Over two years (1984/85 and 1986/87), monthly sampling of shoots of white clover plants compared the populations of white clover in mixed swards at Palmerston North, New Zealand, under set stocking, rotational grazing and a combination of both systems, at a common stocking rate of 22·5 ewe equivalents/ha.

The frequency distributions of shoot (or stolon) dry weight per plant in each population over the study period was described by a log-normal model, which indicated that the populations consisted of many small individuals and few large individuals. Such inequality of shoot dry weight within populations is commonly termed size hierarchy; a statistic giving a measure of such size hierarchy is the Gini coefficient. The populations under different managements had similar Gini coefficients which differed little among seasons or between years. Lack of significant correlation between the Gini coefficient and mean shoot dry weight per plant of each population indicated that, in these white clover populations, size hierarchy was independent of mean plant size.

These results were considered in relation to the clonal growth of white clover in grazed swards and it is suggested that the variable nature of death of older basal stolons makes an important contribution to the variability in size of individual plants and hence to size hierarchy. As size hierarchy, as assessed by Gini coefficients, was relatively stable in these populations over 3½ years, it appears that clonal growth of white clover incorporates sufficient variability within the growth and death processes at the individual plant level to maintain the size hierarchy, irrespective of variations in mean plant size of populations.

During the growing season of 1988 at the Agricultural Research Institute, Hillsborough, cattle slurry was kept whole or was separated through screens with mesh sizes of 5 mm, 3 mm, 0·25 mm and 0·015 mm. The resulting slurry liquids were either left unacidified or were acidified to pH 5.5 with 5M-H2SO4 prior to application at 75 kg NH+4-N/ha to perennial ryegrass in the field. Volatilization of ammonia was measured using ventilated enclosures. Plots treated with a range of rates of inorganic fertilizer N were used to construct response curves to assess the efficiency of N in slurry for herbage production compared with equinitrogenous inorganic fertilizer.

On average over the season, acidification of cattle slurry decreased ammonia volatilization to < 15% of that from unacidified whole slurry. Compared with inorganic fertilizer N, the overall efficiency of NH+4-N was 96% in acidified slurries and 36% in unacidified whole slurry. Ammonia volatilization from separated slurries decreased with decreasing mesh size to 39% of that from whole slurry for a 0·015 mm mesh. The overall efficiency of NH4+-N in slurry separated through a 0·015 mm mesh was 76%. A highly significant linear relationship was found between NH3-N volatilized from all slurry treatments and N offtake in herbage at all three harvests.

The distribution of dehydrogenase activity (DHA) and the activities of phosphatases were studied in the rhizosphere of four varieties each of clusterbean (Cyamopsis tetragonoloba (L.) Taub.), mung bean (Vigna radiata (L.) Wilczek), moth bean (Vigna aconitifolia (Jacq.) Marechal) and pearl millet (Pennisetum americanum (L.) Leeke) grown in pots containing soil low in available P. Activities of dehydrogenase and phosphatases were greatest 25 days after sowing and remained constant from 50 days after sowing until crop maturity. Rhizosphere soils showed higher activities than other soils: 26–158% for acid phosphatase, 66–264% for alkaline phosphatase and up to 292% for DHA. Dehydrogenase and alkaline phosphatase activities were significantly higher in the rhizospheres of legumes than in those of P. americanum.In general, the rhizospheres of C. tetragonoloba ‘HFG314’, V. radiata ‘PDM62’, V. aconitifolia ‘IPCMO344’ and P. americanum ‘RCB2’ had higher activities than those of other varieties of the same species. Acid phosphatase activity was lower than alkaline phosphatase activity and differences between species and varieties were small and nonsignificant. The results suggest that the higher phosphatase activities in the rhizospheres of some crops may increase P availability and utilization from arid soils.

In studies of 36 genotypes of Boehmeria nivea, height of plants grown from rhizomes at 70, 90 and 110 days after planting showed positive and significant phenotypic and genotypic correlations with establishment percentage from stem cuttings, indicating that genotypes producing tall plants from rhizomes could establish more easily from stem cuttings than genotypes producing shorter plants. A higher genotypic than phenotypic correlation coefficient and a higher coheritability percentage indicated that plant height and establishment percentage were genetically linked and influenced little by environment. It was concluded that vigour of plants grown from rhizomes may be used as a criterion in selection of genotypes for ease of establishment of stem cuttings.

Tannin-containing and tannin-free members of two pairs of near-isogenic lines of Vicia faba were studied in glasshouse experiments at Plant Breeding International Cambridge in 1989 to determine the cause of poor establishment of tannin-free lines in the field. Tests in field soils demonstrated marked differences in disease severity and growth, the tannin-containing lines being the more resistant to Fusarium culmorum and F. solani, the principal pathogens isolated. Susceptibility was not attributable to testa damage in tannin-free lines. In further tests on a range of varieties, some tanninfree and low-tannin, coloured-flowered varieties were as resistant as standard high-tannin lines. The results indicate that it should be possible to select for resistance to seedling infection and to subseque1t poor establishment among tannin-free lines and varieties.

The relationships between the amounts of nitrogen fertilizer applied and taken up by sugarbeet crops and the concentrations of sugar and α-amino-N in the storage root were examined using data obtained from fertilizer-response trials on different soils in the UK and Belgium between 1974 and 1985. On unmanured mineral soils, crop uptakes of N without fertilizer ranged from 65 to 190 kg/ha and increased linearly with the amount of fertilizer N applied. On organic soils or mineral soils that had received large applications of organic manure, crop uptakes of N were very large (295–383 kg/ha) and were not increased by applications of fertilizer N.

The amino-N contents of harvested beet increased with crop N uptake. The distributions of crop N to the storage root and of storage-root N to amino-N differed, especially in manured, diseased and drought-affected crops. Greater proportions of crop N were present in the storage roots of manured crops than in conventionally fertilized crops, and more of the storage-root N was present as amino-N in crops affected by virus yellows or drought than in healthy, unstressed crops.

The fresh weight concentrations of sugar in the storage root also differed between sites and years but were not consistently reduced by applications of fertilizer N at individual sites. However, when compared across sites, concentrations were negatively correlated with crop N uptakes and the amounts of N in storage roots. This was because particular crops grown on mineral soils with large applications of manure or on organic soils had large N uptakes and exceptionally low concentrations of sugar.

The physiological implications of these relationships between N uptake and amino-N and sugar accumulation are discussed.

Field trials were conducted in 1988 at the University of Ibadan to determine the effects of cypermethrin + dimethoate (Sherpa Plus®), the oil extract from ripe seeds of Piper guineense Schum & Thonn and the aqueous extract of ripe seeds of Azadirachta indica A. Juss on the pests and yield of cowpea. Cypermethrin + dimethoate was consistently superior to all other treatments in substantially reducing the population densities of Megalurothrips sjostedti Trybom and of Maruca testulalis Geyer, which are serious pests on flowers and buds, and in reducing the densities of four pod-sucking bugs. Pest population densities were also reduced by foliar sprays with A. indica or P. guineense extracts.

Seed yield after treatment with cypermethrin + dimethoate was 0·99 t/ha, more than double the yield from other treatments. A marginal increase in seed yield compared with the control was achieved by foliar spraying with A. indica extract.

An earlier report of leaf scorch and diminished yield when using large amounts of urea on winter oilseed rape (Brassica napus) was investigated by applying 200 kg N/ha as calcium ammonium nitrate (‘Nitro-chalk’) or urea as a single dressing or divided in six ways. The ‘single-low’ variety Mikado (low in erucic acid) was grown in 1986 and was compared with the ‘double-low’ variety Ariana (low in erucic acid and glucosinolates) in 1987 and 1988. No scorch was seen in these experiments. Yield from rape fertilized with prilled urea was, on average, 98% of that from rape fertilized with ammonium nitrate. The timing and distribution of the fertilizer also had little effect on yield, though yield slightly decreased when part of the dressing was withheld during March. The earlier-maturing variety Mikado always outyielded Ariana except when harvest was delayed by bad weather.

When plots were fertilized with urea, the oil content of the seed was a little larger than when fertilized with Nitro-chalk, which compensated for the smaller seed yield, resulting in almost equal oil yield from both forms of N fertilizer. Crude protein content was lower after a large single dose of urea fertilizer but parity with ammonium nitrate was restored by smaller amounts applied on a number of occasions. Neither form nor timing of N fertilizer had any consistent effect on the total glucosinolate content.

The incidence of disease was significantly greater in rape given either form of N fertilizer than where none was given, but when downy mildew (Peronospora parasitica) was prevalent on pods there was significantly less infection in plots fertilized with urea than with ammonium nitrate.

Four soyabean cultivars were grown with two N application rates (50 and 300 kg N/ha) in the field at Hiroshima University, Japan, from June to August 1988. Cell membrane stability (CMS) by the polyethylene glycol (PEG) test, leaf water relations and nutrient concentrations in cell sap and leaf tissues were measured when the plants were 50 days old, in the uppermost fully expanded leaves.

Cell membrane stability was higher at the higher N rate, the increase over the lower rate being greater in the cultivars Lee+ and Lee–than in Tamahomare and T201. Leaf water potential was not affected by the higher rate of N application. Osmotic adjustment, which was independent of water stress, was observed with the higher rate of N and it was higher in Lee + and Lee–than in Tamahomare and T201. It is suggested that osmotic potential in leaf tissues may influence CMS measured by the PEG test. Solute concentrations in cell sap and leaf tissues were higher at the higher N rate. Sugar and K were the major contributors to osmotic potential.

Two-year-old tea bushes were given NPK fertilizer on 12 November 1986 and 14CO2 on 22–23 December 1986 and 9–10 January 1987. Late-autumn fertilizer dressing stimulated photosynthate accumulation in the whole bush, especially in overwintering leaves and roots. Large amounts of photosynthates in overwintering leaves provide the nutrition required for early spring budding. Lateautumn dressing also accelerated the transport of photosynthates from leaves to roots in winter, where photosynthates, with absorbed nitrogen, synthesized more animo acids, especially theanine and phenylalanine. The re-use of photosynthates stored in the roots of the dressed bushes during shoot growth the following spring was also facilitated by late-autumn dressing. The contents of amino acids and caffeine in the shoots of dressed bushes were much higher than those in the control, whereas the content of polyphenol was lower than in the control. The results indicate that late-autumn dressing improves the quality of spring green tea.

Growth, yield and incidence of lodging of poppies were studied in Tasmania at 10–200 plants/m2 and at nominal rectangularities (within-row: between-row spacing) ranging from 1:1 to 10:1. In 1983/84 and 1988/89, there were asymptotic relationships between plant population density and both total dry-matter production and total head (capsule plus seed) yield at maturity. In 1983/84, a season with above-average wind, the incidence of lodging increased as density increased to > 50 plants/m2; morphine concentration decreased as density increased to > 100 plants/m2. This resulted in parabolic relationships between yield of erect (machine-harvestable) heads and yield of morphine from erect heads with plant density, the maximum morphine yield from erect heads being achieved at 70 plants/m2. In 1988/89, a season with below-average wind, the effects of lodging were less severe at high densities and the components of ‘erect’ yield were adequately fitted by an asymptotic function. Rectangularity of 1:1 gave higher total dry matter production, total head yield, yield of erect heads and morphine yield from erect heads than 4:1 and 10:1. Since calm conditions similar to those of 1988/89 occur only once in every 4 years, growers should be encouraged to establish c. 70 plants/m2. As most commercial crops in Tasmania are drilled in 150–175 mm rows, growing at 70 plants/m2 to maximize the effect of plant density would also approximate to the ideal rectangularity (2:1 in this case).

The pollination requirements of the white lupin cultivar Vladimir were investigated in a glasshouse. Five treatments were compared in which the flowers of each plant were (i) left to autopollinate, (ii) shaken, (iii) tripped, (iv) self pollinated or (v) cross pollinated. Pollination treatments had no effect on the numbers of flowers, pods or seeds or weight of seed produced by the plants but did slightly shorten the duration of flowering, the effect being greatest when flowers were tripped or cross pollinated and least when they were shaken or self pollinated.

The proportion of flowers that developed into pods differed with raceme, with secondaries producing more than tertiaries > primaries > quaternaries; the number of seeds per pod differed in the same order, but mean single-seed weight decreased on successive racemes. However, pollination treatments had no effect on the distribution of flowers, pods or seeds on the plant.

This crop species is clearly highly self fertile and self pollinating and likely to yield well without insect pollination.

Crop patterns of natural origin and man-created crop marks are frequently recorded on aerialphotographs taken over England and Wales. They usually indicate subsil variation over short distances, but differences in crop growth may also be evident in relation to topsoil variability. Different kinds of crop patterns and the soils on which crop patterns and marks develop are briefly described. Soil associations in which crop patterns and marks are frequently and extensively recorded cover 25% (37664 km2) of England and Wales; in dry years, patterns and marks are extensively recorded over a further 6·5% (9884 km2). Crop patterns and marks indicate that over much of England and Wales crop growth may be impeded by properties intrinsic to the soil, which are not easily ameliorated by farmers. When siting crop experiments, care should be taken to avoid these areas of complex soil patterns.

Field experiments were conducted during 1983–85 and 1984–86 on an entisol at Lucknow, India. Dry herbage, essential-oil yields and nutrient uptake increased significantly with the application of 83 kg K/ha. Considering the means from both experiments over a two-year cropping cycle, the application of 41·5 kg K/ha in four splits exceeded the zero K control by 6·8 t/ha (dry matter) and 233 kg/ha (oil), and exceeded a basal application of 83 kg/ha K by 2·8 t/ha (dry matter) and 109 kg/ha (oil). Amounts and methods of K application showed no effect on oil quality. Application of 41·5 kg K/ha in four splits, one after each harvest, is recommended to obtain maximum yields in this perennial grass.

The responses to Zn fertilizer of wheat, barley, oats, lentil, chickpea, pea, mustard and linseed were studied on a Typic Ustochrept soil in Pura, India in winter 1982/83 and 1983/84. Application of Zn significantly increased the grain or seed and total biomass yield of all the crops and enhanced Zn concentration and uptake. The response was greatest in lentil, followed by chickpea, pea, wheat, linseed, mustard, barley and oats. Cereals accumulated the most Zn, followed by the pulses and oilseeds. The pulses were more sensitive to Zn deficiency than the other crops.

In studies of carrots sown on three dates at Wellesbourne in 1986, mean time to seedling emergence and spread of times to seedling emergence of untreated and fluid-drilled seeds increased as seed-bed moisture at sowing decreased. These differences were not observed with irrigation before sowing.

Osmotic priming increased the percentage of seeds with emerged radicles at the time of fluid drilling from 17% in the untreated control to 56%. Irrespective of seed-bed moisture, time to emergence was shorter from primed germinating seeds than from germinating seeds, both treatments giving earlier seedling emergence than untreated seeds. Seedling shoot weight was greater from treated than from untreated seeds.

Seed-bed characteristics on unirrigated plots had no effect on seedling emergence when soil moisture was adequate but, where soil moisture was limiting, rolling the seed bed to increase capillarity resulted in 79% emergence compared with the 67% average from seed beds that were not rolled. Application of a soil conditioner to stabilize the seed-bed surface structure generally improved emergence when rain fell soon after sowing. The results suggested that a combination of seed-bed and seed treatments can significantly improve the predictability of crop establishment of carrots on different dates.

Data from 62 field experiments on various crops in 1973–85 at Rothamsted Experimental Station were used to obtain knowledge about the heterogeneity of variance of yield. The results suggest that explaining heterogeneity of variance in terms of a mean–variance relationship is inadequate; better understanding of the patterns of changing variance can be gained by investigating the influence of the experimental factors on the variance. The effects of the factor ‘amount of nitrogen’ on mean yield and on the variance were positively correlated; factors which tend to affect variability but not the mean were identified. Suggestions are given for controlling variance but the need for further experimental evidence is emphasized.

Contents of the caecum and the colon of four steers and four cows fed concentrate-plus-roughage diets were obtained at an abattoir, transferred to the laboratory and incubated anaerobically with maize starch in the presence (10mg/l) or absence of monensin. Samples taken at the end of incubation were assayed for fermentation acids and methane production.

Monensin significantly increased the molar percentage of propionate and decreased that of butyrate. Acetate percentage was not significantly influence by the addition of monensin. There was no consistent effect of monensin on total volatile fatty acid concentrations. Monensin decreased methanogenesis in all incubations. The production of methane was small, only 1 mmol/13–50 mmol of volatile fatty acid.

Eighty autumn-calving (A) and 82 spring-calving (S) British Friesian cows were divided during the grazing season into two groups: one group received silage overnight indoors and grazed herbage during the day (partial storage feeding, P) and the other was conventionally set-stocked (C). The effects of the four treatments (AC, AP, SC and SP) on reproductive performance and herd health are reported for the 27-week grazing season and the subsequent 25-week housed period in 1985/86 in North Wales. Calving to conception interval was not affected by treatment but, in treatment SP, pregnancy rate to all services was lower and number of barren cows was greater than in the other treatments. Partial storage feeding increased the incidence of under-run heel and laminitis in the early part of the grazing season, and this was reflected in poorer locomotion. Treatment SC resulted in an increased incidence of punctured sole with pus later in the grazing season. Both autumn-calving treatments resulted in a large decrease in lameness and poor locomotion at drying off, but these increased in the autumn before housing. The mean duration of each lameness incident was 1·88 months and, in 40 out of 97 incidents, lameness was preceded by uneven gait. The incidence of lameness and poor locomotion was low for all treatments throughout the housed period. It is concluded that a high standard of buildings and reproductive and herd health management is necessary for partial storage feeding to be practised successfully.

This study sought to determine whether increases in live weight (LW) of steers implanted with Compudose 200®, a growth promotant that contains 17β-oestradiol, arose in part from increases in resistance of those steers to cattle ticks and gastro-intestinal nematodes (worms) to which the steers were exposed while they were growing. Half of a group of interbred Hereford × Shorthorn (HS) and interbred Brahman × HS (BX) steers was implanted with Compudose 200 on two occasions 200 days apart. Half of each of the implanted and nonimplanted groups in each breed was treated every 3 weeks to control cattle ticks and worms. All animals grazed together and were regularly monitored for parasite burdens and LW changes. Both breeds responded positively to Compudose 200, to which BX responded most, and to treatment to control parasites. Resistance to either ticks or worms was unaffected by the presence of the implant so that, within each breed, increases in LW gain in response to the implant were similar regardless of parasite control. Thus the increases in LW gain resulting from the use of Compudose 200 arose directly from the action of the implant on metabolism, not indirectly through any effect on resistance to parasites.