Manganese-tolerant strains Mnr-1 and Mnr-5 of Azospirillum brasilense (RAU 1075) were isolated through step-wise transfer to higher levels of manganese chloride. One of the strains (Mnr-5) showed more growth at low pH and greater nitrogenase activity in 10 mM MnCl2. 4H2O than parental and Mnr-1 strains. These tolerant strains also showed cross-resistance to antibiotics such as gentamycin and neomycin but not to streptomycin. Mn-adapted strains also tolerated elevated levels of aluminium (2·5–3·5 mg/kg) and the stability of the Mn-resistance required the presence of Mn2+ ions in the growth medium. It has been demonstrated that the effect of inoculation with Mn-adapted strains was variable with different genotypes of rice in acid soil and that initial low level of nitrogen was essential for maximum associative N2-fixation.

In North West Pembrokeshire, sulphur was determined in soils sampled at 268 sites, and in pasture plants sampled at 172 sites. The sulphur contents of the topsoils ranged from 199 to 3392 mg/kg, with a mean of 710 mg/kg; and the S contents of the subsoils from 115 to 1344 mg/kg, with a mean of 356 mg/kg. Sulphur was concentrated in soils containing much organic matter. There was no clear relationship between plant and soil sulphur contents, though soil drainage influenced both. Poorly drained soils were richer in S than well-drained soils, whereas herbage on poorly drained soils accumulated less S than herbage growing on well-drained soils. Herbage S contents ranged from 0·180 to 0·560%, with a mean of 0·310%. If other factors, e.g. soil N, are not limiting, 14% of the herbage sampled in Pembrokeshire had less than the critical S level recommended by other workers for maximum dry matter yield.

The morphological (using International Union for the Protection of New Varieties of Plants (UPOV) descriptors) and field performance of five clones selected from the globe artichoke landrace Spinoso di Palermo were determined over two seasons, and their amplified fragment length polymorphism (AFLP) profiles detected using seven primer combinations (PCs). The number of heads produced averaged 13·8 per plant (equivalent to a fresh weight yield of 2·1 kg/plant), but two of the clones produced 15·6 heads per plant (2·4 kg/plant). Three clones produced noticeably larger second-order heads (mean of 156 g), and so were considered to be suitable for the production of desirable heads over a prolonged harvesting period. Head yield and the number of heads per plant were associated with a moderate level of broad sense heritability (0·29–0·46), implying that these traits could be viewed as primary selection criteria. From the list of 51 UPOV descriptors, 18 varied among the five clones, but variation at just six, simply scored, descriptors was sufficient to discriminate completely between the examined clones. Full discrimination was also achieved by applying only three of the seven selected AFLP PCs. According to the AFLP profiles, two of the clones were highly similar. The similarity matrices calculated from the UPOV descriptors and the AFLP profiles were highly correlated with one another. The data are optimistic and indicate that the performance of Spinoso di Palermo could be much improved via clonal selection.

1. The reaction of spring and winter types of field beans and of Windsor broad beans to artificial vernalization treatments and to successional field sowing has been studied.

2. The broad bean type came into flower earlier and at a lower node on the stem than any of the field bean types, and this was not affected by either vernalization treatments or successional sowing.

3. The field bean types flowered at a low node when sown in winter, but in summer sowings the level of the first flowering node was much higher; the response of the winter types was more extreme than that of the spring types.

4. In the summer sowings vernalized plants came into flower earlier and at a lower node than unvernalized, but in the winter sowings both vernalized and unvernalized material flowered at an equally low node.

5. A convention for naming the different stems contributing to the yield was evolved, and using this it was shown that the date of sowing affected the stems produced.

6. The survival of plants in the field was not found to be affected by vernalization previous to sowing.

Two field experiments were conducted during 1996–98 at Bangalore, India to study the effect of soil moisture regimes (0·3, 0·6 and 0·9 IW:CPE ratios) irrigation water:cumulative pan evaporation (IW:CPE) ratios and three rates of nitrogen application (0, 100 and 200 kg/ha) and in another experiment, three soil moisture regimes (0·3, 0·6 and 0·9 IW: CPE ratios), two rates of nitrogen application (100 and 200 kg/ha) and modified urea materials [prilled urea (PU) and dicyandiamide coated urea (DCDCU)] on oil content, herbage, oil yield and quality of geranium grown on altisols. Soil moisture maintained at 0·6 IW:CPE ratio significantly increased the herbage and oil yields of geranium. Application of 200 kg N/ha gave the maximum herbage and oil yield compared with those obtained from 0 and 100 kg N/ha. DCDCU produced higher yield than PU. The concentration and quality of essential oil were not influenced either by soil-moisture regime, rates or carriers of N.

Prenatal mortality was examined in 74 primiparous Merino ewes which, after hand mating to fertile rams on the second oestrus following synchronization, were allocated to two groups. One group of 38 ewes was confined to yards and restricted to approximately 30% of their maintenance requirement for 14 days while the other group of 36 remained at pasture. The degree and timing of prenatal loss was assessed by corpora lutea counts, pregnancy diagnosis about day 40, returns to service and lambing records.

The mean ovulation rate was 1·06 and the 19-day non-return rate was 87·8%. Pregnancy failed in a higher proportion of the underfed ewes (45·0%) than in the control ewes (30·8%) but this difference did not reach significance. Of the ewes returning to service, significantly more did so with cycles longer than 19 days in the underfed group (9/12) than in the control group (2/8), indicating that in the latter stages, the treatment may have been detrimental to embryo survival.

In a second experiment, ovulation rate and prenatal mortality, assessed as in the first experiment, were studied in 85 mature Merino ewes subjected to the following nutritional treatments: HH, control; HL, 30% submaintenance feeding for 14 days following mating; LH, 15% submaintenance feeding for 7 days prior to mating; LL, both submaintenance treatments.

Acute undernutrition prior to mating (LH) had no effect on ovulation rate or prenatal mortality. Ovulation rates were low over all groups (mean 1·09) and thus precluded any valid examination of ovulation rate and body weight relationships. The right ovary was significantly more active in producing ova than the left in all groups (P < 0·05). Although ova wastage was apparently higher in. the post-mating undernutrition groups (HL, 44%; LL, 48%; LH, 50%) than in the control group (HH, 35%), the differences were not significant. An increased incidence of extended (> 19 days) first-return cycle lengths in group LL provided some evidence of induced prenatal mortality.

In so far as the experiments can be considered together, they indicate that if body weights are comparable, primiparous 1½-year-old ewes are not necessarily more susceptible than mature ewes to prenatal mortality induced by severe short-term undernutrition.

The gastrointestinal tract (gut) contents of male Zebu cattle (Bos indicus) were studied in the southern Sahelian zone of Mali. Measurements were carried out on 39 animals in mid-dry season (MDS) and 15 at the end of the dry season (late dry season, LDS).

After overnight fasting, the animals were weighed and then slaughtered. The different gut compartments were emptied and representative samples of their fill were analysed for contents of dry matter (all) and NDF (reticulo-rumen only).

Related to fasted live weight (FLW), gut fresh matter (FM) fill (g FM/kg FLW) increased from 165·7±4·81 g in MDS to 227·5±3·05 g in LDS (P[les ]0·001), liquid gut contents (g fluid/kg FLW) increased from 138·9±4·65 to 193·5±2·49 g (P[les ]0·001) and gut dry matter fill (g DM/kg FLW) increased from 26·8±0·88 to 34·0±0·97 g (P[les ]0·001). Fresh matter content of the reticulo-rumen accounted for 77% and 80% of the entire gut FM fill in MDS and LDS, respectively. While the NDF component in reticulo-rumen fill (g NDF/kg DM) increased from 778·5±5·63 g in MDS to 836·6±6·37 g in LDS (P[les ]0·001), the ratio between dry matter and fluid in the reticulo-rumen (g DM/g fluid) decreased from 193·2±10·17 g in MDS to 169·0±5·54 g in LDS (P[les ]0·05).

The data support the notion that African breeds of Zebu cattle adjust to deteriorating feeding conditions by increasing reticulo-rumen dry matter and fluid contents. In-depth studies are needed to quantify the physiological benefits resulting from this strategy.

1. Ayr Line Potato oats was studied in the later stages of development for 3 years under upland conditions in Kincardineshire, Scotland. Some major changes in yield and chemical composition of the crop and certain effects of haymaking have been demonstrated.

2. In each year, between the ‘milky’ stage and full ripeness of the grain, the growth curve falls into the distinct phases of growth, maturity and senescence when dry-matter loss occurs. The position of the peak yield in terms of stage of maturity varies from year to year.

3. Percentage crude protein is low throughout, falling to a minimum after the early ‘milky’ stage and rising again to a maximum at the last cut. Yield of crude protein is highest at the last cut in one year and at the penultimate cut in two years.

4. Percentage crude fibre tends to decrease with increasing maturity, while crude fibre yield is low at both extremes of the experimental period.

5. More detailed chemical analyses at different stages of maturity show total ash content to be low. The content of calcium is especially poor.

6. Separation of the whole of the aerial part of the plant into leaf, stem and inflorescence shows that chemical constituents are being actively re-distributed throughout the plant during the experimental period; with the exception of crude fibre and calcium all constituents estimated tend to be concentrated in the grain with advancing maturity.

7. In one year, dry-matter losses during curing range from 22 to 7% at the first and last cuts respectively, while corresponding figures for crude protein are 18 and 10%.

8. In the absence of digestibility data and feeding trials under Scottish conditions, the tentative conclusion is drawn that in the higher rainfall areas of the north and west where the crop is most likely to be used, cutting between the late ‘milky’ and late cheesy' stages should give optimum results.

9. Attention is drawn to the need for caution in the general application of the results.

Rates of added P required for maximum yields of ryegrass grown in pots and of field tobacco and maize were related to functions of P intensity (I) and capacity (AQ/AI, or C) in soils. It was found that log I alone was negatively correlated with optimum fertilizer for ryegrass and tobacco, but not for maize. Capacity alone had little relationship with P requirements of tobacco but was significantly correlated, although having opposite effects, with those of ryegrass (positive) and maize (negative). Optimum fertilizer rates for all crops were best accounted for by multiple regressions including intensity and a capacity term together, using log C when P requirements were increased (ryegrass in pots, R2 = 0.94) or √C when they were decreased by increasing capacity (field tobacco, R2= 0.96; and maize, R2 = 0.98). Inclusion of both capacity terms with log I in regression was of no advantage with ryegrass and tobacco, but with maize all three terms contributed significantly to the correlation, log C tending to increase and √C to decrease fertilizer needs.

This communication deals with the results of two experiments in which the “nitrogen-balance,” or difference between nitrogen-consumption and nitrogen-excretion by the cow, has been studied over prolonged periods, starting with the “dry” cow, not in calf, proceeding through the whole period of pregnancy and well into the period of active lactation.

Experiment 1 was performed throughout with the two cows, “dry” and not in calf, receiving a basal ration of hay to which was added increasing amounts of maize meal with a view to securing a progressively increasing consumption of nitrogen. This experiment lasted 196 days, during which period determinations of the nitrogen-balance were made on 90 days.

Experiment 2 was carried out similarly with two cows, and covered a period of 722 days, including 546 days on which determinations of the nitrogen-balance were made. Throughout the whole of this period one cow (Cow C) was maintained “dry” and not in calf, as control cow, whilst the other cow (Cow D) after 302 days became pregnant and its record was followed throughout the stages of pregnancy and parturition and for the first 136 days of active lactation.

The outstanding features of the results are as follows:

(1) With the progressive increase of nitrogen-consumption beyond the fundamental requirements of the dry cow the rate of nitrogen-retention steadily increases to a maximum and then falls. The maximum appears to be attained under the conditions of our experiment with a protein-supply in the neighbourhood of 2·4 kg. crude protein per 1000 kg. live-weight. There are indications that this figure may be independent of the nature of the foods fed along with hay.

(2) When the cow is maintained upon a ration which causes an initial nitrogen-retention the rate of retention falls steadily, but a very prolonged period—up to 90–100 days—may be necessary before nitrogenequilibrium is attained.

(3) Even after nitrogen-equilibrium is established and a relatively constant nitrogen-consumption is maintained, there may arise from time to time considerable deviations from equilibrium either in the positive or negative direction. It would appear therefore that for reliable work of this character long experimental periods are essential.

(4) The very earliest stages of pregnancy are marked by a profound disturbance of nitrogen metabolism, the requirement for maintenance of nitrogen-equilibrium being very sensibly increased. This additional requirement persists at a steadily reduced rate for some 15 to 20 weeks, after which it is very small. Over the whole period of pregnancy the average rate of nitrogen-retention was only about 2·4 gm. per day.

(5) During parturition and for a few days subsequently the output of nitrogen is very great and more than can be restored rapidly by food-consumption. With the experimental cow, giving barely three gallons of milk per day at most, some two to three weeks elapsed after calving before nitrogen-equilibrium was restored.

(6) It would appear that to maintain nitrogen-equilibrium during lactation, the food must supply from twice to three times the amount of nitrogen secreted in the milk, in addition to that required for the maintenance of equilibrium in the “dry” state. This represents a food-consumption which would be difficult to attain in the case of cows giving large yields of milk, and accounts for the familiar difficulty of maintaining the “condition” of such cows in the earlier stages of lactation.

As part of the overall programme of research directed towards an understanding of fertilizer needs of crop plants in East Africa a study of the nutrition of maize in sand culture has been made.

The purpose of the work was to study growth and yield in relation to changes in the proportion and concentration of the major nutrients, nitrogen, phosphorus and potassium, and if possible to relate the results to the field behaviour of the crop in fertilizer trials conducted by another section of this organization. Simultaneously studies of the uptake of nitrogen and phosphorus were also undertaken. These latter are discussed in the second paper of this series.

This first paper deals only with growth, yield and nutrient content in relation to the nitrogen phosphorus balance, though the methods now to be described were common to all experiments.

A condition known as ‘scorch” with symptoms similar to copper deficiency often occurs in dry weather on cereals grown on a sandy soil (at Woburn) with an unstable structure. Plants with symptoms contained more sulphur than normal and sulphur/ copper interactions were suspected.

Sulphur fertilizers tested in two pot experiments with this soil did not induce copper deficienciesbut increased grain and straw yields of spring wheat especially at higher nitrogen rates. Yields were increased when the mature grain contained less than 0.12% S and the straw less than 0.5% Sin the dry matter. Sulphur concentrations were larger in plants grown in the greenhouse rather than in growth cabinets and in plants grown in oven-dried rather than air-dried soil.

Soil-applied copper sulphate slightly increased grain yields in pots but in one experiment there were no corresponding increases in copper contents of the crop. In a field experiment where ‘scorch’ symptoms occurred in 1972, copper oxychloride sprays increased copper concentrations but not yields of the grain.

These results suggest that copper deficiency is unlikely to be a primary cause of ‘scorch’ symptoms.

Wheat and sunflower plants were grown in a temperature-controlled glasshouse in Melbourne, Australia (37° 50′ S, 145° 00′ E), from 9 August to 2 October 1991, in cylinders containing two soils (Walpeup loamy sand (LS) and Gombalin clay loam (CL)) of low and moderate N status, respectively. Nitrogen fertilizer was applied by immersion of leaves in 0·18 M urea solution (10·5 atom% 15N).

Plants were N-deficient in the Walpeup LS but not in the Gombalin CL soils. Both species had higher root: shoot ratios, and higher proportions of foliar-absorbed N were transferred to the roots, in the Walpeup LS plants. Plant N derived from the fertilizer and root or shoot dry matter were significantly correlated only when plants were N-deficient.

In the Walpeup LS soil, N-fertilized wheat harvested 33 days after sowing (DAS) took up significantly less soil N compared with unfertilized plants, whereas significantly more soil N was taken up by N-fertilized sunflower compared with unfertilized plants harvested at 54 DAS. The fertilizerinduced response in uptake of soil N was directly related to the observed response in production of root biomass for both species. The different responses were related to the severity of the N deficiency and the limited effectiveness of foliar applications of urea in ameliorating the deficiency.

The objective of the current study was to quantify the dry matter (DM) digestibility, and total ash (TA) and mineral release from 12 concentrate and 12 forage feedstuffs commonly fed to cattle using in situ and in vitro methods. Concentrate and forage feedstuffs were incubated in the rumen of ruminally cannulated beef bulls at eight different time points. Two different trials were conducted for concentrates and forages, with maximum incubation time of 72 and 120 h, respectively. The residue from samples incubated for 24 h were treated with pepsin and hydrochloric acid to simulate abomasum digestion in vitro. The initial and residual samples after in situ and in vitro incubations were measured. An asymptotic model was adopted for estimating solubility of minerals, disappearance rate of DM, and TA. Correlations between feedstuff contents and mineral release were evaluated. Residual samples from rumen fermentation after 24 h were incubated in simulated abomasal conditions and mineral release was measured. Cluster analysis was performed to group feedstuffs in relation to TA release. Large variability was observed between concentrate and forage feedstuffs for all constituents analysed. Large variability was observed for the effective ruminal degradation of TA and individual mineral release. When feedstuffs were clustered according to the immediately soluble fraction (‘a’), the insoluble by potentially releasable fraction (‘b’) and the release rate of ‘b’ (‘kd’,/h) estimates of TA ruminal release, four groups were identified. From group ‘1’ to group ‘4’, an increase in the soluble fraction and a reduction in both moderate releasable fraction and release rate was observed. Neutral detergent fibre content had a negative correlation with mineral release in the rumen, while mineral content had a positive correlation. These results demonstrate that mineral solubilization in the digestive tract is not the limiting factor for mineral absorption from the feedstuffs tested.

The objective of this study was to examine the effect of the chemical growth regulator chlormequat on the yield and yield components of oil-seed rape. Although this chemical is widely used in wheat production systems, its use as a morpho-regulator for oil-seed rape has not been examined thoroughly. A few Eastern European experiments have been published. Voskerusa (1972) applied it at 2, 4, 6 and 8 kg/ha to winter varieties in Czechoslovakia. His results, which agree with those of Fabry & Hannich (1972), demonstrated reduced winter kill using an autumn application. However, studies on modern varieties such as Rafal, now widely grown in European Economic Community countries, have not been reported in detail.

Lignification-associated phenolic acids are widely distributed in graminaceous plant cell walls. Nylon bags containing maize bran, wheat bran, millet husk and rice husk were incubated in the rumens of five Charolais (♂) × Nanyang (♀) crossbred steers for 6, 12, 24, 36, 48 and 72 h. The in situ ruminal disappearance of ester-linked phenolic acids linearly increased in the brans with increasing incubation time, and the disappearance was greater for ester-linked ferulic acid (FAest) than for ester-linked p-coumaric acid (PCAest). The disappearances of FAest and PCAest were positively correlated with disappearances of neutral detergent fibre (NDF), cellulose and hemicellulose. The effective degradabilities of NDF, cellulose and hemicellulose in the brans were markedly greater than the effective degradabilities of these components in the husks, and were negatively correlated with the contents of Lignin (sa), ether-linked ferulic acid, PCAest and ether-linked p-coumaric acid in both the cereal brans and husks. These findings suggested that breeding forage crops with modified phenolic acid contents could represent an alternative strategy to promote further increases in fibre digestibility of cereal residue feeds for ruminant animals.

A high level of resistance to the bean common mosaic virus strains NL3 and NL4 when inoculated separately or together was confirmed in the cultivars Turkish Brown, Valja and 1750–73. Following crosses between the susceptible cv. The Prince and all three resistant cultivars, inoculation of F2 and F3 populations revealed that the cvs Turkish Brown and Valja each differed from The Prince in being homozygous for a major recessive gene conferring resistance to both NL3 and NL4. Homology tests indicated that the same gene was present in both Turkish Brown and Valja. Polygenes in Turkish Brown and Valja also appeared to confer some resistance to NL3, or environmental variation led to continuous distribution patterns in the F2's of resistant parents crossed with The Prince. Although a major recessive gene controlled resistance to NL3 in cv. 1750–73, it differed from that in the two other resistant cultivars. In addition, cv. 1750–73 carried a dominant gene determining reaction to the virus; probably the I gene originally found in Corbett Refugee. An attempt is made to relate these results to Drijfhout's (1978) gene-for-gene model. Using Drijfhout's gene nomenclature all the cultivars tested appear to carry the strain nonspecific gene bc-u. Further genetical tests will be necessary to determine with certainty which, if any, of Drijfhout's strain-specific resistant bc-genes are present in the three resistant cultivars studied here.

1. Investigations of individual soyabean families over a 5-year period showed in some famines that the strain compounded in the F5 generation had a more stable environment × genotype interaction than the daughter strains compounded in the F6 generation.

2. Regression of each strain yield on an ‘environmental’ mean gave values for the slope of the regression line (bi), and the mean square of the regression (s2d) gave a value of deviations from the regression line. The values bi and s2d were used as estimates of stability.

3. Groups of F5 and F6 compounded strains were compared. Analysis of variance for yield over 5 years for twenty-four F5 compounded strains and twentyfour F6 compounded strains gave s2d value of 166·4 for the former and 289·1 for the latter. With 72 degrees of freedom for each group they differed from each other at the 1 % level of P.

4. Multiple correlation analyses were also done on the two groups of strains. It was concluded, all else being equal, that the F5 strains over a period of years would be less liable to give low yields in a bad year than the F6 strains.

(1) The moisture equivalent of a normal soil diminishes as the weight of soil taken for the determination increases.

(2) Some soils are particularly impermeable to water in thick layers: in these cases the moisture equivalent increases with the weight of soil taken and may become very large owing to waterlogging. A soil may, however, have a very high moisture equivalent without showing waterlogging.

(3) Dilute solutions of flocculating salts such as calcium sulphate, or ammonium nitrate or sulphate, reduce the moisture equivalent, and sodium carbonate increases it.

(4) The effect of sodium carbonate is complicated: with gradually increasing concentration, the moisture equivalent first diminishes and then increases to a maximum, after which there is further diminution.

(5) The soil samples which easily showed waterlogging in the Briggs-McLane apparatus had a higher concentration of hydroxyl-ions (pH) than those which did not.

(6) Whilst the colloidal content of a clay seems related to its moisture equivalent, no such connection appears to exist for substances such as kaolin or aluminium hydroxide.

When an organic calcareous soil was air-dried for 2 days and re-wetted to a wide range of moisture contents, well below saturation, nitrite accumulated within 1–2 days. At the same time much nitrate was formed and more carbon dioxide was released than from soil kept moist. On further incubation of re-wetted soil for 3–5 days, the nitrite concentration decreased rapidly. Since 15N-labelled nitrate was reduced to nitrite after air-drying and re-wetting, and no nitrite was formed in autoclaved soil, nitrate was microbially reduced.

Eighty-three per cent of added 15N tracer was recovered from the soil 2 days after re-wetting to 70 % moisture, indicating that 58 ppm N had been lost; 10 ppm N of this was released as nitrous oxide. Autoclaved soil to which nitrite was added did not evolve nitrous oxide, suggesting that nitrite was reduced biologically rather than decomposed chemically.

Three other soils were treated similarly; two, which were non-calcareous, accumulated no nitrite. Fresh calcareous soils with high respiration rates and good capacities to denitrify when waterlogged are most likely to form nitrite after drying and moderate re-wetting.