Response of wheat to fertilizer-P on soils low and medium in available P increased with increasing doses up to 26 kg P/ha; responses were proportionately greater on medium-P soils. Application of 39 kg P/ha increased the response slightly on low-P but decreased it drastically on medium-P soils. The relatively small response on low-P soils may be due to fixation of fertilizer-P. The results indicate that the maximum response to fertilizer-P may be obtained only when P fixing capacity of the soil is satisfied so that sufficient P for the crop remains in the soil solution. The results of this investigation suggest that fertilizer should be applied on the basis of soil test data of individual fields instead of following regional recommendations.

In laboratory studies, the amount of N mineralized under waterlogged conditions during 14 days at 30°C was significantly correlated (P < 0·001) with the activities of amidase, glutaminase and asparaginase in soil when these enzymes were assayed by either a nonbuffer or a buffer method using appropriate substrates. N mineralization under waterlogged conditions was also significantly positively correlated with N mineralization under aerobic conditions, especially at 25 and 35 °C (P < 0·001). Generally, the results indicate that the use of amidase, glutaminase and asparaginase activities in predicting plant-available N in soils deserves more attention.

A trial of open-pollinated (OP) cultivars and hybrids of different origins was conducted in 1986–1988 at two sites in the central clay plains of Sudan, rainfed at one site and under supplementary irrigation at the other. Throughout this study, the patterns of growth of the OP cultivars differed greatly from those of the hybrids, despite differences amongst cultivars within each group. Differences in seed yield between OP cultivars and hybrids under irrigation were not significant; but, under rainfed conditions, the hybrids gave higher yields than the OP cultivars. Partitioning efficiency (PE; reproductive mass: total biomass) increased more rapidly during flowering and seed filling in the hybrids than in the OP cultivars; differences in PE between the two groups were significant. The higher leaf area index, leaf area duration and crop growth rate of the OP cultivars were compensated to some extent by the higher PE and leaf efficiency values of the hybrids, resulting in similar seed yields of all cultivars under irrigation. Overall, irrigation increased seed yield by 0·6–1·9 t/ha and increased oil content by 8–15%.

Whole-body oxygen (O2) consumption was measured continuously in pigs from the product of blood flow through the pulmonary artery and arterio-venous (AV) difference of blood O2 content across the lungs (pulmonary AV procedure). Blood flow in the pulmonary artery, a measure of cardiac output, was monitored continuously using a transit-time ultrasound flow probe surgically implanted around the artery. The O2 content of pulmonary artery blood, which represents mixed venous blood O2 aturation (SvO2) was recorded continuously by fibre-optic oximetry. The relative constancy of arterial blood oxygen saturation (SaO2), obtained by catheterization of the saphenous artery, obviated the need for continuous monitoring. Complete recovery from surgical procedures, as indicated by the absence of infection and a return to pre-surgery food intake, occurred in 3–5 days. The combination of transit-time ultrasound and fibre-optic oximetry allowed the pulmonary AV procedure to provide continuous data on the oxygen consumption of growing pigs at high temperatures.

Several methods for estimating nitrates by reduction to ammonia were examined. The error involved in the use of acid reducing agents in presence of amino groups was emphasised.

A method based on the use of Devarda's alloy and magnesia is recommended.

In the estimation of nitrates in plant extracts, etc., by this method an equal volume of rectified spirit is first added to the solution to precipitate colloidal matter. The precipitate is filtered off and an aliquot part of the filtrate containing the equivalent in nitrate nitrogen of about 0.1 gm. of KNO3 is distilled with steam for 45 minutes with 1 gm. of Devarda's alloy and ½ gm. of freshly ignited magnesia. A blank determination is essential, in which the same volume of filtrate is distilled for the same length of time with ½ gm. of magnesia.

In Kjeldahl estimations in presence of nitrates, where the separate estimation of nitrates is not required, 2 c.c. of 25 per cent. NaOH may be substituted for the magnesia. Relatively this is very much less soda than Devarda recommends. The mixture in this case may be distilled directly for half-an-hour. The nitrates are thus reduced and the ammonia produced is collected before beginning the digestion with sulphuric acid.

This work was carried out under the supervision of Mr F. W. Foreman to whom the author's best thanks are due for much valuable criticism and advice.

The grading-up system, in the Ayrshire Cattle breed, whereby the descendants of non-pedigree cows enter the registered (Herd Book) population, is studied principally from three aspects: (1) its numerical importance in the population; (2) the breeding structure of herds practising grading-up, and (3) the possible genetic effect of grading-up on milk and fat yield.

Cows at various stages of grading-up are noted in an Appendix to the Herd Book. The numerical importance of the grading-up system has varied with the rate of expansion of the breed as a whole—being greatest during the most rapid expansion—but, at all times, Appendix cows have had more registered female offspring than have pedigree cows. The volume of grading-up was regulated by the number of cows in Appendix B. Some 6% of the pedigree females registered in the last 30 years have Appendix A mothers and a further 5% or so owe their existence to grading-up during the last 30 years.

On average, the proportion of herds registering bulls is not greatly different among the herds which grade-up and those which do not. Similarly, the ratio of males to pedigree females registered was about the same in both types of herd. None-theless, there appears to be considerable selection against Appendix animals in the ancestry of bulls compared with cows, and none of the large bullbreeding studs appear to pursue a grading-up policy. A greater proportion of Ayrshire herds were grading-up in Scotland than in England.

Entry into Appendix B of the Herd Book is confined to cows reaching a qualifying yield. The daughters (A) of these B cows mated to unselected pedigree bulls were found to yield significantly more in their first lactation (36 gal. milk and 14 lb. butterfat) than contemporary pedigree Ayrshire heifers in the same Scottish milk recorded herds in 1955. Part, if not all, of this superiority is thought to be genetic.

A comparative study of sorption maxima (simple and double Langmuir equations) and buffer capacity of acid soils was made in order to select the most useful P-sorption parameter. Data were obtained from 20 acid soils from Galicia (north-west Spain) and selection was made by linear and multiple regressions among sorption parameters, and between these and some soil characteristics related to phosphate sorption (clay and organicmatter content, pH in NaF, and 0·5 M-CuCl2-extracted Al).

The phosphate buffer capacity, determined by the slope of the regression ‘sorbed-P v. logc’, was the best parameter to represent soil phosphate sorption behaviour. 0·5 M-CuCl2- extracted Al was the edaphic characteristic which best related to sorption properties.

In each of two experiments the comparative slaughter technique was used to compare the retention of energy by young Border Leicester × Merino wethers when the same total amount of food was offered according to two different feeding regimens. These were designed to simulate, in pens with a diet of pelleted lucerne, feeding patterns typical of continuous and intensive rotational grazing.

In the first experiment ten 9-month-old sheep that were offered the same amount of food daily (mean intake 367 g digestible organic matter) during each of 14 weeks made mean daily gains of 39 g live weight, 6·3 g body fat and 0·59 MJ (140 kcal) energy compared with a gain of 30 g live weight, a loss of 1·4 g body fat and a gain of 0·28 MJ (67 kcal) energy by a similar group that ate the same total quantity of food but in amounts that ranged, during each week, from 1·8 to 0·1 times the daily intake of the other group. This cyclic feeding pattern caused a small decrease in the digestibility of dietary organic matter.

In the second experiment two similar feeding patterns were compared with ten pairs of 3-month-old sheep eating twice as much food each week as in the first experiment. One member of each pair was, in each of 13 weeks, offered food ad lib. for 3 days and then amounts falling to 20% of voluntary intake on the seventh day; the other one ate the same amount of food each week but in seven almost equal feeds. The latter sheep gained, on average, 132 g live weight daily and retained 58 g body fat and 2·96 MJ (707 kcal) energy compared with 124 g live weight, 49 g body fat and 2·61 MJ (624 kcal) energy by the sheep on the cyclic feeding pattern. In neither experiment was wool growth affected by feeding pattern.

The greater effect of the cyclic feeding pattern in reducing the efficiency of energy retention in the first experiment is attributed to the higher number of days each week during which these animals were estimated to be in negative energy balance. These results suggest that adverse nutritional effects of a fluctuating feeding pattern in rotational grazing are likely to be most important where sheep are being rationed near their maintenance level and only small where food is ample.

Initial pH of buffalo semen as measured electrometrically is 7.2 ± 0.025 and the buffering capacity 1.40 ± 0.026. Sulphamezathine in glucose–egg yolk–bicarbonate diluent depressed fructolysis in buffalo semen. This depression is considered to be a factor in the better maintenance of motility in this than in other media investigated. The more alkaline pH of this medium also appears to be beneficial in preserving motility on storage.

The objective of this study was to evaluate the radiation use efficiency (RUE) and canopy structure of elephant grass varieties (Cenchrus purpureus Schum.) of contrasting statures, under monocropping or intercropped with butterfly pea (Clitoria ternatea L.) in cut-and-carry systems. Two tall varieties (elephant B and IRI-381), and two dwarf ones (Mott and Taiwan A-146 2.37), were evaluated as monocrops or binary intercrops with the legume in a 2-year trial with eight harvests. Greater annual leaf biomass accumulation was observed in the monocrops of the tall variety elephant B (7.76 t/ha per year) and dwarf Mott (8.08 t/ha per year). Greater herbage bulk density (59 kg/ha per cm) and leaf area index (3.83) were recorded in canopies of dwarf Mott than in those composed of IRI-381 (37 kg/ha per cm and 3.48, respectively). In the first year, dwarf varieties Mott and Taiwan A-146 2.37 showed less RUE (0.89 and 0.84 g dry matter (DM)/MJ, respectively) than the elephant B (1.46 g DM/MJ). Higher non-fibre carbohydrate (NFC) contents were found in dwarf Mott under monocrop (180 g/kg) and in the intercrop systems. Tall varieties elephant B and IRI-381 showed greater efficiency in intercepting the radiation to accumulate herbage via stem accumulation. Dwarf Mott variety exhibited short stems and great leaf biomass accumulation that favoured denser canopies with higher content of NFCs in vegetal tissue. Planting butterfly pea into rows of elephant grass varieties can be adopted with no significant losses in RUE caused by light extinction, regardless of the grass stature.

The oat kernel, caryopsis or groat, is generally covered with fine silky hairs termed trichomes. The trichomes of naked oat are partly lost during threshing and handling of grains when the lemma and palea are removed and the surface of the grain is exposed. Trichomes can cause itchiness and more serious reactions in those handling the grains. Trichomes also accumulate and form fine dust and can block up machinery. Trichomes are clearly problematic and growers of naked oat are eager to have oat cultivars with reduced numbers of trichomes. Experiments compared the differences in trichome numbers of naked-oat cultivars and threshing settings. The cultivars differed considerably in pubescence. Cultivars Lisbeth and NK 00117 had most trichomes and cv. Bullion the fewest. Completely bare or polished grains were not observed. Pubescence was not associated with grain weight or test weight. However, grains from the lowermost spikelets of the panicle had fewer trichomes than those from the uppermost spikelets. For cv. Bullion, some threshing settings, including increased cylinder speed, slightly increased grain polishing such that grains had some areas completely free of trichomes. Reduction of the concave clearance in the combine harvester had a similar effect. However, threshing settings did not affect the trichomes of cv. Lisbeth. Adjusting threshing machinery settings was generally not an efficient means of solving the problems associated with naked-oat trichomes, but cultivar differences existed and further efforts in breeding to reduce trichome numbers are required.

Several plants are cultivated for medicinal and aromatic purposes. Foxglove (Digitalis lanata) has been introduced into India from Western Europe and is cultivated for medicinal use. The leaves of D. lanata contain various glycosides, namely digoxin, gitoxin and gitalin, which are of medicinal value. This crop is cultivated throughout the year but not much information is available about

seasonal influence on the glycoside content. Hence, attempts are made to assess the effect of seasonal variation on total glycoside content and to arrive at an optimum season for harvesting the crop.

The experiments reviewed in the preceding pages have been carried out on a light loam soil very poor in lime, in a district of medium rainfall (20–25 inches).

The chief conclusions drawn from the results are as follows:

1. Although the heaviest crops have been obtained with an annual application of dung, they are little heavier, and more costly to obtain, than the crops obtained with a biennial application of dung, especially if in the alternate year a light dressing of “artificials” including nitrate of soda be given.

2. A complete mixture of “artificials,” including nitrate of soda, has given good average crops, but not equal to those given by a biennial application of dung.

3. For the soil and other conditions of Garforth nitrate of soda is distinctly better for the hay crop than sulphate of ammonia. This is doubtless largely associated with the poverty of the soil in calcium carbonate.

Forty-eight sows were partially hysterectomized on day 10 (day 0 = 1st day of oestrus) of the oestrous cycle such that the isolated-contralateral ovary received either an ovarian or an ovarian and uterine blood supply. These two treatments were examined for their ability to affect corpora lutea (CL) function when 10, 20, 40 and 80 cm (12 sows/group) of the ipsilateral uterine horn remained intact. Sows with only 10 cm of uterine tissue failed to return to oestrus when observed until day 40. When 80 cm of uterine tissue remained, all the sows recycled between days 20 and 24. As the length of uterine horn increased from 10 to 80 cm the contralateral ovary became susceptible to luteolysis. At these lengths (20–40 cm), increased blood supply to the contralateral ovary afforded the luteal cells resistance to luteolysis (uterine length × blood supply interaction, P < 0·05). An additional four sows received 125I-labelled microspheres for purposes of determining CL blood flow following these alterations of blood supply to the isolated ovary. Blood flow to the CL was increased in three of the four sows when the isolated ovary received an additional uterine blood supply. Results from these experiments support the concept of an involvement of blood flow in the regulation of CL function.

Peking ducklings were classified at 6 weeks of age according to their body weights in two categories: R, below the overall mean of the flock which were considered as retarded growth; and L, those of body weight equal to the overall mean and above which were considered as large. From each group, males and females were chosen to be parents of the next generation in a ratio 1:5 at 6 months of age and four systems of matings were conducted: RR, LL, RL and LR.

At all ages studied the large ducklings were significantly heavier than retarded growth ones and had significantly greater body gain, during the two successive generations.

The RL and LR matings were heavier than the RR and LL groups at the different ages studied, indicating an effect of heterosis and that the retarded growth character is controlled by few pairs of genes. The differences due to mating systems were not significant either in body weight or body gain, except in body weight at 18 and 24 weeks and relative gain at 6 weeks of age in which the differences were significant (P <0·05) in the second generation.

The other environmental factors studied were sex, month of hatch and 6-week body weight.

Heritability estimates were 0·489, 0·509, 0·576, 0·346, 0·713, 0·809, 0·651 and 0·386 for body weight at hatch 4, 6, 8, 12, 16, 18 and 24 weeks of age, respectively, using the data which were adjusted for the effects of sex, month of hatch, 6-week body weight and mating system. The same estimates were 0·482, 0·554, 0·578, 0·352, 0·713, 0·808, 0·650 and 0·386, respectively, using the same data but adjusted for month of hatch and sex only.

Phenotypic and genetic correlations between body weights at different ages for the two sets of data were estimated. The phenotypic correlations were negative between body weight at hatch and each of the body weights at 16 and 18 weeks of age for the two corrected sets of data. The genetic correlations were negative between hatch weight and each of the other body weights for the two adjusted sets of data and between body weight at 4 weeks of age and each of the body weights at 16, 18 and 24 weeks only for the first set of data. Phenotypic and genetic correlations between the body weights in older birds were highly positive.

Three separate nitrogen balance experiments were made in three consecutive years. Comparisons of nitrogen retention were made between late-pregnant (15–20 weeks) Greyface (Border Leicester ♂χ Scottish Blackface ♀) ewes given a basal diet of hay and molassed sugar-beet pulp cubes (SBP, 1·25 em diameter x ca. 3cm length) and when given additional nitrogen supplied as urea contained in molassed sugar-beet pulp cubes (SBPU). Both sugar-beet pulp materials were adequately supplemented with minerals and vitamins. Supplementation with urea significantly increased nitrogen retention.

The deposition on soil of sulphur from the atmosphere through gaseous absorption, or particulate precipitation and deposition on vegetation and to other surfaces, is calculated to account for most of the atmospheric-S deposited in Britain; S collected in rainwater appears to amount to only one-sixth of the total deposition (Chamberlain, 1960). A knowledge of the amounts of S deposited is important agriculturally, particularly in areas far from industry, both where fertilizers are not used, and also when deciding how much fertilizer-S should be used relative to other nutrients. The technical problems of separating the amounts of sulphur deposited by gaseous absorption, particulate precipitation, and in rain are easier in a tropical climate which has well-defined wet and dry seasons and where atmospheric SO2 concentrations are smaller and vary less than in industrial areas.

A feeding and balance trial was conducted for 15 weeks on 25 lambs (aged 3–5 months) divided into five groups of 5 animals each on a basal ration consisting of oats, groundnut cake, barley, common salt, green grass and wheat straw. The five groups were fed a mineral supplement as follows:

Group I. Basal ration plus ‘Supermindiff’ mineral mixture (control group).

Group II. Basal ration plus calcined superphosphate.

Group III. Basal ration plus superphosphate.

Group IV. Basal ration plus superphosphate plus oral cobalt chloride (3 mg Co/10 kg body weight).

Group V. Basal ration plus superphosphate plus parenteral vitamin B12 (50 μg/week/ animal).

Calcination of fertilizer-grade superphosphate at 600°C for 2 h reduced the fluorine content from 23350ppm to 1600 ppm. The results show that high fluorine or superphosphate significantly reduced growth rate and retention of calcium and phosphorus and significantly increased blood inorganic phosphorus. Calcination of superphosphate in Group II gave comparable results to the control group (Group I). The oral Co or parenteral vitamin B12 supplementation (Groups IV and V) did not ameliorate the adverse effects of high fluorine in superphosphate.

It is concluded that calcination of superphosphate at 600°C for 2 h yields a suitable defluorinated product which can be used as a phosphorus supplement in the feeding of animals. Fertilizer-grade superphosphate is unsuitable due to its high fluorine content, the adverse effects of which are not mitigated by oral Co or parenteral vitamin B12 supplementation.

Experiments were conducted in association with farmers during 1977, 1978 and 1979 on a River Estate sandy loam at Valsayn and on a Cunupia clay loam at Piarco, Trinidad, to assess the relative importance of components in a set of practices for wetseason production of ‘yellow shell’ pods of ‘blackeye’ type of cow pea (Vigna unguiculata (L.) Walp.). Though the response of the cow pea growth, yield and seed quality characteristics were similar at both locations, crop performance was consistently better at Valsayn and was attributed to more favourable soil conditions and to a lower incidence of pests (mainly Ceratoma beetles), cow pea severe mosaic virus, and weeds. Overall, it was found that pest control was the most important management factor, accounting for a mean yield increase of 144%. The adoption of the improved cultivar, California Blackeye No. 5, increased yield by 77%. Other inputs resulting in significant yield increases were, in order of magnitude, weed control (40%), roguing of mosaic infected plants (37%) and high plant density of 110000 plants/ha (23%). A fertilizer treatment did not significantly increase yield. The results suggest that adoption of the insect control treatment by farmers in their cultivation of an improved cultivar sown at high plant density, the use of herbicide and roguing of mosaic infected plants have practical potential and would be economically justified for the production of high yields and good quality ‘yellow shell’ pods of vegetable cow pea for processing.