The modified EDTA (ethylenediaminetetraacetic acid) method of determining the ionic activities in soils developed by Norvell was used to measure Zn2+, Cu2+ and Mn2+ activities including the competition of Ca and Mg for the chelating ligand EDTA. In the Zn-EDTA system, the equilibrium mole fraction of CaL2− + MgL2− increased with an increase in pH of the soil solution, thereby leading to a decrease in the concentration of transition metal ions. In view of the pH dependence of the metal ion activities, the values of the expression pM + 2 pOH (where M may be Zn, Cu or Mn) were used to discuss the possible role of various oxides, hydroxides, carbonates, sulphides and unknown solid phases in regulating the activities of Zn2+, Cu2+ and Mn2+ ions in alkaline and calcareous soils.

Abnormally low concentrations of morphine in capsules of poppy (Papaver somniferum L.) in the 1970–1 season were associated with heavy fungal colonization. The effect of fungal colonization on the morphine production of capsules was later studied in a series of field, glasshouse and in vitroexperiments.

In a field experiment morphine concentration of severely colonized (> 30% surface cover) intact capsules was 20% less (P <0·01) than slightly colonized (< 10% surface cover) capsules. Colonization of these field-grown capsules was generally localized in the top half and the morphine concentration of the top half was about 20% less than the bottom half for all colonization categories. In contrast, glasshouse-grown capsules were free of fungal colonization and the top and bottom halves had similar morphine concentrations.

In a field experiment studying the effect of fungicides, 2 kg benomyl (50% a.i.) + 2 kg mancozeb (80% a.i.)/ha were applied as a spray at 10-day intervals from flowering till 1 month after commercial harvest and plants were harvested at weekly intervals from 10 days after full bloom. The mean dry-matter yield of sprayed capsules was 11% greater (P <0·01) than non-sprayed with a similar trend for morphine concentration and morphine yield. In addition, the sprayed treatment significantly reduced the area covered by sporulating lesions on the surface of the capsule after dry maturity. This superficial fungal cover had a NNE orientation in both sprayed and non-sprayed capsules.

In an in vitroexperiment using capsules from the field fungicide study, fungi were isolated from the interior of green capsule wall tissue as early as 17 days after flowering. Colonization increased with successive harvests and culturing of fungi from the interior of capsule wall tissue showed the presence of fungi in both sprayed and non-sprayed capsules with no difference in the degree of colonization.

Two of the major fungi isolated from the field experiment were identified as Dendryphion penidllatum (Corda) Fr. and Alternaria alternata (Fr.) Keissler and the individual effect of these was assessed in an in vitro experiment using ground capsule material. D. penidllatuvi and A. alternata reduced the morphine concentration of ground capsules in 24 days to 7 and 11% respectively of non-inoculated controls.

Theory for the non-steady-state diffusion flow of a spheroidal body is discussed and solutions are presented for estimating the time-dependent diffusivities at small and largo times following sowing in soil of germinating soya-bean, cow-pea and blackgram seeds. The validity and also the limitations of the equation for large times to estimate time-dependent diffusivities are discussed. Assuming that the time of germination was at infinity it was possible to reduce the equation for small times to a simple form. Thus, with the help of these two equations it was possible to study changes in the diffusivity of seeds at different soil matric potentials throughout the period, immediately after sowing until germination. The diffusivities showed gradual decrease at 0 bar potential for soya-bean and cow-pea, and increase at – 2 and – 10 bar potentials for soya-bean, cow-pea and blackgram seeds with time. The decrease in diffusivity with time under non-stress soil water condition is explained as predominantly a physiological phenomenon of the seed due to the increase in seed water content with time, while its increase with time under water stress conditions is probably because of the decrease with time of the initially large seed-coat resistance and tortuosity showing small values of diffusivity. The discussion suggests that the role of area of contact on the water uptake of the buried seeds as reported so far is contradictory and, therefore, not convincing.

The present work was carried out on 24 coarse-wool Barki and ⅝ Merino–⅜ Barki ram lambs to study the effect of vitamin A supplementation on some skin and wool characteristics. Lambs, at the age of 6 months, were allotted to three groups receiving no vitamin A supplement, 50000 i.u. and 100000 i.u. of vitamin A/head monthly. Blood samples were taken monthly for the assessment of vitamin A in the plasma. It was found that vitamin A in the plasma ranged from 42·4 to 17·50 and from 41·67 to 50·03/ μg/100 ml in the control and treated groups respectively, from the start of the experiment till the end at the age of 17 months.

Vitamin A supplementation caused increments in external diameters, of primary and secondary follicles in Barki and primaries in ⅝ Merino, higher than those encountered in internal diameters. An increase in staple length and clean fleece weight of ⅝ Merino and a slight increase in Barki fibre diameter was observed in vitamin-A-supplemented animals.

The high activity of rumen urease is a major limiting factor in the usefulness of urea as a protein replacement supplement in ruminant diets (Bloomfield, Garner & Muhrer, 1960). The efficiency of urea utilization can be increased by decreasing the activity of rumen urease or by modification of urea in the products which are slow ammoniareleasing (Helmer & Bartley, 1971). An arbitrary formaldehyde treatment of urea was observed to lower the hydrolysis in the intact rumen (Pal & Negi, 1977). In a systematic study carried out in our laboratory a series of urea formaldehyde complexes (UFC) was prepared and their in vitro hydrolysis studied (Lall et al.1980; Makkar et al. 1981). Phosphoric acid is known to catalyse the reaction between aldehyde and urea. In the present study the complexes of urea and formaldehyde (UFC) and urea, formaldehyde and molasses (UFMC) in the presence of a catalyst (phosphoric acid) were prepared and their in vitro ammonia production is presented.

The introduction of new protein evaluation systems for ruminants presupposes means to measure the ruminal protein degradability of feeds (Burroughs, Nelson & Mertens, 1975; Roy et al. 1977; Vérité, Journet & Jarrige, 1979). One potentially useful method to get such estimates is the nylon bag technique (Mehrez & Ørskov, 1977). This method, however, does not take into account the flow of feed particles from the rumen. By adjusting rumen degradation results obtained in sacco with the outflow of the feed from the rumen more accurate estimates of the actual degradability is possible (0ørskov & McDonald, 1979).

Urinary allantoin, an end product of purine base metabolism, originates in sheep from three possible sources: exogenous, purine bases of rumen microorganisms and feed purines and ureides, and endogenous, purines catabolized in tissue turnover. Earlier studies suggested that nucleic acid purines of rumen micro-organisms may be a predominant source of urinary allantoin (Antoniewicz, Heinemann & Hanks, 1979, 1981).

Blast, caused by Pyricularia oryzae Cav., one of the major foliar diseases of rice, appears sometimes in a devastating form in the seedling stage. The angles subtended by leaves may affect the establishment of the pathogen. Ono (1965) observed that leaf angles of rice plants, among many other factors, influenced deposition of spores. Gangopadhyay & Chattopadhyay (1974) found that brown spot disease (Helminthosporium oryzae) incidence in rice increased with increase in leaf angles. The present study is intended to find out the role of leaf angles in rice on the incidence of blast disease at the seedling stage.

Abortion and stillbirth ranges of 1·8–16·1% and 1·26–6·5% respectively have been reported among Friesian cattle by Asker & El-Itriby (1957), Ragab & Asker (1959), Juma (1968) and Kassir & Juma (1968). Abortions and stillbirths occurred more frequently among heifers than among cows (Philipsson, 1971). Calving interval varied between 367 and 474 days, the first interval being the longest (Ragab & Asker, 1959; Zaki, Abdel Razek & Dessouky, 1965; Marples& Trail, 1967; Trail &Marples, 1968; Anon. 1969; Knudsen & Sohael, 1970; McLntyre, 1971; Kiwuwa, 1972).

Various species of animals, ranging from ordinary laboratory rats to some high-grade beef and dairy cattle, have been imported from the temperate regions of the world to Nigeria in recent years. Most favoured are Large White pigs and this breed of livestock is proving to have very great potential in the livestock production industry in this part of the tropics. Temperate breeds of livestock when introduced to the tropics are said to decline in their general performance, owing partly to direct effects of high ambient temperatures(Yousef & Johnson, 1965). Some generalized statements have also been made on the adverse effects of tropical climate on growth though very little objective field experimental evidence exists (Williamson & Payne, 1978).

It has been reported that water deprivation reduces feed intake in Chokla sheep (Singh, More & Sahni, 1976; More & Sahni, 1978). Consequently, sheep production in terms of body weight, milk and lambs is also adversely affected (More & Sahni, 1980). However, no information is available on the metabolic aspects, particularly on urinary nitrogen and creatinine changes due to long-term intermittent watering. Creatinine is also used as a reference substance for evaluating urinary excretion rates of minerals (Field, 1964) and nitrogen (Powell, Plough & Baker, 1961) to avoid more laborious and time-consuming procedures, which also disturb animal behaviour and production (Langlands, 1966). The present paper attempts to examine the urinary concentration of total nitrogen, creatinine and their ratios; the ratios of potassium to creatinine and nitrogen are also considered.

It is generally recognized that there is a close relationship between the utilization of roughage feed and rumination behaviour in ruminant animals (Gordon, 1955, 1968; Pearce & Moir, 1964; Campling, 1966; Welch & Smith,1969; Sudweeka et al. 1975; Thomas, Kelly & Wait, 1976; Fujihara, 1981). Likewise, it is also well known that rumination behaviour is clearly affected by differences in the physical and/or chemical properties of the diet (Gordon, 1958; Campling, Freer & Balch, 1962; Balch, 1971; Ørskov, Fraser& Gordon, 1974; Osuji, Gordon & Webster, 1975; Morgan & Campling,1978; Harumoto & Kato, 1978a, b; Fujihara, 1980b). Recently, Fujihara (1980a, b) observed more efficient rumination in sheep offered fresh grass than hay, and suggested that the efficient rumination might induce an efficient utilization of dietary nitrogen when feeding fresh grass.