Normal, self and backcross families in a triple test cross were used to investigate the inheritance of number of days from sowing to flowering and dry plant weight for a population of pure-breeding lines of bread wheat (Triticum aestivum L.). Several tests of non-allelic interaction, additive genetic and dominance variances were made that involved triple test cross and single tester analyses. Non-allelic interaction was found to be a component of the genetic variation for both traits. The additive and dominance variances were prevalent for both traits. Alternative estimates of additive genetic and dominance variance components did not differ significantly when tested by a weighted least-squares model fitting procedure. The results are discussed in relation to genetic improvement of bread wheat.

Experiments made for 4 years in the seasonally dry period of the monsoon environment of north-west India showed that the application of farmyard manure (FYM) with the onset of monsoon rains (in early July) was more advantageous for the growth and yield of wheat than its application at the end of the monsoon season in mid-September. Fertilizer N drilled into the soil with the cessation of rains was better utilized by wheat than that applied at sowing in mid-November. A combination of the organic matter and urea was better than their application separately. N, P and K removal by the wheat crop was significantly increased by FYM and urea application. The time of their application influenced the nutrient removal by the crop in the same way as it affected its growth and yield.

Changes in body weight and body temperature were observed in Sudanese desert sheep and goats, which had been subjected to the summer sun (20 °C min. to 42 °C max.), given water normally and then deprived of water for 3 days. Tritiated water was also used to measure total body water and water turnover in these animals together with measurements of plasma and extracellular space, intracellular fluid volume and blood osmolality. The body weight and the size of the fluid compartments decreased in the two species at varying degrees associated with haemoconcentration. The extent of some changes was more marked in sheep than in goats, suggesting better adaptation of the former species to desert life.

Two varieties of okra were sown at approximately 14-day intervals from 1 April to 1 June for 2 years during the main rainy season in Nigeria. Low soil temperature and moisture, which resulted from a combined effect of high solar radiation, high atmospheric temperature and low rainfall, led to poor seedling emergence at the early sowing dates.

The growth of the fewer plants of the early sowing dates were more vigorous than those of later sowing dates and they attained 50% flowering earlier and had a longer harvest duration. This resulted in increases in number of pods per plant, pod length, pod diameter, pod volume, pod weight and pod yield per ha, indicating compensatory growth by the fewer plants in the early plantings. The relatively lower values obtained for these variables with the late sowing dates were also attributed to possible poor soil aeration arising from the increased rainfall during their growth period.

Sowing dates did not generally affect the percentage moisture, oil and protein in the pods. The effects of varieties on the variables measured were more uniform than those of sowing dates and mostly not significant.

The pollination requirements of three cultivars of winter and one of spring swede rape (Brassica napus), grown in a glasshouse, were compared. All cultivars yielded more when hand-pollinated than when auto-pollinated but were self-fertile and yielded equally well whether self- or cross-pollinated. In most cultivars plants that were shaken to simulate movement of plants by wind yielded more than autopollinated plants and not significantly differently from hand-pollinated plants. Handpollinating and shaking plants also increased the set of early flowers.

Normal and brown midrib-3 (bm3) maize silages were fed to sheep, lactating cows and dairy calves to determine the effect of the bm3 gene on in vivo digestibility, dry-matter intake and animal performance.

In two trials wether sheep were fed either normal or bm3 maize silage at maintenance level. In the first experiment the bm3 gene significantly increased the digestibility of the organic matter(OM), cell wall constituents (CWC), acid-detergent fibre (ADF), cellulose and hemicellulose from 76·9, 74·7, 67·3, 74·2 and 79·5% to 79·6, 79·2, 75·8, 80·8 and 81·5%. In the second experiment the gene increased the digestibility of the OM, CWC, ADF and cellulose from 65·9, 44·7, 28·5 and 38·7% to 701, 59·3, 560 and 66·1, 39·1,32·8, 40·4 and 45·5% to 68·1, 51·9, 53·7, 58·0 and 49·2%. The digestibility of the protein was similar for both diets.

In a feeding trial 6-month-old calves were fed either normal or bm3 silage ad libitum together with 1·6 kg D.M. of a protein supplement. The dry-matter intake of the two silages was similar; however, the daily live-weight gain of 0·92 kg for calves fed the bm3 diet was significantly higher than the 0·83 kg for calves fed the normal diet.

Field experiments were carried out at Ludhiana in Punjab during 1982 and 1983 on the effect of foliar application of water spray or naphthalene acetic acid (NAA) at 100 and 200 mg/1 of water on the growth and yield of rice when applied at tillering and before panicle emergence stages of late-transplanted paddy grown under four levels of nitrogen (0, 60, 90 and 120 kg/ha). Foliar spray of NAA significantly increased the grain yield of paddy as compared with water spray under low levels of nitrogen (0 and 60 kg/ha) owing to increases in the number of ear-bearing shoots per plant, number of filled grains per panicle and grain weight. Chlorophyll content of leaves, leaf area index and interception of photosynthetically active radiation by the crop canopy also increased with foliar spray of NAA and application of nitrogen. Paddy responded significantly up to 90 kg N/ha in terms of grain yield whereas straw yield increased significantly up to 120 kg N/ha. However, grain mass declined significantly with increase in nitrogen from 90 to 120 kg/ha.

Field experiments were conducted in a zinc-deficient flood plain alluvial soil to study the effect of amounts, methods and sources of zinc application on the yield and uptake of zinc by wheat. Zinc was applied at 0, 5 and 10 kg Zn/ha as zinc sulphate and zinc oxide either broadcast and mixed in the soil or drilled below the seed. Spray application of zinc was also tested. Irrespective of the source, grain yield and zinc uptake significantly increased up to 10 kg Zn/ha. Soil-applied zinc was highly correlated with yield and zinc uptake in the two field experiments. Grain yield was also found to be significantly correlated with zinc content of grain (r = 0·78), straw (r = 0·72) and flag leaf (r = 0·66). When applied at the rate of 10 kg Zn/ha, broadcasting of zinc sulphate and drilling of ZnO below the seed were equally effective in increasing grain yield of wheat. Foliar spray of zinc sulphate was an effective emergency method, but in highly zinc-deficient soils it did not compare well with soil application of zinc.

Root and shoot growth and nutrient uptake have been monitored for several winter wheat crops which gave a mean grain yield of 9·5 t/ha (85% D.M.) when grown on three soil types in 1980 and 1981. Averaged over all crops, maximum growth rates were 170 kg/ha/day for shoots and 14 kg/ha/day for roots; maximum nutrient uptake rates for N, P, K, Ca and Mg were 2·75, 0·47, 341, 0·60 and 0·18 kg/ha/day respectively. Maximum uptake of K and Ca occurred at anthesis with values of 239 and 38 kg/ha respectively, whilst for the other nutrients maximum uptake was at final harvest with values of 200, 39 and 14 kg/ha for N, P and Mg respectively. The grain contained 141 kg N, 27 kg P, 41 kg K, 3·2 kg Ca and 7·1 kg Mg/ha.

The quantity of nutrients arriving at root surfaces by mass flow was calculated for one of the crops from measurements of soil solution concentration and potential evapotranspiration data. The potential supply of nutrients by mass flow, as a percentage of that actually taken up between 19 March and 29 June, was 25% for N, 4% for K, 800% for Ca and 32% for Mg.

Nutrient inflows, that is the amount of nutrient absorbed per unit root length per unit time, have been determined for several winter wheat crops (cv. Hustler) with grain yields in the range 8–11 t/ha (85% D.m.). Inflows reached a maximum in April or May with values in the range 13–34, 0·5–1·6, 3·5–13, 0·9–1·8 and 0·35–0·60 × 10–14 mol/cm root/sec for N, P, K, Ca and Mg respectively. The concentration in the soil solution necessary to maintain inflows by diffusion of nutrient through the soil was calculated using a nutrient uptake model. For an October-sown crop the model predicted that soil solution concentrations of 165 μΜ N, 14 μΜ P and 56 μΜ K were needed to sustain the observed maximum inflows, whereas for a September-sown crop, with a larger root system, even lower values of 106 μΜ N, 8 μΜ P and 36 μΜ K were needed. It appears that nutrient transport is unlikely to limit uptake by winter wheat crops growing in moist, well fertilized soils, at least for crops up to about 17 t/ha of total dry matter.

In 1980 a field of winter wheat at Little Raveley, Cambridgeshire (U.K.) suffered a bad attack of take-all, which was confined mainly to areas dominated by Ragdale series, one of five soil types on the field. Take-all and yield were assessed on experimental areas within the field in the three subsequent years (1981–3). On a strip 50 m wide, which was sown with wheat in each of these years, take-all was in decline and although slight differences in take-all occurred between some of the soil types, they had no effect on grain yield. Following a break crop of beans in 1981, the remainder of the field carried wheat in 1982 and 1983. Here take-all was generally less and yields generally greater in the area that suffered the 1980 attack, probably because it had developed a natural partial immunity to the disease. However, measurements of takeall in relation to soil characteristics on 1 m2 plots suggested that the disease was becoming more prevalent on soils that are less well drained in winter, are more deeply decalcified, and contain less extractable phosphorus or more exchangeable potassium.

Poaching damage to a new grass ley was measured over a period of time using a surface profile meter. Individual profiles obtained on different drainage treatments in the ley showed little change over 3 years of measurements. Poaching could be denned visually as a depression greater than 4 cm depth on this site. Degree of poaching was adequately described by the standard deviation of the soil surface. Typically, standard deviations along a poached, undrained transect were twice those of an unpoached, drained one. In this experiment drainage with pipes alone at 12 m spacing controlled poaching as well as mole drainage at 2 m with pipes at 40 m spacing even though watertable levels were usually not lower than those of the undrained control.

The relationships between pairs of characters are investigated using F1 and F2 derived doubled haploids as well as single seed descent lines from spring barley (Hordeum vulgare) crosses. It is shown that linkage disequilibrium and pleiotropy are factors affecting the relationship between characters in barley. In fact, the linkages found are in general in the coupling phase and pleiotropy is usually positive. The consequences of such relations for plant breeding are discussed.

Mature Merino ewes (n = 500) were allotted at random to embryo removal (day 35; day 0 = day of oestrus detection), foetal removal (day 90) or lambing groups. These groups were further randomly divided into four single-sire mating groups. From day 1 until day 35 ewes were individually penned and fed either 50 or 150% of a maintenance ration (0·5 M or 1·5 M respectively). At day 35 single embryos were removed from anaesthetized ewes in the embryo removal group and all other ewes were endoscoped to confirm pregnancy. These ewes were then returned to pasture. Plasma samples were taken from all ewes on days 2, 4, 16, 23, 30 and 35 for analysis of glucose concentration. At day 90, ewes allotted to the foetal removal group were anaesthetized and plasma samples were obtained from the ewe's jugular vein and the umbilical arteryand vein. Ewes were then hysterectomized and the foetus was weighed and measured. Functional cotyledons were dissected from the uterus and chorio-allantois and all tissues were weighed. The remaining ewes (lambing group) were supervised at lambing and lambs were identified, weighed and measured.

Live-weight changes from weaning and wool production and quality were measured in ewe and ram lambs at their first shearing (11 months of age). Ovulation rates in the first two oestrous seasons of the ewes and wool production at their second shearing (2 years of age) were also measured.

During the 35-day treatment period, mean live-weight changes of ewes were –4·9 and + 1·8 kg in the 0·5 M and 1·5 M groups respectively. Pregnancy rates were similar in both groups but embryos from 0·5 M ewes weighed less than those from 1·5 M ewes (1·7 ± 0·04 ν. 1·9 ± 0·05 g; P < 0·005). Foetuses taken at 90 days from 0·5 M ewes were smaller than those from 1·5 M ewes but these differences reached significance (P < 0·025) only in the measurement of chin–crown length (8·0 ± 0·09 ν. 7·6 ± 0·11 cm). Correlations between foetal weight and total cotyledon weight, chorio-allantoic weight and empty uterine weight were all significant. Plasma glucose concentrations of ewes in the 0·5 M group were significantly (P < 0·001) reduced by day 9. Differences between the two nutrition groups in maternal and umbilical plasma glucose concentrations at day 90 were not significant, though foetuses from 0·5 M and 1·5 M ewes removed a mean of 30 and 11% respectively of available glucose from the umbilical vein. Differences in live weight between 1·5 M and 0·5 M animals at weaning and in the post-weaning period were not significant (P > 0·05). Wool production and woolquality were similar for both groups. Spontaneous ovulation rates measured on four occasions during the postpubertal oestrous season and on three occasions the following year were not significant (P > 0·05). Treatment with pregnant mare's serum gonadotrophin (PMSG) increased ovulation rates in the ewes of both groups; however, the differences failed to reach significance (P > 0·05); mean (± S.e.) ovulations per ewe were 4·8 ± 0·61 ν. 4·6 ± 0·60 for 1·5 M and 0·5 M group ewes respectively.

Incidences of pollination and fertilization were surveyed in 21 commercial crops of field beans (16 of winter, 5 of spring) in southern Cambridgeshire (England) in 1982 and 1983. During the first part of the flowering season of winter beans, from 30 to 75% of flowers were not pollinated, and thus could not set pods. Where the pollination was largely spontaneous, relatively few pollinated flowers were fertilized and within them, relatively few ovules were fertilized. Later in the season and through most of the spring-bean flowering season, over 90% of flowers were pollinated and over 75% of ovules were fertilized. Incidences of pollination and fertilization varied greatly among the fields, and provision of hives of honeybees in fields of winter beans was associated with an improvement in the incidence of pollination from poor to moderate in 1983 but not in 1982. It is concluded that the incidence of pollination in many fields of winter beans is too low early in the season for an optimum distribution of yield along the stems.

Genotypes homozygous for specific PGI2 alleles were selected from four existing cultivars of different maturities, Gremie, Aberystwyth S.321, Barlenna and Melle. Each of three groups of plants (early BB selected from Gremie, intermediate CC selected from Aberystwyth S.321 and Barlenna and late AA selected from Melle) was isolated and allowed to interpollinate producing three experimental seed lots or populations. These populations, screened for their electrophoretic purity, were found to exhibit only the selected parental PGI2 genotype.

The three labelled populations were sown in boxes in September 1982 as monocultures, as all possible 50:50 mixtures, and as a three-way mixture to produce miniswards. Following one harvest in the establishment year these were harvested and dry-matter yields determined on a monthly basis from April to October 1983, two horizons in the sward being examined separately at harvests 1–5. Changes in the proportions of populations in each mixture were monitored by random subsampling of the cut herbage and subsequent electrophoretic testing.

The ability to dominate productivity in the top horizon in mixtures was dependent on the timing of reproductive development of any particular population. The patterns of productivity in the bottom horizon and in both horizons combined showed the early population dominating the mixed swards briefly at the beginning of the harvest but the late population dominating from June–July onwards. The intermediate population, although the most productive in monoculture, did not reveal any tendency to dominate productivity in any of the mixtures.

The potential use of electrophoretically labelled cultivars to study complex aspects of plant competition is discussed, along with the possible application of results from these studies to agricultural practice.

Field experiments conducted during wet and dry seasons with Ratna and Jaya varieties of rice (Oryza sativa Linn.) indicated that the use of Azolla pinnata as fertilizer increased growth in terms of number of tillers, leaf area index, dry-matter production, grain yield, N uptake and its accumulation in different plant parts. Azolla incorporation before planting in addition to 30 kg N/ha produced higher grain yields of both the rice varieties than 60 kg N / h a during the two seasons, while Azolla grown as an intercrop with rice plus 30 kg N/ha was superior to the 60 kg N treatment in grain production of Jaya during the wet season. Azolla incorporation before planting and also once intercropped with rice produced more grain yield than 60 kg N during the wet season. Among Azolla treatments, Azolla twice intercropped with rice produced comparatively lower grain yield. Azolla application increased the number of panicles/m2, number of grains/panicle and reduced sterility during both seasons. The N uptake of the rice crop in the treatments of Azolla incorporation before planting or intercropped once with rice in combination with 30 kg N/ha was similar to that of the 60 kg N/ha whereas the treatment of Azolla incorporation before planting plus once intercropped was similar during the wet season only.

Water deficit during the panicle development stage reduced the grain yield of the main shoot panicle of pearl millet but this loss was compensated by increased grain yield of the tillers. The potential extent of compensation in grain yield components by tillers was investigated by removing the main shoot at panicle initiation (PI) and flowering stages respectively, for both irrigated and water-stressed plants. Grain yield loss by removal of the main shoot of plants at PI was fully compensated by tiller grain yield in both the irrigated and water-stressed plants. The compensation was, however, only partial when the main shoot was removed at flowering. The compensation for the grain yield loss in the main shoot due to either water stress or removal was through an increase in number of grains on the tillers. This increase was due to an increase in the number of productive tillers in the case of water stress and to both an increase in the number of productive tillers and an increase in the number of grains per panicle in the case of main shoot removal. This compensatory mechanism by tillers plays an important role in overcoming the effects of pre-flowering water stress damage to the main shoot.

The distribution of carboxymethylcellulase (CMCase) between various rumen fractions has been determined at three times after feeding in sheep containing no ciliate protozoa or five different protozoal populations. The total rumen CMCase was lowest in defaunated animals and tended to be higher in animals containing the amylolytic Entodinium caudatum or a natural mixed protozoal population and highest in sheep containing single cellulolytic species. In animals containing the cellulolytic species, Epidinium ecaudatum caudatum or Eudiplodinium maggii, 70% of the CMCase was associated with the protozoal fraction whereas less than 15% was present in a fraction prepared in the same way from sheep containing no protozoa or only Entodinium caudatum. The activity associated with the free bacteria was higher in sheep containing only Entodinium caudatum than in defaunated animals or those containing the cellulolytic species. Similar results were obtained 1·5, 6·5 or 24 h after feeding. Almost no activity was present in the cell-free rumen liquor under any condition. A variable amount of CMCase (up to 25% of the total) was associated with the plant debris in the rumen and the specific activity of the enzyme released by sonication was often higherthan that released from the free bacteria under the same conditions.

The effects of different severities of continuous grazing imposed during the spring followed by a uniform continuous grazing management from midsummer onwards were examined in relation to sward morphology, herbage quality and the performance of young beef cattle in the years 1980 and 1981. The three grazing severities were based upon maintaining a constant sward height, namely 35 mm (severe), 50 mm (moderate) and 75 mm (lenient). From 1 June onwards a uniform grazing severity with a sward height of 60 mm was imposed. The grazing pressure on each paddock was adjusted by either adding or removing of cattle to maintain the target sward heights. When the grazing pressure was changed in June, the digestibility of both the herbage components on offer and the total herbage selected by the cattle was higher in the swards that had been severely grazed than that in the leniently grazed treatments. This appeared to be due to the combination of a higher proportion of younger, more digestible leaf laminae, less dead and less maturing true stem being present in the swards that had previously been severely grazed. Over the season as a whole, there was no significant difference between the grazing treatments in terms of individual animal performance or overall animal live-weight production per hectare.