Gnotobiotic pigs were fed control and soya-bean protein containing diets in an attempt to identify direct effects of this protein on intestinal structure and function.

Feeding diets containing soya-bean protein for 4 days to 21-day-old gnotobiotic pigs increased crypt depth in the lower half of the small intestine. This increase was accompanied by a corresponding reduction in lactase activity, brought about mainly by a decrease in the apparent rate at which this enzyme appeared in the luminal membrane of developing enterocytes. Sucrase and maltase II and III activities increased slightly in tissue taken from pigs fed soya-bean protein. Alanine transport measured in the presence and absence of Na remained unaffected by change of diet.

The structure and function of control gnotobiotic pig intestine differed from that found in normal unweaned piglets. The possible source of these differences and the probable role played by enteric microflora in amplifying initial effects of soya-bean protein on intestinal function is discussed.

Experiments were carried out in 1985 and 1986 on a sandy clay–loam to investigate the effects of above average rainfall in May and early June on the growth of the spring barley cv. Klaxon in three systems of cultivation. The cultivation treatments, ploughing (P), shallow-tine cultivation (S) and direct drilling (D), had been repeated on the same plots and cropped with spring barley each year since 1971.

A total of 112 mm water was applied to the waterlogged subplots in 1985 and 168 mm in 1986.

Compared with plots receiving the normal seasonal rainfall, extra water had no effect on shoot or grain yield in 1985 (mean grain yield 6·38 t/ha) and there were no significant differences between cultivation systems. In 1986, in contrast, water, in excess of normal rainfall, depressed both shoot growth and grain yield (mean grain yields 4·49 and 4·07 t/ha for the normal rainfall and the additional water treatments, respectively), the effect being greater on P than on either S or D.

In both years, saturation was achieved in the topsoil for a prolonged period during May and early June in the waterlogged subplots. In 1985 this was associated with a period of low oxygen flux and low redox potential, but this did nothave a significant effect on root or shoot growth. In 1986 there was no comparable period of reduced aeration, nor any significant differences in oxygen flux or redox potentials between water and cultivation treatments. In 1986, reduced growth and yield were directly associated with a mean reduction in N recovery by shoots of 36 kg N/ha, the effect being greatest on the ploughed plots where water was added. The results do not support the hypothesis that waterlogging per seaffects the growth of barley more on ploughed than on direct-drilled land.

Field experiments during the wet seasons of 1981–1985 determined the response of soya bean to the application of P, K and Mo at four locations in the Nigerian savanna. Soya bean was grown at factorial combinations of four rates of P (0, 13·2, 26·4 and 396 kg P/ha) and two rates of K. (0 or 41·5 kg K/ha) in 1981, but in subsequent years two or three rates of Mo (0, 0·5 or 1·0 kg ammonium molybdate/ha) were included in a randomized complete block design with three replications at all locations.

Significant yield increases due to the application of P were recorded in 10 out of 11 trials. Yield increases due to 13·2 or 26·4 kg P/ha were from 29 to 210% over the control. The effects of K and Mo application were not significant in 10 out of 11 trials and eight out of nine trials, respectively. Whereas P x Mo interaction effects were significant in three trials only, highest yields were recorded due to application of 26·4 or 39·6 kg P/ha in combination with 0·5 kg ammonium molybdate/ha.

Application of P increased the percentage of P in soya-bean leaves significantly and a range of 0·275–0·330% P appears to be the critical nutrient range of P in soya-bean leaves at full bloom stage. Application of K had no effect on K concentration in leaves.

Two field experiments and one pot experiment were carried out to test the hypothesis that competition and dominance relations between and within inflorescences control seed yield. The experiments compared untreated field bean (Vicia faba L.) plants with others in which the numbers of inflorescences and flowers had been surgically reduced to 18 defined positions at lower or at upper nodes. Growth conditions were varied by sowing date and plant density. Seed yields, yield components and 14C-labelled assimilate distribution were determined.

Most untreated plants set no more than 18 pods while treated ones set 4–7 pods fewer. As variation in seed set per pod was small, the resulting number of seeds remained about 30% less in treated compared with untreated plants. In plants with pods set only at upper nodes, 14C-assimilate distribution shifted in favour of leaf and root production, presumably supporting seed production later on. Concerning seed yield per plant, full compensation was reached as mean weights per seed increased up to 40%. In interactions with growth conditions, small overcompensation effects on seed yield per plant were indicated. Results are discussed in relation to storage capacity and yield stability.

In a field experiment on a typic hapludoll in 1983 and 1984, deep placement of urea supergranules at 40 and 80 kg N/ha proved to be the best N source, of five tested, for grain production, but at 120 kg N/ha it was similar to neem-cake-coated urea. The results showed that deep placement of urea supergranules can save fertilizer use by 60% compared with prilled urea to obtain the same yield. Shellac-coated urea and dicyandiamide-coated urea was more effective than prilled urea in 1984. Differences in dry-matter production and grain yield were directly related to N uptake by the plants. On average, apparent recovery of applied N increased from 35% for prilled urea to 55, 52·5,46·5 and 37·5% for urea supergranules, neem-cake-coated urea, shellac-coated urea and dicyandiamide-coated urea, respectively.

Variations in floral morphology have been observed by most breeders involved in cowpea (Vigna unguiculata (L.) Walpers) improvement. Usually, the most successful pod set is achieved following hand pollination when plants with large flowers are used as female parents because these are easy to manipulate. In breeding work involving wide crosses, unconscious selection of female parents on the basis of flower size could lead to correlated changes in pod and seed characteristics which may or may not be desirable. This would depend on the heritability of flower size and its correlation with the pod and seed characteristics.

Measurements of the area of individual leaves in crops are useful in the analysis of canopy architecture as they allow determination of the structure of leaf area index in a vertical profile. This information may be of use in modelling leaf growth and the assessment of photosynthetic potential of different strata of the canopy with ontogeny (cf. Firman & Allen, 1988).

Atomic Absorption Spectroscopy (AAS) is the usual method for the direct determination of small amounts of manganese in plant materials (Christian & Feldman 1970; Heanes, 1981) and other substances (Carnrick, Slavin & Manning, 1981). However, it uses the highly sophisticated and expensive Atomic Absorption Spectrometer, which requires a reasonable degree of technician expertise, and is therefore not suitable for routine chemical analyses in Third World countries.