In studies at the University of Nottingham at Sutton Bonington in two consecutive seasons beginning in 1986/87, Bourdon, an indeterminate cultivar, and 858, a determinate selection (provided by Plant Breeding International, Cambridge), were compared under six target plant population densities ranging from 10 to 80 plants/m2.

As the season progressed, total dry matter production increased to a maximum and then declined. However, growth rates slowed at pod set because, it is suggested, of the change in the chemical composition of the newly synthesized biomass, from carbohydrate to protein, at that time. Leaf area duration was greater in Bourdon than in 858, especially during pod set, but it bore no relation to seed yield. Specific leaf area was unaffected by competition for light. It is proposed that changes in plant population density affect the competition for assimilates within a plant rather than the competition for light between different plants. Losses of branches and reproductive nodes, with time, are cited as evidence for this. The apparent causes of the lower yield of determinate forms of winter field bean relative to indeterminate forms are discussed.

The susceptibility to drought stress during flowering and grain filling of dwarf hybrids of pearl millet carrying the dwarfing gene d2 was investigated in 1987 at Patancheru, India, under field conditions during the dry season and, in the rainy season, under a rain shelter, using four pairs of near-isogenic tall and dwarf hybrids. Drought stress during grain filling reduced the number of grains per unit area and individual grain mass. Grain yields of the dwarf hybrids were lower than those of the corresponding tall hybrids in the unstressed control and under drought stress and were associated with a lower individual grain mass in the dwarf lines. In the dwarf hybrids, harvest index was similar to or better than that of the tall versions but a reduced biomass resulted in lower grain yields. Dwarf hybrids were not more adversely affected by water stress, however, than their tall counterparts, indicating that susceptibility to drought stress would not be likely to limit acceptance of new dwarf varieties.

In a 2-year field experiment at Hohenheim in 1987–88, with an intact or partly deflowered indeterminate cultivar and a determinate cultivar, light interception and dry matter production were highest in crops grown in isometric stands (equal distances between plants), lowest in double rows and intermediate in single rows. Dry matter production was greater at high than at low population density and in the wetter and cooler weather of 1987. Population density had a greater effect on DM production than on light interception. The greater leaf canopies under high density and in 1987 (Stützel & Aufhammer 1991) reduced light extinction coefficients. In the determinate cultivar, light extinction coefficients were consistently higher and light use efficiencies were consistently lower than in the indeterminate cultivar. Deflowering the indeterminate genotype and different planting designs did not change light use efficiencies and light extinction coefficients. In general, differences in light use efficiencies were inversely related to differences in light extinction coefficients.

Acid and neutral invertase activities in the stem of an early (CoJ 64) and a late cultivar (Col 148) of sugarcane were estimated by incubating stem slices in buffered sucrose solution and measuring the production of reducing sugars. High enzyme activity occurred in young tissue but the activity of both enzymes was considerably lower in the mature internodes. Acid and neutral invertase activity was highest in the midinternode position, corresponding to the region of cell expansion.

In studies of two indeterminate cultivars in field experiments in 1985 and 1986 at Hohenheim University, the hierarchy within the reproductive storage system of field bean plants was manipulated by removal of inflorescences at various growth stages and nodes. Shading reduced pod set and seed weight mainly at basal nodes. Increasing plant population density reduced seed yield traits at all nodes. Removal of basal inflorescences increased pod set and seed weight at the remaining nodes, especially the lower ones. The favourable effects were greater under high light intensities and in sparse stands. The growth stages at which the basal inflorescences were removed and the removal of apical inflorescences were of minor importance.

Two sets of experiments were conducted on oxic Plinthustalf and udic Ustochrept soils in 1983–85 at Ouagadougou, Burkina Faso. One set tested six daylength-insensitive (DI) cultivars and the other set compared four or five daylength-sensitive (DS) cultivars with one or two DI cultivars as controls, sown on three or four dates. Sowing date, cultivar and their interaction significantly affected seed yield in 1983 and 1985. In 1984, yield was not affected by sowing date in the DI cultivars nor by the sowing date x cultivar interaction in the DS cultivars. Optimum sowing dates were mid- and late July. Sowing earlier gave no yield advantage, whereas sowing later reduced yield severely.

The medium-maturing DI cultivar TN88–63 and the DS cultivar Koakin Local, which has a critical photoperiod in late August, exhibited average to below average yield stability but had a high mean yield and were considered well adapted in all conditions. The other cultivars were either moderately or poorly adapted to the Sudan savannah zone. The sowing date experiments were effective in identifying adapted cowpea cultivars, even from a single year's data, and can be used for screening cowpea for adaptation in the Sudan savannah zone.

A trial of open-pollinated (OP) cultivars and hybrids of different origins was conducted in 1986–1988 at two sites in the central clay plains of Sudan, rainfed at one site and under supplementary irrigation at the other. Throughout this study, the patterns of growth of the OP cultivars differed greatly from those of the hybrids, despite differences amongst cultivars within each group. Differences in seed yield between OP cultivars and hybrids under irrigation were not significant; but, under rainfed conditions, the hybrids gave higher yields than the OP cultivars. Partitioning efficiency (PE; reproductive mass: total biomass) increased more rapidly during flowering and seed filling in the hybrids than in the OP cultivars; differences in PE between the two groups were significant. The higher leaf area index, leaf area duration and crop growth rate of the OP cultivars were compensated to some extent by the higher PE and leaf efficiency values of the hybrids, resulting in similar seed yields of all cultivars under irrigation. Overall, irrigation increased seed yield by 0·6–1·9 t/ha and increased oil content by 8–15%.

T-trellis apple trees treated with combinations of fungicides and insecticides applied with a boom sprayer had a lower percentage of fruit damage from diseases and insects than those treated with an airblast sprayer. With the boom sprayer, chemical deposit was uniform in distribution between outer and inner parts of the tree canopy, but with the airblast sprayer there was more than a threefold difference in deposit between parts of the canopy. The boom sprayer was inferior to the airblast sprayer in the control of apple aphids (Aphis pomi) when vertical top growth (watersprouts) had grown to 0·7–1 m. Management of aphids with a boom sprayer would probably require the control or periodic removal of watersprout growth, or the use of systemic insecticides.

Two sets of experiments on cowpea sowing date were conducted in 1983–85 at Ouagadougou, Burkina Faso. One set tested six daylength-insensitive (DI) cultivars and the other compared four or five daylength-sensitive (DS) cultivars with one or two DI cultivars as controls. Sowing after inadequate rainfall, particularly when followed by drought stress, impeded seedling establishment and growth. Severe drought stress during the reproductive growth stages and prolonged drought stress throughout the crop season adversely affected flowering, flowering intensity and subsequent yield. Cultivar differences in ability to withstand drought damage were observed. The ability of cultivars to (i) branch profusely, to compensate for stands lost by drought during seedling growth and (ii) flower at such a time that pod set and fill coincide with favourable climatic conditions appears to be a prerequisite for satisfactory adaptation to the Sudan savannah zone of semi-arid West Africa. Daylength-sensitivity and early maturity per se were inadequate to prevent yield losses under drought conditions.

An experiment was carried out in Normandy between 1986 and 1988 over c. 6 months in each year, using a simplified rotational grazing technique (two paddocks in spring, four in autumn) with a total of 162 high-yielding cows (mean milk yield of 30·0 kg/day at turn-out). Three stocking rates, designated control (C: 2·3 cows/ha over the total area of the system), moderate (M: 2·6 cows/ha = 115% of C) and high (H: 3·0 cows/ha = 130% of C), were compared at two rates of concentrate supplement, 3·7 kg/cow per day and 0·5 kg/cow per day. Individual milk yield differed by a non-significant 5% between the extreme stocking rates (21·3 v. 20·3 kg fat-corrected milk (FCM) for treatments C and H, respectively). Milk production/ha was 23% greater in the H treatment (9816 v. 7970 kg FCM for H and C, respectively). Concentrate supplementation led, on average, to a 9% milk yield improvement (21·8 v. 20·0 kg FCM for high and low rates, respectively), i.e. a mean efficiency of 0·6 kg FCM/kg supplement. This response tended to be greater in the higher-yielding cows and for the high stocking rate. The sward measurements contributed to a better understanding of herbage utilization by the cows.

In three experiments, carried out in 1985 and 1986 in the Netherlands, the effects of herbage maturation and rate of nitrogen fertilization on rumen degradability of organic matter (OM) and crude protein (CP) in fresh herbage (Lolium perenne) were studied using the nylon bag technique. Experimental farms at Lelystad and Swifterbant (clay soil) and Achterberg (sandy soil) provided the herbage samples. From the results, the content of digestible CP entering the small intestine (DPI) was estimated.

Crude protein content and in sacco degradability of OM and CP decreased with increasing grass maturity and with decreasing rate of N application. With every 100 g/kg DM decrease in CP content, the estimated content of DPI decreased by 19 g/kg DM, no matter how the CP content was manipulated.

Field emergence of 11 seed lots from six cultivars of long bean, all having laboratory germination of > 80%, ranged from 0 to 83%, indicating differences in seed vigour. Vigour differences occurred within and between cultivars, seed lots from cultivars with white or partly white testas having particularly poor emergence (0–21%) compared with those with brown or black testas (41–83% field emergence). The significant ranked correlations between field emergence and (i) solute leakage, measured by the electrical conductivity of seed soak water (r = –0·864), (ii) the percentage of cotyledons made up of completely living tissue, revealed by vital staining (r = 0·895), and (iii) the proportion of hard seeds (r = 0·916) indicated that lots with low vigour and potentially poor field emergence could be identified before sowing. Seed lots having low vigour imbibed water rapidly; the improved vital staining when seeds imbibed slowly indicated that damage occurred during imbibition and was a cause of low seed vigour. Rapid water uptake by low-vigour seed lots was partly explained by the incidence of seeds with cracked testas, but other factors could not be eliminated. The significance of differences in water uptake between cultivars differing in testa colour is discussed in relation to breeding for improved emergence.

Catchment basins were prepared within bunded fields from 1986 to 1988, with ratios of catchment area to cropped area of 1:1 or 2:1. Annual rainfall varied from 102 to 282 mm.

Run-off from the catchment basins increased water storage in the cropped areas by 55 and 43% of the rain falling on the catchments in the 1:1 and 2:1 treatments, respectively. Yields increased considerably on a cropped area basis by water harvesting, but not always sufficiently to compensate for the loss of cropped land. Averaged over all trials, yields from the 1:1 treatment were 95% of the control yields. Yields-in the 2:1 treatments were reduced by waterlogging damage.

The cost of catchment set-up was low compared with the reduced seed and ploughing costs in the water-harvesting treatments, resulting in 18 and 31% reductions in overall costs for the 1:1 and 2:1 treatments, respectively. Net benefits for the 1:1 treatment equalled or exceeded those of the control, but were 32% lower for the 2:1 treatment. Within-field water harvesting with a 1:1 crop: catchment ratio thus reduced risk by reducing investments in seed and animal draught power, whilst maintaining yields and net benefits, suggesting that it could be of considerable benefit to farmers in an environment with a high risk of crop failure. Catchment preparation on unused land adjacent to cropped land, and further research aimed at reducing waterlogging damage, could both lead to improvements in farmers' circumstances in upland Balochistan.

A trial was set up in South Wales in 1980 on land replaced in 1972 after opencast coal mining, to assess the effects on soil rehabilitation of regular subsoiling, through an established sward, with and without incorporation of a ‘semi-organic’ fertilizer into subsoiling slots. Treatments were assessed on the basis of yield, soil structure indices, root and organic contents and earthworm population densities. Apart from yields, data are for the eighth year of the experiment (1987), 18 months after the fourth programme of treatments.

Treatments did not markedly affect productivity, although it tended to be higher with subsoiling and fertilizer incorporation. Subsoiling had little effect on root and organic content, but fertilizer incorporation increased the latter, particularly at depth. Earthworm population densities were markedly higher on subsoiled areas, the increase in the deeper burrowing species Aporrectodea caliginosa being largest. Fertilizer incorporation increased abundance of Lumbricus rubellus, but had little effect on other species. Subsoiling reduced surface wetness, but did not result in any significant improvement in structure. Fertilizer incorporation reduced clay dispersion at depth and, with subsoiling, also increased pore space.

Treatment responses in term of soil structure were not large, but the incorporation of fertilizer did markedly accelerate structure rehabilitation at depth. Subsoiling alone contributed to land rehabilitation by controlling surface wetness and encouraging an increase in earthworm populations.

An experiment using 30 Belgian landrace finishing pigs was carried out, in 1989, at the University of Leuven, Belgium, to examine the effect of clenbuterol in the diet (1 mg/kg) on the repartitioning of nutrients and body composition. Clenbuterol was administered for 20 days preceding the week before slaughter. Fifteen animals were fed a diet containing the β-agonist, and 15 other animals served as negative controls. Weight gain, feed conversion and N utilization improved during β-agonist treatment. Removal of clenbuterol from the diet rapidly increased blood urea concentrations, indicating immediate, less efficient, N utilization. In the week before slaughter, the animals did not lose the extra weight gained in the period of clenbuterol feeding. Backfat thickness at slaughter was reduced by 15% in the animals fed clenbuterol. Dressing percentage and post mortem pH decline, colour and water-holding capacity in ham and the longissimus dorsi were not affected by dietary treatment. Clenbuterol was not detected in renal fat and the longissimus dorsi at slaughter.

Two groups of nine wethers, three of which were fitted with rumen cannulas, were used in a digestion trial at the INRA centre in Theix, France, in 1988. Group 1 received 65% maize silage and 35% concentrates; group 2 received 65% hay and 35% concentrates. Concentrates were based on either cereals rich in starch, or by-products rich in fibre and were given either alone or supplemented with lipids as calcium soaps. The fatty acid content of lipid-supplemented diets was c. 9·5 and 8·5% of dry matter, of which 85 and 89% was provided by calcium soaps, for maize silage and hay diets, respectively. For each group, the four diets were tested in four successive periods from January to June 1988.

Total digestibility of dry and organic matter, acid detergent fibre (ADF) and neutral detergent fibre (NDF) was measured in six wethers of each group by total faeces collection. On cannulated wethers, volatile fatty acid content and composition, pH and NH3-N in rumen liquor were determined four times a day; in sacco degradability of dry matter, ADF and NDF of the forage eaten by the wethers was estimated by the kinetics of incubation in the rumen.

In vivo and in sacco results showed that dry matter and organic matter digestibilities were not modified by the nature of concentrates. Cell wall digestibility was higher for fibre concentrates than for starchy concentrates, by 4·1 and 6·2 percentage units for NDF in maize silage and hay groups, respectively. Volatile fatty acids (VFA) and ammonia concentrations were higher and pH was lower with the maize silage than with the hay diet.

Lipid supply slightly increased cell wall digestibility in the group fed maize silage by 7·5 and 2·0 percentage units for starch and fibre concentrates, respectively. This surprising increase was related to an improvement in in sacco degradability. In all diets, lipid supply increased pH, but variations in VFA concentration and pattern were low. Interactions between the nature of concentrate and lipid supply were moderate, but were higher in the group fed maize silage than in the group fed hay, especially for total digestibility.

Plant:soil ratios (CRs) of 85Sr concentration were studied in wheat, lucerne, lettuce, radish, string bean (Phaseolus vulgaris), and cucumber grown in pots in eight Greek soil types in a glasshouse pot experiment in 1989.

The CRs of the crops and of the plant parts studied differed according to soil type. They ranged from 0·034–1·39 for wheat grains to 7·6–36·5 for cucumber stems and leaves. The CRs of the edible parts were much lower than those of the other plant material.

The correlation between CRs and clay content was negative and, in most cases, significant (P = 0·05–0·01) or highly significant (P < 0·01). The negative correlation improved (higher absolute value of r, lower variability) if clay plus silt content or cation exchange capacity was used instead of clay content.

The correlation between CRs and soil properties was greatest for soil pH (r = –0·89) and decreased in the order: pH > total clay plus silt ≃ cation exchange capacity > total clay.

Diets with added fat at 25, 50 and 100 g/kg were formulated with four blends of beef tallow: soya oil, namely 100:0, 75:25, 50:50 and 0:100. An additional diet had no added fat (control diet) to give an experimental design of (3 × 4) + 1. A total of 96 individually penned pigs was used (mean initial and final live weights of 22·4 and 87·5 kg, respectively). The experiment was carried out during the period July 1985 to February 1986 at the Agricultural Research Institute, Hillsborough. Equal numbers of boar and gilt blocks were used and the pigs were fed individually to a scale to give equal amounts of digestible energy: live weight0·75 Neither concentration of fat nor blend of fat had any significant effect on the rates of live weight or carcass weight gain. Increasing concentration of fat significantly improved the carcass feed conversion ratio (P < 0·001), but the blend of fat had no significant effect. Neither killing-out yield nor the intake of digestible energy per unit of carcass gain was significantly affected by the concentration of added dietary fat nor the blend of fat. Fat treatments did not significantly affect the lean plus bone content of the ham joint, drip loss from or the depth of colour of the longissimus dorsi or the weight of flare fat. No evidence was found of synergistic effects between the fat and nonfat components of the diet nor between fats within the blends of fat on growth, digestible energy consumed per unit of carcass gain and carcass attributes. Boars had a more efficient conversion of feed to carcass gain than gilts (P < 0·01).

In laboratory studies, the amount of N mineralized under waterlogged conditions during 14 days at 30°C was significantly correlated (P < 0·001) with the activities of amidase, glutaminase and asparaginase in soil when these enzymes were assayed by either a nonbuffer or a buffer method using appropriate substrates. N mineralization under waterlogged conditions was also significantly positively correlated with N mineralization under aerobic conditions, especially at 25 and 35 °C (P < 0·001). Generally, the results indicate that the use of amidase, glutaminase and asparaginase activities in predicting plant-available N in soils deserves more attention.