The effect of time of application of nitrogen and potassium on the growth, development and yield of the second early variety Craig's Royal was studied by the technique of growth analysis. There was an indication that witholding nutrients led to the earlier initiation of tubers, but this was of no practical consequence and all treatments affected tuber bulking rate rather than the duration of bulking. Compared with early application, late application of nitrogen depressed tuber yield, although total drymatter yield was not affected. Late application of potassium, however, increased tuber yield; this was associated with an improvement in the recovery of applied potassium. Delaying the application of nitrogen also resulted in its more efficient recovery in the crop. Late application of potassium improved the recovery of early applied nitrogen and vice versa. Reasons are put forward to account for these effects.

The diversity of methods for jointing meat animal carcasses is indicated and the need for a standardized method with good repeatability is considered. A standardized butcher-type method of jointing, in which anatomical reference points were used to determine cutting lines, is described briefly. A semi-anatomical method in which the jointing was based still more closely upon the anatomy of meat animals is described in full. Three modifications to the semi-anatomical method are suggested to improve the consistency of jointing.

Groups of ewes kept under hill conditions were killed at intervals during October to July 1965–66. Supplementary feed was given between February and May. The carcasses were divided into soft tissue, uterus and its contents and skeletal fractions. Each fraction was dissolved in HNO3 and its fat and mineral content measured. The sheep were heavier in November and lighter in May during lactation than at other times. The content of fat in the body fell progressively from October to May and then increased; initially fat was withdrawn only from the soft tissues but by April and May the fat contents of both skeleton and soft tissues were exceedingly low. The weight of fatfree soft tissue remained relatively constant but was heaviest in July. Fat-free skeleton fraction was lighter in January than in April.

The contents of the predominantly intracellular ions, P, Mg and K in the soft tissue fell between November and January, remained constant between January and May and then increased. There was an increase in Na towards the end of pregnancy followed by a marked fall after parturition. The contents of Ca and P in the skeleton fell between November and January and during lactation between April and July. There was a marked increase between February and April when supplementary feeding was given. Evidence that Mg was selectively removed from the skeleton was obtained in November and January, two sheep having Ca:Mg ratios in skeleton greater than 100. Na and K contents of the skeleton were greatest at the end of pregnancy in April. For the lambs between 6 and 23 kg live weight, each kg of live-weight gain contained 8·8 g Ca, 5·0 g P, 0·27 g Mg, 0·83 g Na and 1·85 g K.

Two experiments were carried out in which pigs were grown at controlled high, moderate or low growth rates from 18 kg to slaughter at 57 kg live weight. Linear measurements and density determinations were carried out on the carcasses. In the second experiment the right-hand side of each carcass was divided into four joints and each joint was physically dissected into three components, bone, subcutaneous fat plus skin and ‘lean’ meat. The boneless tissue of each joint was analysed for moisture, ether extractable fat and nitrogen.

It was found that an increase in the rate of live-weight gain tended to improve the efficiency with which feed was converted into live weight.

The percentage of fat in the side was significantly increased by more rapid growth rates.

The conformation of the side was altered by treatment, the proportion by weight of the middle region increased with increasing rate of live-weight gain and was accompanied by corresponding reductions in the proportions of the gammon and shoulder regions. These changes were largely due to an effect on the distribution of fat throughout the side, but there were also minor changes in the distributions of bone and fat-free lean.

The high rate of gain was associated with a greater proportion of belly in the side. This was due to an increase in the proportion of lean meat in this region, presumably a functional effect caused by an increased intestinal volume.

There was no treatment effect on the chemical composition of the fat-free boneless meat which was found to differ significantly between joints.

Pigs were grown at controlled rates of live-weight gain from 20 to 55 kg and from 55 to 87 kg live weight, at which weight they were slaughtered. Six growth-rate treatments were compared and were referred to as High-High (HH), High-Moderate (HM), High-Low (HL), Moderate-High (MH), Moderate-Moderate (MM) and Low-High (LH). The right-hand side of each carcass was divided into the four primary jointsand each joint was physically dissected into bone, skin, subcutaneous fat and lean meat. The boneless tissue of each joint was analyzed for moisture, ether extractable fat and nitrogen.

It was found that an increase in the rate of live-weight gain in the first growth period, tended toimprove the efficiency with which feed was converted into live weight. In the second growth period the efficiency of feed conversion was dependent on the rate of gain both in that period and in the preceding period. Restricted growth in the first period improved the efficiency of feed conversion both in the second period and over the entire experimental period compared with rapid early growth. The implications of compensatory growth are discussed.

There was no treatment effect on carcass length, but hindleg length and ham circumference measurements showed that the proportion of gammon in the side was lower in the HH pigs compared with the other five treatments. This was confirmed by the weight of the gammon joint expressed as a percentage of the trimmed side. There was also a decrease in the proportion of shoulder and an increase in the proportion of middle in the HH pigs. Differences between the other five treatments were small. The changes in conformation were due largely to the effect on fat distribution throughout the side particularly in the gammon and back regions.

The HH treatment resulted in a significant increase in the percentage fat in the side compared witheach of the other five treatments. Within these five treatments there was no significant difference in the percentage fat in the side. This suggests that equal importance may be attached to the rate of live-weight gain in both the growing (20–55 kg) and finishing (55–87 kg) periods in determining the fatnessof the bacon weight carcass.

The treatments had little effect on the chemical composition of the fat-free boneless meat.

The results are discussed in relation to current growth theory.

Experiments designed to assess differences between treatments in pasture productivity as measured by the production of animals are complicated by the stocking rates chosen. The paper attempts toderive a simple model relating production per animal and production per unit area to stocking rate for meat animals, based on biological considerations.

A method is proposed which would allow meaningful grazing experiments to be carried out employing only one stocking rate, thus considerably reducing the expense of this type of experimentation.

The model is applied to some recent data obtained by Hodgson (1966) and Appleton (1967, personal communication).

The pattern of dry matter (D.M.) yield, digestibility and nitrogen (N) content of two contrasted grain:straw (G/S) ratio varieties each of barley, oats and wheat grown at three levels of nitrogen was measured over the 30 days after ear emergence, D.M. yield rose with time, while digestibilityand N content declined. Although the D.M. yield was highest in the oat variety, Maelor, one barley variety, Deba Abed, had the highest digestibility and a similar yield of digestible dry matter. Wheat was lowest yielding. The low G/S varieties of wheat and oats had higher yields of digestible D.M., but the high G/S variety, Deba Abed, was the higher yielding barley. Yield of digestible D.M. increased with increasing N fertilizer, due to the increased D.M. yield.

In a series of experiments, each of 6 weeks' duration, non-pregnant Romney, Scottish Blackface and Tasmanian fine-wool Merino ewes were individually penned in an outdoor environment and allocated a constant ration within a range from 8 to 30 g of a standard dried-grass pellet per kg live weight. Maintenance requirements were calculated from the regression of live-weight change per unit weight on intake per unit weight. Comparable values for the three breeds were computed as 8·4, 9·2 and 14·0 g DOM (digestible organic matter)/kg/day for Romney, Blackface and Merino respectively, the latter being significantly higher than for the two British breeds. Estimates of requirements per unit change in live weight, after allowing for maintenance, were 5·1, 4·6 and 3·0 g DOM/g live-weight change for the three breeds. Methods of estimation of energy requirements and the reasons for differences between breeds are discussed.

This experiment was carried out in a newly reclaimed desert area south-west of Alexandria. The purpose was to study the effect of breeding Barki ewes more than once per year on body weights and mortality rates of their lambs. Lambs were weighed 24 h after birth and at the ages of 1, 2, 2·5 (weaning age), 3, 4, 5, 6, 9 and 12 months.

The experiment comprised three groups of single-born lambs of both sexes. The first group included 385 lambs born (in October–November) to ewes lambing once per year; tho second group comprised 155 lambs born (in January–February) to ewes lambing twice in twelve months and the third comprised 102 lambs also born in January–February to ewes lambing thrice in two consecutive years.

Lambs born to ewes lambing once were heavier from the age of 1 month to the age of 5 months than lambs born to ewes lambing twice in the same year or three times in two consecutive years. However, the three groups of lambs did not significantly differ in their body weights from 5 to 12 months of age.

Rebreedi ng did not significantly affect the mortality rate of lambs at the three studied ago periods, i.e. from birth to 1 month of age, from 1 month to weaning and from weaning to the age of 12 months.

Sex had a significant effect on body weights of lambs but did not affect their mortality rates.

During the 4· to 9·week stage Ross Chunky H broilers were fed on diets containing two varieties of field beans at 0, 10, 20 and 30 % rates of inclusion. No significant treatment effects were observed on live-weight gains, amounts of food eaten or food-conversion ratios.

The changes in phosphate availability that occurred when fertilizer phosphate was incorporated in moist uncropped soil were examined by storing fertilized soil in the open for periods up to 3 years before a final test crop was grown. Superphosphate was the standard source as it was fully available initially and therefore provided a measure of the rate of immobilization of phosphate on the four soils used. The extent to which this rate was modified by slower rates of dissolution of non-water-soluble sources was examined, using dicalcium phosphate (powder and granular), basic slag and ground North African rock phosphate (GNAP).

Powdered dicalcium phosphate and basic slag in general behaved similarly to superphosphate, indicating very rapid dissolution. The only exception was a slightly lower rate of dissolution of slag on the calcareous soil. Other than in the very acid soil, the rate of dissolution of GNAP was slow so that the available phosphate was not similar to the superphosphate treatment until after at least the second year. On the calcareous soil GNAP was practically inert. Granular dicalcium phosphate was the only consistent slow-release source. It gave available phosphate levels which were initially lower, but subsequently higher, than those from superphosphate. In the absence of a crop, cumulative assessments of phosphate availability were not possible.

The pertinence of these results to the problem of maintaining a high soil phosphate status is discussed.

The yield of crops in the low rainfall areas of eastern Kenya has been shown to vary within each season according to the crops grown in preceding seasons. This phenomenon of crop sequence was associated more especially with the amount of soil nitrates remaining at all depths in the soil than with the amount of water that may be left. The quantity of nitrates left by a crop was generally related to its vegetative bulk, its rooting habit and duration on the ground, and increased as the crops were ranked in the order: local maize, short-term maize, silage maize, beans and fallow. The beneficial effect of a bean crop or a fallow was reflected in a third crop when the intermediate crop had a low nitrogen requirement.

The persistence of the relative differences in the nitrate levels in the soil would seem to be due to their low mobility under leaching.

The increase in yield of a crop was shown to be due to the more rapid development of the crop when nitrate supplies were more plentiful. When the duration of the rains was short the earlier, more abundant flowering resulting from the rapid growth gave better grain set, and hence greater and more reliable yields. When crops matured in dry weather the availability of soil nitrates at depths of up to 4 ft had a positive influence on yield.

Although rainfall was the main determinant of yield within each season, the use of fallowing to store water from one season to the next was inefficient. Similar amounts could be held in cropped land if late rains occurred. If early rains were plentiful the benefit of stored water could be lost by the thorough wetting of the soil profile.

In many nutritional experiments with cut pasture the voluntary intake and digestibility is determined with pen-fed sheep. However, the voluntary intakes of sheep are extremely variable, the between-animal coefficient of variation varying between 13·1% and 10·5% (Blaxter, Wainman & Wilson, 1961; Minson, Harris, Raymond & Milford, 1964). Thus each pasture cut must be fed to large numbers of animals if differences between pasture species and varieties are to be detected with significance. (Heaney, Pritchard & Pigden, 1968.)

The use of the correct N dressing for beet is important, as any excess decreases juice purity and profit, and may decrease sugar yield, but no analytical method will at present predict the best dressing in any particular field. The concentration of nitrate in leaves and petioles of beet was determined to test if it would determine the need for top-dressings of N. Beet on seventeen field trials in 3 years testing N were sampled. Nitrate in a wet tissue extract was determined by reducing to ammonia with titanous sulphate and subsequent distillation.

The petiole nitrate concentration decreased sharply with time, from around 1000 ppm in wet tissue in early June to less than 100 ppm in early September. The nitrate concentrations were closely related to nitrogen dressing, and the rapid decline in concentration was decreased by top-dressings. Comparison of samples taken in June showed that most of the variation between the experiments could be accounted for by the different ages of the plants. Sodium fertilizer had no effect on nitrate content.

Petiole nitrate was inversely related to juice purity and sugar concentration, especially when the nitrate content exceeded 700 ppm in June.

On average, petiole nitrate concentrations about 800 ppm in June were associated with the largest sugar yields, but the content could not be used to predict nitrogen top-dressing requirement accurately at individual sites.

Measuring NO3-N cannot at present be recommended as a method for deciding how much nitrogen fertilizer to use, but it has value for detecting severe deficiencies and in research.

Results from three trials are presented. The main variables were date of harvest, plant density and variety. Measurements were made of whole-crop yields and yields from plant fractions (leaf, stem, cob). Quality components—digestibility, acid-pepsin solubility, water-soluble carbohydrates, nitrogen and ash—were estimated for whole crop and fractions. There were successive samplings for quality components.

Whole-crop yield from fractions and yield of quality components increased with density. Whole-crop yield differed significantly with harvesting date as did all fractions except cob, although the proportion of cob increased with time. The earlier harvesting date gave greater yields of quality components.

There was no effect of density on the dry-matter content but later harvesting resulted in higher dry matter.

The only quality component affected by density was nitrogen content but there were large effects of harvesting date on digestibility and the acid-pepsin components.

Regressions were computed for quality components on dry-matter proportion of cob and the dry-matter content of the whole crop. Regressions were significant for the acid-pepsin soluble components and the water-soluble carbohydrate component on the proportion of cob. Regressions of digestibility and pepsin-soluble components (total and organic) on dry-matter content were significant.

The implications of these findings to the breeding of maize varieties are discussed.

Twenty-six soils from different parent materials were exhaustively cropped with ryegrass in the glasshouse. Soil and crop measurements revealed inter-relationships similar to those observed with Rothamsted soils (Part I) generally, except that 12 of 20 soils, ‘poor’ in K (as defined by the K intensity of the uncropped soil and the change in soil K intensity with cropping), gave patterns of K uptake by the ryegrass crop similar to those of soils ‘rich’ in K. This indicates that these soils contain some K reserves not differentiated from those accumulated by K-manuring in Rothamsted by laboratory measurements.

The cumulative K yield of ryegrass was very significantly related to the K intensity of the uncropped soil. The relationships were improved slightly by allowing for differences in soil pH and organic carbon content. The cumulative K yields at 16 weeks and at 60 weeks were better related to the total clay (<2 µ) content than to the fine clay (< 0·2 µ) content of the soil. The K intensities of the cropped soils decreased to nearly 10–3 (AR) units after 16 weeks cropping (except the Harwell soil which took 3 years to do so), although large differences in K yield persisted until much later.

Potassium-buffer capacity per unit clay content of the soil (by a laboratory method) was inversely related to the K intensity of the uncropped soil and to K uptakes at 16 and 60 weeks. The rea⋅ons for this apparent anomaly are discussed and a more correct basis for the units for K-buffering capacity is suggested. The buffer capacities of ‘rich’ soils in the laboratory and glasshouse experiments were significantly related but not of ‘ poor ’ soils.

Soils exhausted by cropping released more K to ryegrass after a. drying-and-wetting cycle in amounts proportional to the clay content of the soil. This points to the need for caution in measurements to assess status after air-drying soils.

Three field experiments in 1963–5 compared the effects of three methods of fertilizer application, each at four rates, on the growth and yield of main-crop potatoes. Solid fertilizer was broadcast over the furrows and then concentrated round the seed tubers by splitting the ridges during machine planting. Liquid fertilizer was injected immediately after planting either 2 in below and 2 in to the side (shallow placement), or 6 in below and 2 in to the side of the seed tubers (deep placement). Solid and liquid supplied the same quantity of nutrients.

In two years deep placement of liquid gave larger yields than the solid fertilizer and in all three years larger yields than shallow placement of liquid. Results from growth analysis of the 1963 crop indicated that deep placement of liquid gave the largest yield after a dry period. Growth analysis on an additional experiment in 1964 showed that when the soil moisture deficit was limited by irrigation to 1-6 in, both the yield and nitrogen uptake from shallowly and from deeply placed liquids were similar. However, without irrigation deep placement gave a larger yield and nitrogen uptake than shallow placement. An artificial 'dry climate' emphasized that the magnitude of the response to deep placement was related to the soil-moisture regime. It is concluded that the deepplaced fertilizer was in a region of the soil which remained moist, whereas the shallower fertilizer was in drier soil where it was less available to the potato roots.

Citric acid and three antibiotic-type substances—zinc bacitracin, tylosin and formosulphathiazole—were included in dry-meal diets for early weaned pigs up to 20 kg live weight. Two experiments were carried out and in each copper sulphate as 0.1 % of the diet was tested.

In the first experiment the diets were supplemented with citric acid, copper sulphate or both citric acid and copper. The pigs given the diet containing both citric acid and copper tended to have the greatest daily live-weight gains and there was a similar trend in favour of the diet containing copper sulphate alone, but these advantages did not reach significance.

In the second experiment diets with or without copper sulphate were supplemented with either Zinc Bacitracin, Tylosin or formosulphathiazole. All three ‘antibiotics’ had beneficial effects on rates of gain and feed-conversion efficiency, resulting in average. increases of 15% and 10% respectively. Copper sulphate did not improve the performance of the pigs when included in the basal diet with or without an ‘antibiotic’ and there was no interaction between the copper supplement and any of the other supplements.

The performance of the pigs after 20 kg live weight under standard conditions showed little evidence in these experiments that the beneficial effects of feed additive use before this weight persisted during growth to 90 kg live weight or that any of the major measures of carcass quality were affected by the early treatment.

A standardized butcher-type method (B) in which anatomical reference points were used to determine cutting lines was compared with a semi-anatomical method (A) in which the jointing was based still more closely upon the anatomy of meat animals. Thirty-two lamb carcasses were split by hand sawing and the sides prepared for quartering, quartered and finally jointed into five hindquarter and five forequarter joints by one or other of two operators by either method A or method B according to a pre-arranged plan. Operator bias in the preparation of the sides for quartering was only noteworthy for the removal of internal fats.

Method A proved to be more consistent than method B, but the degree of advantage varied for different joints. In terms of the coefficients of variation for different joints by the two methods, method A had an advantage in consistency over method B for eight of the ten joints into which each side was divided.

The reproducibility of the semi-anatomical method (A) could be further improved by adopting more fully anatomical methods of joining.

The application and implications of an anatomical method in the excision of sample joints is noted.