Field experiments were conducted for 2 years (1977–8 and 1978–9) at the Indian Agricultural Research Institute, New Delhi under semi-arid seasonally dry tropical conditions to evaluate the possibility of growing two crops under natural precipitation, where traditionally one crop is grown. Short-season fodder crops of cow pea (Vigna unguiculata), guar bean (Cyamopsis tetragonoloba), moth bean (V. aconilifolia), soya bean (Glycine max.) or pearl millet (Pennisetum typhoides) harvested before the end of monsoon rains enabled sufficient recharge of the profile from the precipitation received subsequently to enable barley to be sown in the winter season. Although the pearl millet yielded more biomass, the soil fertility enrichment was greater from the legume fodders. The grain yield and total nitrogen removal by barley was higher after the legume fodders than after the non-legume fodder pearl millet. Benefits from the previous fodder legumes were equivalent to or more than 40 kg N/ha applied to barley crop following a previous crop of pearl millet.

Non-breeding groups, I, II and III, each with six high-potassium (HK) and six lowpotassium(LK) Chokla ewes were given water once in 24, 48 and 72 h respectively. In the next summer, seven ewes (4 HK and 3 LK) from each group I, II and III were switched over to a watering schedule of once in 24, 72 and 96 h respectively and were naturally bred. All the animals were maintained on grazing alone.

Water deprivation for 72 h caused 18·8 and 19·2% body weight loss in HK and LKewes respectively; an overall average maintenance of weight loss in LK ewes was significantly higher than in HK ewes from the same group. There were significant differences in water intake due to treatments only. The HK and LK ewes from groups I and III showed a similar trend.

Pregnant ewes of HK and LK types given water once in 96 h lost 21·7 and 23·8% of their body weights respectively. Corresponding weight loss in aborted ewes were 23·8 and 33·3%. Two ewes, each from 3 LK and 4 HK animals aborted owing to water deprivation for 96 h. The water intake reached 30 and 36·5% of body weight in LK and HK pregnant ewes given water intermittently.

The wool attributes of non-pregnant ewes did not indicate a significant influence of blood potassium types. Four out of five ewes of the LK phenotype died during 3 years, irrespective of watering schedule.

An analysis of yield data from 31 tea clones grown in replicated trials at four locations revealed the presence of significant genotype-environment interactions. Joint regression analysisshowed that a significant proportion of these interactions could be attributed to differences in the linear response of each genotype (clone) to the range of environments. However, estimates of the deviations from regression were also significant, indicating the presence of some unpredictable variation.

The response of each individual clone was estimated by computing the regression coefficient of individual yield on environmental mean yield at each location. The clones used in this study had regression values ranging from 0·19 to 2·08, indicating considerable genotypic difference in response to environmental change. Genetic variation in adaptation was also found to be present. Clones of the Assam type were found to possess general adaptation whereas the one clone of Indo-Chinese origin was specifically adapted to low-yielding environments.

Some known features of several tea clones are explained on the basis of the linear regression model and a more scientific basis is provided for the recommendations of clones for differentdistricts. The implications of genotype-environment interactions in practical tea breeding and selection are also discussed.

The indices of susceptibility of five new varieties of maize: TZE 3 (3·01), TZE 4 (6·69), TZSR (5·58) developed at the International Institute of Tropical Agriculture, Ibadan, and MSRB-W (9·53) and MSC-opaque (5·0) at the National Cereals Research Institute, Ibadan, showed that the yellow variety, TZE 3, is the most resistant to post-harvest infestation by Sitophilus zeamais Motsch and Sitophilus oryzae (L.), the latterbeing the more abundant species.

Emerging F1 generation adults of either species of Sitophilusdeveloped longer, and were more numerous in soaked maize seeds without testa than in unsoaked, intactmaize seeds. Seed germinability declined as the number of holes per maize seed caused by adult insect emergence increased.

The determination of in vitro dry-matter digestibility (DMD) of grass and pasture legumes under both temperate and tropical conditions is well established (Tilley & Terry, 1963; Minson & McLeod, 1972). One application of the in vitro DMD estimation of pasture samples is, together with an estimate of faecal output, the measurement of the herbage dry-matter intake of grazing cattle. Pasture samples are usually collected with oesophageal fistulated cattle. This technique is well documented and has been reviewed by a number of authors (Langlands, 1975; Minson et al. 1976).

Low quality roughages are a major feed resource for ruminants in Australia and many other parts of the world. Factors limiting the intake of these roughages include their high cell wall component and low crude protein content. Palatability may also be important. Low quality roughages are frequently dusty. Hence, the present experiment was initiated to determine whether water would affect the intake of paspalum hay (Paspalum dilatatum).

In the Sudan, rice has been grown since 1905, but on only a very limited acreage, and information about methods of production are lacking.

With the introduction of a large number of rice varieties into the country (Moir, 1965, 1966, 1967, 1968), an irrigation and drainage experiment was initiated by Hack (1968) at Kenana Research Station (KRS). Using the variety H.D.41, he found no advantage from very short watering intervals (1–3 days) in the early stage of growth, i.e. up to the boot stage, whereas better results were obtained from watering every 6 days in the early stage, to obtain a large number of flowers, and every other day in the late stage, to obtain relatively low sterility and large grains.

Environmental conditions (Clark & Quin, 1949; Daws & Squires, 1974; Degen & Young, 1980) and total feed intake (Clark & Quin, 1949; Forbes, 1968; Degen & Young, 1980) influence the water intake of sheep. In general, high temperatures increase the requirements for water needed for evaporative cooling and high feed intakes necessitate more water for excretion of waste products. This study was designed to measure water intake and estimate the partition of water output in sheep maintained at four air temperatures and offered four levels of a ration.