Barley (cv. Beecher) was grown at two sites (Jindiress and Breda) in northern Syria, chosen for their contrasting edaphic and climatic conditions. At both sites, three fertilizer treatments were applied zero (Z), 60 kg P2O5/ha (P), and 60 kg P2O5/ha with 60 kg N/ha (NP) and measurements made of shoot and root growth, and water use.

The growth of crops not given fertilizer was similar at both sites and early growth was increased by the application of fertilizers. However, at maturity, yield was increased at Jindiress by giving N and P together, but not by P alone, while at Breda P alone increased yields but additional N produced no additional yield. There were marked effects of fertilizer on crop development at Jindiress; anthesis and maturity were about 14 days earlier in the NP treatment than in the Z treatment.

Root growth was also affected by fertilizer applications and there were small but significant differences in growth between the sites. The proportion of root weight: total plant weight was greater than commonly observed in temperate cereals and there were substantial differences between the sites in the pattern of root distribution within the soil profile.

The total amount of water used by the crops differed between the sites but was largely unaffected by fertilizer treatment at each site. Evapotranspiration during the winter when the soil was recharged with water was about 50% of the seasonal total. At Jindiress, the pattern of water extraction from the profile and the root distribution were similar before flowering but at Breda, there was no correspondence. Rates of water inflow varied with both site and time.

Crop characteristics that may be associated with increased yields are discussed. Deeper, more extensive rooting is unlikely to be useful in such regions but rapid early growth of both shoots and roots may allow water to be used more efficiently.

Root growth is considered in relation to shoot growth for high-yielding crops of winter wheat grown on three soil types in 1980 and 1981. From the time that nitrogen was applied to anthesis, shoot growth was rapid and effectively linear in relation to thermal time, whereas root growth entered a rapid linear phase after about 500–600 °C days, well before the application of nitrogen. Between double ridges and anthesis, shoots accumulated dry matter 10 times faster than roots on average. The relationship between root and shoot growth was different in the two years, which was probably due to reduced assimilate production in 1981 as a result of the dull, cloudy weather. At anthesis, average root: plant ratios for 1980 and 1981 were 0·132 and 0·093 respectively but no significant differences were caused by sowing dates or sites, despite the presence of a plough-pan on one of the soils.

Root:plant ratios declined from about 0·4 in winter and early spring to about 0·1 by anthesis. There was considerable variability in root:plant ratios for different crops during winter and early spring, caused in part by differences in soil-N availability and timing of application of fertilizer nitrogen.

Six experiments which compared a range of contrasting varieties are reported. Two experiments were at a very early, coastal site in N. Pembrokeshire (Trefin), two at a site in South Pembrokeshire (Trefloyne) and two at a coastal site in N. Norfolk (Brancaster). No variety was in every experiment but several were in the majority of experiments. In some experiments sprout growth was manipulated by control of storage temperatures. A variety classified as early or second early produced the highest yields in all experiments but the yields of the best maincrop varieties were high and substantially better than many early varieties. The highest-yielding variety at the first harvest maintained this advantage throughout June and July. At two sites (Trefin and Brancaster) the highest-yielding variety was consistent from year to year but overall the ranking order of varieties for yields was inconsistent, e.g. Arran Comet was the highest-yielding variety at Trefin in both years and one of the lowest yielding at Brancaster.

The results suggest that it is unwise to attempt to rank varieties for early yields by an overall score. The maturity classification of varieties is not necessarily an accurate guide to the utility of a variety. A consideration of the physiological age of the seed and growing conditions provided some explanation of these effects and their implication for breeding are discussed.

Rumen pH was varied and controlled over the range 5·2–7·1 by manipulating the infusions of buffer solution to the rumen and by using an automated system of recording pH. The total concentrations of volatile fatty acids (VFA) in the rumen were not altered by changes in pH but there were changes in the relative proportions of VFA. As the pH of rumen liquor fell, the proportion of acetic acid increased, and the proportions of propionic and butyric acids decreased relative to their respective proportions in the infusate. At rumen pH of about 7·2 the molar proportions found were similar to the molar proportions infused while at pH 5·3 the molar proportion for acetic acid in the rumen was 100 mmol/mol higher than in the infusate. There was no apparent relationship between osmotic pressure and differences between VFA proportions in the infusates and in the rumen liquor.

The sulphur balance in eight lysimeters containing four different soils under grass was examined over a 4-year period during which the annual mean concentration of sulphur dioxide (SO2) in the air at the site decreased from 30 to 14 μg/m3. The amounts of sulphur harvested in the grass and lost in drainage were set against additions in fertilizer, rainfall and from dry deposition. A decline in annual dry-matter yield was accompanied by a decrease in the concentration of sulphur in the herbage and an increase in the ratio of nitrogen to sulphur. It was concluded that atmospheric sources and soil reserves may become insufficient to meet the sulphur requirement of grassland.

The potential benefits of high-energy supplements, such as cereal grains, for grazing ruminants are commonly eroded by an accompanying depression in the digestion and intake of the basal herbage (McCullough, 1959). Low ruminal pH (< 6·0) induced by the rapid rate of production of the acids of starch fermentation, and competition between cellulolytie and amylolytic bacteria for limited nutrients, are known to be responsible for inhibition of cellulolysis (Terry, Tilley & Outen, 1969; Stewart, 1977; el Shazly, Dehority & Johnson, 1961). However, there are reports of reduced roughage digestion when nutrients appear to be non-limiting and pH is maintained above 6·0 (Gilchrist et al. 1979; Henning et al. 1980). The possibility remains that intermediates or end products of starch digestion have specific inhibitory effects on the numbers of cellulolytie organisms or on the activity of their extracellular cellulases.

The measurement of the nitrogen (N) content of plant material, used as an assessment of protein concentration, is important in determining the quality of various crops for feeding and processing. The generally accepted reference procedure for the direct measurement of N is the Kjeldahl method (Horwitz, 1980), first introduced 100 years ago (Kjeldahl, 1883). Recently a number of alternative direct (Williams et al. 1978) and indirect (Starr, Morgan & Smith, 1981) methods have become available.

In the recent past, specific gravity of tubers has been considered an easy means of estimating yield potential of sweet potato cultivars (Bryant, 1979) and their quality characters like starch value and dry-matter content (Ishikawa & Sakai, 1973). Bryant (1979) separated sweet potato tubers with low and high specific gravity at planting time by determining whether or not they floated in water, and observed that the floaters gave 20% higher yield than the sinkers. As this simple test claimed to hold promise for selecting higher-yielding sweet potato genotypes, it was decided to scan its usefulness at the College of Agriculture, Dholi, where a large collection of sweet potato germ plasm is being maintained for research needs.

Major economic losses in many agricultural crops have been attributed to damage caused by insects of Heliothis spp. For example, Alcock & Twine (1980) estimated that in Queensland, Australia the annual losses caused by Heliothis spp. were over $16 million, with major losses in sorghum, cotton, tomatoes, tobacco, and safflower. The increasing resistance of Heliothis spp. to pesticides together with an increasing awareness of environmental problems associated with excessive use of pesticides has encouraged the development of research into the area of host-plant resistance. Naturally occurring toxicants and repellants, feeding deterrents and sex pheromones have been evaluated for some years (Jacobson, 1982; Lukefahr, 1982).