Results obtained previously on distribution and behaviour of phosphate between organic and inorganic forms in pig slurries are extended to slurries from wastes of hens, cows and calves. Organic P in the slurries varied from about 1 to 15% of total P, with slurries from veal calves having the lowest content of organic P. In all slurries roughly half of organic P in solution had a high molecular weight (50000 and higher) and is therefore potentially mobile in soils.

The availability to grass of the nitrogen in liquid anaerobically digested sludge (LDS) and liquid aerobic sludge (LAS) was investigated in a 2-year field trial. The mean availability of the nitrogen in the LDS over the 2 years was 44% on a freely drained sandy soil and 34% on a poorly drained clay soil. The corresponding values for the LAS were 56 and 44%. A greater inhibition or organic-matter decomposition by clay particles or a greater loss of nitrogen by either ammonia volatilization or denitrification were all possible reasons for the lower availability of the sludges on the clay soil. Investigation of the magnitude of gaseous losses of nitrogen from sludge-amended grassland under U.K. conditions is required. Current models of the availability of the nitrogen in liquid sludges may not be realistic if these losses are significant.

Shoot and root growth and associated leaf and soil water potential relations were compared in three consecutive crops of winter wheat grown in the same field. Despite a profuse root system the crop grown in the second drought year (1976) failed to dry the soil as throughly as the crops in 1975 and 1977. Measurements of plant water potential showed that the restricted utilization of soil water reserves by this crop was associated with failure to make any significant osmotic adjustment, leading to premature loss of leaf turgor and stomatal closure. The implications of these results for models to estimate actual crop evaporation from values of potential evaporation are discussed.

The effects on dormancy of post-harvest application of growth regulators to bulbils, tubers and tuber pieces of tropical Dioscorea species were examined. Abscisic acid, kinetin, indole acetic acid and 2-chloroethyltrimethylammonium chloride were found to have little or no effect on either shoot or tuber-root production, while ethrel greatly promoted tuber-root production with little or no effect on shoot development. The germination of slices of tubers of D. alata was delayed by maleic hydrazide but there was no effect on intact tubers of D. alata and D. esculenta. Treatment with 2,4-dichlorophenoxyacetic acid caused massive root and callus development along with delay in shoot development, while gibberellic acid occasioned marked extensions in the dormant period.

A total of 140 British Friesian cows in their second or later lactation and with a mean calving date of 27 October (s.D. 18 days) were used in a randomized-block experiment over a 3-year period. The experiment was designed to examine the effects of level of concentrate given during the winter period, in addition to ad libitum access to grass silage, on total lactation performance. The silage had a mean dry-matter content and digestible organic matter in the dry matter of 206 and 698 g/kg respectively and the mean inputs of concentrates on the five treatments were 0–64, 0–89, 1–14, 1–38 and 1·59 t/cow (treatments 1–5 respectively). Sixteen replicates per treatment were housed in individual stalls during the winter period in order to facilitate the measurement of silage intake and the remaining animals in each year were maintained as a single group.

All animals in each year grazed together as a single group at pasture at a mean stocking rate of 6–0 cows/ha and without supplementary concentrates.

Level of concentrate supplementation had a significant linear effect on the intake of silage dry matter with the relationship between total intake of silage dry matter over the winter period (kg, y) and concentrate dry matter input (kg, x) being described by equation (1)

The heart rates and corresponding energy expenditure of adult Brahman cattle (Bos indicus) and water buffalo (Bubalus bubalis) were measured whilst they were standing, walking at speeds of up to 1 m/sec and pulling loads of up to 50 kg for periods of 1–2 h/day. Correlations of heart rate with energy expenditure showed a positive linear relationship within species although a distinct difference was exhibited between species. However, when heart rate and energy expenditure were expressed relative to their respective resting values (RHR and REE respectively), the results for all animals fitted the same line:

REE = 2·251 RHR – 0·954 (r = 0·93; n = 49).

More importantly, the relative heart rate and actual energy expenditure per unit metabolic body weight (EEW) for all animals fitted a common line:

EEW = 24·94 RHR – 16·25 (r = 0·91; n = 49),

where EEW is in watts/kg0·75 and RHR = heart rate of the working animal/heart rate at rest. This assessment of the energy expenditure from measurement of heart rate and live weight thus allows a prediction to be made of the energy requirements of working draught cattle under field conditions.

Effects of controlled tillage and soil-water conditions at the time of cultivation on emergence and grain yield were measured for a spring barley crop grown on a silty clay loam soil. A range of soil densities was achieved using conventional implements (tine-cultivator and roller) in combination with three levels of soil wetness. Concrete tracks supported both tractor and implements to prevent compaction due to wheelings, and rain-activated mobile shelters excluded precipitation from the field site.

Tillage treatments had large and significant effects on plant establishment. Both rate of emergence and final emergence were lowest where the soil was rolled at a high moisture content, and greatest where it was cultivated dry. Time for 50% plant emergence, rate of emergence and final plant population density all tended to be linearly correlated with the bulk density of the prepared seed bed. Despite large differences in plant establishment, later compensatory growth caused final yields of grain to show no significant response to tillage treatment.

The effects of post-harvest application of gibberellic acid on dormancy of tubers of Dioscorea alata and D. esculenta were examined. In both species, gibberellic acid extended the dormancy of immature and mature tubers but when GA3 application was made after storage for varying lengths of time, there was a decreasing effect with increased storage time. Dormancy was also reinduced in germinating tubers, that had gone through a normal dormant period, as a result of gibberellic acid treatment. A possible mechanism of dormancy in tropical yams is discussed. It is concluded that use of gibberellic acid as a means of extending the storage life of yam tubers by post-harvest application is a distinct possibility.

The growth of Huia white clover was followed in undisturbed and unsterilized soil cores containing a normal endomycorrhizal fungal population which had been inoculated with one of eight additional endomycorrhizal fungal isolates. Most of the endophytes significantly stimulated growth over filtrate controls at some stage in the experiment. Glomus mosseae, G. tenue and Gigaspora margarita produced large growth increments over a range of applied phosphorus levels. The inocula also contained a filtrable agent that was capable of reducing the growth of white clover.

Four field experiments were established to gauge the effect of inoculating white clover with selected strains of vesicular-arbuscular mycorrhizal (VAM) fungi. The four sites chosen ranged in fertility from undeveloped, phosphorus-impoverished tussock grassland to high fertility alluvial flats. As far as practicable conventional agronomic practices were followed prior to and during sowing. The soils were otherwise untreated and contained the normal complement of indigenous VAM fungi. Infested soil pellets were used to introduce the fungi into the soils as this was considered more appropriate to pastoral farming than for example transplanting infected seedlings.

Initially the introduced fungi tended to have little or no effect on dry-matter yields but by the end of the first season there were significant responses to Gigaspora margarita, Glomus mosseae, Glomus macrocarpum or a mixed inoculum of Glomus pallidum and Glomus tenue. In the second season, dry-matter yields were increased on the two tussock grassland sites by up to 760 kg D.M./ha (ca. 30%), 825 kg D.M./ha on the moderately fertile site (14%) and 640 kg D.M./ha (5%) on the high fertility site. The growth responses tended to decrease with time probably owing to the spread of fungi from the inoculated to the control plots though growth responses were still present at the end of the 3rd year on two of the sites. Within each experiment the application of up to 50 kg P/ha per year did not reduce the size of the responses to inoculation. This and herbage chemical analyses suggested that a more efficient use of phosphatic fertilizers may have been only part of the reason for the responses to inoculation.

When pre-harvest foliar applications of growth regulators were made to vines of Dioscorea esculenta cv. Chinese Yam and D. alata cv. White Lisbon there were no obvious effects on tubers of D. alata, but dramatic effects on tuber development, storage and germination were obtained with D. esculenta tubers. Gibberellic acid caused marked extensions in tuber dormancy, 2,4-dichlorophenoxyacetic acid resulted in marked callus development, delayed germination and abnormal shoot and root development and indole acetic acid resulted in fingering of the tubers. It was concluded that there was potential for commercial exploitation of pre-harvest gibberellic acid treatments in extension of dormancy in Chinese Yam tubers and that the lack of response of D. alata tubers to foliar application of growth regulators warranted further investigation.

The incidence of lantana poisoning and its effect on mortality, growth rate and fertility were recorded from 1975 to 1982 in seven lines of Bos taurus and Bos indicus cattle and their crosses.

Two Bos taurus Hereford × Shorthorn (HS) lines had higher incidences of poisoning and higher mortalities after poisoning than the Bos indicus based breeds.

During the period of poisoning, live–weight gains of affected animals of all breeds were reduced but subsequent recovery was rapid. Lantana poisoning had no detectable effect on the fertility of animals affected at least 10 months prior to their first mating, irrespective of breed.

Parasite control influenced the incidence of poisoning and mortality in genetically similar groups of HS cattle. This observation, when combined with the between-breed relationships between the incidence of lantana poisoning and susceptibility to environmental stresses suggests that the marked breed differences in susceptibility to lantana poisoning stem from differences in resistance to other environmental stresses, including cattle ticks. This offers little scope for selection of animals that are resistant to lantana poisoning per se but has practical significance in lantanainfested regions.

Three American crisp lettuce varieties Ithaca, Pennlake and Saladin, formerly called Salinas, were sown on three occasions between April and July in 1980 and 1981 and on six occasions in 1982 between March and July. The rate of emergence of all three varieties increased with mean soil temperature at seed depth. The number of leaves was linearly related to air temperature measured on an accumulated day-degree scale > 0 °C from emergence. Pennlake had the highest rate of leaf production and Saladin the lowest rate. The relative growth rate of Ithaca increased with later sowing, while that of Pennlake declined. The time of maturity of one variety relative to another changed with sowing date but in all three varieties a quadratic curve relating the time of maturity to the time of sowing accounted for a high proportion of the variance in the time of maturity. When the times of sowing and maturity were both expressed on a day-degree scale > 0 °C a linear relationship accounted for more than 98% of the variance in time of maturity. These data provide the basis for planning a continuity programme. Within a variety there was considerable variation in mean head weight between sowings in the same year and different responses of head weight to sowing date from year to year. Using data from all 12 sowings, there was shown to be a significant association between head weight and the mean temperature up to 42 days from emergence but there was no association with radiation. Low mean temperatures (< 12 °C) were associated with lower head weights of Ithaca but higher head weights of Saladin. The opposite was true for mean temperatures greater than 16 °C. The reasons for this are discussed.

Most commercial cultivars of Cucurbita pepo L. reacted by producing severe leaf symptoms when infected with either of two British strains of cucumber mosaic virus. Resistance was identified in some pumpkin-types of C. pepo, with the highest level in cv. Cinderella. Studies with selfed populations produced from selected resistant plants demonstrated that resistance in cv. Cinderella is heritable.

Isogenic fertile and sterile forage maize (cv. LG 11) grown in separate fields were harvested at regular intervals during growth between mid-July and early October 1979. Leaf, stem and ear components and whole plant (before and after ensiling) were examined for changes in the concentration of dry matter (D.M.), soluble sugars, starch, hemicellulose, cellulose, neutral detergent fibre (NDF) and acid detergent fibre (ADF). In vitro digestibility values for D.M., organic matter (OM) and OM in the D.M. were also determined in fresh and ensiled whole crops.

Prior to ensiling the concentration of non-structural carbohydrates in the two crops was markedly different. Fresh fertile plants contained (as g/kg D.M.) 369 and 101 of starch and soluble sugars respectively. Corresponding values for sterile plants were 54 and 343 respectively. Sucrose was the most abundant soluble sugar present and contributed 64 and 74% of the totals in fertile and sterile plants respectively, prior to ensiling. Increases in plant D.M. during growth were significantly affected by the deposition of starch and are described by the following equation:

y = 13·6 + 0·49 (±0·073) x(r = 0·93)

where y = whole-crop D.M. concentration and x = starch concentration in D.M. The concentrations of hemicellulose and cellulose of both types of fresh plants were similar but those of ADF and NDF were lower in sterile plants. Xylose was the major constituent neutral sugar in the hemicellulose fraction and formed 68 and 76% of the total hemicellulose in the fertile and sterile plants, respectively. In vitro digestibility values of sterile plants tended to be higher than their fertile counterparts.

After ensiling, the concentration of soluble sugar in the sterile and fertile crops decreased from 343 to 8 g/kg D.M. and 101 to 5 g/kg D.M. respectively. The in vitro DOMD values of the sterile and fertile crops decreased by 16 and 11 percentage units respectively; both final values were recorded as 61.

In vivo digestibility values determined in 18-month-old wether sheep fed at maintenance, for NDF, ADF, cellulose, hemicellulose, nitrogen, OM, D.M. and OM in D.M. were 60·2, 58·0, 65·8, 64·1, 32·9, 66·6, 65·4 and 63·7 respectively for fertile plant silage. These were all markedly lower than the corresponding values for the sterile plant silage which were 68·3, 70·3, 74·8, 73·3, 60·3, 71·3, 69·6 and 67·7 respectively. Within the hemicellulose fraction the digestibility values for xylose in both sterile and fertile plant silage were considerably lower than the values recorded for either arabinose or galactose. In vitro digestibility values for D.M., OM and OM in the D.M. were similar to in vivo values for fertile plant silage but were lower than in vivo values for sterile plant silage.

Dairy herd replacement heifers (aged 3–6 months) had higher D.M. intakes when given fertile plant silage ad libitum than with sterile plant silage. However, the liveweight gains of the heifers on sterile and fertile plant silage differed little.

A variety of chemical reagents and treatment methods have been tested for their potential to enhance the digestibility of crop residues. The most universally used chemicals for animal experimentation in residue treatment are sodium or ammonium hydroxide (Chandra & Jackson, 1970; Koers, Prokop & Klopfenstein, 1972; Klopfenstein, 1978; Arndt & Richardson, 1982). These chemical treatments usually improve digestibility of roughages by solubilizing hemicellulose, and increasing the extent and rate of cellulose and hemicellulose digestion (Klopfenstein, 1978). Delignification is not usually considered to be an important aspect of chemical treatment (Klopfenstein et al. 1972), and increases in digestion are usually attributed primarily to breaking of bonds between lignin and carbohydrates rather than lignin removal. The aromatic nuclei of the lignin molecule are quite susceptible to oxidative attack (Sarkenen & Ludwig, 1971), and crop residues may be significantly delignified by oxidative chemical reagents (Sullivan & Hershberger, 1959; Sherrod et al. 1978; Ben-Ghedalia, Shefet & Miron, 1980). Ozonation is a chemical treatment method which is known to oxidize lignin and disrupt the lignocellulose complex. Several researchers have successfully applied the delignifying capability of ozone to improve the in vitro digestibility of roughages (Weakley & Owens, 1975; Ben-Ghedalia & Miron, 1981; Tock et al. 1982). Very little, however, is known of the actual in vivo feeding value of crop residues treated with ozone. These studies were conducted to determine the effect of ozone treatment on the feeding value of sorghum stover.

S.184 white clover was established on an unimproved brown earth hill pasture using both surface seeding techniques and conventional cultivation. Inoculation with selected Rhizobium trifolii improved clover dry-matter production by 0·017 t/ha on the cultivated trial in the establishment year and by 0·13 t/ha in the first harvest year. On the uncultivated site, clover dry-matter production was increased 1·88 t/ha by the best inoculation treatment in the first harvest year and 1·01 t/ha in the second harvest year. Rhizobium strains differed in their ability to promote clover growth. Clover yields were substantially better on the uncultivated than on the cultivated trial. The implications of the results for hill land pasture improvement are discussed.

The development of statistically sound methods of summarizing the results from germination tests appears to have been neglected. This paper reviews the literature critically, proposes the use of maximum likelihood techniques to summarize such data and develops an appropriate routine, available as a computer program ‘DISTGERM’.

Changes in soil fertility status brought about by the application of P and K fertilizers and farmyard manure (FYM) to a fixed wheat-maize rotation for 10 years in a calcic ustochrept are reported. The treatments comprised three rates of P (0, 30 and 60 kg P2O5/ha), two rates of K (0 and 30 kg K2O/ha) and two rates of FYM (0 and 15 t/ha) applied to maize or wheat alone or to both the crops. Organic carbon and available P and K contents of the soil increased significantly with the addition of FYM. P application at 60 kg P2O5/ha nearly maintained the original level of available P even after 10 years of continuous cropping. However, a considerable and highly significant increase in available P was obtained with the combined application of P and FYM. Available K status of the soil remained more or less unaffected by K application. Organic carbon content, and available P and K contents were significantly higher in the plots that received fertilizers and manure for both the crops than in those where the application was to maize or wheat alone.