH, electrical conductivity and exchangeable Na.

Two sets of experiments were carried out to compare methods of selecting Festuca arundinacea (tall fescue) for improved seedling vigour.

In the first, germination and seedling growth of four varieties (Goar, Lironde, S. 170, and ZW 42–6) were compared in hydroponic growth tanks. From each variety, groups of seedlings were selected for each of four vigour characters (speed of germination, leaf length, root length and speed of production of the second leaf) and a fifth group was selected at random as a control. Plants of each group were intercrossed in isolation and their progeny compared.

In the second, S. 170 was studied through two cycles of selection in a soil-based compost. In the first cycle, groups of seedlings were selected for each of five characters (speed of emergence, leaf length, and speed of production of the second leaf, first axillary tiller and coleoptile tiller). Two further groups were selected randomly. In the second cycle, the progeny of each group were reselected for the same character as their parents. Both first- and second-cycle progeny were compared among themselves.

Significant direct responses to selection were obtained in all characters except speed of germination in hydroponics. Indirect responses also occurred but were mostly smaller and in response to selection for a related character, e.g. selection for early tillering resulted in early second leaves and vice versa. Two cycles of selection raised the frequency of coleoptile tillers from about 5 to 55 %, but the concomitant advances in vigour characters were smaller than those achieved by direct selection. It is argued that for practical purposes the basic criterion in selecting for improved seedling vigour should be rapid attainment of a particular growth stage such as appearance of the first tiller. Since speed of emergence itself responded to selection, the attainment of such a stage should be related to date of sowing rather than of emergence or germination.

In the progeny of the hydroponic selections, all characters showed significant varietal differences, some of them the reverse of differences between the parent populations of the varieties. These results illustrated the importance of seed provenance as a determinant of seedling vigour, and suggest that choice of parent material is important in breeding for improved vigour.

Forty-eight Friesian cows in weeks 4–20 of lactation at the start of the trial were used in a comparative evaluation of Desmodium–grass silage, Rhodes grass silage, maize silage and lupin green forage. The forages were group-fed ad libitum and a concentrate was offered according to a standard lactation of 4200 kg milk in a 12-week test period. A digestibility trial with five wethers was used to evaluate the nutritive value of the forages.

Cows offered the Rhodes grass silage had the highest forage dry-matter intake and those on maize silage had the lowest intake. There was no significant difference between the intake of Desmodium–grass silage and lupin green forage. Milk and FCM production were not significantly different on the four treatments although lupin green forage gave appreciably less than the silages. The expected milk production from the energy and protein consumed suggested that the milk produced was mainly from the concentrate. It is concluded that low energy concentration in all the forages, and low crude protein content in the silages, were the main limiting factors for high milk production.

Two experiments investigated the effects of raising crisp lettuce seedlings under different environmental conditions prior to transplanting, on transplant size and weight and head weight at maturity.

The use of tungsten lighting for 4 h after the end of a 12 h period of fluorescent and tungsten lighting increased transplant size and weight and the weight of heads at maturity compared with fluorescent and tungsten lighting only. Glasshouse-raised transplants were larger than those raised under artificial lighting but gave heads of similar weight to transplants which had supplementary tungsten lighting for 2 weeks. Both these treatments gave significantly heavier heads than a drilled crop or plants raised without supplementary tungsten lighting. Increasing the number of weeks of the supplementary lighting treatment tended to increase the coefficient of variation (c.v.) of head weight. Nevertheless the drilled crop had a higher c.v. of head weight than any transplanted treatment.

The variety Pennlake produced pointed (‘coned’) heads when grown in the open and its leaves were shorter and broader than those of plants grown in polyethylene tunnels, which did not show ‘coning’. It is suggested that ‘coning’ occurs primarily as a result of either lower mean temperatures or a lower amplitude of temperature when grown in the open. It occurred most frequently with glasshouse-raised plants indicating that a higher raising temperature may also contribute to the problem.

A pot culture experiment was conducted on 11 soils differing in their physicochemical characteristics to study the occurrence of Zn-Cu interaction in relation to plant growth and Zn and Cu concentrations of wheat. The nature of the interaction was found to vary with the soils and the amounts of applied nutrients. The plant growth showed antagonistic interaction between Zn and Cu when one of the two elements was added in low amounts. However, when the two elements were applied in large amounts, their concentrations in the plants increased but the plant growth was adversely affected. The applied Zn generally failed to affect the uptake of native or low amounts of applied Cu whereas the applied Cu decreased the uptake of native zinc in five out of 11 soils.

The DTPA extractable amounts of Zn in experimental soils were not affected signicantly by Cu application and vice versa. The fact that the application of Zn or Cu may not affect or increase the uptake of each other may depend upon the soil characteristics and the rates of their application.

Two experiments at Wellesbourne studied the effects of cold treatments on the leaf and curd production characteristics of a range of annual and biennial varieties of cauliflowers.

Cold treatments delayed curd initiation and had a variable effect on the final number of leaves, but reduced the spread of curd initiation of plants which were 5 weeks old when cold-treated. The overall rate of leaf production and the final number of leaves generally increased with later-maturing varieties while initial rates of curd expansion generally declined.

The annual varieties produced a small number of leaves and fairly synchronously formed a curd which developed rapidly; the biennial varieties had a higher rate of leaf production after transplanting and then changed to the generative state over a more prolonged period, following which the curd developed slowly.

Infiltration is the most important aspect in the hydraulics of surface irrigation, since the design of irrigation systems depends to a large extent upon the infiltration characteristics of the soil. Many workers have contributed to the theoretical understanding of the infiltration phenomenon (Kirkham & Powers, 1972). However, very little work is available on the evaluation of infiltration into cracked soils. Measurement of infiltration into these soils poses a special problem. Depending on the degree of cracking, a fraction of the water added on the soil surface flows down through cracks and goes to waste. The water flowing through the cracks does not contribute to the moisture storage of the soil profile which may subsequently be used by the crops. Also, infiltration rates measured using ring infiltrometers are erroneous. In order to have an efficient design for an irrigation system, realistic estimates of infiltration characteristics for this type of soil are essential. In the present paper an attempt has been made to estimate the effective infiltration rate into such cracked soils. The procedvire suggested has been tested under limited conditions and found useful under field conditions. However, extensive field testing under various soil conditions is necessary before it can be recommended for general use.

Three successive generations (parents, F1, F2) and backcrosses of the common bean (Phaseolus vulgaris L.) hybrid between the cultivars Swedish Brown and Seafarer were used in this study.

The investigation has concentrated on assessing the relationship between the seed weight per plant and the protein percentage of the seed. Protein percentage showed a higher estimated heritability and a greater stability over environments than seed weight.

Partial dominance for low percentage protein and low seed weight was noted. Negative and low regression coefficients between these two characters was also observed.

SDS-gel electrophoresis was used to examine the variation in banding patterns of total seed polypeptides and their stability over environments.

Two potential new kale cultivars were compared with five control cultivars in 12 trials involving five sites in the north of England and the south of Scotland, 2 years, and a range of sowing and harvest dates.

The differences between cultivars were small for dry-matter and digestible organic-matter yield. Genotype-environment interactions were relatively large by comparison and hence only tentative estimates could be made of relative yield performance in a wider range of environments. However, the set of trials was satisfactory for determining the heights, dry-matter contents and digestible organic-matter contents of the cultivars despite the presence of statistically significant genotype-environment interactions.

Joint regression analyses revealed that the two cultivars with the lowest mean freshweight yields were also the least responsive to environmental change and that environments resulting in low digestible organic-matter contents were best for discriminating between cultivars.

Fungicide applications to wheat have been reported to maintain the green area of the leaves (Dickinson & Walpole, 1975; Stevens & Palmer, 1980). It is not known, however, whether the photosynthetic rate of the leaves is also maintained. It was therefore decided to investigate disease development, green leaf area and photosynthesis of the flag leaf of winter wheat in response to the fungicide propiconazole, which has not previously been reported to influence senescence in the field.

Physiological problems in some Fife dairy herds were thought to be associated with mineral imbalance in grass cut for silage. Consequently trials at two sites were conducted to study the effects of three levels of nitrogen and phosphorus and two levels of potassium on yield and composition of pasture cut for silage.

Nitrogen increased yield of herbage and reduced its clover content whereas phosphorus and potassium had little effect on yield or clover content. Herbage clover content and calcium concentration declined over the period of the experiment. Mean concentrations of calcium, magnesium and phosphorus were 5·8, 1·7 and 3·4 g/kg respectively. Concentrations of these minerals varied more with time of cutting and with season than with level of applied phosphorus and potassium.

Nitrogen tended to reduce calcium concentration in mixed herbage and to increase magnesium concentration in the grass component; it did not affect herbage phosphorus concentrations, but narrowed the calcium-phosphorus ratio in the second cuts. Applied phosphorus increased herbage phosphorus concentration only at the site with the lower soil phosphorus status. Potassium tended to reduce magnesium concentration in clover and, at one site, in mixed herbage; it also tended to reduce herbage phosphorus concentrations in second cuts.

Mineral uptake was increased by applied nitrogen. Mean annual uptake of calcium magnesium and phosphorus was 34, 10 and 20 kg/ha respectively.

The effects of treatments on concentration and balance of these minerals are discussed in relation to ruminant requirements and maintenance of suitable levels of the minerals in the soil.

It is concluded that normal applications of NPK fertilizer are not detrimental to satisfactory mineral balance in pasture.

The effect of treating soya-bean meal with formaldehyde was studied in cattle by supplementing a hay–barley diet with two levels of either untreated or formaldehydetreated soya-bean meal. The formaldehyde treatment had no significant effect upon apparent N digestibility in the whole tract; it increased the amounts of non-ammonia N and amino acid N entering the small intestine but this increase was not statistically significant. However, increasing the proportion of either soya-bean meal in the diet increased the flow of non-ammonia N to the small intestine and apparent N digestibility in the whole tract. The formaldehyde treatment reduced the apparent degradability of the soya-bean meal N, determined in vivo from 0·74 for the untreated meal to 0·38 for the formaldehyde-treated meal. The in sacco technique produced values for the apparent degradability of the two soya-bean meals which ranked them in a similar manner as did the in vivo technique but gave lower values for degradability than the in vivo technique.

Phaseolus vulgaris is grown in the U.K. primarily for its edible immature pods (dwarf French beans). The possibility of also using this species as a combinable break crop in south-east England was investigated during 1972–80 when trials were undertaken on the nitrogen fertilizer requirement for commercial seed production.

Hanley & Ridgman (1979) reported the results from three cycles of six-course rotations on light land. The report was based on a rotation of sugar beet, barley, barley, potatoes, barley, barley, with treatments involving replacement of one, two or three of the first three crops by 1-, 2- or 3-year leys, the last three crops acting as test crops. One of the problems of drawing general conclusions from rotation experiments is that the test crops are really part of the experimental treatments and may not be the most suitable crops for determining either the direct effects of the ‘treatment’ crops or the longer-term effects of the rotations themselves.

Growing beef cattle grazed six pasture types (all-grass or grass-legume mixtures) for 4 months on each. Live weight (mean of ten animals) and dietary energy concentration were measured at 2- or 3-weekly intervals. Values for feed intake estimated by back-calculating from feeding standards were on average 2·5% higher (range, 10% less to 12 % higher) than intake values estimated directly from dietary energy concentration and live weight. In contrast to this level of agreement of means, differences between methods within pastures were so large as to suggest the presence of overriding effects on predictors of voluntary intake. It was concluded that until these overriding effects are explained, there are no means of validating measured intakes in grazing cattle, or of accurately predicting the amount of beef produced from pasture.