Water and energy metabolism were measured in six growing female New Zealand White rabbits placed individually in metabolism cages within chambers at 20 or 30 °C and offered a diet high (H) or low (L) in roughage. For water balance measurements, feed intake was higher at 20 °C than at 30 °C; mean water balance of rabbits on diet L was 7 g/day at 20 °C and 36 g/day at 30 °C. Total daily water consumption was 84–96 g/kg body weight (W), and the ratio of free water to feed intake was 1·6:1 at 20 °C and 2·3:1 at 30 °C.

Calorimetric measurements showed no differences in energy metabolism of rabbits due to diet or temperature. Metabolizable energy needed for maintenance was 357 kJ/kg W0·75 per day and was used with an efficiency of 0·44 for weight gain.

The influence of addition of sulphate on acetylene reduction in three paddy soils differing in their properties under two water regimes was investigated in a laboratory experiment. Nitrogenase activity was high in a P-deficient alkaline soil and addition of sulphate further enhanced the activity under two water regimes, with a pronounced stimulation under non-flooded conditions. Sulphate application to submerged alluvial soil enhanced nitrogenase activity with no apparent effect under non-flooded conditions. In acid sulphate saline Pokkali soil sulphate addition had little effect on the nitrogenase activity. Sulphate addition did not result in significant changes in the soil pH and redox potential. No relationship seemed to exist between the sulphate disappearance and stimulation of nitrogenase in these soils. A differential stimulation of N2-fixing microorganisms was noticed as a result of sulphate application. Results suggest that sulphate-induced stimulation of nitrogenase activity occurs in non-flooded soils.

Field experiments with rice were conducted on a flooded soil comparing two standard fertilizers with N fertilizers with various release rates. For each of these fertilizer materials two methods of application were compared: broadcast and incorporated, and placement at 15 cm depth. The .slow release materials resulted in a lower grain yield than did fast or medium release rate or standard fertilizer materials. They released N too slowly during the early growth of rice to permit optimum plant growth and development.

Placement of 80 kg/ha N at 15 cm depth increased the plant N content at all stages of growth and significantly increased the grain yield compared with the broadcast-and-incorporated fertilizer treatment. The highest grain yield in the experiment (7701 kg/ha rough rice) was obtained from a medium release material, which was 88 % more efficient in increasing grain yield per unit of N when placed at 15 cm than when broadcast-and-incorporated.

The recovery of fertilizer N was 68% when deeply placed and 38 % when broadcast-andincorporated.

The effects of nitrogen treatment on blade length and longevity were studied in primary growth of early and late varieties of perennial ryegrass, timothy and cocksfoot. Reproductive and vegetative tillers were examined in cocksfoot, but in perennial ryegrass and timothy the study was restricted to reproductive tillers, which accounted for a large proportion of the primary growth in these species. Results obtained by a technique which involved repeated recording of tillers were corroborated by those obtained by destructive sampling of tillers.

With respect to the blade length of culm leaves, responses to nitrogen shown by S. 23 ryegrass and S. 48 timothy were greater than those of the early-heading varieties S. 24 ryegrass and S. 352 timothy. However, blade longevity was appreciably reduced by nitrogen in the late varieties whereas the early varieties showed a much lower response.

Implications of these results in relation to the accumulation of senescing material in primary growth are discussed.

The pattern of leaf expansion in vegetative tillers of cocksfoot is discussed in relation to regrowth.

In order to determine the accuracy of controlling the time of maturity of a cauliflower crop by regulating the planting date, a series of transplantings of the variety White Fox was grown on a range of sites over 3 years and sampled throughout growth.

The time from transplanting to maturity and the time from curd initiation to maturity were both quadratically related to the time of transplanting but there were marked differences in the relationships between years. Differences between years in the time taken to reach maturity tended to increase with later transplanting; for example, cauliflower crops transplanted in May took between 77 and 94 days to mature, while those transplanted in July matured in as few as 67 or as many as 106 days. These differences resulted from a combined effect of the time taken to satisfy the vernalization requirement and the duration of curd growth, both of which are temperature-mediated and therefore subject to seasonal and annual variation. Differences in the vernalization requirements of different cauliflower crops are illustrated by the number of leaves formed before curd initiation, which varied from 22·5 to 37·3.

Variation in the time to maturity between crops transplanted at similar times of the year, in the same and different years, resulted in large deviations from planned production programmes and it is suggested that a complementary technique to aid crop marketing would be prediction of the time of crop maturity. However, the data collected in this study show that predictions based on the duration of crop growth from transplanting or curd initiation are unlikely to be sufficiently accurate and it is argued that predictions should be based on changes in curd dimensions with time.

Three experiments were conducted to assess the effects of several methods of dietary presentation of 250 g/day of a fully soluble liquid supplement (LS) on the voluntary intake of oat straw by non-productive cows fitted with a rumen fistula (Expt 1), pregnant beef cows (Expt 2) and lactating beef cows (Expt 3). In each case the cows received fixed daily amounts of barley (2 kg for Expts 1 and 2; 3 kg for Expt 3). LS contained (g/kg) about 1100 crude protein (as urea), 30 calcium, 15 phosphorus and 50 salt plus trace elements and vitamins. In Expt 1, provision of LS in either the drinking water, or via the rumen fistula or sprayed on to the straw increased voluntary straw intake by about 12%. In Expt 2, provision of LS, whether by spraying on the straw or in a molasses lick, increased straw consumption, but giving LS in the drinking water did not. In both Expts 1 and 2 the digestibility of the oat straw was not significantly affected by the dietary supplement, any increases in metabolizable energy intake being reflexions of increased intakes. In Expt 3 there was no difference in the voluntary intake of oat straw by group-fed lactating beef cows offered LS in either the drinking water or as a molasses lick.

Giving LS sprayed on the straw, or incorporating it into a molasses lick to housed animals, are convenient and practical methods of supplementing ruminant diets to increase their voluntary straw consumption. Inclusion of LS in drinking water gave inconsistent results, but the method warrants further investigation.

1. Sodium, potassium, calcium, and magnesium balances in seven Hereford and seven Zebu steers have been determined during two 10-day trials. Values for phosphorus, omitting urine excretion, were also determined.

2. No breed differences were found apart from a tendency for Zebu steers to excrete less potassium in their faeces and more in their urine than Herefords.

Setts of white yam (cv. Ogojo) each weighing 225 g were planted in mid·February. They were double-harvested, first in early August, early September or early October, and second in early November. The control was single-harvested in early November. The later the time of the first harvest, the greater the first-harvest yield and the higher the percentage of mature and marketable tubers. Delaying the first harvest, however, led to decreasing yields from the second harvest. Double harvesting never gave a significantly higher yield than that obtained from a single harvest. When the first harvest was taken in September, the combined yield from double harvesting was significantly lower than that of the single November harvest. In a study of the effect of sowing date on yield, late planting (April) resulted in lower first harvest and total yields than early (February) planting, but the second-harvest yield was the same. Supplementary watering of early yam plantings did not markedly accelerate emergence or increase yield.

Spring postpartum reproductive performance was investigated in 19 Awassi and 15 Finn×Texel×Awassi (FTA) crossbred ewes, weaned at 2 months postpartum and simultaneously exposed to rams for a period of 48 days. The study was conducted in 1991/92 in the Bekaa Valley of Lebanon.

Postpartum FTA ewes tended to have higher fecundity and prolificacy than those of Awassi ewes. Forty percent of the FTA ewes conceived and gave birth to 1·3 lambs per lambing, while 31·4% of the Awassi ewes conceived and lambed (1·1 lambs per lambing). Lambing to lambing and ram introduction to lambing intervals were similar in both genotypes and confirmed that a sizeable proportion (30–40%) of Awassi ewes and their crosses may rebreed during spring postpartum anoestrus and lamb at c. 8 months interval. Furthermore, relative progesterone values revealed continuous ovarian activity in 16% of Awassi ewes and 40% of FTA ewes and confirmed estimates of conception in ewes. All ewes with continuous ovulation mated and lambed. Weekly estimates of milk production over a 2-month period, starting the second week of lactation, showed that daily milk yields were almost twice as much in Awassi as in FTA ewes (P<0·01). These results indicate the potential for Awassi ewes and their crosses to be incorporated into frequent lambing systems. Reproductive efficiency in these ewes could be monitored efficiently by measuring progesterone at 2-weekly intervals.

Lime-induced Fe chlorosis is often a severe problem on calcareous and saline alkali soils. Symptoms of apparent Fe deficiency and responses to its application on several field crops have been observed under such soil conditions (Indian Council of Agricultural Research, 1980–81; Sakal, Singh & Singh, 1982, 1983). Rice varieties exhibit variable reaction to Fe stress when cultivated as an upland crop especially at seedling stage in the nursery (Patel, Ramakrishanyya & Patel, 1977; Singh et al. 1984). Plant analysis is one of the accepted tools for diagnosing nutritional disorders. Chlorotic plants often contain more total Fe than the green plants (Katyal & Sharma, 1.980; Voigt et al. 1982). In order to overcome this elusive behaviour of Fe it has been suggested that in place of total Fe the plants should be analysed for active Fe or dilute HCl-extractable Fe (Machold & Stephen, 1969). Iron is important for chlorophyll biosynthesis and is linked with a number of enzyme systems. The change in the activities of the enzymes has beenused as a yardstick to distinguish Fe deficiency in plants (Del Rio et al. 1978). Wallace (cf. Katyal & Sharma, 1980) and Patel et al. (1977) suggested analysing the plants for that fraction of Fe which correlates well with occurrence of chlorosis.

Skin samples were used to evaluate the developing skin follicle population of Cheviot × Dorset Horn cross foetuses. The follicle population was studied from the first appearance of skin follicles (55 days' gestation) to the end of gestation. The pattern of development of primary and secondary follicles is described, and compared with the data available for other breeds. The occurrence of secondary follicle branching, previously confirmed only in the Merino, is described, and the ‘prenatal check’, an important feature of follicle development which had not previously been investigated in prenatal studies, is briefly discussed.

In a clay loam at Rothamsted, inoculated with lucerne stem nematode (Ditylenchus dipsaci) and a leaf nematode (Aphelenchoides ritzema-bosi), lucerne herbage yields were increased on average by 17 and 59% respectively, in the first and second years of a 4-year experiment (1988–91), by carbofuran granules applied around the seeds at sowing in spring 1988. In seven-row plots over the 4 years of the experiment, 1·65 kg a.i./ha increased total yield as much as did 3·3 kg a.i./ha (11 and 12%, respectively). In four-row plots over the same period, 1·9 kg a.i./ha increased total yield by 9%. The cultivars Euver and Vertus, which are partially resistant to D. dipsaci, yielded 44·3 and 48·5 t dry matter/ha, respectively, whereas Europe and Vela, which are susceptible to the nematode, yielded less (36·3 and 28·6 t/ha, respectively). When sown in summer 1990 in four-row plots, cultivars Europe and Euver yielded larger crops in 1991 in plots given 1·2 or 2·3 kg a.i. carbofuran/ha in 1990 (on average 34 and 48%, respectively) than in untreated plots. As little as 0·6 kg carbofuran/ha increased the yield of cv. Europe in infested soil.

The stunting of lucerne plants, associated with D. dipsaci infestation, was greatly decreased by carbofuran, which prevented infestation of the first crop by D. dipsaci and A. ritzema-bosi. Stem nematode infestation of lucerne plots was adequately and quickly assessed by measuring the lengths of rows stunted by D. dipsaci. Other methods of assessment were laborious and no more reliable.

From the results presented it may be permissible to point out the following:

Fungi are responsible for the fixation of very small quantities of nitrogen, while the Azotobacter and B. amylobacter groups are the important nitrogen fixers in the soil.

B. amylobacter is able to fix from 4 to 5 mg. of nitrogen per gm. of dextrose consumed.

B. amylobacter has an optimum range of pH. between 6·0 and 7·0, and Azotobacter between 7·0 and 8·4.

Azotobacter utilises the organic acids produced during the fermentation of dextrose as sources of energy for nitrogen fixation in the absence of dextrose. B. amylobacler does not, or does only to a limited extent, utilise such products.

Large quantities of dextrose do not favour an efficient nitrogen fixation, as large quantities of the organic acids produced effect the reaction of the media rendering the organisms inactive.

The nitrogen fixing organisms seem to be equally well represented in the heavy and light soils.

Semen samples of five Dexter bulls were mixed and the effects of mixture on the live/dead ratio, the percentage of abnormal cells and on motility and survival of motility as measured by impedance change frequency were studied. Altogether fifty-six samples and mixtures were examined. No effect of mixture on live/dead ratio nor on percentage abnormals was found, but mixtures of semen had a motility which was slightly nearer the value of the less active component of the mixture than that of the means of both components. No explanation for this effect is offered.

1. A study was made of nitrogen-fixation by Azotobacter chroococcum alone in a medium containing dextrose (which it can utilize) and in mixture with a coliform organism on a medium containing no carbohydrate except starch, which Azotobacter cannot utilize unless it be hydrolysed by the coliform organism or some other agency.

2. The amount of nitrogen fixed in the mixed cultures was found to be maximal at two temperatures, and a discussion is given of the causes thought to be operative in producing the double maximum.

I. As a result of withholding food for a few days, together with an injection of phloridzin, thereby reducing the nutrition, the daily yield of milk in goats was diminished and in one case the flow was actually stopped. On giving food again the yield returned almost to normal within a few days.

II. As the daily yield of milk diminished under these conditions so the percentage of fat in the milk rose. Limitation of the available nutriment in the body (change from a high to low state of nutrition) did not reduce the percentage of lactose or protein in the milk (Paton and Cathcart) but reduced the quantity of milk (together with the amounts of protein, sugar and salts) produced. The secretion of fat was not at first affected by the change in metabolism and as a consequence milk rich in fat was produced.

III. The amount of fat secreted per day under these conditions of diminishing yield was however not constant but became reduced, possibly as a secondary effect of the decreased secretion taking place in the gland cells.

IV. On again giving food to animals in such a reduced state of nutrition, the percentage of fat in the milk decreased as the yield increased, in some cases to such an extent that it was below that of the normal milk before the experiment began.

Assessment of the value for cultivation and use (VCU) of a new cultivar, essential for its official registration, is done through a series of trials carried out over a 2–3-year period and across many locations. In a set of multi-environment VCU trials, evaluation of new genotypes can be a laborious task due to the presence of genotype by environment interactions, which can hide their true genetic value. In an attempt to reveal the true genetic value of new cultivars, a good starting point is investigation of the importance of various genetic and environmental sources of variation, which can be done by estimating relative magnitude of corresponding variance components within the mixed model framework.

Genotype × location × year (G × L × Y) data set for seven crops taken from the 10-year period 2001–10 was used in the present study to estimate the variance components for main effects and their interactions in Croatian VCU trials. Depending on the crop, the most important and least important components were Y or LY, and L or GL, respectively. Genotypic effect was relatively small, ranging from 2·1 to 13·4% of the total variation. The current results are comparable with the relative sizes of the variance components obtained in studies from four- to sixfold larger countries, indicating that the environments within Croatia, if sufficiently widely sampled, can provide as extreme cultivar responses as a geographically more dispersed set of VCU trials. The gap range in different crops is much wider (30–60%) than in Western Europe (up to 30%), but it remained constant over the 10-year period.

Crotonylidene di-urea (CD-urea) in a sandy-loam and two clay-loam soils decomposed slowly at 7°C, and from 8 to 15% was recovered as mineral-N after 24 weeks. At 25°C, it decomposed faster in the sandy-loam than the clay-loam soils; with 100 ppm N, a maximum of 86% was recovered after 16 weeks, and 80% of 1000 ppm N after 24 weeks. Recovery after 24 weeks ranged from 30 to 60% in the clay loams.

Ryegrass grown in pots produced more extra dry matter, containing more N, during 16 weeks when given ammonium sulphate than it did during 50 weeks with CD-urea.

The nodal distribution of free polyamines (important regulators of flower induction) in cotton (Gossypium hirsutum L.) ovaries was determined by high-performance liquid chromatography (HPLC). The objective of the study was to investigate the nodal distribution of putrescine (Put), spermidine (Spd) and spermine (Sp) of cotton lines (G. hirsutum L.), and to determine whether there are differences in ovarian polyamine content among three commercial cotton cultivars. A field study was conducted in 2005 and 2006 using the cultivars FM960BR, ST5599BR and DP444BR. Free polyamines Put, Spd and Sp were determined in ovarian tissue of first-position white flowers starting at the beginning of anthesis and collected from the 7th, 9th, 11th and 13th main-stem nodes for four consecutive weeks. There was no significant nodal position by cultivar interaction; thus, the main effects were tested. Put content decreased acropetally along the main stem of the cotton plant with the highest content observed at the 7th node and the lowest at the 13th node. Spd content decreased below and above the 9th node, with the 9th node showing the highest amount of Spd and the 13th node the lowest in both years of the study. Similarly, Sp content decreased below and above the 9th node. In general, the 7th and the 9th node had the highest titre of free polyamines. Among the cultivars tested, FM960BR showed higher polyamine content in one season; however, the observation was not consistent from year to year. The highest amounts of polyamines were observed at the 7th and the 9th node of cotton and this may be associated with the known yield distribution: almost 0·80 of the total yield of cotton is derived from these nodal positions.

Sixty families of each of two tomato triple test crosses (S 120 × EC 61747 and EC 31513 × Pusa Ruby) were raised in completely randomized blocks in two replications with two fertilizer levels. Perkins & Jinks' (1971) analysis was used to detect and measure the interactions of additive, dominance and epistatic effects of genes with micro- and macro-environments for flowering time, maturity period, number of branches, final height, number of locules, number of fruits per plant, yields per plant and weight per fruit. Additive and dominance gene effects were almost equally sensitive to micro- and to macro-environments. The j and l type epistasis was more sensitive to the environments than the i type epistasis.