Effectiveness of the polyethylene glycol (PEG) test for measuring cell membrane stability (CMS) to select drought-tolerant genotypes in wheat was investigated. PEG test was compared with two other tests. Genetic variability of CMS was also investigated.

Drought was induced artificially in pot-grown plants and in excised leaves, and percentage injury in leaf tissues by drought stress as measured by CMS was compared with that by PEG test. Percentage injury in leaf tissues of pot-grown plants was not correlated significantly with that by PEG test. However, percentage injury in excised leaves was well correlated with that in PEG test. The results suggest that the PEG test has merit in measuring drought tolerance in wheat. Frequency distribution of CMS in winter wheat lines was closely related to the characteristic pattern of quantitative inheritance and therefore CMS of wheat seems to be controlled by polygene action.

Multiparous Corriedale ewes were maintained on a constant feed intake such that the body weight (i.e. live weight less gravid uterus) of single-bearing ewes at the end of gestation approximated their live weight at mating. The ewes were allocated to one of five groups, designated for slaughter at 0, 50, 90, 120 and 140 days of gestation. At slaughter, the gravid uterus was removed, weighed and its components dissected out and the contents of all sections of the gastro-intestinal tract were removed, weighed and sampled.

Foetal growth was described by a Gompertz model. It was predicted that, at day 150, a twin foetus would have been 0·95 of the weight of a single foetus but this difference was not statistically significant. The foetal proportion of the gravid uterus followed a sigmoid curve during gestation to reach a predicted value of 0·60 at day 150. Predicted birth weights represented 10·4 and 18·6% of maternal body weight in single- and twin-bearing ewes.

The digesta content of the rumen and of the whole gastro-intestinal tract was not significantly affected by gestation. However, there was a tendency for the values to decline to day 90, then increase during the last third of gestation. It was suggested that the decline was due to hormonal rather than direct physical effects. By contrast, the amounts of organic digesta constituents in the rumen descreased as gestation progressed (P < 0·01) indicating an effect of gestation on rumen propulsive activity.

Dihaploids obtained from two tetraploids showed variation in tuber deformation resistance using a pendulum test and there were significant differences between them when used as parents in 2x × 4x crosses. Their ranking by tetraploid progeny means was the same as by clonal performance.

However, whereas the pendulum test was useful for the rapid measurement of rheological properties of tubers, there was found to be no correlation of control cultivar rankings using this test with those obtained using the squeezing test or farm survey data.

The tubers of Dioscorea composita Hemsl. contain a high level of diosgenin, and hence there is economic interest in this plant. Levels of diosgenin vary greatly in different clones of the species. Vegetative propagation was studied with a view to obtaining plants with high levels of diosgenin. In this study cuttings from 1-year-old vegetative plants were used for propagation. The cuttings were treated with a single application of indole-3-butyric acid (IBA) and several applications of 6 benzyladenine (6-BA). Rooting was never observed in untreated cuttings. Cuttings treated with IBA produced callus and roots. Early application of 6-BA delayed senescence but inhibited callus and root formation. New plants were obtained with one application of IBA followed by applications of 6-BA at 48 h intervals initiated 2 weeks after IBA application. In some experiments, all cuttings treated this way produced new plants.

Three experiments which measured seed production and seed survival of annual medics (Medicago spp.) were conducted at Tel Hadya in north Syria. In Expts 1 and 2, conducted in consecutive years, the effects of rate and date of sowing on seed yield and its components were measured, while in Expt 3, the residual seed under summer grazing was monitored. In all three experiments seed permeability was observed at frequent intervals in summer and autumn. Selected ecotypes of three native medics (Medicago rigidula (L.) All., M. rotata Boiss. and M. noeana Boiss.) were compared with cultivars of M. truncatula Gaertn. and M. polymorpha (L.).

Seed production was greatest at sowing rates of 20–40 kg/ha. The native species produced more seed (up to 1000 kg/ha) than the cultivars (less than 500 kg/ha), although not significantly so in the case of the late-flowering ecotype of M. noeana. Seed yields of 500–1000 kg/ha were considered to be sufficient to perpetuate the pastures, but even higher seed yields are desirable.

Seed yield was closely related to number of pods in all ecotypes and, in Expt 2, up to 95% of flowers failed to produce mature pods. Flowers were more likely to mature at high sowing rate (256 kg/ha), in striking contrast to flower production itself which was greatest at sowing rates of less than 30 kg/ha. Flowers produced early in the season (before mid-April) were far more likely to give mature pods than late-produced flowers.

In late October, seeds of the native species were less permeable (10%) than those of the cultivars (30%), although their permeability was similar to that of the cultivars in Australia. In the three experiments the seasonal pattern of permeability varied, although there was a tendency for seeds to gain permeability in autumn. In Expt 1 there was a strong suggestion that the change from impermeability to permeability was reversible.

Ewes grazing mature pods gained weight, apparently as long as pod availability exceeded 10 kg/ha. It was clear that the condition of ewes was not a good guide to appropriate stocking rate for persistence of pastures, and that farmers will have to use other methods to assist them in grazing management.

Responses in live weight, milk production and calf growth to cobalt supplementation of groups of three and four pregnant heifers were measured to assess the value of serum vitamin B12 concentrations and the urinary concentrations of methylmalonic acid (MMA) and formiminoglutamic acid (FIGLU) for the detection of cobalt deficiency in cattle.

The administration of cobalt bullets to pregnant heifers, grazing pastures containing between 0·03 and 0·05 mg/kg cobalt, had no effect on either their live-weight change or milk production, or on the birth weight of their calves. MMA and FIGLU concentrations in the urine of unsupplemented heifers were low for the majority of the experimental period, although the concentrations of vitamin B12 in their serum (< 100 pg/ml) were in the range usually considered indicative of cobalt deficiency.

Calves from unsupplemented heifers had lower growth rates during the first 3 months of life and this was associated with intakes of 0·24–0·46 μg/day of vitamin B12 from milk, only 1–3% of those received by calves from supplemented heifers. Poor growth was associated with high urinary FIGLU concentrations, which increased from 500 to 2000 μmol/l between 1 and 3 months of age but decreased to less than 100 μmol/l between 3 and 4·5 months of age. Urinary FIGLU was a more reliable indicator of vitamin B12 deficiency in suckled calves than was urinary MMA, elevated levels of which were observed only at 3 months of age. The concentration of vitamin B12 in the serum of calves from unsupplemented heifers was consistently less than 100 pg/ml, but was not a reliable indicator of their functional vitamin B12 status, as judged by urinary concentrations of FIGLU and/or MMA.

Crosses between two cultivars of tomato (Lycopersicon esculentum Mill.), and two accessions of the wild species L. pimpinellifolium (Jusl.) Mill, were made and F1, F2 and backcross generations were developed and studied. Significant differences in number of fruits per plant, yield per plant and fruit weight were found between means of the different generations. Variation in number of fruits per plant and yield was also found between plants within generations. Number of fruits per plant was a highly heritable character (average h2 = 73·6%) and closely correlated with yield per plant, indicating that it may be a suitable selection criterion for yield improvement in tomato crosses.

Field experiments were conducted in wet seasons (June-December) for 4 years on a clay loam Haplaquept, to study the effects of different N management practices on yield, urea and ammonium-N in flood water and N nutrition of an clite rice cv. CR 1009, grown in rainfed lowlands. During the first 3 years of the experiment, fertilizer management practices like band placement of neem-cake-coated urea (NCU), broadcast application of sulphur-coated urea (SCU) at sowing, or point placement of urea supergranules (USG) 3 weeks after germination at 40 kg N/ha gave grain yields of 3·1–3·4 t·ha, which were almost equal to that of split application of prilled urea (PU). In the 4th year of the experiment, besides NCU and USG, single dose applications of PU as band placement, incorporation in the soil at sowing or broadcast incorporation of soil-treated urea at early tillering was also found to have similar effect on grain yield and N uptake as split application of PU. The flood water of the treatment receiving broadcast application of PU at tillering contained some urea and ammonium N, which rapidly decreased to negligible amounts in 3·4 days.

The results suggest that, depending upon the feasibility, any one of the single dose application methods at sowing time or 3 weeks after germination may be adopted in this system of rice culture, which avoids top-dressing of PU to surface flowing flood water of greater depths at later stages of crop growth.

Soil disturbance caused by a slant-legged subsoiler (Trade name, ‘Paraplow’) and the duration of its effect was investigated in an experiment comparing long-term direct drilling with shallow tine cultivation and mouldboard ploughing. The ‘Paraplow’ significantly reduced soil strength, measured by cone resistance, to the depth of cultivation (33–35 cm) for up to 20 months, after which soil recompacted. The ‘Paraplow’ increased the volume of soil with cone resistance < 1·5 MPa by 52% within its working depth, compared with an equivalent depth of undisturbed soil. Contour diagrams of cone resistances clearly illustrate the patterns of soil loosening caused by the ‘Paraplow’.

Measurements on soil cores (73 mm diameter × 50 mm) show that the ‘Paraplow’ did not appear to increase significantly the volume of macropores (> 60 μm) in direct-drilled soil, nor did it reduce the bulk density in the top 5 cm as effectively as the mouldboard plough.

The root density of spring barley, measured at the beginning and end of tillering, was significantly increased within the horizon disturbed by the ‘Paraplow’ but below the depth of loosening there were no differences. This improvement of root growth probably resulted from an increase in the number of large pores (which could not be measured adequately in the soil cores), as well as the reduced soil strength. Better drainage of the soil loosened with the ‘Paraplow’ suggested that macroporosity was improved. The need to sample large volumes of soil to detect changes in bulk density and macroporosity is stressed.

The mineralization kinetics of nitrogen in acid soils, and their modification by the addition of an organic fertilizer (cattle slurry), were studied by incubating a humic cambisol for 36 weeks using a method based on that of Keeney & Bremner (1967). The cumulative curve of the quantity of nitrogen mineralized in soil not given fertilizer departs significantly from Stanford's theoretical model, which predicts linear dependence of nitrogen mineralized upon √t. The observed kinetics are interpreted as due to the superposition of two mineralization processes involving different substrates.

The cumulative mineralized nitrogen curves for soil samples enriched with the various slurry fractions likewise reflect complex kinetics involving at least two main substrates. Consideration of the net mineralized nitrogen shows that F,, the solid fraction with the highest C/N ratio, clearly induced immobilization of nitrogen during the first 130 days of incubation, and analysis of the NO3/NH4 ratio suggests that this immobilization was probably at the expense of nitrate. F3, the liquid fraction, first induced a brief period of mineralization and then stabilized nitrogen levels, giving rise to a reduction in net mineralized nitrogen. The addition to the soil of F2, the semi-liquid fraction, produced results intermediate between those of the other two fractions.

In conclusion, the increase in organic nitrogen in the soil after addition of cattle slurry depends in the short term on the liquid and semi-liquid fractions, whereas long-term effects involve both the stable residues of these fractions and the more solid fraction. The labile fraction of the pool of mineralizable N benefits more than the recalcitrant fraction, and the time constants of the mineralization process are reduced.

The results of a long-term field experiment conducted from 1977 to 1984 on alluvial (Ustochrept) soil of Jalandhar showed positive responses of the crops to N. The responses of potatoes to N were reduced by farmyard manure (FYM), green manure of dhaincha and moong and the responses to the organic manures were also reduced by N. The N responsesof potatoes were, however, not affected by the N applied to preceding maize. FYM was better than the green manures in augmenting total tuber yield, large-grade tuber yield and K concentration in the plants.

The N applied to the potatoes showed significant residual effect on succeeding wheat crops, reducing its optimum dose of N by about 50%. The residual effect of N on wheat was highly correlated with nitrate status of the soil. The organic manures applied to potatoes improved the yield of the succeeding wheat but did not differ from each other.

The fodder crop of pearl millet raised after 7 years also indicated the superiority of FYM to the green manures. There was a build-up of organic carbon, N, P and K in soil and the build-up was maximal with the use of FYM. The application of N had no effect on the organic carbon and nitrogen status of the soil. N improved the availability of P but decreased that of K.

Laboratory and glasshouse experiments were conducted to study P release kinetics and uptake of P by wheat (Trilicum, aestivum L.) in ten benchmark soils of Punjab (India). Phosphorus desorption, determined by successive extraction with 0·01 m-CaCl2 solution, was lower in calcareous soils (group I) than in non-calcareous soils (group II). Desorption of surface P in soils followed pseudo-first-order kinetics. The values of the kinetic constant of desorption and the radial diffusion coefficient of P increased with the amount of added P in soils.

A significant linear relationship between cumulative desorbed P and both dry-matter yield and P uptake indicated that the rate of release of P from the solid matrix is important in determining P uptake by wheat crop. Phosphate uptake was less dependent on the initial solution P concentration than on the rate of phosphate release.

Statistical equations were derived for estimating three soil moisture constants, i.e. field capacity (FC), wilting point (WP) and available water capacity (AWC), from soil saturation percentage (SP), which is an easily determinable parameter. The regression equations were evaluated from a data set obtained on 438 soil samples collected from different horizons of 111 profiles of the Indogangetic Plains in northern India, having a wide variation of texture and other physico-chemical properties. The three soil moisture constants were positively correlated with logarithms of SP (r = 0·985 for FC v. In SP, 0·979 for WP v. In SP, and 0·914 for AWC v. In SP). The regression equations were thetested on an independent set of experimental data on 57 samples collected from 14 representative soil profiles of the study area. Values of the three moisture constants of this data set, predicted from the regression equations, were in exceptionally good agreement with the observed values. The mean estimation error (the error of the estimated value relative to the measured value) was only 0·55% for FC, 0·12% for WP and 0·67% for AWC.

In a field experiment conducted from 1981 to 1984 on alluvial soil (Ustochrept) of Jalandhar, green manure (GM) of dhaincha, sannhemp, pearl millet and moong did not affect tuber yield in the 1st year but increased it in the 2nd and 3rd years. GM of dhaincha and sannhemp were more effective than the moong in reducing responses of potatoes to K. GM of pearl millet was as effective as the dhaincha or sannhemp in 1981–2 and 1982–3 when buried 55 days after sowing but was inferior in 1983–4 when buried 85 days after sowing and resulted in reduced concentrations of N and P in potato plants. GM of dhaincha, sannhemp and pearl millet increased concentration of K in potato plants and available K in soil. GM of dhaincha and sannhemp, in particular, increased soil available K by decreasing non-exchangeable K whereas GM of pearl millet increased soil available K without affecting non-exchangeable K.

Twenty potato cultivars and breeder's clones were subjected to tests of external damage susceptibility at two sites. At one site tubers were, as in usual agricultural practice, lifted by mechanical harvester, and damage indices were subsequently assigned to each clone. At the other site tubers were harvested by hand on two dates. Drop tests were carried out on this material after 1 week in store and also, in the case of the laterdug (maincrop) material, after 3 months.

Ranks based on damage indices were approximately as expected from previous cultivar assessments carried out by other workers. The mean drop test scores showed varying degrees of rank correlation with the damage indices. The highest correlation was with ranks obtained from the drop test on early-harvested material. It was concluded that this was because damage had been inflicted in both cases before skin curing had occurred.

Ninety 4-month-old wether lambs were allocated to an initial slaughter group (n =10) or to one cell (n= 5) of a 4 × 4 factorial treatment design involving four levels of infection with Ostertagia circumcincta (0, 1000, 2000 and 4000 larvae/day) and Trichostrongyluscolubriformis (0, 1000, 2000 and 3000 larvae/day). They were maintained indoors in individual pens and offered freshly cut ryegrass-white clover herbage during an 84-day period of infection after which they were slaughtered. Body protein, fat, water, Ca and P contents were determined. Feed digestibility was determined in all sheep during 5-day periods during weeks 2, 5, 8 and 11. Faecal egg counts were determined and blood samples obtained at intervals and total worm counts done at slaughter.

The effects of mixed infection on feed intake and body-weight gain were multiplicative. Mean D.M. intake of sheep infected simply with 3000 larvae of T. colubriformis or with 4000 larvae of O. circtimcincta was reduced by 10 and 8% respectively, but in those infected simultaneously intake was reduced by 30%. Energy retention was depressed mainly by reduction in gross efficiency of use of metabolizable energy in infections with T. colubriformisand by reduction in feed intake in infections with O. circumcincta. The additional effect of mixed infection occurred mainly through further depression in feed intake.

There was no interaction between infections in effect on deposition of Ca or P in the body, both species having significant effect. Infection with T. colubriformis caused hypophosphataemia and hypocalcaemia, but infection with O. circumcincta had no effect.

The number of worms established by the infections was generally low compared with previous studies with conserved and concentrate feeds. This was associated with relatively low pathogenicity in infection with O. circumcincta and normal pathogenicity with T. colubriformis.

Infection with T. colubriformis reduced the number of adult worms of O. circumcincta present at slaughter.

Dry weight, nutrient content and other properties of winter wheat were measured from anthesis to maturity between 1969 and 1984. From 1969 to 1978 the cultivar Capelle- Desprez was grown either as a first wheat, in the rotation potatoes, beans, wheat, or as a second wheat, in the rotation fallow, wheat, wheat. From 1979 to 1984 the cv. Flanders was grown in the rotation fallow, potatoes, wheat and in this period the wheat was given fungicide sprays. Grain yield of Cappelle-Desprez grown as a first wheat was greater with 96 than with 144 kg N/ha in spring. First wheats yielded much more than second wheats with 96, but not with 144 kg N/ha. Second wheats had more eyespot and take-all, but less mildew, than first wheats. Mildew was more severe with the larger amount of N. Grain yield of Flanders as a first wheat was greater than that of Cappelle-Desprez. Yield of Flanders was greater with 144 than with 96 kg N/ha and it was greater still on plots given 96 kg Nha plus 35 t/ha farmyard manure. Other properties in addition to grain yield were changed by cultivar, rotation and manuring.

Examination of the variation between years showed relationships among properties and between some of them and grain yield. Many of the relationships were independent of cultivar or husbandry. Relationships between weather factors and some properties, but not grain yield, were detected. Grain yield of first wheats was closely related to number of grains/m2, but the relative importance of number of ears/m2 and number of grains per ear varied from year to year. Yield was positively related to dry weight per grain in Flanders, but negatively in Cappelle-Desprez. The weight of straw was usually less than that of the total above-ground crop at anthesis, but varied between years in a similar manner. The amount of N in grain plus straw was generally well related to the amount of N in the wheat at anthesis, although the changes in N content after anthesis ranged from a loss of 9 kg/ha to a gain of 51 kg/ha. The uptake of N, P and K was more closely related to dry weight than to nutrient concentration.

Variation between years in the proportion in the ear of 14C supplied to the flag leaf was similar to that of 14C supplied to the next lower leaf, but was different for 14C supplied before and after anthesis, and did not relate to other properties.

Date of anthesis ranged from 7 June to 5 July. A model incorporating responses to photoperiod, vernalization and temperature accounted for 78% of the variance in date of anthesis. The duration of the period from anthesis to leaf senescence ranged from 33 to 60 days and was linearly related to mean temperature above a base of 7·5 °C. Dry weight per grain was negatively correlated with mean temperature between anthesis and leaf senescence; a relationship including an adjustment for number of grains/m2 fitted both cultivars.

The amount of N in grain plus straw and percentage of N in grain dry matter were decreased by increased rainfall during the 3-week period following the application of N fertilizer in spring. An additional 10 mm of rain decreased N uptake by 2–8 kg/ha and N percentage by 0·055. N uptake in grain plus straw decreased with progressively later sowing. Grain N% was positively correlated with temperature and with radiation during parts of the period of grain growth, but only 10% of the variance was accounted for by the combined effects.

The relation between the dry-matter degradability (DMD) of different cultivars of barley straw and their colonization by rumen micro-organisms was studied in incubations of straw with the mixed population in situ and with pure cultures of rumen bacteria in vitro. The total attached population in situ was quantified by particle-associated i glutamate dehydrogenase (GDH) activity, while the cellulolytic population was assessed by bound carboxymethylcellulase (CMCase) activity. CMCase reached a peak between 24 and 36 h incubation, and the peak activity was highly correlated with DMD between 24 ) and 96 h. After 36 h, CMCase activity declined, particularly with the more degradable (varieties. GDH continued to increase after 36 h and had no relation to DMD. The adhesion of pure cultures of both cellulolytic and non-cellulolytic bacteria was measured i turbidimetrically in a 30 min incubation. No relation was found between DMD and the extent of adhesion by any of Ruminococcus flavefaciens, Bacteroides succinogenes, Butyrivibrio fibrisolvens or Selenomonas ruminantium. It was concluded the rate of degradation of straw is not determined by the initial rate of attachment of cellulolytic micro-organisms, but by the way in which colonization subsequently develops after attachment takes place

The intercropping of Azolla pinnata (Vietnam) with rice varieties transplanted in rectangular (40×10 cm) and double-narrow-row (15 × 10:65–80 cm) spacings showed faster growth and nitrogen fixation than in square (20 × 20 cm) spacing with the same number of hills per unit area. Inoculation of 2·0 t/ha fresh Azolla, 10 and 30 days after transplanting, produced Azolla mats on the water surface 25 and 50 days after transplanting, respectively. The total fresh biomass of Azolla grown with different rice varieties in square spacing was 26·7–33·0 t/ha; this produced 41·9–61·3 kg N/ha. However, rectangular and double-narrow-row spacing produced 28·7–37·7 and 34·4–39·6 t/ha fresh Azolla containing 53·9–69·0 and 58·0·73–3 kg N/ha, respectively if the rice rows were transplanted in north-south direction and 36·3–41·5 and 40·0–43·7 t/ha fresh biomass containing 63·4–74·2 and 65·3–83·3 kg N/ha, respectively in east-west direction.

The grain and straw yields of rice grown in rectangular and double-narrow-row spacing with north-south row orientation were lower than the yields of rice in square spacing, but the east-west row orientation of these spacings showed yields similar to those obtained by growing rice in square spacing.

Calves were fed continuously at 4 h intervals a low P basal diet with or without P supplementation to give three levels of dietary P intake: one was deficient in P (2·5 g/day), the second adequate (6·0 g/day) and the third contained an excess of P (10·0 g/ day) according to Agricultural Research Council (1980) recommendations. Once steadystate conditions were achieved (after 2–3 weeks on the diet) 32P and 46Ca kinetic studies were carried out, together with measurements of P flow rates at the reticulorumen and P and Ca balances. With increased dietary P intake, the amount of dietary P absorbed increased as initially did the efficiency of P absorption. Both the serum P concentration and the rate of P retention increased in direct relation to increased P intake and increased P absorption. Salivary secretion of P increased with increased P absorption and in direct relation to serum P concentration. Endogenous faecal losses of P were also directly related to P intake and P absorption and results suggest that increased loss with increased P intake is inevitable.

Despite a constant and adequate Ca intake, the rate and efficiency of Ca absorption, which was low on the low-P diet, increased significantly on the adequate and high-P diets. Similarly, Ca retention increased substantially on the higher P diets, showing that Ca metabolism can be controlled according to P status.