The effects of inoculation with the vesicular-arbuscular mycorrhizal fungus Olomics mosseae(Nicolson & Gerdemann) Gerdemann and Trappe, fumigation of soil with methyl bromide, and addition of superphosphate (up to 60 kg P/ha) on growth and phosphorus nutrition of spring wheat (Triticum aestivum L. cv. Highbury) were investigated in two experiments (in 1980 and 1981 respectively) on plots that had been fallowed and recently limed.

Fumigation severely reduced natural levels of infection, and slightly reduced yield of above-ground dry matter in both years. In 1981 a decrease in grain yield of about 25% was accompanied by an increase in growth of straw. Plants on fumigated plots contained appreciable amounts of bromine in shoot tissue.

Inoculation increased and added P decreased infection in all treatments. In 1980 inoculation had little effect on above-ground dry matter, but it increased concentration of P in shoots especially on plots without added P. In 1981 added inoculum increased yield of grain on fumigated plots by about 0·75 t/ha at all levels of added P, but had little effect on non-fumigated plots, though responses in grain production to added P were similar with and without fumigation. Increases in yield resulting from inoculation were generally accompanied by increases in concentration of P in plant tissue.

Winter barley was sown on the plots after their use for spring wheat, without further application of the fumigation, inoculation or phosphorus treatments used in those experiments, to determine any residual effects on mycorrhizal infection and on growth. The levels of mycorrhizal infection on non-fumigated, inoculated plots were relatively constant in successive crops, although numbers of propagules of mycorrhizal fungi increased significantly with time for all treatments. Infection levels on fumigated and non-inoculated plots increased in successive crops, so that the relative effects of fumigation and of inoculation declined with time.

The effects of inoculation on infection levels persisted for longer than those on yields, suggesting that maximum effects of mycorrhizal infection on growth did not require the maximum levels of infection found in the roots. Harvest yields continued to respond to applied phosphorus even when uniformly high levels of infection had been established, suggesting that the ability of the root system to absorb phosphate was not greatly increased by mycorrhizal infection.

The importance of mycorrhizal infection for the growth of wheat and barley sown in winter and spring was assessed in two field experiments. Low temperatures during winter restricted the development of mycorrhizal infection, and calculations of ‘thermal time’ indicated that the percentage of root length infected did not increase when mean temperatures were less than 5 °C. Hence infection was less in the winter-sown crops than in the spring-sown crops at early stages of plant development. However, the effects of mycorrhizal infection on growth were greater in winter-sown than in spring-sown wheat.

At all levels of applied phosphorus up to 60 kg P/ha, artificial inoculation with mycorrhizal fungi increased the yields of both cereals at each sowing date by 17–25% after indigenous mycorrhizal fungi had been removed by fumigation, but the effects were smaller on non-fumigated plots. The results confirmed the potential importance of mycorrhizal infection for the growth of cereals.

Mycorrhizal infection increased the phosphorus concentration in the plant tissue at very early stages of growth, but the effect generally declined with time.

Inheritance of resistance to leaf curl disease in tomato (Lycopersicon esculentum) was studied in F1F2 and F3 generations in a cross between a cultivated tomato variety and a related wild species (L. pimpinellifolium). The wild species carries a dominant factor for resistance. Other useful variation was also observed in plant size, leaf characters and fruit size. The implications of these variabilities for tomato improvement are briefly discussed.

The digestive efficiency, rumen fermentation pattern, nitrogen balance, water intake and urine excretion were compared using four mature vasectomized Chios rams and four Damascus goats for each of five roughages (barley, lucerne or sudax hay, barley straw and leaves and twigs of acacia) offered alone or with concentrates (1:1 ratio), at approximately the maintenance energy level.

There were no species differences in the apparent digestibility of nutrients when the roughages were offered alone except for the significantly higher digestibility of dry matter, organic matter (OM), and gross energy (GE) of straw by goats. Sheep exceeded goats significantly in the digestibility of D.M., OM, GE and crude protein (CP) of lucerne hay plus concentrate and of CP when barley hay or sudax hay were supplemented with concentrate.

Compared with sheep, goats tended to consume more D.M. per kg W0·75 and drink less water and excrete less urine, but significant differences for water were obtained only with barley straw plus concentrate and for urine with barley hay and acacia.

Daily protein retention (g/kg W0·75) was consistently lower in goats than sheep but significant difference was obtained with acacia and with lucerne hay or straw plus concentrate. These results would suggest that Damascus goats require more protein for maintenance than sheep.

Compared with sheep, goats had significantly higher rumen NH3·N concentration with both acacia diets but lower with lucerne hay.

Total VFA concentration tended to be higher in sheep with all diets, but significance was observed only with barley hay although rumen pH was lower (acacia diets) or similar compared with goats. The molar proportion of acetic was significantly higher in sheep than goats with barley hay plus concentrate. Goats exceeded sheep significantly in the proportion of propionic with straw, of butyric with both barley hay and sudax hay plus concentrate diets, and of isobutyric with barley hay or acacia plus concentrate; with the other diets goats tended to have higher proportions of butyric and isobutyric.

Transpiration rate, diffusive resistances, canopy conductances and water potentials were determined at three canopy positions in non·stressed and stressed plants of sunflower hybrid BSH·1 and five other cultivars of sunflower under field conditions. The leaf area (LA) and stomatal frequency (f) was determined at the three canopy positions in field·grown plants and the total number of stomata per plant was calculated as the product of LA and f. These variables were then related to the dry·matter accumulation and seed yield in these cultivars. Cultivars with either a high leaf area or high number of stomata per plant were more productive under non-stress conditions. Under stress conditions, cultivars differed in the extent of change in conductance (g) and transpiration rate at different canopy positions. In the hybrid BSH·1, g was low at all levels in the canopy associated with a higher (less negative) water potential and this hybrid had lower transpiration rates at all canopy levels under stress although the number of stomata per plant was high. Stomatal sensitivity associated with a higher threshold water potential for stomatal closure is discussed as a possible explanation for the higher dry·matter accumulation and productivity of hybrid sunflower BSH·1 under moisture stress conditions.

Development of the fibrous root system of sugar beet was studied by washing soil samples taken from field experiments through the growing season. At the beginning of June the root system was still poorly developed but during June there was rapid proliferation. In the top 70 cm there was only little further increase in root density after the end of June. Below 70 cm root density increased up to the end of August. Throughout the season fibrous root density decreased with depth. Despite the origin of the lateral roots from two grooves on the storage root, fibrous root distributions at each depth around individual plants were essentially uniform from mid-June onwards. In the absence of nitrogen fertilizer, fibrous root development exceeded that of a crop given fertilizer, particularly at depths greater than 50 cm early in the season. The maximum value of root density was 2·8 cm/cm3 soil recorded in the top 10 cm in mid-September. Compared with published data for other crops, the sugar-beet root system was sparser than that of winter wheat or maize but denser than that of a soya bean or cassava.

Soil water content was measured with a neutron probe. Inflows to roots were calculated from soil water content changes in different soil layers. In the top 30 cm, inflows ranged up to 10·8 μl water/cm root.day and were up to five times higher than published inflows for winter wheat. At 30–100 cm sugar beet and winter wheat inflows were generally similar. The 0–30 and 30–120 cm layers contributed about 80 and 20% respectively of the total water use by sugar beet while no uptake was recorded below 110 cm. Previous studies have shown that sugar beet often takes up water from soil deeper than 110 cm, although it is not unknown for the depth of water removal to be restricted.

A field experiment was made in rabi seasons (November–April) of 1981–2 and 1982–3 to study the relative efficency of urea and urea supergranules (USG) for spring wheat. USG showed no advantage over prilled urea for spring wheat.

Experiments comprising various ratios of wheat and lentil in a mixed cropping system under two irrigation regimes and three levels of N application are described and the results discussed. In all experiments the highest yield of grain was obtained by growing wheat alone and the highest yield of lentil grain by growing lentil alone. No mixture could equal the yield obtained by wheat alone.

Measurements were taken of the draught force, speed and power of three pairs of oxen performing a variety of tasks for long (30 sec) or short (5 sec) periods. True draught force was measured by integrating the force exerted with respect to distance (DADF) and apparent draught force by integrating with respect to time (TADF). The latter type of measurement is that normally obtained from commercially available dynamometers.

In the first experiment short TADF measurements were found to be greater and more variable than long DADF measurements by up to 38% for a variety of jobs. In the second and third experiments in which TADF and DADF were measured completely simultaneously, TADF was nearly always larger than DADF, and the difference tended to be greater with large or jerky loads and smaller, less experienced oxen.

For any given task, the observed variability in replicate measurements of draught force or power was substantially reduced by using long rather than short measurements. However, this effect was not observed in the case of speed of travel.

Two groups of pregnant ewes were given either 1 (control) or 31 (treatment) mg fluoride/1 drinking water. Weekly blood samples were tested for serum fluoride, haematocrit, T3, T4, cortisol, calcium and magnesium. At parturition, serum fluoride was measured in both ewes and lambs. Later, parallel blood and milk samples were taken from ewes and measured for fluoride. Weekly blood samples from the lambs were measured for the same variables, as well as serum phosphate, body weight, bone fluoride and wool production. Serum fluoride in control ewes ranged from 0·6 to 1·9 μmol/1 and in treatment ewes from 8·7 to 35·4/ μmol/1. At birth, serum fluoride of control lambs averaged 0·50 ± 0·042 μmol/1 and of treatment lambs 1·72 ± 0·167 μmol/1. In milk from the control group mean fluoride concentration was 7·11 ± 0·403 μmol/1, and from the treatment group 22·0 ± 1·48 μmol/1. No differences in haematocrit T3, T4, cortisol, calcium or magnesium of ewes were apparent during pregnancy. At birth, body weight of the treatment group lambs was reduced, and T3, calcium and magnesium increased. At 3–4 weeks mean bone fluoride of lambs was higher in the treatment group (580 ± 117 mg/kg) than the control group (105 ± 26·9 mg/kg). After 7 weeks there was an upward trend in serum phosphate of treated lambs, and their wool production (clean fleece weight) at 17 weeks was reduced by 18%, primarily because of decreased staple length.

Much of the recent increase in crisp lettuce production in the U.K. has been marketed as heavily trimmed solid ‘Iceberg’ heads, wrapped in plastic film. Supermarkets want ‘Iceberg’ lettuce with a minimum trimmed weight of 450 g (Anon. 1983) and consistency of product, but the mean head weight of crisp lettuce at maturity can vary considerably from one sowing to another as a result of environmental conditions earlier in growth (Pew, Gardner & Bessey, 1984; Wurr & Fellows, 1984). In midsummer, some sowings of the most popular variety Saladin can produce larger and heavier heads thanc supermarkets require and the cause of this variation needs to be understood in order to increase the proportion of crops meeting supermarket needs.

Biomass accumulation in cereals is an important determinant of grain yield (Green, 1984). However, when attempting to maximize dry-matter production a taller crop more prone to lodging may result (Boothroyd & Clare, 1984). While many contemporary triticale cultivars contain a dwarfing gene, most are very tall relative to wheat and barley (McDonald, 1984) and lodging is a particularly important factor in growing triticale crops.