A low sodium diet was given to Scottish Blackface ewes over two reproductive seasons. It provided a total of 3–7 mmol sodium per day, except during lactation when the intake was about 11 mmol sodium per day. Control ewes were given the same diet supplemented with sodium chloride to Agricultural Research Council recommended concentration which was about ten times greater than that in the experimental diet.

The ewes remained clinically healthy throughout the experiment. The length of gestation and the birth weight of lambs were unaffected by diet. The number of lambs born alive per ewe lambing was unaffected by year or diet.

The percentage of ewes producing twins was similar in control ewes in both years at about 64; in treatment ewes this was 70% in year 1, and 50% in year 2. Lamb mortality was higher in both years in the treatment ewes than in control ewes. None of these differences reached significance.

The United Kingdom produces enough barley grain to meet its needs for animal feed and brewing. The Scottish grain whisky trade, however, imports large quantities of high-diastase barley from Canada (Hayter & Allison, 1975). The breeding of highdiastase cultivars which could be grown in Scotland and so replace these imports has been pursued at the Scottish Crop Research Institute (SCRI).

A study designed to investigate the effect of K nutrition on the yield, components of yield and on macro- and micronutrient concentration of maize showed no significant effect of K on yield in forest alfisols derived from basement complex rocks and in savannah alfisols derived from sandstones in the tropics. Potassium addition significantly decreased lodging, but had little influence on cob length, ear weight, shelling percentage or moisture content.

Ear-leaf N and K were significantly increased, while Ca and Mg were decreased by K application. All the micronutrient concentrations (Zn, Fe, Mn, Cu) were significantly increased by K application in the forest and savannah zones. Yield was positively correlated with ear-leaf N on both soils.

The effects of season and altitude on floral initiation of two Trifolium repena L. cultivars, Haifa and California Ladino, were tested in the area of Ayacucho, Peru (2730 m, 13° S), with regard to their seed production potential. Specific effects of daylength at a constant temperature (20 °C) were examined in growth chambers.

In Ayacucho, the proportion of inflorescence-bearing nodes was found to be lowest between December and June (Haifa 10–20%, Ladino 0–10%) and highest in August (Haifa 30%) and September–October (Ladino 15%). Late in the cool season, floral initiation of Ladino, but not that of Haifa, increased strongly at a high altitude (3250 m). In growth chambers, Haifa initiated few inflorescences and Ladino none in a 10 h daylength. In 16 h, the floral initiation of Haifa was very limited but Ladino formed many inflorescences. Floral initiation of Haifa was most pronounced and lasted longest after a daylength shift from 10 to 13 h.

It is concluded that seasonal and altitudinal variations in low temperature were the main factors influencing floral initiation in the region of Ayacucho. Haifa is considered to be an intermediate-day plant, suited for seed production in the region because of its marked and early flowering. Ladino was classified as a quantitative longday plant, unsuitable for seed production at this low latitude because of its retarded floral response to low temperature.

Leucaena leucocephala (Lam.) de Wit, a leguminous shrub, has come into use as a fodder plant for animals in the Ryukyu Islands as it provides highly palatable, high quality feed (Kitamura, 1985). It is superior to other feeds available in this regard (Higashiohmine, Aramoto & Yamashiro, 1971; Isa et al. 1982).

A non-surgical device which collects a pre-determined proportion of the urine voided by free grazing male cattle is described. The behaviour of animals trained to wear the collection equipment was similar to that of their contemporaries without the equipment. The performance and maintenance of the device are discussed.

During 1899–1964 various levels of 0·5 M sodium bicarbonate-soluble P had been established in an experiment on a sandy clay loam (pH 6·5–7·0) at Saxmundham, Suffolk. Modification made between 1965 and 1968 widened the range of soluble P values to 3–67 mg/kg. Relationships between these soluble P values and yields of potatoes and sugar beet in 1969–74 and cereals in 1970–7 were assessed. Responses by potatoes and sugar beet to freshly applied superphosphate were also determined at each level of soluble P. Residual effects of these dressings and responses to fresh superphosphate between 1974 and 1976 were measured by barley. Two amounts of N were tested on spring barley in 1976–7 and two cultivars of winter wheat were grown in 1977 and yields related to soluble P.

Relationships between yields and soluble P were described by an asymptotic regression equation. This model represented the measured yields well for all crops except barley, in one 4-year-period, when there were insufficient data at low soil P values and a linear regression model was fitted. The asymptotic model was used to estimate plateau yields each year and soluble P values at which yields were less than plateau values by one standard error. Average plateau yields, and associated soluble P values were: potatoes, 43 t/ha and 25 mg P/kg; sugar (from sugar beet) 6·8 t/ha and 20 mg P/kg; spring barley, given 63 kg N/ha, 4·7 t/ha and 25 mg P/kg; barley given 94 kg N/ha, 5·3 t/ha and 33 mg P/kg; winter wheat, 6·5 t/ha and 20 mg P/kg.

The model was further used to estimate responses to dressings of superphosphate at three levels of soluble P (9, 15 and 25 mg/kg) in the soils. Yield responses to 55 kg P/ha were 3·9, 2·1 and 1·8 t tubers/ha and 1·1, 0·3 and 0·0 t sugar/ha, for potatoes and sugar beet respectively, at the three levels of soluble P.

On impoverished soils (soluble P < 10 mg/kg) even the largest fresh applications of broadcast superphosphate did not raise yields to those achieved on enriched soils (soluble P > 25 mg P/kg) in the absence of fresh phosphate.

Soluble P in the soils accounted for much of the within-year variation of yields and estimated reliably and quantitatively the value of phosphate residues derived from both superphosphate and farmyard manure which had been applied in varying amounts and at different times between 1899 and 1976.

Classically the plant-growth regulator chlormequat (2-ohlorethyl trimethylammonium chloride, CCC) is applied to bread wheat crops (Triticum aestivutn L.) to shorten the basal internodes of the culm (Koranteng & Matthews, 1982) and thus prevent lodging (Cyanamid, 1966). Further, yield variations in cereal crops can be induced by chlormequat application in the absence of lodging. These effects may result from a manipulation of growth (e.g. barley: Koranteng & Matthews, 1982; wheat: Wunsche, 1971; triticale: Hankins, 1975) or development (e.g. barley: Wunsche, 1972; wheat: Harris, 1978; triticale: Green & McDonald, 1985).

Intake and faecal and urinary output of nitrogen, potassium and phosphorus by steers grazing high quality pasture at either of two intake levels were measured in three trials lasting 10–12 days. Intake was estimated from total faecal D.M. and in vitro D.M. digestibility of hand-plucked pasture. A known proportion of urine was sampled by a nonsurgical technique.

Average urinary mineral output between trials ranged from 93 to 134 g N/day, or 40 to 51% of consumed N; 74 to 137 g K/day or 33 to 76 % of consumed K and no more than 1 g P/day, or 2 to 4% of consumed P. Faeces contained 36–62 g N/day, or 16–24% of consumed N; 12–46 g K/day, or 8–21% of consumed K and 10–23 g P/day, or 44–74% of consumed P. The volume of urine passed differed widely between days for individual steers and between steers within each trial. In trial 3, daily output ranged between 5–8 and 54.71 by different animals. For two steers over three 24 h periods, frequency of urination ranged between 13 and 73/24 h; urine volumes between 7.6 and 51.2 1/24 h; urinary excretion of N between 81 and 137 g/24 h and of K between 58 and 90g/24h.

Urinary N and K concentrations were higher at night than during the day, ranging in trial 3 from 0.8 to 14.1 mg N/l, and 0.6 to 9.9 mg K/l. No clear diurnal patterns were found for P.

In a 3-year study, maize (Zea mays L.) sown on 11 November or 1 December produced longer ears, higher grain yield per plant and greater grain yield per hectare than maize sown on 21 October. However, 100-kernel weight was greater when the crop was sown on 21 October and 11 November than on 1 December. There were no differences in yield characters or grain yield between cultivars or between row orientation. The sowing dates, maize cultivars and row direction had no influence on the number of ears per plant.

In a long-term experiment with maize-wheat rotation, no response to zinc application was observed, even after 13 years of cropping though the status of zinc had decreased to a deficient level (0.35 mg/kg; DTPA). A study was, therefore, planned to find the reasons for lack of response, and the zinc fractions in the soil were analysed to assess their contribution to plant growth. All the zinc fractions other than organic zinc decreased as a result of continuous cropping without zinc application. Depletion was from the 0-30 cm layer and mainly from acid-soluble and weakly adsorbed Zn fractions. Applied zinc remained mainly in the 0-30 cm layer as acid soluble and weakly adsorbed Zn pools. All the fractions were strongly related to each other. The acid-soluble zinc fraction contributed 54 % to zinc uptake by the crops. Thus release of zinc from this pool was perhaps the main reason for lack of response to zinc.

Andropogon gayanus Kunth var. bisquamulatus Hack, is a polymorphic bunch grass, widely distributed throughout most of the tropical and subtropical savannahs of Africa, south of the Sahara in areas with a long dry season. This grass was introduced into the Colombian Llanos from the Shika Agricultural Research Station, northern Nigeria, in 1974. Subsequent to its introduction, a series of agronomic trials were initiated by Centro Internacional de Agricultura Tropical (CIAT) at the Carimagua Research Centre and various national research institutions in Latin America to evaluate the potential of A. gayanus, primarily in the vast Ultisol and Oxisol savannah regions of the continent. As a result of further evaluation at a number of locations, accession A. gayanus var. bisquamulatus CIAT 621 was released in 1980 in Brazil as cv. Flanaltina and in Colombia as cv. Carimagua 1. During 1982–3 Peru, Venezuela and Panama subsequently released the same accession under the cultivar names of San Martin, Sabanero and Veranero, respectively. It is estimated that 168000 ha have been sown with A. gayanus in Brazil since 1982 (J. E. Ferguson, C. Sere and R. de Andrade, personal communication). Smaller areas have been established in other countries.

Three techniques designed to increase radiation interception, and thus yield, in potato crops by extending the duration of the crop canopy were investigated over a period of 2 years. These were: mixing contrasting varieties; mixing seed tubers of contrasting physiological ages of the same variety, and early planting with protection from frost.

The first technique was partially successful; increases in total tuber fresh weight of the mixture over either of its components grown alone were recorded but the mixtures generally did not have any advantage in terms of ware yield (40–80 mm tubers) and total yield advantages were found in only 1 year. The second technique was unsuccessful in both years with all seven varieties tested. The third technique was successful with the long-lived variety Cara; large advantages both in ware yield and total tuber dry weight yield were obtained under two irrigation regimes. No advantages from early planting were obtained with the shorter-lived variety King Edward.

Radiation interception was estimated for all treatments by means of relationships established between intercepted radiation and percentage ground cover. None of the three techniques increased radiation interception; the yield advantages obtained could be ascribed either to an increase in the proportion of assimilates allocated to tubers or possibly to improvements in the efficiency of use of intercepted radiation.

A ruminant animal is largely dependent upon microbial protein synthesized within the reticulorumen for amino acids to meet its requirements for maintenance and production. The major precursor for rumen microbial protein synthesis is ammonia arising both from degradation of feed proteins within the rumen and from nitrogen recycled to the rumen. The concentration of rumen ammonia-N required to sustain maximal rates of microbial protein synthesis in vivo has been variably reported to range from 22 to 235 mg ammonia-N/1 rumen fluid (Miller, 1982). Most experiments which have investigated the concentrations of rumen ammonia-N required for maximal rates of microbial protein synthesis have used the addition of urea to the diet as the means of increasing rumen ammonia-N concentrations. However, little attention has been paid to the effects upon rumen ammonia-N concentrations and upon the efficiency of rumen microbial protein synthesis of supplying increasing amounts of a readily degradable protein in the diet, although Beardsley et al.(1977) found that as increasing amounts of soya-bean meal were fed to sheep, net losses of N across the forestomachs of the sheep were increased. In this paper, two experiments are described in which increasing amounts of soya-bean meal were fed to sheep receiving a basal ration of rolled barley and hay; the digestion of organic matter (OM) and of amino acid N (AAN) within the rumen, the net quantities of microbial AAN entering the small intestine and the efficiency of rumen microbial AAN synthesis were measured.

The sweat rates, skin and rectal temperatures and other components of the heat budgets of cattle were measured in Kenya and in England. Mean sweat rate (Ec) was more closely related to mean skin temperature (T8) than to rectal temperature. The results were described by an exponential relationship between T8, (°C) and Ec (mg/m2.sec) of the form Ee = E0 exp (T8, — T0)/B, where T0 and B are parameters (both with units of °C) which describe the sweating response of the animal, and E0 is 1 mg/m2.sec. T0 was 30·8 °C for a single Bos taurus in England and 33·8 °C for five animals in Kenya suggesting that chronic acclimatization to a hot environment resulted in the cattle being able to tolerate a higher mean skin temperature. The effect of species (Bos indicus cf. B. taurus) was small compared with the effect of acclimatization, although the mean value of B was significantly higher for B. indicus (1·58 cf. 0·94 °C) indicating that the physiological mechanism controlling sweat rate in B. indicus was less sensitive to skin temperature.

A field experiment was made during the rainy season of 1982 and 1983 at the Indian Agricultural Research Institute, New Delhi to study the relative efficiency of prilled urea, urea supergranules (USG) and USG coated with neem cake and DCD. Prilledurea was applied at 60, 120 and 180 kg N/ha, while the other sources of N were applied only at 120 kg N/ha. Nitrogen was added to rice in a single application 20 days after sowing (20 DAS) or in two applications, half 20 DAS and the rest at panicle initiation. Response of rice to prilled urea was linear up to 180 kg N/ha, the highest dose in the present study. Two applications produced more rough rice and straw and resulted in higher nitrogen uptake and apparent recovery than a singleapplication. Neem-cakecoated USG was superior to prilled urea in respect of panicle characters, rough rice and straw yield, nitrogen uptake and apparent nitrogen recovery. Coating USG with DCD also showed some advantage. Uncoated USG was only slightly better than prilled urea.

Differences in the field emergence of 30 commercial seed lots of dwarf French beans were associated with the colour of the testa, the 11 lots with a white testa having a lower mean field emergence of 67% compared with 91% for lots with black (11 lots) or brown (8 lots) testae. The white-seeded lots also had higher leachate conductivities (mean 42 μ S/cm/g) and imbibed more rapidly (an average 43% weight increase after 6 h imbibition) than black- or brown-seeded lots (average 25 μS/cm/g; 30% weight increase). The extent of damage to the testa which was slight in all lots was not related to differences in either the field emergence or rate of imbibition of the lots. In two successive imbibition cycles seeds of Provider (brown testae) took up water far more rapidly in the second imbibition (78% weight increase after 3 h) than the first (25% weight increase). The coloured testae normally adhere very tightly to the cotyledons but were loosened following the first imbibition leading to a more rapid uptake of water. The rapid imbibition of Tenderette (white testae) which has a loose fitting testa even in the dry seed was increased only slightly by a second imbibition. When seeds were imbibed from one end only from which the testa was removed Tenderette imbibed rapidly (90% weight increase after 12 h) whereas in Provider the tightly adhering testa limited the rate of water uptake (42% weight increase after 12 h) despite the ready access of water to the seed. It is suggested that the degree of adherence of the testa to the cotyledons is the major factor influencing the rate of imbibition of cultivars of dwarf French beans differing in testa colour and its role in determining seed vigour is discussed.

The soluble tuber proteins of potato (Solatium tuberosum) may be separated by electrophoresis on the basis of charge or molecular weight (Stegemann & Schnick, 1982; Maier & Wagner, 1981: Park et al. 1983). Considerable cultivar specific variation exists in the band patterns of these proteins and separation of native proteins in 6% polyacrylamide gels at pH 7·9 has been used as the basis of characterizing cultivars for the Index of European Potato Varieties (Stegemann & Schnick, 1982).