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.

Effects of three levels of N application and four intervals between harvests on field swards of perennial ryegrass (Lolium perenne L.) were studied during 6-week periods in summer and spring. Ryegrass was compared with tall fescue (Festuca arundinacea Schreb.) in spring and autumn.

An increase in the interval between harvests from 1 to 6 weeks allowed a larger, positive response to applied N to develop in respect of dry-matter yield, weight per tiller, and leaf blade and sheath length. Response to N was expressed more in terms of larger leaf blades than in a larger number of tillers. Tall fescue leaf blade size was increased more than that of ryegrass by a period of uninterrupted growth in May.

Within 1 week of its application, N had increased the N content of both emerging and dying leaf blades and had increased the width and reduced the weight per unit area of the emerging blades. The positive effect of N on blade width (and on blade length where uninterrupted growth was allowed) and its negative effect on weight per unit area were ‘carried through’ the sward, to be recorded a second time when that generation of blades had become the dying blades.

Applied N increased the number of tillers, the rate of emergence of new tillers, the proportion of tiller buds which developed into tillers, and the proportion of relatively young tiller buds which developed.

Four inexperienced operators used a Smith's Essem Metatest ultrasonic grader and a Philips Sonatest instrument to estimate the thickness of tissue overlying the M. longissimus dorsi at three sites over the tenth intercostal space of live steers. They also measured skin fold thickness over the central site using a micrometer. Suprafascial (selvedge) and total carcass fat were measured at corresponding sites on the chilled carcasses.

The residual standard deviations from multiple and simple regressions of suprafascial and total carcass fat thickness on the ultrasonic readings of different operators, using both instruments over the three sites with and without a measurement of skin thickness were compared.

The following conclusions were drawn. Use of a constant distance from the midline of the live animal to locate the site for ultrasonic point measurement would lead to errors in estimating fat thickness at a specific anatomical location. If the edge of the M. 1. dorsi is palpated to locate the measurement site, estimates of carcass fat thickness with a residual standard deviation of 2·5 mm are possible by relatively inexperienced operators using single point reading ultrasonic instruments. Fat deposition between the fascial sheath and the underlying M. 1. dorsi is a source of inaccuracy when estimating carcass fat cover particularly at sites closer to the midline and on fatter animals.

Using the Metatest instrument, fat cover could bo estimated in the live animal with an accuracy similar to that reported by other workers using the Scanogram. Using the Sonatest instrument the estimates were generally slightly less accurate especially at the most lateral site. Inclusion of a measurement of skin thickness gave a very slight but consistent improvement in accuracy of estimation of carcass fat cover.

An experiment was conducted over a 2-year period at two sites in the central rainlands of Sudan under rainfed conditions at one location and under supplementary irrigation at the other to investigate the effects of cultivars and spacing on yield and yield components of sunflower. Row spacing had no significant effect on grain yield under either system of production. Under rainfed conditions, the late maturing cultivar Manchurian performed better under wider row spacing than Hungarian-A which is a medium late maturing variety. Size and number of seeds weie significantly affected by row width. It is argued that the choice of a row spacing for sunflower production on a commercial scale in dry regions should be evaluated in association with machine efficiency which is affected by plant height, stem circumference, head diameter and lodging, all of which were significantly affected by row width. Also the number of plants established per unit area of land differed between systems of farming.

In studies of the seasonal distribution of nitrogen fertilizer dressings on grassland using conventional experimental designs it is usually not possible to separate the true effects of an individual fertilizer dressing on the yield at a particular cut from the residual effects of previous dressings. An experiment is described which was designed to allow separation of the direct and residual effects, with certain restrictions, for a system involving five cuts and five possible fertilizer dressings per season on perennial ryegrass swards. From the results obtained over two harvest years on swards on two adjacent sites equations were derived relating the dry-matter and crude-protein yields of herbage to the rate of nitrogen application at five dressings in the season. Predictions of yield distribution patterns from the equations are compared with observed yields from various sequences of nitrogen dressings included in previous experiments at this Institute. Examples are also given of the prediction of sequences of nitrogen dressings required to obtain certain patterns of yield distribution.

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.

Field experiments on ryegrass leys at Rothamsted in 1981, 1982 and 1983 examined the eifects of injected aqueous urea and of broadcast prilled urea applied alone or with one of several nitrification or urease inhibitors, on yields and N, K, Ca and Mg uptakes. Aqueous urea, prilled urea or ‘Nitro-Chalk’ were applied as single 375 kg N/ha dressings, and prilled urea or ‘Nitro-Chalk’ as three 125 kg N/ha dressings. The nitrification inhibitors etridiazole or nitrapyrin were injected with aqueous urea, but dicyandiamide (DCD) was broadcast with prilled urea. Neither the urease inhibitor hydroquinone nor the nitrification inhibitors slowed the rate of urea hydrolysis. Neither hydroquinone nor DCD diminished volatilization losses of ammonia from broadcast urea which ranged from 8 to 25 kg N/ha; they were less than 4 kg N/ha from injected urea or broadcast ‘Nitro-Chalk’. Nitrapyrin, etridiazole and DCD effectively inhibited nitrification. DCD, and to a lesser extent hydroquinone, increased yields and nitrogen uptakes from a single broadcast application of prilled urea given either in winter or in spring. However, these yields were still smaller than those given by injected urea or by divided dressings of urea, whether or not an inhibitor was used. The inhibitors did not increase yields with divided broadcast dressings of urea, which were slightly smaller than those with equivalent dressings of ‘Nitro-Chalk’. Inhibitors did not consistently increase yield when injected with aqueous urea. Inhibitors applied with injected or broadcast urea slightly increased K uptakes, and slightly decreased Ca and Mg uptakes.

Normal and brown midrib-3 (bm3) maize plants of three genotypes (Inra 188, Inra 240 and Inra 258) were sampled at three stages of maturity. Whole crop and plant components were analysed for in vitro digestible organic matter in the dry matter (DOMD) and the concentration of neutral detergent fibre, cellulose, hemicellulose, xylose, soluble sugars, starch and total nitrogen in the dry matter.

The concentrations of total nitrogen, neutral detergent fibre, cellulose, hemicellulose and xylose were similar in both normal and bm3 plants. Xylose was the main constituent sugar of hemicellulose forming 70–75% of the total hemicellulose. The higher concentration of soluble sugars and lower concentration of starch in the bm3 plants was attributed to the later maturity of the bm3 plants.

The bm3 gene significantly reduced lignin synthesis in the whole plant and plant components at all harvests. The mean concentration of lignin in the normal and bm3 plants were 2·2 and 1·4%, respectively. The ferulic and p-coumaric acid concentrations in the bm3 plants were 1·31 and 0·93 mg/g D.M. compared with 1·59 and 1·16 mg/g D.M. for the normal plants, respectively.

The in vitro DOMD values for the bm3 plants were significantly higher (P < 0.05) than their normal counterparts.

An approximate analytical method derived by Wilson & Gelhar (1981) is a powerful and flexible one for calculating solute distribution profiles developing under steady state and transient water flow conditions. Solute concentration profiles developing from an initial deposition in the surface layer, as the soil profile returns to field capacity, have been calculated using the method for idealized representations of the two principal forms of water redistribution.

The profiles depend very strongly on the mode of redistribution of the water. However, the small spread of the final profiles (at field capacity) across the range of water redistribution types examined suggest that, for agricultural application, it might be accurate enough to use a simplified representation of the actual redistribution rather than the correct, and inevitably more complicated, water flows and distribution.

Recent studies on maize in Nigeria showed that the new ‘FARZ series’ of maize, which were specially bred for high yield, respond to high density treatments (Lucas, 1981; Remison & Lucas, 1982). The optimum maize grain yields were obtained by these workers at density treatments 6·6 and 5·3 plants/m2. Prior to the release of these varieties, optimum grain yields were obtained between 3·7 and 4·3 plants/m2 (Fayemi, 1963; Chinwuba, 1967).

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.

Daily supplements of dried Leucaena leaf meal (500 g/head) were offered for 3 weeks to steers in metabolism cages. The steers had previously been fed diets of oaten chaff (5 kg/head/day) ormclasses and urea (4·5 kg/head/day) with restricted forage (2 kg/head/day). Excretion rates of the primary degradation product of mimosine, 3-hydroxy-4(1H) pyridone (DHP) by steers fed the two diets were compared. These compounds appeared in urine on the 1st day after Leucaena feeding had commenced and output remained fairly constant after 4 days. Mean weekly urinary outputs (g) of DHP from steers fed the oaten chaff or molasses + urea diet were 13·45 and 7·50 respectively. These levels corresponded to 0·23 and 0·13 of the amounts ingested. When steers were fed the molasses + urea diet, DHP continued to appear in urine up to 5 days after Leucaena had been withdrawn from the diet. On the oaten chaff diet no DHP was detected after 3 days following withdrawal of Leucaena.

The effects of casein or formaldehyde-treated casein supplements on the output of urinary DHP by steers fed oaten chaff plus Leucaena was evaluated in a second experiment which ran concurrently. The animals were fed the test diets for 3 weeks before collections were made. Mean DHP outputs (g/day) from animals fed the control diet, control diet plus casein or control diet plus formaldehyde-treated casein were 1·89, 2·21 and 2·44 respectively.

These results confirm substantial degradation of DHP and that the extent of degradation can be affected by the dietary regime in which Leucaena is fed.

It is well known that the uptake of fertilizer-N by crops is relatively inefficient, often amounting to less than half the quantity applied. Some becomes unavailable by combining with soil organic matter and some is lost from the system by surface runoff, leaching, denitriiication or ammonia volatilization. Most research has shown urea to be less effective than other sources of N when applied under conditions where ammonia volatilization becomes significant, especially when broadcast on the surface of alkaline and calcareous soils. Devine & Holmes (1964) found that ammonium sulphate was less effective than ammonium nitrate for wheat on a calcareous soil. Nitrogen recovery by wheat and barley tended to be similar for various N-fertilizers but further recovery in the following year was highest from calcium nitrate followed by ammonium sulphate and ammonium nitrate (Alessi & Power, 1973). On the other hand the efficiency of nitrate-N for flooded rice is less than that of ammoniacal fertilizers, owing to denitrification and leaching. Sarkar et al. (1978) found that rice grain yields with ammonium sulphate were significantly higher than with urea whereas Narain & Datta (1974) reported that urea and ammonium sulphate were equivalent and gave significantly higher yields of rice than ammonium nitrate. Therefore, yield responses to different sources of N vary depending upon soil, crop, climate and management factors; the study reported here was initiated to provide information on the relative performance of various N carriers applied to wheat and rice in the Punjab.

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.

is generally used to describe the lactation curve in cattle, where yn (kg) is the average daily milk yield in the nth week of lactation (n = 1, 2, 3, …, N), a is a scale parameter, and b and c are shape parameters. The model was first proposed by Wood (1967) and is widely used in practice to describe the lactation curve for fat, protein, lactose and wholemilk production; it has also been used as a basis of a mathematical model for poultry egg production (McNally, 1971). Having estimated a, b and c by regression analysis, the total lactation yield Y (kg) can then be calculated as

Crop residues, consisting of cereal stovers and hays made from the vegetative parts of grain legumes, are important dry-season feeds for ruminant livestock in the Savannah Zone of West Africa (van Raay, 1975; McCown, Haaland & de Haan, 1979; Jahnke, 1982). With the increasing demand on land to produce more crops and animal products, traditional systems are under pressure. There is need for a reliable means to quantify the supply of feed from various sources and to monitor the type, quantity and quality of crop residue available to livestock.

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.

The changeover from fertilizers containing calcium or ammonium sulphate to those containing little or no sulphur has led to the occurrence of sulphur deficiency in many areas of the world (McNaught & Christoffels, 1961). In the United Kingdom, it was thought that even in the absence of fertilizer sulphur, atmospheric inputs were sufficient to ensure an adequate supply for crops. Recent work in the north of Scotland has shown that this is not so, that many soils in the area are low in sulphur, and yield responses have been obtained following application of sulphur to grass (Soott et al. 1983; Scott, 1984). The purpose of the present experiments was to extend the work to cereals, in particular to examine the response to added sulphur of the grain yield of winter barley, and to measure the effect of sulphur on the chemical composition of plants.