Introductions of red clover indigenous to the Atlas mountains of North Africa were shown to have a high degree of resistance to Sclerotinia trifoliorum when a natural attack occurred in field trials at Cambridge. Differences between the two classes of clover varieties: (1) North African populations, and (2) the British varieties Essex broad red and S. 123, were highly significant for the proportion of row affected, the number of affected areas and the average length of affected area. The North African material is expected to be a useful source of resistance to Sclerotinia trifoliorum, in breeding programmes.

We are indebted to Mr H. H. Rogers for his guidance and for collecting the red clover plants during the 1962 North African expedition which was supported by the Agricultural Research Council. We also acknowledge valuable criticism of the manuscript and provision of a computer programme by Mr J. L. Fyfe and help with field records by Mr M. Pope and Mrs H. E. Pape.

The total metabolism of the pregnant goat remains at a steady rate from the 4th to the end of the 13th week of pregnancy. It increases steadily from the 14th to the 21st week, when a value is attained about 50 per cent, above the rate at the 14th week. Just before delivery the rate drops slightly. The increased metabolism is due partly to the increase in the mass of active protoplasm and partly to the stimulus exerted by the growing ovum on the maternal tissues. This stimulus tends to fall off slightly in intensity in early pregnancy and increases markedly in late pregnancy.

Post partum the total metabolism drops suddenly and continues to fall until the end of the 5th week; but the metabolism per unit of weight increases steadily until the 4th week and then declines. This increased activity of the maternal protoplasm is due to the processes of involution and repair.

In early pregnancy the increasing intra-abdominal pressure cuts short fermentation of food and causes the R.Q. to be higher in the pregnant than in the non-pregnant animal. As the pressure increases it begins to impede slightly the evacuation of the rumen so that the food ferments more thoroughly and the R.Q. falls slightly. After parturition the low intra-abdominal pressure aggravated by the laxity of the abdominal walls allows the food to remain longer in the rumen so that fermentation is more thorough and the R.Q. lower than in late pregnancy.

A study has been made of variations in the shrinkage from the live pig to the carcass and from the carcass to the side of Wiltshire bacon. Most of the variation occurs at the first stage when the losses have a variance of 17·67 lb. compared with only 4·59 lb. and the second stage. Similarly, breed differences were found at the first stage, Wessex and Essex pigs giving 1·1 and 2·7 lb. more carcass respectively than the Large White pigs, but not at the second stage. On the other hand, differences between litter groups were found at both stages.

Correlations made between carcass measurements and yield of carcass and bacon were generally found to be small and positive. Antagonisms were indicated between quantity and quality of bacon, in particular by positive correlations between thickness of back-fat and weight of carcass, and between a desirable proportion of cuts and losses on slaughter. The problem of deciding the relative attention which should be paid to various carcass characteristics is discussed and the need for an index of total carcass merit is pointed out.

Seeds of okra were sown in moist soil and subjected to heat stress of 45 °C for 10 h on day 0 (day of sowing), day 1 or day 2 after sowing. Stresses on day 0 and, to a lesser extent, on day 1 promoted hypocotyl elongation and accelerated seedling emergence. Stress on day 2 retarded hypocotyl elongation and did not accelerate emergence. The results were similar for seeds sown at depths of 1, 4 or 7·5 cm. For 10-h stresses on day 0, 40 °C was slightly less promotive than 45 °C; but 50 °C or above resulted in no emergence whatsoever. Subjecting dry seeds to 40–60 °C for 24 h before sowing gave no appreciable acceleration of emergence; instead, at 60 °C there was a 24-h delay in the onset of emergence. Seeds were also incubated for 1·5 h in water at temperatures ranging from 40 to 80 °C. Emergence was accelerated at 40 to 65 °C, with the greatest acceleration at 45 °C. It is suggested that incubating the seeds at 45 °C for 1·5 h before sowing could afford a practical means to accelerate field emergence of okra.

Recent developments in chemical weed control in sugar beet have been reviewed. Two main approaches to the problem of providing reliable season-long control of annual weeds in sugar beet are, (a) the use of mixtures of herbicides applied pre-planting and incorporated into the soil during seed bed preparation, and (b) the use of split applications with a residual herbicide applied pre-emergence followed by a contact herbicide applied post-emergence.

The second approach (b) was examined in a series of field experiments from 1967 to 1969, on light to medium sandy loam soils in the West Midlands. Comparisons were made between pre-emergence application of lenacil and pyrazon, pre-emergence application of lenacil and pyrazon followed by post-emergence application of phenmedipham, and post-emergence application of phenmedipham for weed control in sugar beet.

Under dry soil conditions in April 1967, lenacil and pyrazon controlled only about 40% of the annual weeds, but in 1968 and 1969, when moist soil conditions predominated in April and May, lenacil and pyrazon controlled 80–95% of the annual weeds.

Phenmedipham applied post-emergence gave about 90% control of annual broadleaved weeds initially, but it seemed unlikely that a single application of this herbicide would provide satisfactory weed control in sugar beet.

In each of the 3 years 1967–9, a split application of a soil-acting residual herbicide (pro-emergence) followed by phenmedipham (post-emergence) gave outstanding weed control and enabled sugar beet to be established and grown until mid-June at least, in a near weed-free environment. It was concluded that this technique was the most effective for weed control in sugar beet on light to medium sandy loam soils in the West Midlands.

Seven non-destructive field measurements were made on 1270 pigeon-pea plants varying widely in age, size and plant type, before determining their dry weight. The non-destructive measurements were generally highly correlated with one another, and were all significantly correlated with total, total above-ground and structural dry weights. In one experiment dry weights were best predicted by a multiple regression using stem diameter, length of longest branch and number of branches as predictors. Field height and stem diameter were the best predictors in a second trial. It is suggested that dry weights can be estimated by taking certain measurements at regular intervals, simultaneously sampling a number of plants to determine the best predictive equation. Where it is unnecessary or impracticable to do this, stem diameter appears to be the best single index of dry weight.

The influence of dietary nutrients on carcass composition, rate of tissue deposition and the development of specific tissues, major and minor muscles in particular has been well documented for pigs reared in a temperate environment. Attempts have also been made in this environment to simulate artificial tropical conditions and, on the consequence of such conditions, to predict the nutrition and growth of the pigs.

An experiment in which all combinations of four rates of N fertilizer soon after sowing, four in early spring and nine in late spring were applied to the same plots of winter wheat for 6 years is described and the effects discussed.

It was found that although the yield varied considerably from year to year the regime leading to greatest yield was fairly consistent. If the farmer had used the regime which gave the greatest average yield (0, 90, 180 kg N/ha in autumn, early spring and late spring, respectively) he would have averaged only 0·12 t/ha less than the maximum attainable each year.

Application of N increased protein concentration in the grain more or less linearly but the latest application increased it most. Since the regime which gave greatest yield on average produced grain which qualified for bread-making premium from the protein point of view in all years except 1981, adopting the regime which gave maximum yield would reduce the potential maximum gross margin by only £30/ha.

Analysis of the soil showed a reduction in pH down to 15 cm and of available P2O5 down to 10 cm.

Corolla colour in chickpea (Cicer arietinum L.) is white or various shades of pink or blue (Smithson, Thompson & Summerfield, 1985). Normally, a leaf axil subtends a single peduncle bearing a single flower but ‘double-flowered’ types, where a pro-portion of the peduncles subtends two flowers, are not uncommon and produce 6–11 % more seed yield than the normal single-flowered type (Sheldrake, Saxena & Krishnamurthy, 1978)

Bleasdale & Nelder (1960) refer to several models which have been used in studying the relationship of yield and density in crop plants and indicate that they regard as most satisfactory the equation:

where ω = yield/plant, ρ = number of plants/unit area and A and B are constants. The estimation of the constants for any given case is a very unattractive arithmetic exercise requiring a fairly large number of observations and a tedious iterative calculation; Nelder (1961) has discussed the least squares fit with the equation in the form

which may readily be derived from (1) by the substitutions

The data in the present case do not justify attempting this process but some progress can be made by the substitutions

by means of which it is easy to derive from (1) that

The extent of variation in ratoonability was examined in a range of recently bred short-duration pigeonpea [Cajanus cajan (L.) Millsp.] genotypes in 1989/90, 1990/91 and 1991/92 at the ICRISAT Asia Center, Andhra Pradesh, India. Traits with which this variation could be associated were assessed. Differences in the total ratoon yield of two flushes were significant among the genotypes in each season. In a few genotypes, ratoon yield constituted 50% of the total yield, which could be as high as 5·6 t/ha. Total ratoon yield was positively correlated with leaf area index in the last 2 years of experimentation. The relationship of total ratoon yield to main crop yield was significantly positive in 1991/92 only. The results suggest that there is a large variation in ratoonability among short-duration genotypes and that high leaf area retention at main crop maturity appears to contribute substantially to this variation.

The relative unreliability of Bouyoucos's suction method for moisture equivalent determinations is a consequence: (1) of the variation of the suction force maintained with the nature of the soil, (2) of bad reproducibility of the results.

Constant and equal suction for all soils is secured by Schofield's silt-suction method, which may also be made to give fairly well reproducible results. The moisture content at pF 2·9 determined by this method should give a fairly close measure of the moisture equivalent.

While investigating this possibility it was found that the pF curves of stored soil samples may shift considerably with time. In the samples studied the pF at the moisture equivalent has dropped from 2·9 to about 2·4 in 7 years. In view of this shifting the reliability of the silt-suction method for moisture-equivalent determinations has not been definitely ascertained by the experiments reported.

1. Continuous waterlogging and 4 weeks' waterlogging immediately after transplanting produced plants with higher leaf and shoot numbers.

2. There was no difference in the final shoot number between plants continuously waterlogged and those waterlogged for 4 weeks, immediately and 4 weeks after transplanting. The shoot mortality was higher in the continuously waterlogged plants and those waterlogged for 4 weeks immediately, 8 weeks and 12 weeks after transplanting than in those waterlogged for 4 weeks, 4 weeks after transplanting.

3. Continuously waterlogged plants and those waterlogged for 4 weeks, 4 weeks after transplanting, were taller than those waterlogged for 4 weeks, immediately, 8 weeks and 12 weeks after transplanting.

4. Leaf area per bucket, leaf area per shoot and per leaf lamina were higher in continuously waterlogged plants and those waterlogged for 4 weeks, 4 weeks after transplanting, than in those waterlogged for 4 weeks immediately, 8 weeks, and 12 weeks after transplanting.

5. Continuous waterlogging and waterlogging for 4 weeks, 4 weeks after transplanting, increased the physiological age of the plants as evidenced by earlier ear emergence and grain ripeness.

6. Fresh-weight yield, yield of grain and panicle were greater in continuously waterlogged plants and those waterlogged for 4 weeks, 4 weeks after transplanting, than in those waterlogged for 4 weeks immediately, 8 weeks and 12 weeks after transplanting.

7. The critical period for waterlogging in the cultivation of the rice variety studied is 4 weeks after transplanting and waterlogging applied during this critical period for 4 weeks favours higher yield of grain than when applied for the same period earlier or later than this period. Where water supply is limited the plants should only be waterlogged at this period and the soil kept moist throughout the remaining growing period. However, where there is enough water to waterlog the plants for 8 weeks this should be started immediately after transplanting.

1. Four varieties of marrow stem kale, three of thousand headed kale, Hungry Gap Kale, Rape-Kale and five other rape varieties were sampled at two centres in mid-Wales and separate leaf and stem samples analysed for manganese, molybdenum and boron. Similar samples of four varieties of marrow stem kale, two of thousand headed kale, Hungry Gap Kale, Rape-Kale and two other varieties of rape were taken from two further centres and prepared with the most stringent precautions to prevent contamination. Iron, copper, zinc and lead were determined in these samples.

1. The age of 210 days was selected for calf weight standardization. In general this is a preweaning weight under prevailing Jamaican conditions, and it represents a compromise between a very early age (90–120 days) which would reflect closely the milking ability of the dam, and the actual weaning age (approximately 260 days) when the grazing management of the herd would constitute a major unpredictable variable.

2. Either one or two weighings taken between the fourth and the ninth months of life was used to standardize calf weights to 210 days of age. In either instance for groups of calves, a mean estimate was derived which was very close to the actual mean 210-day weight, and which was suitable for data relating to groups of animals.

Two methods of determining the weight and one method of determining the volume of water imbibed by a soil have been discussed. The results of these methods have been shown to be concordant by an independent method.

The tentative conclusion reached is that the weight of water a soil imbibes can be readily determined by Fisher's method or from the Keen-Raczkowski box, but that the volume of imbibed water cannot yet be directly determined accurately.

Maize or lucerne silages were fed to two groups of cows in a large dairy herd. Metabolic profile tests carried out during the trial showed that abnormal blood chemistry such as might lead to production disease did not occur in either group.

The results of feed analysis and digestibility trials showed that the two silages provided equal quantities of digestible energy but that the lucerne silage provided more digestible protein than the maize silage. Blood glucose concentrations were similar in both groups of cows but serum urea and albumin concentrations were significantly higher in the cows fed lucerne silage than in those fed maize silage. There was also evidence that lucerne silage provided slightly less available phosphorus but more calcium than the maize silage.

It is concluded that maize silage, as used in these experiments, showed no tendency to lead to production disease, and furthermore the metabolic profile test provided additional information to feed analysis in making this assessment.

The possible adaptive significance of the occurrence of HK and LK red-cell types in Murrah buffaloes was investigated. Judged by haematological indices and thermorespiratory responses under conditions of moderate thermal stress, LK animals appeared to have a greater adaptive potential than HK animals in a hot arid environment. Dry matter percentage, packed cell volume (pcv), haemoglobin concentration (Hb), red blood corpuscles (RBC) and plasma protein values were significantly higher in LK-type animals. In addition, under identical conditions of thermal stress the LK animals exhibited significantly less rise in rectal temperature and respiratory rate than the HK animals.

1. An experiment was performed to compare some methods of supplying calcium to intensively kept chickens.

2. The calcium content of a mash was adjusted to contain low (0·13%), normal (1·16%) and high (2·14%) amounts, and each of these mashes was fed to groups of chicks having access to: (a) no grit, (b) flint grit alone, (c) limestone grit alone, (d) both flint and limestone grit.

3. The addition of flint grit significantly improved the efficiency of food utilization on all diets, whether limestone grit was provided or not.

4. On all three mashes the total amount of calcium grit consumed was greater in the presence of flint grit than when it was fed alone.

5. As the level of calcium in the diet increased, the amount of limestone grit consumed decreased, whether it was fed alone or in the presence of flint grit.

6. The best results, judged on a live-weight basis, were obtained when the normal calcium mash was fed with flint grit alone, followed by the low calcium mash with both flint and limestone grit, followed by the normal calcium mash with no grit.

7. On the basis of the efficiency of food utilization, the low calcium diet with flint and limestone grit was best followed by the normal calcium diet with flint grit alone.

8. Access to limestone grit reduced the efficiency of food utilization in all but the low calcium diet.