Two steers (Bos indicus and Bos indicus x Bos taurus) were acclimatized to an ambient temperature of 30 °C before working at this temperature on two treadmills (gradients 0 and 6°) for 2 h (one on each treadmill) whilst carrying a load equivalent to 10% of body weight. The study was then repeated at an ambient temperature of 15 °C. The effect of variation between animals, ambient temperature and rate of energy expenditure were tested on the linear regression model EEw = A PHR + B (where EEw is the energy expenditure (w/kg0·75) and PHR is the percentage increase of working heart rate over resting heart rate).

Animal and ambient temperature had no significant effect on the model. The gradient of the regression line was significantly greater (P < 0·01) when the animals were expending energy at the higher rate (about 30 W/kg live weight0·75) than when they were expending energy at the lower rate (about 14 W/kg live weight0·75).

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 results of a preliminary investigation on this subject, in which single plots were used, which were published in 1921, tended to show that the following inferences, in respect to the relation of size and type of tuber-set to crop, might be drawn.

1. The size of the crop varied directly with the weight of the set up to a certain point, viz. 2 ozs., the crop then sinking slightly to a more or less constant level, whilst the weight of the set increased.

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.

The writers do not mean to infer that the maintenance requirement of the adult sheep, as calculated by Wood and Capstick, is incorrect. The value obtained by these investigators is probably as reliable as any other which could be calculated from their data. The writers fully agree that Wood and Capstick's value is probably more accurate than previously estimated values of the maintenance requirement of the adult sheep.

Leucaena leucocephala (Lam.) de Wit, a leguminous shrub, has come into use as a fodder plant for animals in the Ryukyu Islands as it provides highly palatable, high quality feed (Kitamura, 1985). It is superior to other feeds available in this regard (Higashiohmine, Aramoto & Yamashiro, 1971; Isa et al. 1982).

The relationship between rate, spray interval and number of applications of Decis for pest control in cow pea was investigated. In 1978 and 1979, neither the rates nor the interaction effects were significant in grain yield when 12·5 and 25·0g a.i./ha of Decis were applied three times weekly or twice at intervals of 10 or 14 days.

Further trials in 1980 showed that for the contro l of thrips (M. sjostedti), rate, interval and number of applications were significant for samples at 49 days after planting and beyond, suggesting that the residual life of Decis is about 10 days. Three applications were significantly better than two for lowering the population of C. tomentosicollis and the number × interval interaction was also significant. The number, rate and interval were significant without interaction effects for shrivelled pods caused by all hemipteran pests. In all the trials in 1980 and 1981, damage by the pod borer M. testulalis was low. Rate and number × interval interaction were generally significant but no differences were observed in grain yield. However, in 1980 the higher rate and three applications gave better quality crop, resulting from less hemipteran damage.

An analysis of cost–benefit of the trial showed that 12·5 g a.i./ha gave higher returns than 25 g, as did two applications than three, but the trend in the spray interval was less consistent.

The growth and yield of maize grown on an unploughed newly opened secondary forest in Nigeria in 1985–87 was studied. In each year, trash was either removed or burnt in situ and each of these treatments was given N fertilizer or none. In the first year, only N fertilizer increased yields. In the second and third years, yields were increased by N fertilizer and by trash burning. Trash burning consistently increased the amount of P in the soil.

1. Loss of ignition at 450°C. and the organic carbon content of some shale soils are positively correlated (r = +0·99).

2. Base exchange capacities and exchangeable cations were determined on soils, treated and untreated with hydrogen peroxide solution.

3. Oxidizing the organic matter lessened the exchange capacities of all samples; the exchange capacity of the organic matter varied from 67·5 to 97·0 m-equiv./1OO g. dry material.

Frequently in near-infrared reflectance spectroscopy, a calibration is developed using very restricted data sets, e.g. material from one season, a small area or of a limited type: consequently, the predictions may have limited validity. This paper describes the use of both restricted and wide calibration sets for the prediction of crude protein in grass, silage and hay. Results show that predictions from the wider calibration sets are often as good as or better than predictions from restricted calibration sets. Therefore the use of wide calibration sets should be considered much more frequently in near-infrared reflectance.

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 response of three spring cultivars of oilseed rape to five levels of nitrogen fertilizer (0 to 200 kg/ha) was studied during 1978–9 (Scarisbrick, Daniels & Alcock, 1981). Sampling problems, practical difficulties of measuring yield components, and the high co-efficients of variation for these data were discussed. During the course of further investigations on the winter cultivar Jet Neuf (established on approximately 75000 ha in the U. K. during 1980–1) within-plot variability for plant weight was assessed in order to indicate the size of sample necessary to compare treatment means.

Experiments were conducted over two cropping seasons at the Sugar Cane Estate of the Nigerian Sugar Company, Bacita, Nigeria to determine the effectiveness of additional nitrogen fertilizer, chemical sprays and delayed planting in controlling flowering in two commercial sugar-cane varieties (Co. 1001 andCp. 29/116). Application of 150 and 250 kg N/ha, 8 weeks before initiation, reduced flowering in Co. 1001 by up to 13·5 and 11 % respectively. Flowering was as low as 2% in some of the above treatments while the average flowering in plots with no additional nitrogen application was more than 80%. imilarly, application of diuron (4·0 kg/ha) and paraquat (0'5 kg/ha) to the top leaves (3 weeks before initiation) of Co. 1001 reduced flowering in this variety up to 45 and 35% respectively. Neither the application of diuron and paraquat nor additional nitrogen fertilizer sufficiently reduced flowering in Cp. 29/116. The time of planting affected flowering. Over 85% flowering was observed in November 1982 from Co. 1001 fields planted in January 1982 (10 months before initiation time). However, fields of the same variety planted in June 1982 (4 months before initiation time) did not show any initiation until harvest in May 1983. The implications of the above results are discussed.

In a recent number of this Journal, T. B. Wood and F. J. M. Stratton have discussed the probable error of field and feeding experiments, but in the latter case their investigations included only cattle and sheep.

The following work was undertaken as a necessary preliminary to a series of pig feeding experiments which are in contemplation. It is published at once in the hope that the results obtained may be of use to others who may be engaged in planning similar feeding trials.

The C3 and C4 plant components in extrusa samples from oesophageally fistulated cattle can be estimated by δ13Canalysis. However, contamination with saliva containing bicarbonates could cause bias in the estimation of the C3 or C4 components. Saliva from animals fed C4 and C3 diets had δ13C values of – 4.37/103 and –15.97/103, respectively. Both values showed a large positive shift of c. 10 units relative to the diets, but the difference between feeds was maintained in the saliva. On theoretical grounds, contamination of the ingested feed with saliva should have caused a small (1·3–3·4% legume) negative bias when estimating legume percentage in the diet. This did not occur when saliva of known (PC was added to mixtures of C3 and C4 forages which were dried, ground and analysed for δ13C. It is postulated that CO2 was lost from bicarbonate when saliva was dried in contact with fresh plant material, and so no significant bias was detected. It would appear that the δ13C technique can be used to estimate the proportion of C3 and C4 components in oesophageal extrusa samples without significant bias from salivary contamination.

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.

It has been found from controlled environment studies that high temperatures lead todepressions in milk production (Johnson, 1965; Hafez, 1968; McDowell, 1972). Under outdoor situations where all climatic variables may act simultaneously on the animal, responses may vary from the classical chamber studies.

1. The efficiency of food conversion of Brown Leghorn fowls inbred for egg number, or egg size, or egg number and egg size have been compared.

2. Comparison between the lines was made for egg numbers, total egg weight and total egg energy. Egg energy was the best measure of production, total egg weight was the next best and egg number the poorest.

3. When allowance was made for differences in rates of egg production and egg size, there were no differences in the efficiency of conversion of food to eggs between the lines.

4. The standard errors of the means for the analytical data on the twelve replicate mixes of the diet were relatively small, but the range in values was appreciable. The importance of analysing diets in nutrition experiments is stressed, particularly for ‘iso-caloric’ diets.

Periwinkle (Catharanthus roseus (L.) G. Don) is an important medicinal plant grown in different parts of India. Its leaves contain vincristine and vinblastin, alkaloids which are used in the treatment of various leukaemias and limphomas, and its roots contain ajmalcine, another alkaloid, used in the manufacture of antihypertensive drugs. Cultivation of periwinkle has recently gained importance in India. The yield of periwinkle can be increased with the use of mineral fertilizers (Pareek et al. 1981, 1982; Rajasekharan et al. 1982; Reghunath & Sethumadhavan, 1982a, b; Hegde, 1986). The effect of fertilizer application on the alkaloid concentration is not clearly established though there are a few reports which suggest that application of N increases alkaloid concentration in roots (Rajasekharan et al. 1982; Reghunath & Sethumadhavan, 1982a) and leaves (Pareek et al. 1982). Therefore, the present experiment was designed to study the effect of application of nitrogen and phosphatic fertilizers and farmyard manure on the root and leaf yields, and total alkaloid concentrations in roots and leaves in Catharanthus roseus (L.) G. Don.