Experiments were devised to establish suitable techniques of screening seedling material of Lolium perenne for cold tolerance under controlled conditions: these techniques were then used to distinguish between varieties and ecotypes from contrasting climatic regions. For the wide range of material used, greatest discrimination was achieved by 14 days hardening at 2 °C and 8 h photoperiod, followed by 2–4 days freezing at -8 °C in the dark. There were indications that the light intensity and/or temperature before and during hardening could considerably modify the cold tolerance.

The most useful criterion of cold tolerance was the percentage of tillers surviving 14 days after thawing. In some instances, death of tillers and whole plants continued after this time, and this tendency appeared to be related to growth habit; southern ecotypes were particularly susceptible.

Varieties from north Europe were generally more cold tolerant than ecotypes from the Mediterranean region, but tolerance depended also on the altitude of the original habitat. The cold tolerance of a population could, in part, be related to the average lowest temperature in the coldest month and in part to environmental conditions of solar radiation and/or temperature during the autumn in its place of origin.

Along with the experiments under controlled conditions, spaced plants of the same populations were grown in the field in order to evaluate winter hardiness under local conditions. The overall correlation between winter hardiness in the field and cold tolerance as assessed in the growth rooms was not high. Results from one year's field testing showed that indigenous varieties such as S. 23 and S. 24 were more winter hardy than foreign ecotypes and varieties, even if these came from colder climates and showed greater cold tolerance in the growth room.

Fibres of anomalous length or diameter are undesirable in the Merino, a breed noted for uniformity of fleece characters. Previous studies which have aimed at estimating adult fleece quality have been based on visual appraisal of the birthcoat. This study was undertaken to test the prediction of uniformity of fibre length at 10½ months and fibre diameter at 15 months from the objective measurement of birthcoat fleece and skin follicle characters.

The results indicated that fibre length uniformity at 10½ months cannot be predicted from measurement of fleece or skin characters at birth. It was found that fibre diameter uniformity at 15 months can be predicted from objective measurement of mean fibre diameter of the birthcoat but not by visual appraisal.

The metabolizable energy (ME) values and net absorption of tallows containing 20, 40, 60, 80 or 98% free fatty acids were determined using mature laying hens. By restricting food intake, the intake of the tallows was controlled to 3, 5, 10 or 20 g per bird d. The tallows were added to a diet of known ME content and the ME's of the tallows were calculated from the data collected from 6- or 7-day energy balances.

ME and net absorption values of the tallows were significantly (P < 0·001) lowered when the level of intake was increased from 3 to 20 g/bird d. The values were also significantly (P < 0·001) lowered when the free fatty acid content was increased from 20 to 98%. The effects of free fatty acid level (F) and level of intake (L) on the ME and net absorption values were considered in terms of curved surfaces represented by equations embracing the factors and their product. The equations obtained were:

ME(kcal/g) = 8·745 – 0·004F – 0–361 log10L–0·011 F log10L,

Net absorption (%) = 95·82 + 0·02F – 4·65 log10L – 0.13F log10L.

In a pot experiment, the growth of sugar beet on one soil with three levels of exchangeable Na ceased when the intensity of K measured as the activity ratio aK/√[a(Ca + Mg)] in the equilibrium soil solution had fallen to 6 × 10–4 (mole per litre)½;, the intensity of Na, aNa/√[a(CaH-Mg)], to between 1·7 and 4 × 10–3 (mole per litre)½;and exchangeable Mg to 0·14 m-equiv per 100 g soil. It was concluded that both the Na and the K intensities were exhaustion values but that K supply was preventing further growth. The additions of Na did not affect either yield or the uptake of K, Mg and Ca, but more Na was taken up from soils with higher Na levels.

A Lolium perenne L. population derived from a very productive 6-year-old S.23 ley was compared with that obtained from breeders' seed of S.23. The ryegrasses wqre grown in boxes sown separately, together, and also with Poa trivialis L. Three rates of nitrogen were applied equivalent to 28, 336 and 672 kg N/ha.

The results obtained when the two ryegrasses were sown separately differed from those obtained in mixtures. When sown alone, the difference between the two ryegrass populations was small, but the ‘survivor’ ryegrass had a slightly higher yield of dry matter and nitrogen at some sampling dates and fertilizer nitrogen rates. In the mixture of the two ryegrasses, S.23 was higher yielding than the ‘survivor’ population when the equivalent of 672 kg N/ha was applied, but not at lower nitrogen rates.

When grown as pure swards, P. trivialis did not yield as much dry matter and nitrogen as L. perenne at the highest N application. In the intergeneric mixtures, the total yield of ryegrass × P. trivialis was not very different from that of ryegrass sown alone. P. trivialis depressed the yield of ryegrass in May and June, particularly when fertilizer N was applied; the reverse effect was recorded later in the year. Total drymatter yield of ryegrass and P. trivialis grown together was similar at the highest fertilizer N rate, but the yield of N was much higher in ryegrass than in P. trivialis.

The relationship between digestibility (% DOMD in-vitro)and voluntary drymatter intake of a range of grasses conserved as artificially dried grass, has been studied in two experiments with reference to growth stage, percentage of leaf, stem and dead material, number of days to harvest and dry-matter yield.

In the first experiment digestibility accounted for 69% of the variation in intake during first growth and differences were established between varieties of the same and of different species in (a) intake at similar levels of digestibility and (6) the rate of change of intake per unit change of digestibility. In the second experiment differences in intake were established between varieties, within and between first growth and regrowth, when compared at a similar level of digestibility.

The variation in intake between varieties at a similar level of digestibility was not correlated with stage of growth or percentage leaf, stem and dead material in either first growth or regrowth. However, number of days to harvest and to a lesser extent, dry-matter yield, were associated with this variation, but only in first growth.

regrowths of grasses generally resulted in higher intakes than first growths, but the varietal variation in intake was not correlated between growths.

The effect of seedling disturbance on the yield and growth habit of swedes was studied in ten experiments during the period 1960–3. Seedling disturbance consisted of the removal of soil from around the seedlings during singling, thus exposing the hypocotyl and leaving the seedlings prostrate.

Plant numbers were reduced slightly by seedling disturbance in half the experiments but not sufficiently to be a source of yield loss at the populations attained.

Seedling disturbance greatly increased the incidence of prostrate growth in swede varieties of intermediate shape, such as Victory. Two globe-shaped varieties, Bangholm and Pentland Harvester, grew erect irrespective of singling technique.

Disturbance of seedlings reduced yield when it increased the number of prostrategrowing plants. The yield depression ranged from 0·2 to 5·2 cwt D.M./acre.

The metabolizable energy values of eleven samples of field beans (Throws M.S.). representative of different generations, locations and soil types, were determined using 3-week-old broiler chicks. A mean ‘classical’ value of 2·40 ± 0·09 kcal/g (10·09 kJ/g) was obtained, together with a mean nitrogen-corrected value of 226 ± 0·11 kcal/g (9·47 kJ/g). There was a considerable variation within groups of samples classified according to generation, location or soil type, so that no distinct relationships were detectable. Supplementary analytical data relating to moisture, crude protein, oil and fibre of the samples are also presented.

Five experiments (1965–9) on calcareous sandy loam tested all combinations of four amounts of nitrogen (0–1·8 cwt/acre N) and four plant populations (8000–54 000 plants/ acre) given to sugar beet grown with and without irrigation. On average, nitrogen and plant population influenced yields greatly but irrigation relatively little. In all years between 0·6 and 1·2 cwt/acre N and between 17000 and 32000 plants/acre gave largest sugar yield. Giving more nitrogen or increasing the plant population neither increased nor decreased sugar yield much in any year. Irrigation was beneficial in only two out of five years.

Sugar yield was linearly related to root dry-matter yield. Although total dry matter was greatest when the largest plant population was given the largest dressing of nitrogen and irrigation, the proportion of dry matter in the roots was decreased by all three factors.

The concentration of nitrogen, phosphorus, potassium, sodium, calcium and magnesium was measured in the dry matter of sugar beet from four field experiments (1966–9). All combinations of four amounts of nitrogen fertilizer (0–1·8 cwt/acre), four plant populations (8800–54000 plants/acre) and irrigation were tested, which gave a wide range of plant size and yield. Nutrient concentration and uptake by the crop were also greatly affected by the treatments.

Nitrogen fertilizer and irrigation increased uptake of nitrogen by the crop but increasing the plant population had little effect on uptake and decreased the concentration of nitrogen. Sugar yield was related to the total nitrogen concentration in tops and roots and to uptake. There were optimal values of nitrogen concentration for maximal sugar yield, but the optima were greatly affected by plant population. Leaf colour was a good guide to nitrogen concentration.

Phosphorus concentration was affected little by the treatments but cation concentrations were greatly affected. In general, uptake of all the elements was increased by all treatments – the exception was sodium, which decreased as the plant population increased but this was balanced to somo extent by increased potassium uptake.

A neutron moderation meter was used to measure soil moisture 0–4 feet deep in plots of sugar beet carrying two plant populations (8800 and 54000 plants/acre), each with and without irrigation. Recordings began in April or May in each of three years (1967–9) after sowing the crop and continued at 1 or 2-;week intervals until harvest in October.

The measured soil moisture deficits were very similar to potential deficits calculated from meteorological measurements. This indicates that the crop could extract the water needed for transpiration from the soil even when the deficits were quite large (more than 5 in in 1967), which probably explains the small response to irrigation by sugar beet in England.

When the soil moisture deficit increased rapidly early during the season (1967), the crop extracted water from the soil by exhausting the available water from progressively deeper horizons, whereas when the deficit increased rapidly late during the season (1969) water was still being extracted from all horizons until harvest. Both decreasing the plant population and irrigating decreased the amount of water used from depth in the profile every year.

The total amount of water used (evaporation plus transpiration), on average, from soil reserves and rainfall, was 12·2 in by the small population and 13·4 in by the large population. When irrigated, the consumption increased to 14·2 and 15·4 in. respectively. The difference in usage between populations was almost entirely from the difference in leaf cover early during the season. The water consumption in 1968, when the summer was wet, was only two-thirds of that in 1967 and 1969 when the summers were drier.

To produce forage crop varieties of improved quality, the plant breeder must consider both the content of the quality components and their interrelationships. The methods used to examine the interrelationships involve simple correlations and path analyses. In the path analyses a dependent variate is specified which is completely and additively determined by a number of independent variates. The amount of variation present in the dependent variate accounted for by variation in each of the independent variates is calculated. The effects of an increase in the mean content of one of the quality components on the other components in the path system is predicted.

As an example of the method, data for two years is analysed from timothy polycross progenies grown as swards and spaced plants. Primary and subsequent growths are compared.

There are inconsistencies in the interrelationships of the quality components between years and between swards and spaced plants. Although only phenotypic statistics were calculated, the findings have implications in relation to plant breeding.

A study of the theoretical expectation of F1 hybridity resulting from bulk interpopulation hybridization in herbage grasses has been made. It is concluded that the main factor affecting the percentage interpopulational F1 hybrid content of the seed product of a two-population mixed sward is degree of coincidence of population flowering patterns. The effects of differences in population parameters are examined for a range of population types. Other factors such as differences in total gamete frequencies, preferential fertilization and differential pre- and post-harvest seed losses are also considered.

A method of analysis of two factor experiments is given. This involves a development of the regression analysis used by Finlay & Wilkinson (1963) and others, and allows for the regression of interaction components onto both main effects. The usefulness of the single joint regression parameter for prediction is outlined.

The applicability of the analysis to three situations commonly found in grass breeding is illustrated by means of examples. It is concluded that the model may frequently describe variation due to genotype-environment interactions, and among diallel arrangements of binary mixtures of genotypes, but is likely to be of little utility for genetic diallel or other mating schemes unless the genes have a strongly correlated distribution among the parent plants.

1. A field trial in which a sward, predominantly of S. 24 ryegrass was fertilized with 248, 301, 532 or 589 kg N/ha showed that a maximal yield of 13·1 tonnes/ha of artificially dried grass could be obtained from four harvests in the year.

2. The materials harvested ranged in crude protein content from 10·1 to 23·6% and in apparent digestibility of dry matter from 72 to 76%. The amounts of the grasses voluntarily consumed by sheep were slightly and significantly lower for those containing the least N × 6·25.

3. In feeding trials with twenty-five steers, a barley diet was compared with a diet entirely of dried grass from the 3rd and 4th harvests from an area in the same field which had received 487 kg N/ha. The cattle given the barley diet consumed 8·7 kg/day and gained 1·22 kg/day. Those given dried grass consumed 8·9 kg and gained only 0·85 kg/day. Carcass quality of animals given dried grass was significantly lower than of those given the barley diet.

4. Calorimetric trials were made using two herbages from the first harvest (501, 532 kg N/ha) and all four herbages from the third harvest. In each of the six experiments three sheep were each given three amounts of a herbage, and in addition were fasted. Fifty-four calorimetric observations each lasting 5 days and eighteen fasting metabolism measurements were made.

5. With both 1st and 3rd harvests, methane energy losses fell and urinary energy losses increased with the level of N fertilization. Faecal energy losses were little affected by fertilizer application and the metabolizable energy (kcal/g D.M.) was 2·8 (11·7 kJ/g) for 1st harvests and 2·6 (10·9 kJ/g) for 3rd harvests. There was a slight decline in metabolizable energy/g D.M. with N application for the 3rd harvests.

6. The net energy values of the grasses for maintenance were 1·99 kcal/g D.M. (8·4 kJ/g) for the 1st harvested material and 1·84 kcal/g D.M. (7·7kJ/g) for the 3rd harvests. Net energy values for fattening, however, were 1·28 kcal/g D.M. (5·4kJ/g) for 1st harvests and 0·87 kcal/g D.M. (3·6kJ/g) for 3rd harvests. There were no significant effects of level of N fertilization.

7. The poorer nutritive value for fattening of the 3rd harvested grass, corresponding to an efficiency of utilization of metabolizable energy of only 33%, was contrary to prediction from equations relating nutritive value to either chemical composition or to metabolizable energy. The results of the calorimetric work, however, agreed with those of the feeding trial with cattle.

8. Combination of the results of the various trials showed that it was possible to obtain 1400 kg live-weight gain/ha from a system of husbandry based on high fertilizer use and artificial drying of herbage. With a barley system a maximal output/ha would be less than half this amount.

During the nineteenth century several parts of Wales were intensively mined for lead, zinc and copper ores. Fields adjacent to and downstream from the mines became contaminated by air- and water-borne heavy metal compounds. Such fields still contain high concentrations of total lead, zinc and copper together with silver and cadmium, the chief ‘guest’ elements in lead and zinc ores. Extraction of the soils with dilute acetic acid suggested that contaminated soils contained more of these metals that were available to plants (Alloway, 1969; Alloway & Davies, 1971). Some studies of plant composition were made to confirm the evidence from soil extraction and to indicate the extent to which these metals were entering the food chain.