Between 1972 and 1976 a series of 15 trials was carried out at various climatically favoured sites throughout Scotland to assess the potential of new hybrid maize varieties of European origin under Scottish conditions. No meaningful differences were found between varieties in respect of dry-matter yield or maturity.

Seed rates ranged from 100 to 200 × 103 seeds/ha giving final stands from 40 to 194 × 103 plants/ha. Regression analyses for the variety Dekalb 202 included in 54 treatments indicated that the relationship between plant population density and dry-matter yield was partly linear with an important quadratic function, suggesting an optimum of 179 × 103 (± 80 × 103) plants/ha. Plant population density accounted for 65·9% (P < 0·01) of the variance in dry-matter yield but was not significantly related to dry-matter content.

Climatic variation between years had no overriding influence on growth and development. Dry-matter production for the variety Dekalb 202 sown in mid-May ranged from 2·86 (1972) to 14·54 t/ha (1975) with associated dry-matter contents of 15·1 and 24·1% respectively. In a few instances slightly higher dry-matter contents (maximum 28·6%) from mid-May sowings were associated with lower yields.

Neither date of sowing nor accumulated temperature to harvest measured as Ontario Heat Units was significantly related to yield but date of sowing accounted for 29·5% (P < 0·01) of the variance in dry-matter content. Accumulated Ontario Units at harvest were not significantly related to dry-matter content.

An interesting relationship between dry-matter yield and the date on which the crop had received 1379 Ontario Units was found. This relationship may be useful in selecting sites at which maize may be grown or to predict maximum potential final yield in any given season.

Three methods of controlling swede mildew were compared. Mildew infection was reduced by delayed sowing but yields from later sown plots were seriously reduced. Infection was reduced but not eliminated on resistant varieties. Highly effective chemical control was achieved with the fungicide Persulon, which showed both eradicant and protective properties. The yield differences between a genetically resistant and a susceptible variety were eliminated when Persulon was used.

A series of laboratory silages were prepared and opened after 2, 20, 60 and 150 days. The silages were made without any additive and with formaldehyde, formic acid, hexanoic acid, benzoic acid or sulphuric acid. The cellulose, hemicellulose, acetyl, alkali-labile phenolic acids and core lignin were determined in all silages as well as the composition of the hemicelluloses. In all the silages, the core lignin remained unchanged while the cellulose content only decreased by up to 5%. Large losses of acetyl residues and alkali-labile phenolic acids were observed in all the silages and losses of 10–20% of the hemicelluloses were found. The losses of hemicellulose were not uniform. The arabinose side chains were preferentially cleaved relative to the xylose residues. It was shown that part of the loss of carbohydrate could have been caused by the acidic conditions in the silage as well as by microbial activity. The silages made using the acidic additives with the highest pKa values lost the greatest proportion of carbohydrate. The implications of these results on rumen activity are discussed.

Origins of the monogerm character are described and a programme to produce a wide range of monogerm fully fertile lines is discussed. Back crossing to multigerms and hybridization among accessions of monogerm lines with relatively poor performance, together with selections from monogerm commercial varieties, provided sources from which improved lines were derived by recombination and selection. In the fifth year, experimental multiline varieties were synthesized which gave promising performance when evaluated in Institute trials at several locations in 2 years.

Diurnal variations in microbial protein nitrogen, total volatile fatty acids and ammonia were examined in two wethers fed once and twice daily with 0·4 kg of concentrateand 0·4 kg hay/day. The total protein nitrogen varied during the day from 76·9 to 130·2 mg/100 ml of rumen fluid. The greatest amount of protein nitrogen was noted immediately before feeding and the smallest 4 h after feeding. The protein nitrogen of rumen protozoa formed about 39·8–53·4% of total protein nitrogen in rumen fluid. Volatile fatty acids varied from 74·0 to 130·5 m-mol/1 of rumen fluid and ammonia from 187·0 to 305·6 mg/1. The higher concentration of total and protozoal protein nitrogen and of VFA was observed when animals were fed twice daily. The changing of feeding frequency from once to twice daily caused an increase of ammonia concentration in the rumen of only one wether. The results obtained are discussed.

During summer the morning (08.00 h) to afternoon (15.00 h) increases in rectal temperature, respiratory rate and pulse rate of free grazing Marwari and Magra sheep (rams) of the desert areas of north-western India were compared with those of Corriedale rams, which are being imported into India to improve the productivity of local stock through cross-breeding. Basal (morning) values for all three measurements were similar in the three breeds. While the afternoon values in respect of all three characters were significantly higher than the morning values in all the breeds, the increases were greatest in the Corriedales.

Dissection data for 1006 pig carcasses taken from the first 2 years of the Meat and Livestock Commission's (MLC) Commercial Pig Evaluation (CPE) were used to examine the relationships between carcass components and carcass weight over the growth period from 46 to 92 kg carcass weight. Alternative models were tested and parameters examined for different genotypes (pigs from different companies in CPE), sexes (barrows and gilts), feeding regimens (ad libitumand restricted feeding) and years.

Generally, linear allometry provided an acceptable description of carcass development, although some curvilinearity was indicated for the head, kidneys, rump back joint, M. psoas and total dissected lean. Growth coefficients conformed to the generally accepted pattern of carcass development in pigs. Using linear allometry, proportional weight increases were comparable for all genotypes and sexes, but dissected fat increased relatively faster on the restricted feeding regimen.

At a constant carcass weight of 66·5 kg, all tissue weights and the weights of primary components and most joints differed by genotype. The ratio of carcass lean weights for the two extreme genotypes was 1·04; comparable ratios for carcass fat weights were 1·13 (restricted-fed pigs) and 1·07 (ad libitum-fed pigs).

Significant differences were recorded between sexes and between feeding regimens, largely reflecting differences in fatness. Some important year differences were also found.

Field studies were made of tritiated water turnover, drinking water and dietary water intake throughout the year, in 212 animals of the following species: African buffalo, dromedary camel, zebu cow, eland, small East African goat, fringe-eared oryx, and Dorper sheep.

There were significant differences (P< 0·005) in the water drunk and water turnover between species and between seasons. Furthermore the species (or season) differences were also significantly different (P< 0·005) for each season (or species). The lowest turnover rates were found in oryx, then camel, sheep, goat, eland, cow and buffalo, when expressed in ml/l0·82/day, which was the appropriate metabolic unit for these species.

The restraints imposed by traditional African animal husbandry have drastically reduced the natural ability of eland to conserve body water but had much less effect on buffalo and oryx. The reason appears to be that eland is behaviourally adapted to a semi-arid environment, whereas a species like oryx is more physiologically adapted.

The results of observations begun in 1973 and of disease surveys carried out on winter oil-seed rape crops on ten farms in Hertfordshire and Bedfordshire between 1975 and 1978 are reported. The major diseases encountered in the surveys, namely downy mildew (Peronospora parasitica (FT.) Tull.), canker (Leptosphaeria maculans (Desm.) Ces. & de Not.), light leafspot or scorch (Pyrenopeziza brassicae Sutton & Rawlinson) and grey mould (Botrytis cinerea Fr.) are discussed in relation to diseases of rape grown elsewhere and the results of experiments on disease control reported. Symptoms of virus infection and root disease were rare.

Early (before stem extension) use of two applications of benomyl (1·2 kg a.i./ha) decreased the incidence and severity of light leaf spot and canker and increased yield by up to 33%. Benomyl plus thiram seed treatment (5 and l·5ga.i./kg) was less effective than a benomyl foliar spray. In field experiments differences in severity of light leaf spot and canker explained a substantial part of variation in yield but downy mildew did notaccount for further variation.

Dissection data for 1006 carcasses taken from the first 2 years of the Meat and Livestock Commission's (MLC) Commercial Pig Evaluation (CPE) were used to examine the growth of tissue weights in joints relative to the corresponding total tissue weight in carcass, and the growth of fat depots relative to total fat over the carcass weight range, 46–92 kg. Growth relationships were examined using a linear allometric model. Differences in tissue weight distribution between genotypes (pigs from different companies in CPE), sexes (barrows and gilts) and feeding regimens (restricted and ad libitum feeding) were examined at constant lean, bone or fat weight as appropriate, common allometric regression slopes being assumed.

Lean and bone showed the same pattern of development. Relative growth was lowest in the proximal limb joints (ham and hand) increasing inwards to the joints of the back. With minor differences, the same pattern was found for subcutaneous fat and intermuscular fat. Fat depots differed considerably in their growth relative to total fat: intermuscular fat grew more slowly (allometric growth coefficient, b = 0·87), subcutaneous fat at the same rate and perinephric and retroperitoneal fat (flare fat) more rapidly (b = 1·24).

Significant differences were recorded between genotypes in lean distribution and in the distribution of fat depots. However, the differences were small and of little commercial importance. There were also differences in fat partition between genotypes, flare fat being the most variable depot.

Sex and feeding regimen also influenced tissue distribution and fat partition.

The results are discussed in relation to the robustness of regression equations for predicting overall carcass composition from subcutaneous fat measurements and sample joint dissections.

This paper presents an iterative analysis of incomplete variety × environment tables. The analysis estimates potential differences in the sensitivity of varieties to environment effect. It is noted that the technique allows unequal weighting of data, and the special case of a complete table is discussed.

Four experiments were conducted to examine the extent to which some sampling procedures may bias the estimation of the nutritive value of herbage consumed by cattle which have been fistulated at the oesophagus.

In one experiment the nitrogen, sulphur and calcium contents (g/100 g organic matter (OM)) and organic matter digestibilities (OMD %) of 15 herbage samples were determined and compared with those of extrusa collectedfrom Hereford cattle fistulated at the oesophagus. The extrusa samples were analysed both as total extrusa, which included saliva, and as extrusa which had been squeezed through muslin and the solid and liquid fractions separated. The herbage samples covered a wide range of nutritive values (0·78–4·92 g N/lOOg OM; 0·08–0·27 g S/100 g OM; 0·17–1·43 g Ca/100 g OM and 34·4–85·7% OMD).

It was concluded that satisfactory estimates of nitrogen, sulphur and calcium contents and digestibility of herbage prehended by cattle can be made from oesophageal fistula extrusa and that the precisions of the estimates will not be increased if extrusa are separated into solid and liquid fractions immediately following collection. Corrections are not necessary for estimates of herbage sulphur, calcium and digestibility made from total extrusa but may be necessary for nitrogen values in excess of 2·74 g N/100 g OM. If extrusa are squeezed it is necessary to apply correction factors for nitrogen and sulphur but not calcium or digestibility.

In the other experiments three factors were examined in relation to the nitrogen content and digestibility of extrusa. They were the effects of (i) previous grazing experience of the pasture (ii) fasting for 0, 3, 6 and 23 h prior to sample collection and (iii) collection of extrusa during the morning or afternoon.

It was concluded that the lack of previous grazing experience of apasture or the length of a pre-collection fast up to 23 h will not significantly bias the estimation of the nutritive value of extrusa, but that it is preferable to collect extrusa samples from cattle in the morning and that sampling on rainy days should be avoided.

The time of parturition was recorded for 522 Friesian cows. Calvings were evenly distributed throughout the 24 hours with no bias towards day or night calving. Cows about to enter their third or subsequent lactation, but not younger cows, showed a significantly lower incidence of calving during the hours when milking was occurring. Possible mechanisms which would account for this rinding are discussed.

Experiments, conducted over 3 years, investigated the effect of all combinations of two storage periods at low temperature (0 or 2 °C) and two storage periods at 10 °C on the sprout growth, numbers of stems per tuber, foliage development and subsequent tuber yield of the two maincrop varieties Maris Piper and Désirée.

Although the number of day-degrees accumulated during sprouting was the same for all treatment combinations, there were large effects of treatments on the number of sproutlets per tuber and the total sprout length per tuber. However, there was no effect on the number of stems per tuber, foliage development or saleable ware yield inany year.

Because of environmental and economic constraints, we need to determine the effects of nitrogen fertilizer application on nutrient availability and fertilizer recovery, especially in regions of limited rainfall. This study was conducted to provide information on effects of N rate on yields and N recovery by standard and semi-dwarf spring wheats (Triticum aestivum L.) sown at two dates.

Ammonium nitrate was applied to spring wheat at rates up to 272 kg N/ha each year for 4 consecutive years. Only grain was removed from the plot at harvest. Wheat types did not differ in grain yields, but these yields were significantly reduced in 2 of 4 years by late sowing. Average grain yields for late sowing were greatest at 34 kg N/ha, but yields for early sowing approached maximum at the 68 kg N for semi-dwarf wheat and 136 kg N/ha for the standard wheat.

Semi-dwarf wheat was lower than standard wheat in grain and flour protein concentration and baking absorption. Late sowing (May 30) reduced test weights, flour yield and baking absorption, but increased wheat protein concentration as compared with early sowing (April 30). Leaching of fertilizer N below the 90 cm depth ranged from 152 to 378 kg/ha at the 272 kg N/ha/year rate, and was greater for the late than for the early sowing. Fertilizer N that could be accounted for averaged 87 and 82% for early and late seeding respectively. Water-use efficiency was reduced by late sowing.Soil-water extraction by wheat to the 120 cm depth was greater for high N rates.

These 4-year results showed that semi-dwarf and standard wheats had only slight differences in total grain production. Also, for efficient use of applied fertilizer and available soil water, wheat should be sown in the spring as soon as soil and weather conditions permit.

Growth and nitrogen fixation of three cultivars of Phaseolus vulgaris L., inoculated with strain CIAT 161 of R. phaseoli, were compared at day-night temperatures of 36–25, 30–20 and 26–15 °C.

Temperature affected the duration and magnitude of N2 (C2H2) fixation. Maximum fixation increased from 33·8 μmol C2H4 produced/plant/h at 35–25 °C to 73·0 μmol C2H4 produced/plant/h at 25–15 °C, but the peak in fixation was increasingly delayed as growth temperature was reduced. In the 25–15 °C treatment this delay in the onset of fixation led to decreasing leaf nitrogen concentrations and visible N-deficiency symptoms at the 28 day harvest.

Varietal differences in response to temperature were not marked, though one cultivar achieved greater nodule development at 35–25 °C than the others. This earlyflowering cultivar again appeared weak in N2 (C2H2) fixation with low specific nodule activity at all temperatures studied.

Results are related to bean production in Latin America, and to the possible need for ‘starter’ nitrogen in the cooler bean-producing regions.

Two field experiments with cotton were conducted over two growing seasons on calcareous, heavy to medium textured, alluvial soils, to study the influence of N and P fertilizer rates, the method of fertilizer placement and the time of N fertilizer application on cotton yield, product quality and fertilizer utilization.

Nitrogen application up to 50 kg/ha in the first experiment and up to 120 kg/ha in the second experiment increased seed cotton yield; higher nitrogen rates in the first experiment had an adverse effect on seed production due to abnormal rainfall which caused an intense vegetative growth and delayed the time of maturity.

Split application of N at sowing and at early flowering was slightly superior to a single application at sowing or to split applications at sowing, early flowering and initiation of fruiting. Addition of nitrogen during the flowering stage failed to influence cotton production significantly.

Banding P and N fertilizers increased plant height significantly, compared with the broadcasting method; placement methods, however, did not significantly affect seed yield.

Increasing amounts of N and P fertilizers had essentially no effect on lint quality.

The phosphate concentrations in the tops derived from fertilizer phosphate, were low ranging from 1–2 to 2–4 % of the P concentration in the tops and it was not affected by the different treatments.

The utilization coefficients of the nitrogen fertilizer sources by cotton were high, nitrate N being utilized much more efficiently than ammonium N.

A laboratory incubation study followed by a field experiment was made in a silty clay loam soil (pH 6·9) at Pantnagar, India, on the effectiveness of ordinary urea, coated urea (sulphur and shellac-coated), urea-isobutyraldehyde condensation product (isobutylidenediurea, IBDU) and urea blended with nitrification inhibitor AM (2- amino-4 chloro-6-methylpyrimidine) and neem (a non-edible oil seed obtained from Azadirachta indica) cake. Whereas untreated urea and IBDU hydrolysed rapidly leaving no trace of urea-N after 2 weeks, sulphur-coated urea mineralized quite slowly and retained urea-N for as long as 4 weeks after incubation. Urea blended with neem cake was intermediate. Of all the materials tested, sulphur-coated urea showed maximum nitrification inhibition. A combination of one third sulphur-coated urea at planting + two thirds ordinary urea 30 days later yielded 12·3% more maize grain than ordinary urea in the same proportion at the same times of application.

The effect of a gradual increase in dry-matter concentration from 140 g/kg (LD diets) to a maximum of 215 g/kg (HD diets), and the effect of an increase in fat concentration from 225 g/kg D.M. and reduction in protein concentration from 298 g/kg D.M. (LF diets) to 254g fat and 211g protein/kg D.M. respectively (HF diets) was examined with 32 Friesian bull calves in a 2 × 2 factorial experiment. Milk substitutes were offered ad libitum in two feeds daily from 2 days of age. The dietary changes were first introduced at 7 weeks of age and differences became progressively greater as further changes were made at 9, 11 and 13 weeks. The calves were slaughtered at 16 weeks of age.

Dry-matter intake for calves given the HD diets increased faster with age after 7 weeks than that for calves given the LD diets. For the period 7–16 weeks, calves given the HD diets consumed 17% more D.M. than those given the LD diets and had a 13% greater rate of live-weight gain (1·57 v. 1·39 kg/day), although most of the increase in weight gain occurred between 9 and 13 weeks of age.

There was no significant effect on D.M. intake or on live-weight gain of altering the fat and protein concentrations in the milk substitute, although feed conversion ratio (kg D.M. intake/kg weight gain) was higher for the HF than for the LF diets. Apparent digestibility of D.M., crude protein and fat were reduced with the HF diets, but the efficiency of retention of the digested nitrogen was improved. During the second and third weeks of life, D.M. intake reached a peak at approximately 67 g/kg0·75 and subsequently declined to stabilize at about 56 g/kg0·75. However, a gradual increase in concentration of the milk substitute from 140 to 215 g D.M./kg increased intake to about 62 g D.M./kg0·75. The results clearly indicate that, at a dietary concentration of 140 g D.M./kg, maximum D.M. intake cannot be achieved because the volume of fluid that needs to be ingested exceeds the capacity of the digestive system. In contrast, at reconstitution rates increasing from 140 to 215 g D.M./kg, distension of the stomach becomes less important and physiological and metabolic factors seem to assume a greater role in the control of feed intake.

The Rothamsted ley–arable experiments were on two fields with similar soils but with contrasting previous cropping: old grass on Highfield, old arable on Fosters field. Damage by take-all (Qaeumannomyces graminis var. tritici) occurred sooner in successive wheat crops grown after a lucerne ley and arable sequence (LU) than after a grass-clover ley and arable sequence (LC). On Highfield the difference was consistent and large, it occurred as soon as a second wheat crop was grown and resulted in wheat yielding 1 t/ha less after the LU than after the LC sequence. This difference did not persist in the next wheat crop where take-all was prevalent after both sequences. On Fosters field take-all developed more slowly and differences between sequences were mostly smaller.

Wheat seedling bio-assay of soil cores from the LU and LC sequences showed that little take-all fungus persisted through the leys and that soils were much infested after a first wheat crop in the LU sequence on Highfield, but not in the LC sequence on Highfield or in either sequence on Fosters field. Microscopic examination of roots from assay seedlings and from field plants showed that Phialophora radicicola var. graminicola (PRG) was most common in soils where take-all developed slowly, but our results did not show if this was a causal relationship. The occurrence of much PRG in the LU sequence on Fosters conflicts with previous reports which associate large populations of this fungus only with grassland soils.