The effects of part, age and species of plant and some soil characteristics on the relationships between (a) sum of the cations (Σ cations)–% total N and (b) ratio of sum of the cations sum of the anions (R)–% organic N relationships in crops were tested in four experiments in the glasshouse. Crops were grown in soil and given four or five amounts of N03-N and sometimes a uniform dressing of other nutrients.

Results confirmed that there was a positive linear relationship between S cations in plants and their % total N when N03-N was supplied and the proportions of cations and anions entering roots from the soil solution (R values) were not constant but were in some way related to the elaborated nitrogen status of the plant, suggesting they may be linked with nitrogen metabolism. The cation-anion relationships were of the same general type regardless of the part of the plant that was analysed, its age or species, or of the type of soil in which it was grown. Analysis of leaves adequately reflects relationships in whole plants. Although the relationships had the same form with all species, dicotyledons had greater Σ cations and R values than monocotyledons at equal % total N and organic N respectively. Within the group of relationship curves obtained with different soils, at equal % total and organic N, 2 cations and R values were greater in grass grown in alkaline than in acid soil. Soil properties that affect the proportions of NH4-N and N03-N presented to plant roots probably have an important influence on the relationships. These cation–anion relationships in crops were not changed when yields varied greatly.

Data from 692 daughters of 38 Red Danish bulls, tested as heifers in the Danish cattle progeny testing stations 1963–64, were analysed to provide information on the efficiency of feed utilization by dairy cows. The results showed that because of, the feeding system adopted, efficiency measured as FCM per food unit was automatically closely related to FCM yield.

Analysis based on pooled, within-bull, values showed that (a) both efficiency and FCM were negatively associated with body-weight gain during lactation, suggesting that feed allowances per unit FCM were low in relation to those for maintenance, (b) weight measured after calving was positively associated with efficiency and FCM yield whereas the association of these latter variables with weight at the end of the winter period was negative, and (c) the gain in weight during lactation was much lower in cows heavy at calving and higher in those heavy at the end of the winter.

The between-bull correlations, although less reliable than the within-bull values, clearly indicated that the selection for FCM yield would result in increased cow weight.

It is suggested that the selection of dairy cattle should not be based solely on milk yield but that suitable adjustments should be made so that selection for efficiency is safeguarded. Quantitative assessment of such adjustments would necessitate changing feeding procedures at central testing stations.

Four barley varieties were grown in a greenhouse with varying levels of nitrogen fertilizer in two experiments. One experiment was sown in late September and received supplementary light, the other in March without supplementary light.

Varietal responses to nitrogen were essentially the same in both experiments. At low levels, differences in yield and protein content between varieties were small and inconsistent; at high levels, differences were pronounced and consistent. Betzes and Hannchen were highest in yield and lowest in protein, Palliser was intermediate in both, and Compana was lowest in yield and highest in protein. The results correspond with the known behaviourof these varieties under field conditions in Canada, except that Betzes yields more than Hannchen.

We suggest that relative potential yields of genotypes can be estimated under similarly controlled conditions.

The interactions between nitrogen fertilizer and crop rotations in their effects on the yield of cotton in the Sudan were studied by superimposing fertilizer treatments on a rotation experiment which was already more than 30 years old. This experiment compared ten rotations comprising various combinations of cotton with fallow and an alternating crop of dura (a sorghum millet) and lubia (Dolichos lablab. L.). The results support the concept that low basic yields in the absence of a nitrogen dressing are primarily due to nitrogen deficiency. In general the response to nitrogen was greater on rotations which led to low yields of cotton so that rotational effects were greatly reduced or eliminated when a nitrogen dressing was given. Although in some cases cotton following fallow out-yielded cotton following dura, in general rotations containing dura and lubia gave higher yields of cotton than rotations with the same intensity of cotton cropping combined with fallows only. These beneficial effects of other crops instead of fallows in the rotation, although not in agreement with the long-term averages wereto be expected from the long-term trends in yields with time. Combined with the finding that even the most adverse effects of dura could be largely compensated for by a fertilizer dressing, this indicates that cropping in the Gezira could be considerably intensified without loss of cotton yield per acre per year. The difficulties of such intensification would centre around weed, disease and pest control rather than soil fertility. Further experiments are required to determine the fertilizer nitrogen requirements of cotton following different crops.

In a pot experiment providing for rapid growth of sorghum plants in the red clay loam soils of the Cotton Research Station, Namulonge, in the Buganda Province of Uganda, large yield increases were obtained from added phosphate. In an uncultivated soil which had carried undisturbed natural vegetation (Pennisetum purpureurn)for at least 10 years the response curve had negative curvature throughout. In an arable soil, yields without added phosphate were very poor and the response curve was sigmoid in form. With the arable soil, liming did not modify the form of the response curve for added phosphate but at the heaviest dressing lime decreased yield.

A sigmoid curve for response to superphosphate has been demonstrated in field experiments in a Buganda red clay loam. There was evidence that the curve was abnormal; with small dressings of triple superphosphate yield of cotton and beans, and their phosphorus uptake, were decreased, but these characters were increased with larger dressings. Heavy dressings, from 4 to 16 cwt triple superphosphate, increased yield of these crops. Similar effects were observed with maize during growth and maturity was advanced, but final yield of grain was not affected by applied phosphate. The suggestion is made that in a long growing period the maize was able to absorb adequate phosphorus, even though the phosphate intensity in the soil was low, to achieve its potential yield.

Solubility products (pKsp) for iron and aluminium hydroxides and phosphates have been determined in a Buganda acid clay loam. Significantly greater values, i.e. lower solubility products occurred when determined at a soil:solution ratio of 0·4 than at 0–8. In the most acid soils, pH 4·8–5·0, values of pKsp) were consistent with the possibility that iron and aluminium concentrations were controlled by goethite and gibbsite. Above pH 5 the data indicated that these minerals were not effective. The maximum pKsp) value for iron phosphate was too small to be consistent with that for strengite, indicating that this mineral did not affect phosphate concentration in the soil; the maximum value for aluminium phosphate was consistent with that for variscite but the occurrence of this mineral cannot be deduced from the data. Triple superphosphate applied at 8 cwt per acre or less was converted within 2 years to a very insoluble form, having a solubility similar to that of variscite; with 16 cwt per acre the phosphate concentration was much greater than with the smaller dressings after this period and the soils appeared supersaturated with variscite.

In a randomized block experiment, seventy-two Large White type weaner pigs (thirty-six hogs and thirty-six gilts) were individually and restrictedly fed to 200 lb live weight six diets (as wet mashes). Five of these diets contained high levels (85 % in the starter diets and 90 % in the finisher diets) of either maize, flaked maize, sorghum, wheat or barley. The sixth diet, which acted as the control diet for the experiment, was similar to the barley diet except that 25 % of weatings replaced a similar percentage of barley. A further three groups of six litter-mate hog pigs per group were used to measure the digestibility of these diets.

For the starter diets the maize diet had the highest digestible energy content, for the finisher diets the highest values were for the wheat and sorghum diets which in turn were similar to each other. The digestible energy content of the flaked maize diet was higher than the contents of the barley and control diets but lower than the contents determined for the other three diets.

Three of the pigs fed the sorghum diet developed leg weaknesses and this affected growth rate and food conversion efficiency. The symptoms suggested a pantothenic acid deficiency but the results of assays carried out on all the diets indicated that the condition was not necessarily due to a deficiency of this vitamin. Growth rates in the starter period (up to 115 lb) did not differ significantly between diets but food conversion for the maize and barley diets was significantly superior to that for the wheat and sorghum diets. In the finisher period growth rate and food conversion efficiency for the maize and wheat diets was significantly superior compared with that for the other four diets. Overall, from start to slaughter, the maize diet was significantly superior to the flaked maize, sorghum and control diets in both these parameters of performance. The energetic efficiencies of growth tended to be poorer for those diets with the better food conversion ratios, the best efficiency being for the control diet.

Carcass length differences were not significant but backfat thickness and eye muscle area differences followed closely the pattern found for lean and fat content of the carcass. In this context the highest percentages of lean were found first in the control and, secondly, in the barley treatment carcasses. Some differences were found in the development of anatomical regions and tissues within these regions. In particular, and relative to the five other diets, there were in the control diet carcasses (1) higher percentages formed by the leg and shoulder and (2) a higher percentage of lean in the middle.

Studies were made of the proximate and mineral compositions of modern strains of both spring· and winter-sown beans. The majority of the winter beans were of the Throws M.S. variety, of the spring beans Minors. On the dry-matter basis spring beans averaged 31·4% crude.protein, winter beans 26·5%—a highly significant difference. The true protein values showed a parallel trend. Winter beans averaged 9% crude fibre, spring beans 8%, again a highly significant difference. The strains confirmed the usually accepted levels of oil and of the principal mineral components, except that modern beans appear to be richer in phosphorus.

In an 8-year field experiment, potassium sulphate and to a lesser extent magnesium sulphate increased yields of all crops both when applied alone and together. Although K/Mg interactions did not affect yields they considerably affected the ratio of concentrations of these elements in the dry matter of the crops. Sodium chloride increased yields of kale but not of barley harvested at ear-emergence.

Percentage yield response to potasium followed the order

Potatoes (218%) < clover = barley < sugar beet < kato; < ryegress (17%).

Magnesium increased yields from 3 to 10%, most with potatoes.

Changes in exchangeable magnesium in the soil reflected differences between applied magnesium and crop uptakes. Changes in exchangeable potassium were less than expected, probably because non-exchangeable potassium was released on plots without added potassium and ‘fixed’ in non-exchangeable forms on plots where much fertilizer potassium had been given.

Increase in the incidence of magnesium deficiency symptoms reported recently in South. East England are attributed to the local liming materials containing only small amounts of magnesium and to less F.V.M being applied to crops than previously.

Between 1964 and 1966 thirty-one field trials were completed in twelve factory areas of the British Sugar Corporation to examine the feasibility of using mechanical thinning in conjvinction with low seed rates (3–6 in spacing) and chemical weed control to minimize the demand for labour in the spring. The results showed that where chemical weed control was effective in machine-thinned crops no hand labour was required for establishment, but there were mean losses in yield of 1·3 tons per acre (7%) compared with similar crops that were hand singled. These losses in yield were unaffected by variations in seed rates. Mechanical harvesters worked more efficiently in low seed rates, especially where monogerm seed was used.

Soil samples taken in the autumn after ploughing ryegrass, clover, and ryegrass/clover leys were used to measure the mineral-N (ammonium-N + nitrate-N) in the fresh soil (mineral-Nfresh), the increase in mineral-N on incubating the fresh soils (Δmineral-Nfresh), and the increase in mineral-N on incubating the re-wetted air-dry soils (Δmineral -Nair-dry). Mineral-Nfresh and Δ mineral-Nair-dry were measured on further soil samples taken the following spring. Values of Δmineral-Nair-dry, not only correlated best with grain yields and N uptakes by wheat without fertilizer-N, but also with yield responses and fertilizer-N recovered from fertilizer-N applied to the winter wheat.

Treatment of the ley altered measurements on samples taken in the autumn but not those taken the following spring.

Soil samples taken in the autumn 1960 from under three-year grass leys were used to measure mineral-Nfresh, Δ mineral-Nfresh and Δ mineral-Nair-dry Spring wheat was grown in 1961 followed by spring barley in 1962. Further soil samples were taken in spring 1962 after cultivations were complete and before the barley was sown or fertilizers applied.

A mineral-Nair-dry was the best measurement to use on soils from under grass leys. Values depended on grass species, and were increased by N applied to the ley. Differences had largely disappeared 18 months later. A mineral-Nalr.dry was positively correlated with grain yields of spring wheat grown both with and without fertilizer-N, and with the yield response or the nitrogen recovered from, a dressing of 56 lb N/acre.

With fertilizer-N yields of winter wheat after the mixed leys tended to the same maximum value independently ofmineralizable-N in the soil. After grass leys maximum yields of spring wheat given fertilizer-N increased with increasing mineralizable-N in the soil.

Approximately 15 weeks before parturition, forty-eight pregnant Blackface ewes were divided into three similar groups. During the 15–6 weeks prepartum period the ewes were fed to increase the live weights and body condition scores of ewes in each of groups A and B and to decrease those of ewes in group C. At 6 weeks prepartum mean differences of approximately 11 kg live weight and two grades of body condition had been created. Food was rationed to the ewes in all groups per kg live weight based on their weights 6 weeks prepartum, to provide the theoretical requirements of Blackface ewes bearing twin lambs. All groups of ewes made similar live-weight gains in late pregnancy and the mean birth weights of the lambs were also similar. Blood plasma F.F.A. values confirmed that the ewes were similarly nourished in late pregnancy regardless of live weight or body condition. During lactation the ewes were fed 9·2 g D.O.M./kg based on their immediate post-partum live weights, plus an allowance for a predicted level of milk production. Ewes in groups A and C were fed 0·5 and ewes in group B, 0·25 g D.O.M. per g of predicted milk production. The ration was increased after the 1st and 2nd weeks of lactation, then maintained at a constant level for the remainder of lactation. Milk production of the ewes was measured using a lamb suckling technique during a 10-week lactation. The mean daily milk production of ewes in groups A and C were similar and the yield of each of these groups was substantially greater than that of group B ewes. The mean total milk production of ewes suckling twin lambs in groups A, B and C was 127, 108 and 142 kg respectively, and of ewes suckling single lambs 104, 81 and 91 kg respectively. The mean live-weight changes of ewes in groups A and C were similar during lactation. Except for group A ewes suckling single lambs, which maintained their mean live weight, all ewes lost weight in early lactation and consistent gains were not made until late lactation. Greatest live-weight loss occurred in group B ewes and extended further into lactation. Changes in body condition followed a similar course to live weight changes. The mean daily live-weight gain of twin lambs in groups A, B and C was 279, 275 and 284 g respectively, and of single lambs, 318, 300 and 319 g respectively. The evidence indicates that ewes in lean body condition have a higher efficiency of food conversion to milk and that in situations of continuous undernourishment a high state of body condition is undesirable during lactation.

The survival of potted plants of the North African Festuca arundinacea populations syn. 1 and syn. 2 was compared to that of the British cultivar S. 170 following 18 h periods in a growth cabinet at 24 °F, 21 °F and 18 °F. No plants in any of the three populations were killed by the 24 °F or 21 °F treatments but, following the 18 °F treatment, survival of both synthetics was greatly reduced, especially amongst plants that had been cut back to 1 in. (2·5 cm) 6 days prior to the cold treatment. Reduction in tillering and deaths in syn. 1 were both greater than in syn. 2. Both cut and uncut plants of S. 170 survived the 18 °F treatment, their tillering being relatively little affected.

In a subsequent study, survival of syn. 1 and syn. 2 at temperatures decreasing to 16 °F was less amongst plants cut back to soil level than amongst those cut back to 3 in (7·5 cm) or left uncut. No differences were detectable between survival in the two synthetics, nor was there any significant effect, on such survival, of time interval prior to the cold shock.

The results showed close agreement with previous patterns of winter survival of these populations in the field.

Following three differing pre-stress temperature treatments, potted plants of three populations of Festuca arundinacea, syn. 1 and syn. 2 (North African) and S. 170 (British) were subjected to a cold stress of 20 h at – 8 °C in a growth cabinet.

In all populations, survival was greatest when the cold stress followed continuous low temperatures for 2 weeks, was intermediate after part-day low temperatures for the same period, and poorest after continuous warmth. The hardening response, especially after the fluctuating regime, was greater in S. 170 than in either syn. 1 or syn. 2, between which little difference was detectable.

There was no overall difference in survival between spring-sown and autumn-sown material, nor any apparent relationship between survival and relative growth rate.

In a further trial, the same three populations were subjected to differing periods of cold stress at — 9 °C-single exposure for 12 or 18 h periods, or one, two or three 6 h periods.

The synthetics were progressively weakened by repeated stresses, and were almost completely killed out by 12 or 18 h exposure. Differences in mortality following short and longer periods of exposure were associated with differences in soil temperatures.

Plants of three populations of Festuca arundinacea, syn. 1 and syn. 2 (North African) and S. 170 (British) were subjected to 3 h cold stress treatments in the range 13–25 °F. Such treatments were applied independently to either roots or shoots, the untreated plant portions remaining at 35–40 F°.

In all populations considerable tiller death occurred following exposure of roots to temperatures of 17 °F or below; however at no temperature was there complete killing of tillers. Tiller deaths occurred following shoot exposure to temperatures below 21 °F in syn. 1 and syn. 2, and below 19 °F in S. 170. Universal mortality occurred in all populations after shoot exposure to 13 °F.

The degree of insulation of the root: shoot junctions affected survival of both roots and shoots in all populations. Discrepancies between apparent damage to plant parts following treatment, and subsequent survival, suggested that the ability of plants to replace damaged parts might influence survival.

Conclusions are included from the completed programme of growth cabinet studies on cold tolerance of F. arundinacea populations reported in the present series of papers.

The effects of N, P and K applied broadcast on yields, percentage nitrogen and kernel weights of barley were studied over two seasons.

The average yield increase over thirteen sites was 5·1 cwt and 8·2 cwt from applications of 35 lb and 70 lb/acre of fertilizer N respectively. A mean yield increase of 4·4 cwt/acre was obtained from 27 lb P at four sites where the soil phosphorus test did not exceed 2 ppm P. Potassium applied at rates varying from 0 to 168 lb K/acre increased yields at one site only and decreased them at another site.

The mean grain nitrogen percent without fertilizer N was 1·47 and applications of 35 and 70 lb N/acre gave increases of 0·06 and 0·19% respectively. The overall effects of P and K on the percent nitrogen in the grain were small.

Applications of 35 and 70 lb N/acre increased the mean 1000 kernel weights by 0·7 and 1·0 g respectively. When lodging occurred kernel weights were decreased. Fertilizer P and K had little effect on the kernel weights.

The significance of these data are discussed in relation to previous cropping and rainfall during the growing season and during the previous winter.

The effects of changing plant density and nutrient supply on the yield of swedes were measured in nine experiments over 3 years. With small populations, a large nutrient supply was required to reach the maximal yield of roots, but with large plant populations the same nutrient rate depressed yield. This interaction is illustrated by a response surface, and reasons for it are discussed. The interaction is of limited importance in practice because it was small over the range of population and nutrient supply commonly used. Even with small populations, the compensation achieved by applying more fertilizer was uneconomic. On crops with large populations, such as swedes for human consumption, however, the normal recommended rate of fertilizer should not be exceeded because of loss of yield as well as increased cost. More fertilizer and greater plant density were needed to give maximal total yield (roots + tops) than of roots alone. Effects of nutrient supply and plant population on plant establishment and dry-matter content of the swedes are discussed.

Percentages of soluble dry matter (S.D.M.), determined in expressed sap from the pith of kale stems by using a hand refractometer, were higher near the vascular bundles than in the centre of the pith and also varied from the top to the base of any one stem. Sampling errors were minimized by taking vertical borings midway between the vascular bundles and the pith centre and by taking two bores per stem (base and top). Inbred lines varied for mean S.D.M. Relative S.D.M. values for two inbred lines were maintained through wet and dry periods in the autumn, and values for fifty-eight inbred lines were significantly correlated in the successive years, one with a dry autumn and the other with a wet.

S.D.M. values were positively and significantly correlated with dry-matter percentage (D.M.) of the pith and with total water soluble carbohydrates (W.S.C). Close correlations were also found between S.D.M. and resistance to cold damage, both in the field and in freezing cabinets for inbred lines of marrow-stem kale and for other cultivars of Brassica oleracea. Although there are some exceptions to these correlations, the rapid method for determining S.D.M. should be very useful in screening breeding material for cold resistance. The combination of high percentage digestibility of the dry matter of stems and improved winter-hardiness can be achieved by selecting in addition for low fibre content using penetrometer tests.

In a 2-year experiment conducted on a pure S. 24 perennial ryegrass sward, fertilizer nitrogen in the form of ‘Nitram’ (34·5%) N was applied at rates of 100, 200 and 300 lb/ acre either as single dressings in the spring or as two, three, four or five split dressings at successively later dates in the growing season. Total yields of herbage dry matter and of crude protein, and their distribution over the season, were determined by cutting the herbage five times at intervals of approximately 5 weeks. Yields of herbage dry matter were increased by increasing the nitrogen application rate and by splitting the total amount of fertilizer nitrogen into either three or four equal dressings. The mean crudeprotein content of the herbage dry matter was increased by increasing the nitrogen application rate, but it was reduced by splitting the total amount of fertilizer into several dressings. The nitrate content of the herbage was higher after a single heavy dressing of fertilizer nitrogen than after several split dressings. It is concluded that the optimum application programme for a total rate of 100 lb nitrogen/acre was three split dressings each of 33J lb/acre, and for the 200 and 300 lb nitrogen/acre rate, four split dressings of 50 and 75 lb/acre respectively.