A preliminary investigation on interplanting of maize with nine different tropical legumes in the rain-forest zone of the Western State of Nigeria at Ibadan indicated that Popondo (Phaseolus lunatus) and Mucuna (Mucuna utilis) lowered maize yield, while calopo (Calopogonium tnucunoides) Cowpea (Vigna sinensis) and greengram (Phaseolus aureus) had much less effect on maize and were themselves tolerant to maize shade. These three legumes were interplanted with maize continuously for four growing seasons, during which there was a significant response of maize to fertilizer treatment only in the control (no legume) treatment. Maize interplanted with the legumes gave no response to applications of 50 lb N per acre.

High yields of maize were maintained during the four growing seasons in both the fertilized control plots and those interplanted with different legumes without fertilizer, whereas the yield of maize in plots with neither legume nor fertilizer was reduced to half of the yield of the first maize crop.

Starting from the third cropping season, there was a significant interaction between the presence or absence of legume and fertilizer.

The planting pattern of the maize and legumes (intercropping or growing maize after the legume harvest) did not affect the yield of maize.

Legumes tended to compete with maize during the late cropping season. This did not affect the maize yield seriously during the investigation, but legume yield was significantly suppressed by maize shade.

Although it is not always valid to regard ‘within herd variation’ as a true measure of experimental error there are occasions when this may be the only feasible measurement. The effect is considered of regarding the animal as the experimental unit on the estimation of the ratio of production of two treatments and an approximate variance for the ratio is obtained. The conditions under which the approximation is valid are considered.

A technique is described for speeding germination of monogerm sugar-beet seed. The optimum treatment was four cycles of wetting seed with its own weight of water and storing it in a sealed container for 24 hours before drying for 48 hours. The number of cells per embryo was doubled, seedlings emerged approximately 2·5 days sooner and seedling shoot weight was increased by 31 to 53%.

Soluble ammonium nitrate (AN) and urea were compared with slow-release oxamide and sulphur-coated urea (SCU) as N sources for clipped annual ryegrass (Lolium multiflorum) or common bermuda grass (Cynodon dactylon) in four greenhouse experiments. Mixed and surface applications of a wide range of N rates were evaluated for 9 to 14 cuttings of grass forage. Both granular oxamide and SCU exhibited slow-release N properties, especially when surface-applied. Uptake distribution of N with high application rates of AN and urea tended to resemble that with the slow-release sources. Slow-release properties of oxamide and SCU were accentuated at high application rates. Lower N recovery from surface-applied urea than from AN indicated volatilization loss of urea N. Volatilization loss also occurred with oxamide, but low N recovery from oxamide and SCU resulted largely from incomplete dissolution of the granules during the 18- to 34-week experimental periods. Very low N recovery was obtained from urea formaldehyde having an activity index of 42.

The crude protein content and in vitro dry-matter digestibility (I.V.D.) of leaves and stems of Andropogon gayanus, grouped into four different age categories, were measured at weekly intervals during the secondhalf of the 1968 wet season. The crude protein content of all categories of leaf and stem rose to a maximumat ear emergence; significant reductions occurred thereafter, especiallyin the younger categories of leaf and stem. At any point in time the younger leaves and stems contained significantly more crude protein than the older leaves and stems.

Although the mean crude protein content of each stem category was significantly lower than the corresponding leaf category, the young, elongating stems had a significantly higher crude protein content than the older, mature leaves at the time of ear emergence.

The mean I.V.D. of all leaf and stem categories was highest at the start of the recording period. At ear emergence the I.V.D. of the young elongating stems was at least as high as the mature leaves. After ear emergence the I.V.D. of the stems fell more rapidly than the leaves.

The results support the principle of cutting at ear emergence to achieve maximum yields of digestible nutrients.

Experiments were conducted at Gezira Research Station during the 1964 and 1965 seasons to determine the effect of time and number of weedings on pod yield of Ashford groundnuts.

Natural stands of annual weeds, mainly Ipomoea cordofana and Rhynchosia memnonia, reduced the pod yield by an average of 80%. Results showed that groundnuts must be weeded at least once after the first 30 days from sowing. Groundnut pod yield was increased from 986 kg/ha in the unweeded plots to 4690 kg/ha in the plots weeded 30 and 60 days after sowing. Three weedings, i. e. 15, 30 and 45 days from sowing, yielded less than 30 and 60 days from sowing because weeding stopped too soon. For practical purposes weeding at 30 and 60 days only was adequate.

Number of pods per plant was the most important factor determining yield. Maximum pod yield was obtained from 15–20 pods per plant, and the earlier the 20 flowers produced, the higher was the pod yield.

Weeds decreased number of branches per plant and consequently number of pods per plant. Weight of 1000 seeds, shelling percentage and harvest index was also affected by weeds.

Ipomoea cordofana was the most noxious weed because it emerged about the same time as the groundnut plants and also the seeds germinated throughout the growing season.

The efficiency of utilization of the energy of food in White Leghorn laying hens for egg production was measured. A ration with a gross energy of 4469 kcal/kg dry matter and 19·4% crude protein had a metabolizable energy of 80·1±1·7% of the gross energy, and 78·5±5·3% of the metabolizable energy was present as net energy.

The maintenance requirement of metabolizable energy of White Leghorn hens weighing 1·723±48·5 kg and a production of 19·3±0–49 eggs per month was 125·8 kcal/kg0·75/24 hr.

The energy cost per g of protein and fat synthesized by laying White Leghorn hens was estimated to be 7·20 and 12·13 kcal metabolizable energy respectively.

A sheep-feeding experiment was carried out to compare the influence of starch supplementation on the utilization of protein contained in a roughage (lucerne hay) and in a concentrated feed (soya-bean meal). Twelve young rams were divided into four groups, all of which received 150% of the theoretical protein requirement for maintenance. Two groups received soya-bean meal, and the two other groups were given alfalfa hay as protein source. One soya-bean group and one lucerne hay group served as control groups and received the theoretical requirement of energy, whereas the energy content of both experimental groups was raised by addition of grain to 150% of the theoretical energy requirement.

A N-balance experiment carried out with both control groups did not indicate the superiority of lucerne hay over soya-bean meal as had been found in previous experiments in which the sheep were fed diets just supplying the theoretical protein requirement. The advantage of roughage protein disappeared as a result of changes of dietary regime, such as the ingestion of protein surpluses and the reduction in the amount of cottonseed hulls.

The N retention from the lucerne-hay ration was enhanced much more than the soya-bean meal ration by the addition of maize. Biochemical analyses of the rumen oontent showed that a much higher metabolic activity of the micro-organisms was induced by feeding a lucerne-hay diet supplying 150% of the theoretical protein requirement than that induced by ingestion of a corresponding amount of soya-bean meal. It was concluded that the increased biochemical potential of the lucerne-hay diet could be used advantageously only in presence of ample amounts of soluble carbohydrates. The digestibility of the carbohydrates contained in all four diets was examined by in vivo and in vitro methods. The digestibility of crude fibre in the lucerne-hay ration was somewhat raised by the addition of maize whereas the digestibility of crude fibre in the soya-bean meal ration was considerably depressed by the addition of maize.

The digestibility of the carbohydrates contained in all four diets was examined by in vivo and in vitro methods. The digestibility of crude fibre in the lucerne-hay ration was somewhat raised by the addition of maize whereas the digestibility of crude fibre in the soya-bean meal ration was considerably depressed by the addition of maize.

In a series of field experiments from 1966 to 1969, on light sandy loam soils in the West Midlands, comparisons were made between two levels of application of herbicides based on urea, triazine and bipyridil compounds for weed control in early potatoes.

Under conditions of adequate nutrient and water supply, the high application rate controlled about 94%, and the low application rate about 88% of the annual weeds. At equivalent application rates, urea compounds and herbicide mixtures containing ureas, gave superior weed control to triazine compounds and herbicide mixtures containing triazines, but the ureas were apparently more phytotoxic to the potatoes.

In 1970, comparisons were made between three levels of application of ametryne and monolinuron, high, medium and low and an unsprayed control treatment.

The highest yields of potatoes were associated with the low application rates of herbicides from 1966 to 1970.

It was concluded that, on these light sandy loam soils, when irrigation is available, relatively low application rates of either monolinuron or ametryne, or mixtures of ureas or of triazines, or mixtures of bipyridils and ureas or triazines could give adequate control of annual weeds in early potatoes at low cost.

In field experiments carried out over a period of three years studies were made of the effects on soil moisture characteristics and crop yields of incorporating pulverized fuel ash into the surface 30 cm of a sandy loam and a coarse sand. Ash from two different sources was used at rates equivalent to 0, 125, 251, 502 and 753 t/ha and crops of carrots, lettuce, radish and red beet were grown.

On every occasion when determinations were made the available-water capacities of the soils treated with 251 t/ha or more of ash were greater than the untreated soils; the largest increase (93%) was obtained with the highest rate of ash. Moisture release characteristics indicated that the increased amount of available water was retained in the soils at matric suctions between 0·05 and 1·0 atmospheres.

Despite the increased amount of available water retained in these soils there was generally no beneficial effect on crop growth and yields.

Ten experiments (1967–9) on sandy soil in East Anglia measured the effect of magnesium fertilizer on yield and cations in sugar beet. Magnesium fertilizer increased sugar yield by up to 0·80 t/ha and on the three most responsive fields it consistently increased top and root dry·matter yields throughout the growing period.

On average, without magnesium fertilizer, the concentration of magnesium in tops progressively decreased from 0·33% at singling to 0·15% at harvest, and in roots from 0·39% to 0·09%. The corresponding decreases with magnesium fertilizer were (tops) from 0·68% to 0·20% and (roots) from 0·48% to 0·10%. Yield was increased by magnesium fertilizers when tops contained less than 0·35% Mg during May, 0·30% during June, 0·22% during July and 0·17% during August. Deficiency symptoms were not visible until the concentration in tops averaged less than 0·2% – the percentage of plants with symptoms increased rapidly at smaller concentrations. Magnesium fertilizer decreased the concentration of calcium in tops and roots but did not affect the concentration of potassium or sodium.

The maximum amount of magnesium, potassium, sodium and calcium in tops (August–September) was 11, 218, 75 and 62 kg/ha respectively; these decreased to 8, 168, 55 and 50 kg/ha at harvesting, showing that only about 75% of the largest amount in tops was present at harvest. The amounts removed in roots at harvest were 9 kg/ha Mg, 75 kg/ha K, 11 kg/ha Na and 26 kg/ha Ca. A dressing of 100 kg/ha magnesium increased the amount of magnesium in the crop at harvest by only 4·5 kg/ha.

Recent developments in chemical weed control in sugar beet have been reviewed. Two main approaches to the problem of providing reliable season-long control of annual weeds in sugar beet are, (a) the use of mixtures of herbicides applied pre-planting and incorporated into the soil during seed bed preparation, and (b) the use of split applications with a residual herbicide applied pre-emergence followed by a contact herbicide applied post-emergence.

The second approach (b) was examined in a series of field experiments from 1967 to 1969, on light to medium sandy loam soils in the West Midlands. Comparisons were made between pre-emergence application of lenacil and pyrazon, pre-emergence application of lenacil and pyrazon followed by post-emergence application of phenmedipham, and post-emergence application of phenmedipham for weed control in sugar beet.

Under dry soil conditions in April 1967, lenacil and pyrazon controlled only about 40% of the annual weeds, but in 1968 and 1969, when moist soil conditions predominated in April and May, lenacil and pyrazon controlled 80–95% of the annual weeds.

Phenmedipham applied post-emergence gave about 90% control of annual broadleaved weeds initially, but it seemed unlikely that a single application of this herbicide would provide satisfactory weed control in sugar beet.

In each of the 3 years 1967–9, a split application of a soil-acting residual herbicide (pro-emergence) followed by phenmedipham (post-emergence) gave outstanding weed control and enabled sugar beet to be established and grown until mid-June at least, in a near weed-free environment. It was concluded that this technique was the most effective for weed control in sugar beet on light to medium sandy loam soils in the West Midlands.

The contribution of the legume Stylosanthes gracilis to the nitrogen economy of mixed swards was assessed under both cutting and grazing conditions. In a cutting experiment, carried out during two wet seasons, a S. gracilis/Chloris gayana sward gave the same yields of dry matter and crude protein as a C gayana sward receiving 75 lb N and 167 lb N/acre (84 kg, 187 kg/ha) respectively. Lower yields were obtained from mixed swards containing Centrosema pubescens and Desmodium scorpiurus.

In a grazing experiment the mean live-weight production from a S. gracilis/Digitariasmutsii sward was equivalent to that produced from a pure grass sward receiving only 13 lb N per acre (5·9 kg/ha), although greater beneficial effects of the legume were apparent under high stocking conditions. In both experiments the legume tended to become dominant after 2 years.

Herbage yields from a S. gracilis/C. gayana pasture were significantly increased by phosphorus and sulphur; S. gracilis was particularly responsive to these elements. Under lenient defoliation, nitrogen reduced the proportion of the legume in the mixed sward, although frequent defoliation reduced the harmful effect of the nitrogen.

The results are compared with other published data and are discussed in terms of ways in which the grass/legume balance can be altered by different management practices.

Symptoms of magnesium deficiency and take-all disease occurred during 1967 in wheat grown for the second year in succession on the ‘Classical’ cereal site at Woburn. Magnesium fertilizers, which cured the deficiency symptoms and increased wheat yields in 1968 and 1969, had no effect on take-all. Leaves from crops severely attacked by take-all contained less nitrogen and potassium than leaves from unattacked plants but not less magnesium. In 1969 magnesium fertilizer did not increase yields or affect takeall of spring barley on the site but, in contrast to 1968, increased potato yields. Magnesium fertilizer improved the establishment of clover, especially on soil containing least magnesium.

Soil analyses show a tenfold decline in exchangeable Mg since 1888. Losses were most from soil given ammonium sulphate and more from the site where wheat was long grown than where barley was. Differences in soil magnesium did not explain large differences in yields of potatoes or leys between blocks of the experiments.

In an 80 acres (32·4 ha) grazing trial carried out over a 2-year period significant increases in cattle live-weight gains were achieved following the oversowing of savanna grassland by 4 lb/acre (1·8 kg/ha) of Stylosanthes gracilis (stylo) seed. The beneficial effects of the stylo was particularly apparent during the early part of the dry season. The early growth and subsequent survival of the stylo was not outstanding.

Better results were achieved in a second experiment where stylo was grown as a pure crop and ration-grazed in the dry season in association with unimproved savanna. The live-weight gain of cattle grazing the stylo only during the 12 h night period was the same as cattle receiving 1·8 lb (0·82 kg) whole cotton seed per day. In general, cattle live-weight gains were directly proportional to the time spent on the stylo.

Two perennial ryegrass swards – one consisting of S. 24, a diploid variety, and the other of Reveille, a tetraploid variety – were compared in a 20-week grazing experiment with 16 Ayrshire cows in 1968 and again with 12 cows in 1969. Each grass sward was grazed at either a high or a low rate of stoeldng and no other feeds were offered to the cows. On average, the amount of herbage dry matter on offer to the cows was slightly greater on the S. 24 than on the Reveille sward but the contents of total soluble sugars and digestible organic matter were significantly higher in the dry matter of the Reveille than in that of the S. 24. The crude protein contents of the herbage dry matter were similar on the two swards. The mean daily milk yields from cows grazing at the high and the low rates of stocking in 1968 were 14·0 and 15·7 kg/cow respectively on the S. 24 sward and 14·7 and 16·1 kg on the Reveille sward. In 1969 the milk yields from these same treatments were 15·4 and 17·2 kg on the S. 24, and 16·5 and 17·7 kg on the Reveille. The fat content of the milk was not significantly affected by the treatments. In both years the solids-not-fat and the crude protein contents of the milk were higher on the Reveille than on the S. 24 sward, but these differences were significant at the low rate of stocking only. The live weight of the cows did not differ significantly between the two swards. The average output of milk per hectare was approximately 4% higher from the Reveille than from the S. 24 sward but the major factor influencing milk production per hectare was the stocking-rate. On average over the 2 years the output of milk per hectare was 36% higher on the high than on the low rate of stocking. It is suggested that in selecting herbage for milk-production purposes attention should be paid to material with a high digestible organic-matter content and a high content of soluble sugars.

Two barley experiments are described in which a range of plant populations were shaded during different periods of development. Shading during the ear development period caused considerable reductions in grain yield, largely by reducing the number of grains per ear. Shading during the grain-filling period caused no reduction in grain yield. It is suggested that under conditions of these experiments there was probably a potential surplus of carbohydrate available for grain filling and that grain yield was largely determined by the storage capacity of the ears. The importance of the number of grains per ear as an indicator of individual ear capacity is emphasized.

The effects of plant population on grain yield and its components are also examined. It is concluded that the number of grains per ear is the component having greatest influence on the decrease in grain yield at above-optimum populations and attention is again drawn to the possible importance of ear capacity. It is argued that on an area basis the number of grains per unit area may give a good indication of ear capacity. Examination of this parameter shows a close relationship with grain yield per unit area for both the shading and population treatments. It is particularly evident that a decrease in grain yield at high populations was associated with a comparable decrease in the number of grains per unit area. It is suggested that this decrease in grain number may be due to a lower production of total dry matter during ear development rather than an unfavourable partitioning of this dry matter between the ear and the rest of the plant. This lower production of total dry matter is attributed to the crop growth rates of the higher populations having reached their peak and then having declined before the end of the ear development period. This crop growth rate pattern, through its effect on grain number per unit area, is put forward as the basic reason why, in the final crop, grain yield per unit area decreases at above-optimum populations.

Forty cross-bred ewes were individually fed from the end of week 13 of pregnancy to parturition on two diets whioh were designed to provide intakes of metabolizable energy above (treatment El) and below (treatment E2) the maintenance requirement of the non-pregnant ewe.

Energy intake had no significant influence on birth weight of single lambs but twin lambs from ewes on treatment E1 were 25% heavier than twins from ewes on treatment E2. A net loss of body weight occurred between week 13 of pregnancy and the day following parturition in all groups of ewes. These losses represented 5 and 10% of body weight in ewes carrying singles on treatments E1 and E2 respectively. In ewes carrying twin lambs losses represented 11 and 16% of body weight on treatments E1 and E2 respectively.

Levels of plasma N.E.F.A. and acetone were used to characterize the state of nourishment of ewes at 16, 18 and 20 weeks pregnant. Values obtained indicated that ewes carrying one lamb on treatment El were ‘moderately’ undernourished. Ewes carrying one lamb on treatment E2 and those carrying twin lambs on treatment E1 were undernourished to a similar degree characterized as bordering between ‘moderate’ and ‘severe’. Ewes carrying twin lambs on treatment E2 and all those carrying triplets were ‘severely’ undernourished.

The absorption and translocation of phosphate by roots of intact seedlings of rape, oats, flax and buckwheat were studied. Two hydroponic experiments were conducted in the greenhouse. A split-root technique was used in which a single root of the culture plants was grown in one solution and the rest of the roots in another solution in a twocompartmented glass jar.

The presence of other nutrients had a favourable effect on root growth and was essential for efficient phosphate absorption. There was a positive relation between the extent of root growth and phosphorus uptake. On the basis of unit weights of a single root, rape was not any better than oats and buckwheat. A single root of rape, in the presence of other nutrients, absorbed two-thirds of the phosphorus absorbed by all the other roots, whereas single roots of buckwheat, oats, and flax were much less efficient than the rest of the roots. In the absence of other nutrients, single roots of buckwheat, rape and oats absorbed 4·61, 0·18 and 3·49%, respectively, of the phosphorus supplied. However, in the presence of other nutrients, the corresponding values were 21·68, 43·86, and 7·62%, respectively. Both in the presence and absence of other nutrients the single root of flax did not absorb phosphorus from solutions high in phosphate. The results indicate that the age of the plant has an important bearing on the uptake and translocation of phosphorus.

Three wheat experiments are described in which a range of plant populations were shaded during different periods of development; in two of the experiments plant thinning was also carried out at a number of growth stages. Shading during the period of ear development caused an appreciable decrease in grain yield by decreasing the number of grains per ear. Shading during the grain filling period also reduced grain yield, this being brought about by decreased grain size. Thus in contrast to the barley experiments reported earlier (Willey & Holhday, 1971), these particular results gave no indication of a potential surplus of carbohydrate for grain filling and an associated limited ear capacity. However, when plant thinning was carried out at anthesis to make more carbohydrate available for grain filling in the remaining ears, grain yield per ear did not increase. It is argued, therefore, that grain yield probably was determined at least partly by a limited ear capacity. Plant thinning at earlier stages showed how the development of competition during the ear development period progressively reduced the potential capacity of the ear; the greater competition of higher plant populations accelerated this reduction in ear potential.

From an examination of the effects of plant population, it is suggested that the number of grains per ear is the component having greatest influence on the decline in grain yield at above-optimum populations. The possible importance of the number of grains per unit area as an indicator of ear capacity on an area basis, and as a determinant of grain yield per unit area, is emphasized. A close relationship between grain yield per unit area and number of grains per unit area is illustrated for a number of plant-population response curves, and it is suggested that the decrease in grain yield at high populations is probably determined by a decrease in the number of grains per unit area. Evidence is presented to substantiate the idea put forward in the barley paper that this decrease in the number of grains per unit area may be attributable more to a lower production of total dry matter by the high populations during the later stages of ear development, than to an unfavourable partitioning of such dry matter between the ear and the rest of the plant.