Two experiments compared yields of spring barley following barley, oats, beans (Vicia faba), red clover (cut) and (one experiment only) oil-seed rape, and tested effects of trefoil (Medicago lupulina) undersown in the preliminary crops of barley and oats. N fertilizer was applied at two rates to preliminary crops, and four rates to the final crop in each experiment. Barley following barley suffered severely from take-all disease (Gaeumannomyces graminis var. tritici); barley after other crops was little affected. Other recognized soil-borne diseases were unimportant. Barley yielded less after barley than after other crops except where excessive N fertilizer caused lodging. Clover and beans left N residues equivalent to about 88 and 44 kg fertilizer N/ha respectively; undersown trefoil left inconsistent N residues. Couchgrass (Agropyron repens) was more prevalent after barley than after other crops.

Four experiments with 133 piglets of between 21 and 55 days of age were used to examine, by slaughter and chemical analysis, the composition of the body of young pigs. Following removal from the sow, the lipid content of the empty body decreased from about 15 to 7·6%, and in the subsequent 4 weeks had recovered only slightly to between 7·7 and 10·9%; with the exception of pigs with a particularly high intake of energy whose 42-day lipid content had increased to 13·2%. Where Y3 was the lipid gain, X1 the digestible energy intake (MJ) and X2 the ratio of digestible energy to digestible crude protein (g), over all experiments Y3 = 7·83X1 + 4945X2−1260. There was little change in the protein content of pigs consequent upon the effects of either removal from the sow, pig age, diet type or nutrient intake. Over all experiments and slaughter weights; P = 0·164W−100, where P was the protein content of the body (g) and W the empty body weight (g). The efficiencies of conversion of digestible energy to energy gain in body protein and lipid were 0·36 and 0·33 respectively, associated with a constant (daily maintenance) term of 0·462 MJ ME/kg LW0·75. The low value for lipid is as would be expected for animals catabolizing lipid within the experimental period.

Results are described of an experiment made at the Indian Agricultural Research Institute, New Delhi, for 4 years under semi-arid seasonally dry tropical conditions to explore the possibilities of double cropping in the traditionally monocropped areas. Use of straw mulch did not increase mung yield in the monsoon season with welldistributed rainfall but increased its yield in a year when the monsoon receded early. Irrespective of rainfall pattern, mulching helped conserve enough moisture in the top 30 cm of soil to enable germination and quick establishment of the rapeseed crop. Mulching continued in the rapeseed crop conserved soil moisture until the flowering stage and increased the yield of rapeseed by 23%. Kaolin, a reflectant material applied at the preflowering stage, also increased seed yield of rapeseed.

During the early period of infestation of winter rape, pollen beetles and seed weevils were mainly feeding and attaining sexual maturity. Before a crop flowered pollen beetles fed on buds but only some of those which they had perforated to obtain pollen dropped off. When flowering started adults obtained pollen from flowers rather than from buds. They laid their eggs in the buds but not in the flowers. Larvae moved from flower to flower up the raceme and caused no damage. Probably many podless stalks have been wrongly attributed to pollen beetle damage.

Overwintered seed weevils caused no damage by feeding on rape pods. New generation seed weevils caused some loss of seed weight and viability when feeding on pods of spring rape; this is probably unimportant on a field scale.

Pollen beetles and seed weevils mated from mid-May until the emergence of new generation adults; these did not mate before hibernating.

A field experiment testing the effects of potassium and magnesium sulphates applied from 1960 to 1967 and sodium chloride applied in 1966 and 1967 on a range of crops (Bolton & Penny, 1968) was sown with ryegrass in 1967. Only basal N and P was given to all plots until 1971 when basal K was also applied. The experiment terminated in autumn 1974.

Grass yields were increased by K residues for 3·5 years but overall yields became small due to K deficiency. After giving basal K, residual K no longer increased yields but did slightly increase % K in the grass until the end of the experiment. Some residual K from the 1960–7 dressings was found in the sandy loam soil after the final harvest.

Magnesium fertilizer residues slightly increased grass yields in the 1967–70 period but not later. However, % Mg in the grass dry matter was increased by the residues for the whole 7·5 year period. Exchangeable Mg was also increased in soil sampled after the final harvest, especially in the 23–46 cm subsoil.

Sodium fertilizer residues increased grass yields until the basal K was applied, especially on plots without added K. Significant increases in % Na in the grass and Na uptakes were detectable in all years, i.e. up to 7·5 years after the last Na application. This finding is contrary to most accepted views on the longevity of Na fertilizer effects and could be important in areas where sodium deficiencies in cattle and sheep occur.

Increases in % Cl in the grass from the sodium chloride were only detectable in the first two cuts in the year following the final application.

Mature plant characters and yield components were measured on a two-row (Proctor) and a six-row (Clermont) spring barley variety, the F1 of the cross between them, and the first back-cross to each parent.

Whereas shoot dry weight in the F1 significantly exceeded the mid-parental value, and chaff dry weight, stem length and weight per grain showed positive heterosis, grain yield did not exceed the mid-parental value and number of grains per plant showed negative heterosis.

A scaling test showed that an additive-dominance model fitted the data in all cases except possibly for dry weight per grain, where the χ2 test approached significance.

The partial dominance of the two-row allele (V) for grains set per rachis node exhibited in the mature ears of the F1 was not apparent at anthesis when all the lateral florets were found to have large, apparently normal stamens. However, the ratio of median to lateral grains set over all main shoot ears of the F1 was 1:0·21 with an average of six lateral grains per ear.

The results presented indicate that the factors determining total dry-matter production and grain yield are inherited in such a way that the restriction upon grain yield in the F1 is due not to a deficiency of dry matter but to a limited capacity of the plant to store dry matter in the form of grain. This may indicate some developmental interdependence in the expression of yield component characters.

Leaf and tiller production, ear development and ear growth were measured on a two-row and a six-row spring barley genotype, on the F1 between them and on the first backcrosses.

Among the developmental differences between the parental genotypes the following appeared to be of particular significance: the two-row genotype bore more leaves on the main shoot than the six-row genotype and these were initiated more slowly, but emerged more rapidly; the two-row genotype had a proportionately longer ear initiation phase than the six-row; the apical dome was bigger in the six-row than in t he tworow; the two-row genotype produced more tillers.

The association of characteristics with ear type may depend on a pleiotropic effect of the ear type (V – v) locus or, alternatively, some of these characteristics may be under independent genetic control. The latter hypothesis was supported by the developmental pattern of the F1.

It may be that well-adapted two-row and six-row genotypes have patterns of development balanced for the particular ear type. Hybridization between ear types may disrupt these balanced developmental patterns producing a high frequency of poorly adapted genotypes in the progeny.

Silages were made from lucerne using either a flail or a precision-chop harvester without additive, with 8 1 formaldehyde (35% w/w/)/t or with 1·5, 3·0 or 6·01 formic acid (85% w/w)/t. The silages were deep frozen and later offered to young sheep with and without intraperitoneal injections of DL-methionine. Fresh lucerne, cut with both machines from the same crop, was deep frozen and offered to sheep with and without methionine injections in a separate experiment.

The untreated silages were characterized by extensive protein degradation, high contents of ammonia and acetic acid and low contents of lactic acid. Formaldehyde markedly reduced protein degradation and carbohydrate fermentation in the silo and caused a large reduction in nitrogen digestibility; these effects were of greater magnitude with precision-chopped than with flail-harvested silage. Voluntary intake and nitrogen retention were increased by formaldehyde application.

Increased rate of addition of formic acid reduced the overall extent of carbohydrate fermentation, decreased the proportion of fermentation products Which could be attributed to clostridial activity, and decreased protein degradation, though not by the same extent as did formaldehyde. With the precision-chop harvester, formic acid addition increased both voluntary intake and nitrogen retention. Intakes were low on the three flail-harvested silages made with formic acid, as these were heavily contaminated with soil. However, the additive improved nitrogen utilization and within this group of treatments intake increased with increasing rate of formic acid application. The increases in nitrogen retention with additive treatment resulted from increases in the quantity of nitrogen truly retained per unit of nitrogen intake as well as from increases in intake.

Methionine supplementation had no effect on voluntary intake, but caused a small and consistent improvement in nitrogen utilization except with the soil-contaminated silages. There was no effect of methionine supplementation on utilization of nitrogen in the fresh lucerne.

Voluntary intake, apparent biological value and nitrogen retention all decreased linearly with increasing protein degradation and formation of acetic acid and ammonia. Separate regression equations were calculated for the prediction of organic-matter intake for silages made with the two types of harvester. These were parallel, but with intakes from the precision-chopped silages higher by ca. 20 g D.M./kg W0·75 per day. Precision chopping produced a similar advantage with the fresh lucerne. Data from silages made by the two harvesting methods fitted the same regressions for nitrogen retention, which decreased by 0·3 g/day for each 1% increase in ammonia-N (% total N). It was deduced that to produce silage with high nutritive value it is particularly important that the degradation of amino acids by proteolytic clostridia is prevented; restriction of the degradation in the silo of true protein to amino acids is apparently less important.

The protein contents of plants decline with increasing size and age even when the plants are adequately supplied with nitrogen. The quantitative nature of this decline needs to be defined for use in models for nitrogen response and to improve diagnostic criteria for detecting nitrogen deficiency. For this reason we have considered the use of photosynthate for the synthesis of the organic constituents within a plant and for maintenance purposes. It has led us to deduce that

In (P/P0) = (δβ/a) In (F/F0) – βMG(T–T0),

which in the special case of exponential growth approximates to

In (P/P0) = (δβ/a) In (F/F0),

where P is the critical protein content at time T, F is the total weight of nitrogen-free organic matter at time T, P0 and F0 are the corresponding weights at some initial time T0; δ is a coefficient related to the relative rates of production of protein and the nitrogenfree constituents of plants. β and α. are energy coefficients for the conversion of glucose into protein and nitrogen-free organic matter and MGis the maintenance respiration rate in g of glucose/g of protein/day.

The values for β and α depend on the chemical composition of the crops but for forage crops appear to be about 0·62 and 0·76 respectively over a wide range of temperatures. MG is temperature dependent and experimental evidence suggests that it is about 20 mg of glucose/g of protein/day at 15 °C. Less information is available about δ although when there are ample supplies of nitrogen it is probably near unity.

A seedling test for measuring cold hardiness in Lolium perenne cultivars is described. Seedling performances of the cultivars in this test were closely related to those of mature plants in an artificial freezing test and to reported survival under field conditions in U.K. winters.

With two-leaf seedlings it was possible to analyse hardiness into leaf damage, regrowth and plant kill enabling an index of hardiness to be compounded. Using this index in conjunction with lethal dose 50% estimates, meaningful separation of cultivars was possible.

The possible application of this technique for screening breeding material and for detailed physiological work is discussed.

Lucerne was made into ten silages using either a flail or a precision-chop harvester with application of formaldehyde or a range of rates of formic acid during harvesting. Amino-acid analyses were done on the silages and on samples taken from the herbage at ensiling.

In excess of 70% of aspartic acid, serine, glutamic acid, tyrosine, threonine, lysine, histidine and arginine were destroyed in untreated silages when a flail harvester was used and in excess of 50% when a precision-chop harvester was used. Glycine, leucine, iso-leucine, valine and methionine showed little change, with net losses or increases of up to 10%, whilst proline, cystine + cysteine and phenylalanine were intermediate between these two categories. Net synthesis of alanine and α and γ amino-butyric acids occurred in the untreated silages. Increasing rates of formic acid addition, and the use of the precision-chop harvester, reduced the loss of the amino acids which were extensively degraded in the untreated silages and minimized the increases in alanine and α and γ amino-butyric acids. Formaldehyde treatment also reduced amino-acid degradation, apart from apparently high losses of lysine, histidine and tyrosine. It was concluded, however, that these losses arose through problems of estimation in formaldehyde-treated silages following HCl hydrolysis.

It is suggested that the most probable precursors for alanine and α and γ aminobutyric acids were respectively aspartic acid, threonine and glutamic acid. Voluntary intake and the utilization of silage nitrogen by young sheep were related to the net changes in amino acids involved in decarboxylation reactions, the best measures of this being the interconversions involving the formation of alanine and α and γ aminobutyric acids. Deamination reactions appeared to be of much less importance in limiting silage nutritive value than those involving decarboxylation.

A theoretical model for the influence of plant size and age on plant protein content was tested against the results of 13 field experiments on vegetable crops grown with high rates of application of N, P and K fertilizers.

For each crop the protein contents of individual plants of similar age (but of different sizes) harvested at regular intervals during growth were found to bear a linear ln-ln relationship to their contents of nitrogen-free organic matter. The slopes of the lines of best fit were almost the same at each harvest date. The intercepts were similar irrespective of harvest date when growth was exponential but showed an approximately linear decline with length of growing period when it was not. These features are in agreement with the theory.

Maintenance respiration rates were deduced by interpreting the data in terms of the theoretical model. The values determined in this way were between 8 and 21 mg of glucose/g of protein/day for the above ground parts of the plant compared with values of between 8 and 87 mg that have been obtained by entirely different methods.

It is concluded that during the exponential phase of growth the critical protein and, thus, nitrogen contents depend primarily on plant size and on the chemical composition of the nitrogen-free organic matter, but that when growth is not exponential plant age and maintenance respiration are also of importance. The models should facilitate the determination of the critical nitrogen contents for crops grown under different conditions.

Seeds from individual heads of wild safflower (Carihamus oxyacantha Bieb.) plants collected from five locations were used in this study. Locations were situated on a roughly east-west transect passing through Shiraz, Iran. The western locations were cooler with higher annual rainfall than the eastern sites. Wild safflower plants of different locations produced about an average of 150 heads per plant, but only 60% of them contained seeds. Frequency distributions constructed for number of seeds per head, germination percentage, and seedling length showed trends of change in the skewness of the distribution for the latter two characteristics parallel to the environmental selective pressure, i.e. the skewness was towards the left for eastern locations but it gradually moved to the right for western ones. Striking amounts of polymorphism were also observed for these characters. A very high proportion of total variance was concerned with differences between heads of the same plant for number of seeds, germination ercentage, and seedling length. Very little variability was found among plants of the same ecotype.

Heifers and suckled cows in 34 herds were included in a field trial using prostaglandin F2α (PGF2α) to control ovulation. Oestrus was induced by two intramuscular injections of PGF2α 10–12 days apart in 592 animals. Of these, 264 were inseminated once at 80 h and 328 were inseminated twice, at 70 and 88 h, after the second injection of PGF2α. Pregnanoy was confirmed by palpation or by calving without further insemination. After adjustment for independent sources of variation in fertility, estimated true pregnancy rates were 59·6 ± 3·0% for cattle inseminated once, and 61·3 ± 2·7% for those inseminated twice at one oestrus, compared with 66·4 ± 3·2% for 220 animals allowed to cycle normally in the same herds (controls).

In a sub-sample of 538 animals, semen usage was 15% higher for the treated group inseminated once and 107% higher for the group inseminated twice, than for the controls. The breeding season extended over about 80 days for the control groups, and about 30 days for the treated groups.

No side effects attributable to prostaglandin were observed among the treated cattle.

Mature cyclic ewes were treated intravaginally with sponges impregnated with 30 mg SC-9880 (G. D. Searle) or intramuscularly with 100 μg Cloprostenol (I.C.I. 80, 996) and examined subsequently for oestrus, ovulation and fertilization. At 70 h after the end of treatment, 90% of ewes treated with SC-9880 and 45% of those treated with Cloprostenol had ovulated. Of ewes yielding eggs at 100 h a significantly higher proportion of SC-9880 treated sheep showed evidence of fertilization (69% v. 7%).

Milled barley straw, either untreated or treated with 70 g of NaOH/kg straw was supplemented with four levels of urea, namely 0, 6, 12 or 18 g/kg and fed ad libitum to young sheep. For the untreated straw, dry-matter intakes were (g/day) 423, 451, 441 and 463, while the digestibility of organic matter was 458, 467, 490 and 483 g/kg, respectively. For the treated straw, the intakes of dry matter were 355, 402, 531 and 567 g/day and the digestibility of organic matter was 423, 480, 589 and 628 g/kg respectively.

The different responses to urea supplementation of treated and untreated straw are discussed in relation to a new system of estimating protein requirements for ruminants put forward by the Agricultural Research Council.

Crop yield results from three long-term drainage experiments are analysed and show that increases of up to 1 t/ha of winter wheat can be attributed to the effect of drainage. Mole drainage is clearly the preferred treatment on heavy clay soils. There is also a suggestion that drainage permits more efficient utilization of nitrogen.

Gibberellic acid (GA3); monophenols, salicylic acid (SA) and β-naphthol (β-N); diphenols, catechol (CT) and resorcinol (Res); and polyphenols, chlorogenic acid (CA) and tannic acid (TA) hastened the emergence of ears and increased the numbers of branches and ears, number of seeds, seed weight and the 1000-seed weight in cheena millet (Panicum miliaceum L.). The results show that the action of phenolic compounds is not related to their structural configuration as is considered by some workers.

Diploid and tetraploid perennial ryegrass (Lolium perenne L.) cultivars were compared sown alone and in mixtures, with and without cattle treading for 4 years after the year of sowing. Data were also obtained on the survival of tetraploid ryegrass in mixtures under farm conditions.

The overall effect of treading was not large but annual yield of dry matter was reduced by cattle treading every year (mean 9%). Sheep grazing and treading also reduced yield below that of cut plots. The reduction depended on the sampling date and varied from 40% to nil. In two instances treading increased yield.

Interactions between cultivars/mixtures and treading occurred in 22% of the occasions when treading influenced yield. In the first harvest year the tetraploid Reveille was more resistant to treading than the diploid S. 24. In older swards (3rd and 4th harvest year) the situation was reversed. The occurrence of cultivar/mixtures × treading interactions and the effect of mixing diploid and tetraploid ryegrass on resistance to treading were unpredictable.

The evidence from the main trial and the farm survey showed that tetraploid ryegrass could persist for at least 3 years after the seeding year when exposed to periods of high stock density. In addition, in mixtures there was no initial domination of the sward by either component when cut or when subjected to severe treading. In the third harvest year of the experiment the proportion of tetraploid ryegrass decreased considerably. Total yield of the mixtures was not significantly different from that of pure swards of the components though seasonal distribution of yield could be modified. The contribution of tetraploid ryegrass to swards up to 4 years old was in proportion to the percentage of tetraploid in the seeds mixture. Evidence from both the experiment and farm survey demonstrates that it is possible to exploit advantages claimed for tetraploids in mixtures for three harvest years without detrimental effect on sward performance.

Seven experiments carried out over 3 years investigated the effects of the date of defoliation of the seed crop and the storage temperature of the seed on subsequent sprout growth.

The time of defoliation of the seed crop had a small, variable effect on the number of sprouts but with all varieties in every year, early defoliation gave the greatest total sprout length. The effect of later defoliation on sprout length varied according to the variety and the year. Most of the variation in total sprout length per tuber appeared to be attributable to differences in the date of dormancy break of the seed tuber.

Storage throughout the winter at 15 °C gave fewer sprouts but a greater total sprout length per tuber than storage at 9 °C. A linear relationship between total sprout length per tuber and accumulated day degrees above 0 °C from dormancy break accounted for most of the variation in sprout length occurring in Désirée, Pentland Crown and Majestic as a result of storage at 9 °C and 15 °C for different periods of time.