Losses of NH3 from a number of swards grazed by cattle were measured through 2 (1986–87) grazing years using a mass balance micrometeorological method. Comparisons were made of grass swards receiving 420 or 210 kg fertilizer N/ha per year and a grass-clover sward (GC) dependent upon fixation under rotational grazing managements. In one year a continuously grazed sward was also examined. Rates of NH3 loss were usually greatest whilst animals were present, especially during early and late season. This was not always the case, however, and losses sometimes continued into the next grazing period; there were also large day-to-day variations in fluxes. Seasonal trends were also not distinct, but losses tended to be lower during early and late grazings.

The annual losses from 420 and 210 kg N/ha and GC treatments were 25, 10 and 7 kg N/ha, respectively, and the differences between treatments were still marked when losses were expressed on a per animal basis. Total loss under continuous grazing was 61 % of that under the rotational system. Although the losses represent only 7·8, 5·6 and 3·7% of the inputs to420N, 2 ION and GC treatments, there was a good relationship between inputs and total losses, and also between the concentration of N in the herbage and losses per animal. The effects of the measured rates of loss on the input of NH3 from grazed grassland to the atmosphere are discussed.

The effects of chlormequat chloride on grain yield and its components in spring barley (Hordeum vulgare)cultivars were studied in five field experiments conducted at two sites near Belfast over 3 years (1982–84). Grain yield was significantly increased by chlormequat chloride treatment in only one experiment, where ear loss was less in the treated plots. Number of ears per plant was increased by treatment in another experiment but yield was unaffected. It was concluded that chlormequat chloride applications are unlikely to produce consistent yield increases in field crops of spring barley.

Use of a one-dimensional neighbour method of analysis in 1019 variety trials of a range of crops conducted by plant breeders in four states of Australia in 1985–87 resulted in an average reduction of 42% in variances of varietal yield differences compared with conventional randomized complete block analysis. Of these trials, 219 were designed as square, rectangular or generalized lattices and the average reduction in variances of varietal yields with incomplete block analysis and recovery of interblock information was 33%. The results emphasized that plots should be wide enough to avoid interplot competition, and that neighbour analysis is of most benefit in trials with short plots or when the field layout has many plots in a row.

The rumen anaerobic fungus Neocallimastix sp. LM1 was specifically labelled in batch culture with either [14C]lysine, [14C]lysine + [3H] tyrosine, [14C] methionine, or [35S] sulphide. Fractionation of acid hydrolysates of fungal biomass on an amino acid analyser showed that the labelled amino acids were directly incorporated into fungal protein with little or no degradation. [35S] Sulphide was incorporated into cysteine and methionine.

Absorption of amino acids from the small intestine was measured in sheep with permanent fistulae in the abomasum and terminal ileum, by introducing radiolabelled fungal biomass into the abomasum together with Cr-EDTA as the marker for digesta flow. The proportions of [14C] lysine (Expt 1), [14C] lysine + [3H] tyrosine (Expt 2), [14C] methionine (Expt 3) and the sulphur amino acids from [35S] sulphide (Expt 4) which appeared unabsorbed at the terminal ileum averaged 0·13, 0·07 + 0·08, 0·13 and 0·02, respectively. These proportions reflect the high digestibility of certain essential amino acids and the sulphur amino acids of fungal proteins. The results indicate that the true fractional digestibility of fungal proteins is c. 0·9. Consequently, a large biomass of anaerobic fungi in rumen digesta would be expected to provide a valuable source of digestible amino acids to ruminants.

Topping of tobacco (Nicotiana tabacum L.) plants (removal of the inflorescence) is not practised in Cyprus. Two field experiments were carried out at Akhelia Station, in 1985 and 1986, to test whether topping increased the yield or improved leaf quality of flue-cured tobacco grown under different types of irrigation. In contrast to the results of other studies, topping when the corolla had appeared on half the flowers did not increase yield. Topping when the inflorescence was just clear of the leaves (21 leaves harvested from topped plants v. 32 leaves from untopped plants) increased fresh yield by 7·0% but dry matter yield by 18·0%. The effects of topping were more marked on the leaves reaped at the third and fourth harvests, which constituted 52% of the fresh yield or 60% of the dry matter yield. At these harvests, leaves from topped plants had a lower percentage of midrib material (18·5 v. 21·0%) than leaves from untopped plants but a higher dry matter content (19·2 v. 17·2%) and specific leaf weight (80·0 v. 56·0 g/m2). Leaves of the fourth harvest from topped plants (27% of the total fresh yield) contained appreciably more nicotine (1·34%) than leaves from untopped plants (0·40%) but had a similar content of reducing sugars (20%). Topping did not influence the N, P and K contents of the leaves.

Irrigation increased fresh yield from 12·0 t/ha (225 mm water) to 24·0 t/ha (450 mm water) and dry matter yield from 2·0 to 3·8 t/ha, respectively, in Expt 1.

As Cypriot tobacco growers are paid for fresh yield delivered to the curing plant, the marginal increase of fresh yield with topping will hardly cover the cost of the extra operations involved.

Pig and cow slurries were applied to bare soil surfaces in the laboratory. Volatilization of NH3 was measured using ventilated enclosures for 3·25 days after slurry application. Slurries were acidified to pH values between 7 and 4 with 5 M H2SO4. Lowering cow slurry pH to 5·5 decreased NH2 volatilization by 95%, while lowering pig slurry pH to 6·0 decreased NH3 volatilization by 82%. A field experiment, measuring the volatilization of NH3 for 2 h after application to grassland stubble of slurry acidified to pH values between 7·5 and 5, gave similar results to the laboratory study.

Titration curves were constructed within the pH range of 9 to 4 with cow and pig slurries. There was a significant (P < 0·05) positive correlation between the NH4+-N content of the slurries and the volume of acid required to attain a target pH of 6·0 for pig slurries and a pH of 5·5 for cow slurries. One litre of slurry containing 2 g of NH4+-N required c. 20 ml of 5 M H2SO4 for acidification.

Root biomass of timothy grass (Phleum pratense L.), at low and high N fertilization rates, and of red clover (Trifolium pratense L.) were estimated with soil cores and in mesh bags in a field trial on a sandy loam in central Sweden. First and second full-harvest year leys were sampled three times each year from May to October. Mesh bags were inserted in the soil in autumn shortly after sowing (longterm bags); in spring and autumn of the first year and in spring of the second year (medium-term bags); and every third month during both years (short-term bags). Mesh bags of each type were sampled when the soil cores were taken.

Root biomass in the long-term bags was generally about the same as that in the soil cores, but taproot biomass in the clover crop was underestimated in the bags. In the grass plots, differences between soil cores and mesh bags were probably caused by ingrowth of weed roots in bags and by larger root biomass in plant rows than between rows. If soil cores and long-term mesh bags are sampled in exactly the same way identical estimates of biomass should be obtained.

Root biomass in short-term and medium-term bags was about the same as that in the soil cores and long-term bags on many of the sampling occasions. Thus a stable level of biomass was reached in a rather short time, i.e. after 3 months or less. Then root production, root mortality and root decomposition occurred simultaneously at a fairly constant level.

The bags did not contain residues from earlier crops, which reduced the amount of separation work necessary. The absence of crop residues in the bags did not seem to affect root biomass.

The mesh bag method is a useful alternative to soil core sampling for studying root biomass and root dynamics in perennial and annual crops. However, the bags must be inserted into the soil just after sowing and they must be placed in, as well as between, plant rows.

Losses c. off. 95 % in dry herb yields of Egyptian henbane (Hyoscyamus muticusL.) were observed due to natural weed growth in experiments conducted on a sandy loam soil of pH 7·8 during the winter (rabi) seasons 1984/85 and 1985/86 at the Central Institute of Medicinal and Aromatic Plants, Lucknow. The period between 30 and 75 days after sowing was most critical for weed competition, when weeds with 12·5% of their total growth (in terms of dry matter) reduced henbane dry herb yields by 60%.

Recovery of applied nitrogen by the rice crop is invariably low, often 30–50% (Prasad & De Datta 1979). The poor recovery has been attributed to different types of losses occurring in the rice field. Recovery improved with split application, delayed application or deep placement (Pillai & Vamadevan 1978; Craswell & Vlek 1979), indicating that the management factor plays an important role in increasing fertilizer nitrogen efficiency. To investigate such factors, and seasonal effects, field experimentswere carried out using 15N-labelled urea (PU) and urea supergranules (USG). The recovery of fertilizer 15N by the plant and retention in the soil were studied in both dry and wet seasons.

Two field experiments, at Woolly Hills Farm, County Durham, UK, and a glasshouse experiment were carried out in 1977. Early in the growing season (May-July), a covering of bracken litter increased the number of ryegrass and clover seedlings which became established both in an area where bracken had been removed and where there were developing fronds. In a second experiment (August-October), bracken litter had no effect on seedling establishment in the open. Under the frond canopy, the absence of litter was beneficial to clover establishment. The frond canopy reduced the number of ryegrass seedlings by half compared with the numbers in the open. In the glasshouse, litter caused a small reduction in the numbers of ryegrass and clover seedlings becoming established.

The results suggest that litter may be either beneficial because of the prevention of desiccation in dry periods or detrimental, perhaps through allelopathic effects or shading. In terms of the successful establishment of a sown grass and clover sward, it would seem that litter removal by incorporation or burning is more justified in upland hill pastures because of the need to improve soil fertility than because of adverse effects of the litter itself.

Two small-grained cereals, Mulga oats and a triticale line, and two legumes, local vetch and local peas, were grown in pure stands and in mixtures at various cereal: legume seed ratios (20:80, 40:60, 60:40 and 80:20) for three successive cropping years, 1981/82 to 1983/84, at Laxia and Dromolaxia, Cyprus, in each year.

The cereal pure stands produced, on average, more dry matter, 8·40 t/ha, and more digestible organic matter, 4·12 t/ha, than the legume pure stands, 3·68 and 2·18 t/ha, respectively. On average, total dry matter production decreased linearly as the seed proportion of the legume component in the mixture increased. The proportion of the legume in the harvested material was much lower than expected from the seed ratios. The highest proportion of legume was seen in the mixtures of peas with triticale and ranged from 8·1 to 35·5% at the various sowing rates. Digestibility and crude protein content were highest in the mixtures of triticale and peas.

The extent and rate of N release from nylon bags containing green panic (Panicum maximumvar.trichoglume)litter was measured for up to 319 days (long-term studies) in 1978/79 and 1979/80 in Gayndah, Australia. Dry matter (DM) decomposition rates were measured in 41 periods of 39 days and related to environmental variables and initial litter N concentrations (short-term study).

About half of litter DM decomposed during the long-term studies, while N concentration in the remaining litter increased from an initial average of 0–57 % N, to 0–95 % N. Net release of N from bags began when its concentration in the residue increased to c.0–65% N (or when the C:N ratio decreased to 75:1). Only a net 20–30 % of the initial N was released for potential plant uptake by the end of the study. The short-term study showed that DM decomposition was rapid and independent of pasture age. Decomposition rate increased with soil moisture and average daily temperature but was unaffected by initial litter N concentration. Release of N from decomposing litter was slow, despite rapid DM decomposition. It was concluded that a major cause of declining productivity in sown grass pastures is the immobilization of N in decomposing grass litter.

Water metabolism of two breeds of sheep (Uda and Yankasa)and two breeds of goat (Sahel and Maradi) was studied. Tritiated water space as a percentage of live weight was 80·5 and 73·6 % for Uda and Yankasa, respectively, and 77·8 and 66·1 % for Sahel and Maradi, respectively. The biological half-life of tritium was least in Yankasa (115 h) and longest in Sahel (173 h). Water turnover (I/day per animal) was 2·52, 2·63, 0·86 and 1·09 for Uda, Yankasa, Sahel and Maradi, respectively.

Chickpea is the most important pulse crop of the arid and semi-arid areas. In India, it is cultivated during winter, depending on soil moisture stored from the preceding summer rain, which is often inadequate to ensure a satisfactory crop.

In most such areas, saline ground water is the only source of supplementary irrigation to which chickpea, like other pulses, is highly sensitive (Maas & Hoffman 1977). Field observations indicate (Manchanda et al. 1981) that chickpea is more sensitive to chloridedominated than to sulphate-dominated saline water irrigation. Since most saline ground water and saline soils are dominated by chloride or sulphate salts, this study evaluated the effects of these salts on the yield and mineral composition of chickpea at different electrical conductivities. (ECe).

In 2 years two groups of 32 grazing cattle were used to examine the effects of previous grazing treatment and of body size on grazing behaviour and herbage organic matter intake (HOMI). Compensatory intake resulted from differences in grazing time only in the first year. There were no sex differences in intake when account was taken of differences in mature size raised to the power 0·73. Bite weight was related to the degree of maturity by the allometric coefficient of 0·46, and HOMI was similarly related by the coefficient of 0·36. This accords with the predicted effects of restricted grazing conditions on animals of different weight, and with allometric changes with weight in incisor breadth. Decreases in intake under grazing were similar in animals differing in maturity and weight. It is suggested that under constant grazing conditions the change in grazed herbage intake as animals mature reflects the allometric change in bite weight and a corresponding decline in bite numbers, resulting in consumption of a constant proportion of ad libitum intake.

Shearing causes a rapid increase in plasma cortisol concentrations (Kilgour & de Langen 1970; Purchas 1973; Fulkerson & Jamieson 1982), indicating that acute physiological responses are associated with the procedure. Environmental stress before mating can result in a delay in the onset of oestrus (Doney et al. 1973) and a reduction in ovulation rates (Doney et al. 1976). Dobson (1988) demonstrated that shearing caused a reduction in the luteinizing hormone (LH) response to exogenous gonadotrophin releasing hormone (GnRH) in anoestrous ewes. Such a response to shearing could influence the incidence of oestrus and ovulation.

Herbage and oil yields of Mentha arvensis (Japanese mint), M. piperita (peppermint) and M. spicata (spearmint) increased significantly with N fertilization up to 100 kg N/ha and those of M. citrata (bergamot mint) with up to 150 kg N/ha. Plant height, leaf: stem ratio and leaf area index increased with N application; and oil content decreased in all the species. Economic optimum doses of N for M. arvensis, M. piperita and M. spicata were 167, 153 and 145 kg N/ha, respectively and their oil yields expected from the response equation were 190, 103 and 50 kg/ha, respectively. The calculated optimum fertilizer rate for M. citrata was 225 kg N/ha, giving a yield of 193 kg oil/ha. Oil quality did not vary appreciably with N fertilization.