An experiment is described in which plots of a silt loam soil were compacted by ploughing and rotary cultivation when the moisture content was high. Kale and barley were grown on these plots in 2 years.

Compaction of the soil was not as great as anticipated, but there were marked reductions due to wet cultivation in the dry-matter yield of kale and the vegetative growth of the young barley. Seed yield of barley was relatively unaffected, although there was a significant reduction due to wet ploughing in one year.

The implication of these results for experimentation on the effects of soil structure on crop yield are discussed.

Four swede varieties and their six F1 hybrids were grown for 2 years in plots varying in pH from 4·2 to 8·4. Yields were highest at intermediate pH's and the average yield of the hybrids was greater than that of the parents. The plants on the low pH plots (4·2, 4·6, 4·7) were less infected with mildew than those at high pH (6·7, 7·7, 8·4). There was no marked resistance to mildew amongst the varieties. The response by the parents and hybrids was assessed by regression analysis and showed that the variety Reform was most reactive and Harvester most stable. Stability patterns appeared to be inherited. Inheritance patterns for yield and number of leaves were determined. It was concluded that selection for better swedes should be carried out in environments other than those to which the crop is currently restricted.

Two experiments were made to measure the dry-matter intake of grazing sheep. Three groups of five ewes grazed three plots of young barley. The mean daily drymatter intake per ewe from each group was estimated from the water turnover which was measured by the tritium dilution technique. The mean intake was also estimated by the double sampling technique for measuring standing crops. The mean estimate of one technique was within the standard deviation of the mean estimate of the other. The difference between the mean estimates from each technique did not exceed 18 %. It is concluded that water turnover could be useful for the measurement of the intakes of animals grazing green pastures.

An experiment was designed to assess the effect of thermal stress and protein value of the diet on the productivity and some of the blood organic constituents of lactating Holstein cows. Two groups of eight animals each were used in 2 × 2 Latin-square designs with two experimental diets. The percentage of crude protein in the diets was 14.3 and 20.8 %.

Rectal temperature and respiration rate were recorded twice weekly and jugular blood samples were collected at weekly intervals for analysis. Daily feed intake, refusals and milk production per cow were recorded. Representative samples of morning and afternoon milk were taken three times a week for chemical analysis.

Data on respiration rate and rectal temperature suggested that both groups of animals were under thermal stress. However, significantly lower values were found by increasing the protein level of the diet. The higher level of protein significantly increased total milk production, 4 % fat-corrected milk (4 % FCM), total solids, solidsnot-fat, protein percentage and yield, casein and non-protein-nitrogen in milk. The increase in milk production and 4 % FCM was found to be associated with the increase in total feed and total-digestible-nutrients intake but not with crude-protein intake. Protein levels in the diet had no effect on fat percentage and yield nor on whey protein.

The correlation coefficients between respiration rate and rectal temperature with some of the blood organic constituents suggested an inverse relation between thermal stress and the blood organic constituents. The higher level of protein in the diet significantly increased haemoglobin levels but had no effect on oxyhaemoglobin, haemoglobin:oxyhaemoglobin ratio and haematocrit value. Total serum protein was not affected by thermal stress or by the protein value of the diet. Increasing protein levels in the diet increased albumin but decreased the globulin fraction of serum protein. Plasma glucose and non-protein nitrogen were increased by increasing the protein in the diet.

Cowpea and hyacinth bean nodulated and grew well at 11–14 h and poorly at 8 h light duration. Nodulation and plant growth increased with increase in light intensity from 1·4 to 17·1 W/m2 but the natural light intensity (228·3 W/m2) inhibited nodulation in July and plant growth in December.

Nodulation and growth of both crops were best at ‘moderate’ temperature and cowpea tolerated ‘warm’ more than ‘cool’ temperatures whereas hyacinth bean showed the reverse situation.

Inoculation improved nodulation of cowpea but not hyacinth bean. Application of nitrogen did not improve the growth of plants affected by light and temperature.

A comparison of ammonium sulphate (AS) with and without N-Serve and sulphurcoated urea (SCU) as N sources for sugarcane, studied in a pot experiment, showed that although the tillering, the leaf N concentration and cane yield were increased by adding fertilizer N there were no significant differences between N sources. However, AS and AS + N-Serve depressed the soil pH, especially that of acidic soils, much more than SCU. In a field experiment where AS, urea and SCU were compared on a calcareous soil, it was observed that urea gave significantly lower cane and sucrose yields than AS and SCU when N was applied on the surface, possibly due to greater volatiliization losses from urea. Subsurface application increased the efficiency of urea, although the method of placement had no significant effect on the N efficiency of AS and SCU. AS was as effective as SCU. Thus the coating of urea by sulphur increased its efficiency for sugarcane only when applied on the surface of a calcareous soil.

Five groups of four 8-week-old Blackface lambs were used to compare the effects of dietary deficiencies of calcium and/or phosphorus: four were given for 16 weeks a semi-purified diet low in Ca (0·07 %) and P (0·13 %), either unsupplemented (LCaLP) or supplemented with 0·3 % Ca (NCaLP), 0·3 % P (LCaNP) or both (NCaNP), and the remaining group was slaughtered initially.

The only clinical abnormality observed was twisting of the forelegs in group LCaLP. Food intake was depressed by 26 % in LCaNP group, by 41·5 % in NCaLP group but was largely unaffected in group LCaLP. Apparent D.M. digestibility was lower for group NCaLP (57·7 %) than for other groups (61·2 %). Differences in live weight and body fat reflected the differences in food intake between treatments but the weights of fat-free body components were lowest in the groups given low P diets.

The LCaNP diet decreased plasma Ca and increased plasma P but the NCaLP diet had the opposite effects. The LCaLP diet had no effect on plasma Ca and decreased plasma P less than the NCaLP diot.

The three mineral deficient diets caused equally marked decreases in Ca and P retention but did not induce negative balances; they also impaired the quality of bone in the tibia and lumbar vertebra, by reducing both the amount of bone matrix and the degree to which it was mineralized, and produced histological lesions of rickets and osteoporosis. Diets low in P caused a marked fall in Mg content of the skeleton.

Urolithiasis was common in lambs given diets adequate in P.

The fraction (f) of surface-applied nitrate leached below any depth h cm in a uniform soil profile may be calculated from the equation

where P is the quantity of water draining through the soil (in cm) and Vm is the percentage volumetric field capacity. The fraction of nitrate retained is then (1—f).

This equation has been tested using published data. Values of h corresponding to the mean displacement (f = 0·5) were calculated for a wide range of soil and weather conditions and the results compared with mean displacements measured in the field. Similar comparisons were made with the leaching equation of Rousselle (1913) and Levin (1964). The new equation gives good agreement with the observed data, whereas the Rousselle-Levin equation generally overestimates the mean displacement of nitrate. Methods of applying the equations to field situations are discussed.

Results are presented from four experiments in which comparisons were made between isogenic sterile and fertile plants of maize to study the effects of grain content on yield and quality of shoot dry matter. In two experiments comparisons were made over a range of densities, extending from 5 to 25 plants/m2 in 1972 and 5 to 20 plants/m2 in 1973. The other two experiments, grown in 1974 at a density of 10 plants/m2, were sampled 30, 60 and 90 days after flowering.

In 1972 and 1973 yield of shoot dry material was about 10% higher in fertile plants at the lowest density, 5 plants/m2, but grain formation had a negligible effect at higher densities. In 1974, at 10 plants/m2, the yield advantage for fertile plants was 6–7%. These results are in line with other European data, but show a much smaller effect of grain formation on shoot dry matter yield than is normally recorded in USA trials. The discrepancies probably reflect differences in environmental conditions.

Absence of grain had little effect on contents of nitrogen, ash and in vitro digestible dry matter, and increased content of pepsin soluble material and hot water soluble carbohydrates. Percentage content of dry matter in the shoot was higher in fertile plants in 1973, and during the later stages of crop development in 1974.

The results suggest that the importance attached to high grain content as an essential requirement for yield and quality in forage maize is exaggerated, and that the restriction of maize breeding and testing programmes to assessments of grain production, in the belief that the best grain varieties will also be best for forage, can no longer be justified in northern European countries.

One hundred and fifty-six Scottish Blackface ewes were differentially group-fed over a 2-month period to achieve three distinct levels of body condition (good, moderate and very poor). Over 5 weeks prior to mating, one group of good-condition ewes was maintained in that condition, one group of good- and one of moderate-condition ewes were brought down in condition by restricted feeding and one group of moderate and the very poor condition ewes were raised in condition by a high level of feeding. Ewes were therefore in good, moderately good or poor condition at mating. After mating, ewes were killed either on return to service or at 25 ± 5 days for counts of corpora lutea and viable embryos.

Poor body condition, irrespective of feeding level, was associated with a delay or suppression of oestrus and with a high return-to-service rate. Ovulation rate was positively related to body condition at mating but not to the level of pre-mating food intake at the condition levels studied.

Embryo mortality decreased as body condition at mating increased and the interaction between condition and the level of pre-mating food intake had a differential effect on mortality of single- and multiple-shed ova. The lowest rate of embryo mortality was found in ewes in moderately good condition which had been well-fed before mating.

Soil amendments, gypsum, wheat straw mulch and animal manure, were tested on P. vulgaris at toxic and nontoxic sodium chloride levels in the soil. Slower growth rate and gradual death of seedlings were found under saline conditions.

Gypsum and straw mulch increased bean tolerance to salinity which was associated with higher plant survival and greater plant vigour.

Seed yield/ha was increased by an average of about 30 and 50% with gypsum and straw mulch treatments, respectively, and the gypsum plus straw mulch treatment resulted in an increase of about 100% in seed yield. Number of plants survived and to a lesser degree seed weight were the predominant factors affecting seed yield/ha. The analysis of multiple correlation showed that variation in yield/ha was attributable most to the number of plants/m2.

Much has been written and said about genotype-environment (GE) interactions and the particular problems which they pose for plant breeders. It is not the purpose of this article to dwell upon every aspect of this story, but rather to discuss how these problems came to be recognized, to comment upon the various techniques which have been employed in seeking a solution to them and to suggest what developments might lie ahead.

It has been shown that structural failure in small grain cereals occurs by buckling rather than by loss of anchorage. A theoretical study established the relationship between a lateral force applied to the head, and failure of the straw. Resistance to bending is determined by two factors, Young's modulus and outer diameter of the straw. These were determined in laboratory tests. The value of Young's modulus was affected by stage of maturity of the straw. Wind-tunnel experiments established a relationship between air velocity and deflexion of the head. An attempt was made to calculate the wind speed necessary to cause straw breakage in the field. The kinetic effect of raindrops was not a significant factor in lodging. Attention has been drawn to the possible importance of taper in the straw.

Use of flower and seed colour genetic markers showed that in plots, each 4·5 m × 4·5 m in size, the genetic contamination decreased from 16·96% at 0·9 m to 1·25% at 92 m, and 0·59% at 184 m distance. Maximum contamination from other Viciafaba outside the experimental field and at least 1·1 km away was 0·44%. Implications for the multiplication of stocks in breeding programmes are discussed.

Experiments with main-crop potatoes were made at Rothamsted and Woburn in 1971 and 1972 to measure the effects of applying four amounts (1260, 1880, 2510 or 3140 kg/ha) of granular NPK fertilizer (containing 13% N, 13% P2O5 and 20% K2O)for two pairs of varieties (Pentland Crown and King Edward at Rothamsted; Pentland Crown and Record at Woburn) planted either 30 or 45 cm apart in the row.

Yields of each variety were greatly increased by the first and second increments of fertilizer at each farm each year (mean increases of 5·5 and 5·2 t/ha respectively), but less by the third (2·1 t/ha); total yields were increased from 35·7 t/ha with 1260 kg/ha of fertilizer to 48·5 t/ha with 3140 kg/ha. As yields increased the proportion of small tubers (< 44 mm) decreased, whilst that of medium (44–70 mm) and large (> 70 mm) tubers increased.

The removals of N, P and K by each variety of potato were calculated; for those given 2510 kg/ha of 13·13–20 fertilizer, the mean amounts (kg/ha) removed were 154, 20·6 and 242 of N, P and K respectively, or 47, 14 and 58% of the amounts given. A balance sheet showed the amounts remaining in the soil after potato harvest.

Winter wheat was grown after the potatoes to value residual N. In 1972, when average amounts of winter rain fell, grain yields were increased by these residues on the heavy Rothamsted soil, but not on the sandy Woburn soil. In 1973, after an unusually dry winter, the residues consistently decreased yields because of lodging, showing that little N had leached during the winter. % N in the grain was increased by the fertilizer residues each year.

Milk production (305 day lactations, 3·5% fat-corrected milk), and lengths of time between calving and conception for 541 heifers and 1127 older cows were examined. These data were collected from 11 herds in collective farms in Israel during two successive years. Herd lactation means ranged from 5046 to 8570 kg for cows and from 5021 to 7250 for heifers; the ranges of time between calving and conception were 89–123 days and 99–141 days, respectively.

A significant correlation was found between the weight of milk given per lactation and the length of the interval between calving and the next conception, with coefficients of 0·298 (cows) and 0·333 (heifers). There was a positive non-linear regression of length of calving to conception interval on production of milk, the regression line becoming steeper, both for cows and heifers, as yield rose.

All herds practised first insemination at the first heat exhibited after 60 days from calving. The results indicate that, when this is done, cows yielding 8000 kg or over per lactation, and heifers yielding 6750 kg or over, will show calving to conception intervals exceeding a mean length of 110 days.

Experiments with winter wheat in 1972 and 1973 tested all combinations of ‘Nitro-Chalk’ ν. liquid N-fertilizer, 56 ν. 112 kg N/ha, 0 ν 5·6 1/ha of herbicide (2·8 kg acid equivalent/ha) and 0 ν 0·7 1/ha of mildew fungicide, all applied at growth stage 4–5 of the Feekes scale. The liquid fertilizer (26 % N) was a solution of ammonium nitrate and urea, the herbicide was a mixture of dichlorprop and MCPA and the mildew fungicide contained 75 % (w/v) of the active ingredient tridemorph.

The herbicide and mildew fungicide were sprayed either alone or together and neither scorched the wheat leaves. Liquid N-fertilizer by itself slightly scorched the wheat leaves and scorch was increased by adding herbicide to it, but more by adding the fungicide and most by adding both; it was then severe, especially with 112 kg N/ha.

Weed control after adding herbicide to the liquid fertilizer was at least as good as from herbicide sprayed alone.

In July, foliar diseases were much more severe with 112 than with 56 kg N/ha, but effects of the other treatments, including fungicide, on foliar diseases, were then very small.

With 56 kg N/ha, yields were slightly larger with ‘Nitro-Chalk’ alone than with the liquid N-fertilizer alone, but with 112 kg N/ha they were slightly larger with the liquid fertilizer; adding herbicide to the liquid fertilizer did not change these results. With either amount of N, adding mildew fungicide to the liquid fertilizer made it less good than ‘Nitro-Chalk’, presumably because of the damage from leaf scorch; adding both herbicide and fungicide to the liquid fertilizer increased the damage.

The mechanical and eleetromyographic activity of the pyloric antrum and duodenum of sheep has been studied both under resting conditions and while infusing various solutions to alter the chemical composition of the chyme.

Bursts of spike-type electrical activity, synchronized with the depolarization phase of slower potential variations, accompanied duodenal contractions. Both mechanical distension and chemical stimulation of the proximal duodenum influenced the electrical activity and led to changes in the frequency, duration and amplitude of contractions.

The effect of age on the fatty acid composition of depot fat of Jersey cattle has been investigated. Serial samples of subcutaneous fat were obtained by biopsy of the same animals from 3 months to 2 years of age. Samples of depot fat were also obtained from various anatomical locations of animals slaughtered between birth and 11 years of age.

In subcutaneous fat at biopsy the percentage stearic acid remained constant to 1 year of age and then declined from 20% to 5% during the period 1–2 years post partum.

In perinephric fat the stearic acid content increased from 10–15% at birth to 40% at 1 year of age, and then declined during the period 1–2 years post partum.

Changes in the percentage stearic acid above the 10% level were accompanied by inverse change in octadecenoic (C18:1) acid, and below 10% mainly by change in hexadecenoic (C16:l) acid.

There was a gradient of unsaturation between subcutaneous and internal body fats, and also within the subcutaneous fat itself.

Evidence is presented to suggest that the decrease in the unsaturation of depot fat during the period 1–2 years post partum is associated with the deposition of more unsaturated fatty acids during the fattening phase of development.

Varietal and environmental factors which influence test weight were investigated in a field trial with ten varieties of winter wheat and two rates of nitrogen fertilizer. Varietal differences in test weight were correlated positively with the protein content of the grain and inversely with grain yield but they were not related to 1000-grain weight or to flour yield. Variation in test weight associated with varietal and environmental effects in protein content was due to differences in the density of the grain, as measured by displacement of xylene. Separation into density grades within a sample by a flotation method showed a similar relationship with protein content. There were also varietal differences in packing efficiency of the grain. In the case of Maris Huntsman a poor packing efficiency was considered to stem from morphological features of the floret and developing grain which lead to characteristic transverse folds in the ventral surface of the mature grain. For wheat grown in the United Kingdom, test weight may provide a useful guide to flour yield for samples of one variety but it is likely to be misleading for comparisons between varieties.