The objective of this study was to examine the effect of the chemical growth regulator chlormequat on the yield and yield components of oil-seed rape. Although this chemical is widely used in wheat production systems, its use as a morpho-regulator for oil-seed rape has not been examined thoroughly. A few Eastern European experiments have been published. Voskerusa (1972) applied it at 2, 4, 6 and 8 kg/ha to winter varieties in Czechoslovakia. His results, which agree with those of Fabry & Hannich (1972), demonstrated reduced winter kill using an autumn application. However, studies on modern varieties such as Rafal, now widely grown in European Economic Community countries, have not been reported in detail.

Two experiments were carried out with adult sheep to investigate the effects of chloral hydrate (CH) on rumen metabolism and on the sites and extent of digestion.

Experiment 1 confirmed that CH is a very potent methane inhibitor; doses of 1 or 4 g/day reduced methane production to 4% of that observed in the absence of the drug. In both experiments, CH administration altered the proportions of volatile fatty acids in rumen fluid. The main changes were an increase in propionic acid and a decrease in acetic acid with smaller increases in the proportion of isovaleric, valeric and caproic acids. Stoichiometric calculations indicated that only 21% of the hydrogen saved by prevention of methanogenesis was diverted to the synthesis of additional propionic and butyric acids and the fate of the remaining hydrogen was not determined unequivocally.

CH had little effect on the extent of biohydrogenation in the rumen of the long-chain fatty acids in dried grass.

The apparent digestibility of ether extract was reduced (P < 0·05) by CH but those of other proximate constituents and energy were little affected. There were no s gnificant effects of CH on the extent of digestion of dry matter, organic matter, non-ammonia nitrogen or ash between the mouth and abomasum, abomasum and terminal ileum or ileum and anus.

Pyrethrum flowers are widely used in different insecticidal formulations for controlling household insects and crop pests. The quick knock-down effect on insects, the low mammalian toxicity and the rapid decomposition of pyrethrins in the soil make it an ideal and safe insecticide. The flower yield in pyrethrum is influenced by plant population density and phosphate fertilizer application (Nair, 1955; Kroll, 1962, 1963; Parlevliet, Muturi & Brewer, 1968a, b). Parlevliet et al.(1968a, b) recommended a spacing of 60 × 30 cm whereas Nair (1955) suggested a spacing of 75 × 60 cm for obtaining higher flower yields in this crop. The present investigation was made to compare the effects of different spacings and rates of nitrogen application on the flower and pyrethrin yields of pyrethrum.

It has long been known that the size and shape of sampling units used to assess crop yield may have significant effects upon the precision of the estimates (Smith, 1938; Hudson, 1939) but little is known about the effects when estimating incidence of disease. Gilligan (1980) showed that estimates of the incidence (i.e. presence or absence of disease) of stem canker (Phomx, lingam, perfect state Lepto sphaeria maculans)of oil-seed rape were more precise when large square sampling units rather than long rectangular units of similar area or small square sampling units were used. Moreover, estimates derived from the frequently used method of sampling by removal of 25 stems, supposedly at random from each plot, were shown to be biased.

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.

The area of groundnuts in the Sudan has greatly increased in the last few years, as a result of introducing the crop in the Kenana Scheme (15000 ha) and the Rahad Scheme (50000 ha), as well as the intensification of the Sudan Gezira Rotation (225000 ha).

The apparent digestibility of a diet can be calculated from the amounts of food eaten and excreta voided. This ‘total collection’ method is laborious because it requires a period lasting several days. It can be circumvented by the inclusion in the diet of a suitable reference substance (Kotb & Luckey, 1972). From the concentration of the reference substance (marker) in the diet and in the droppings, apparent dry-matter digestibility can be calculated.

Harvest index has become a character used in plant breeding programmes and in evaluation of responses to agronomic treatments (Donald & Hamblin, 1976). Donald (1962) defined harvest index as the ratio between weight of grains and the weight of total dry matter, and later described it as a measure of partitioning of photo - synthates (Donald, 1968)

That rhizobial strains belonging to pulses not only differ among themselves but also show differences in their effectiveness when Azotobacter isolates are used as co-inoculants has been shown by Sanoria & Ram (1979) and Sanoria & Mallik (1981). This has now been further demonstrated in trials conducted over 2 years using bengal gram. These trials also included a phosphate solubilizing bacterium (Pseudomonas spp.) as an extra inoculant but it had no effect on the responses obtained.