Crinkle-leaf is an abnormal condition of the leaf of coffee in Kenya, the cause of which is unknown. Preliminary observations showed that its symptoms are suppressed by spraying with captan and experiments were carried out to investigate whether this material would provide an economic coivtrol. Spraying at the rate of 4 lb per acre, when symptoms of the condition first appeared, gave good control but lower quantities were less effective. Means of predicting the severity of the condition have not yet been evolved and the spray programme must therefore be adjusted each season to meet the local conditions. The spraying of nurseries and young suckers is recommended as soon as early symptoms are noted, since the cost is low, whereas the spraying of large areas of mature coffee requires a careful assessment of the possible economic advantages. Susceptibility to crinkle-leaf was found to differ between cultivars.

Responses of crop yield to water stress are classified on the basis of physiological considerations. Crop growth is sensitive to water stress, particularly because of the physiological effects of stress on the production and maintenance of photosynthetic tissue. Crop yield, depending on the nature of the harvested organ and the origin of its constituents, may be more or less sensitive to water stress than crop growth. In applying this information to irrigation management, there is a need for simple quantitative measures of plant water status. The problem of avoiding water stress during critical ontogenetic stages and, conversely, the possibility of using moderate water stress at certain times to improve yield and the efficiency of water usage, are discussed.

The study of climate deals with the analysis of seasonal levels of various meteorological factors which influence us through the aerial environment. Short-term deviations from the expected climatic pattern are described as weather. In agriculture, a knowledge of both climate and weather is an essential basis for the adoption of any farming system and practical farmers all over the world have discovered, by trial and error over long periods of time, patterns of farming suited to their respective climatic areas. In many cases today these farming patterns are no longer economically feasible or socially acceptable and, with the present urgent need for increased agricultural production in the developing countries, there is not time for a leisurely approach to the problem of modifying the systems or finding new ones.

The analysis of radiation climate is a central problem of agricultural meteorology because rates of photosynthesis depend on the receipt of visible light and rates of transpiration depend on the net exchange of radiation by a crop canopy. Both short-wave (solar) and long-wave (terrestrial) radiation are correlated with cloud amount, and in south-east England the income of net radiation in summer is proportional to the income of solar radiation.

In principle, the fraction of total radiation in the visible waveband depends on cloud cover and on the amount of absorption and scattering in the atmosphere, but in practice the fraction is often between 0·40 and 0·45. The calculation of photosynthetic efficiency needs a figure for the number of quanta (or Einsteins) per unit energy, and this figure can be calculated from the mean wavelength of the radiation weighted by energy, about 0·55μ for direct sunlight.

The reflection of radiation by vegetation changes with solar elevation, and at angles between 40° and 60° it ranges between 0·15 for a rough crop (e.g. pineapple) to 0·26 for smoother crops (e.g. sugar beet, kale). The transmission of radiation through the canopy can be expressed as a function of the leaf area index and a parameter that depends on the distribution and orientation of leaves.

Nitrogen is the most important, and usually the only, nutrient necessary for high yields of rice in the South Western Riverina of N.S.W. Inclusion of a legume pasture phase in the rotation is a very effective method of improving the nitrogen status of the soil, but small additions of artificial fertilizer at sowing may still be necessary for maximum yields. The addition of phosphatic fertilizers is rarely necessary, except on a few isolated virgin soils, and where pastures are included in the rotation ample phosphate for the rice crop is usually present as a residue from topdressing. Potash and trace-elements do not improve rice yields in this area.

A two-year field experiment was conducted with fifteen varieties of cowpeas to evaluate responses to three different planting dates in relation to flowering and yield of beans. It appeared that most of the cowpea varieties required a day length of more than 12 hours to initiate flower formation. During both years 1962 and 1963, May plantings gave the best results, and July, August and September plantings failed to form flowers.

A survey of citrus groves was conducted by analysing leaf and soil samples from the main citrus growing areas of the island. The leaf data, evaluated by comparing them with the California leaf analysis standards for assessing the nutrient status of citrus leaves, indicated that the California standards are of limited value in attempting to assess the nutritional status of citrus in Trinidad, particularly with reference to the elements zinc and magnesium. The possibility of using soil analyses as an index to the mineral nutrition of citrus is worthy of consideration. Although symptoms of zinc and magnesium deficiencies had often been observed, these elements had not been given the attention they deserved in the regular fertilizer programmes.

Ten weighable containers, the same size as 4-gallon petrol tins, were located in a plot 80 metres from the leading edge of a 2-acre field of irrigated alfalfa growing under advective conditions in the Sudan. Evapo-transpiration from alfalfa growing in these containers was compared with evaporation from a series of small evaporimeters level with the top of the plants and from a standard U.S. Class A evaporation pan, and also with estimates of evaporation calculated by the Penman formula. Evaporation from the free water surfaces in evaporimeters or pan was always greater than from alfalfa in the containers when the crop was 25 cm. high or less, but lower when the crop was more than that height, whilst the figures calculated by the Penman formula were much lower than either. Cumulative water losses were also recorded from containers where the soil was kept wet or allowed to dry out, and these were compared with evaporimeter losses up to the stage where no further water was being lost from the dry containers.

A NPK factorial experiment was conducted during two successive cropping seasons to study direct and residual effects of various treatments on the flower initiation and yield of soybeans. Plants were slower to reach the maximum flowering stage in the year of fertilizer application than in the following year. During the first year potassium in association with phosphorus delayed the flower forming process, whereas potassium alone hastened flowering in the second year unless associated with a high dosage of nitrogen. All the treatments gave far greater yields in the first season, suggesting that fertilizers should be applied during every cropping season. Nitrogen and phosphorus at 20 pounds of N2 and P2O5, per acre gave the biggest yields, but potassium failed to show any response. The residual responses to potassium and phosphorus during the second year were significant but not to nitrogen.

The effect of available water on yield (e.g. Waring, Fox and Teakle, 1958) and of nitrogen on yield and quality (e.g. Waring and Teakle, 1960) have been examined for wheat grown on black earths of the Darling Downs in Queensland. However, the joint effect and individual contributions of nitrogen and water to this effect in the field appear to have been neglected. Further, the condition known as mottled wheat, described by Wood (1960), is an important problem in the wheat industry, and it was felt by the authors that this condition was the result of a water-protein yield complex. It was therefore decided to examine the effects on yield, total protein and mottling of applications of nitrogen and water in a soil where these were deficient.

A factorial (3 × 3 × 3) experiment using three levels of nitrogen, phosphate and potassium was conducted to evaluate the effects of these elements on the formation of nodules. Results indicated that increasing levels of nitrogen depressed the formation of both effective and ineffective nodules, but phosphorus and potash did not produce any significant effects. Although the soils of the experimental plots were highly leached and strongly acid in nature, the native strains of rhizobia were able to produce copious amounts of effective nodules on plants growing on plots where no nitrogen was applied. It appeared that the naturally occurring rhizobia strains in these soils are well adapted to their natural environments.

It is suggested that irrigation should ideally be based on two sets of measurements, i.e. of conditions in the leaf and of cumulative evaporation rates respectively, on the assumption that the question 'When to irrigate ? ’ can best be answered from a knowledge of leaf water potential and the daytime behaviour of stomata, and the question ‘How much water to apply?’ from a knowledge of the current soil water deficit. It is emphasized that there is no unique or fixed relation between leaf water potential and soil water deficit, and since neither can be deduced from the other it is advisable to measure both in critical experimental work on irrigation. Various methods of measuring leaf water potential and evaporation rates are discussed, and their value in experimental work assessed.

An experiment was carried out in the glasshouse to determine the availability of P, and utilization of added phosphate fertilizers from three fertilizer materials, applied by two different methods to sugar cane grown in four diverse soil systems. Phosphorus was applied at the equivalent rate of 175 pounds P (400 pounds P2O5) per acre. A larger response from added P in terms of plant yields was obtained from an aluminous ferruginous latosol and least from dark magnesium clay. Differences in yields of sugar cane were evidently associated with differences in P content in the cane plants and, in certain cases, with a reduction in Al content in plant tops, and the less soluble superphosphate increased yields more than the highly soluble NH4H2PO4. Phosphate fertilizers applied as foliar spray greatly increased the P content in the plants, and plants contained twenty times more P when sprayed with NH4H2PO4 than when the same fertilizer was applied to the soil. However, increased P content in the plants did not necessarily indicate that the P was translocated within the plants or that the added P participated in metabolic processes. The evidence indicated that in soils where the ‘A’ value was high the P status of the sugar cane tops was not correspondingly high.

Pot experiments were used to test the effect of incorporating various organic materials in the soil on the nodulation of peas (Pisum sativum). Only farmyard manure gave a consistent increase in the number and weight of nodules, and also in plant growth, increases which were also produced by the aqueous extract of farmyard manure, although none of these increases were as large as those obtained by the addition of a combination of P and K fertilizers or activated vermiculite. Field beans (Vicia faba) and French beans (Phaseolus vulgaris) in general reacted in the same way as peas.

Lagière's B9 from Allen 51–296 (Gossypium hirsutum) was found to be non-homologous with Knight's B genes B1–B7, B9 and Bherb. To differentiate between this gene and Knight's B9 from G. herbaceum the symbols have been changed to B9L and B9K respectively. It was impossible to test Knight's B10 from Kufra Oasis G. punctatum and Lagière's B10 from Allen 51–296, but to avoid confusion it is proposed that these genes should be known as B10K and B10L.

A method is described whereby starch level in wood of Coffea arabica L. was estimated by means of visual scoring. The correlation between the amount of starch thus found and the quantity established by chemical analysis proved to be + 0.925, +0.932 and 0.819 in young, semimature and mature wood respectively. No satisfactory way was found for making a similar estimate of the amount of starch in the leaves.

The dry-matter and organic-matter digestibilities of eight samples of fodder maize and five samples of maize silage were measured, using sheep. The maizes were harvested and ensiled in such a way that comparisons could be made between the digestibilities of either the same maturity types, harvested on different dates, or of different maturity types harvested on the same date, or of maize and silage made from similar material. The total range of organic matter digestibility for all types of maize on all dates was within the range 70·6 to 75·2 per cent. The digestibilities of maize silages were found to be slightly lower than those of the original materials.

A perennial rye-subterranean clover pasture in Western Victoria, Australia, was fertilized at three levels of sulphate of ammonia and subjected to eight cutting treatments over four months in autumn–winter. The cutting treatments simulated deferment of grazing for different periods followed by fortnightly defoliation. Both nitrogen and cutting had significant effects on first cut and total yields for the period. There was interaction between nitrogen, cutting and first cut yield but not between nitrogen, cutting and total yield for the period. The results are used to argue that, in the year of the trial, deferred grazing was likely to have been profitable and nitrogen fertilization to have been unprofitable.

The amount of starch in branches of Coffea arabica L. was studied by means of a method of visual scoring. In cropping branches, the variation in starch level was greatly, but not completely, determined by the growth of the crop. More knowledge of the formation and distribution of the products of photosynthesis is needed before a satisfactory explanation can be offered. Starch levels in non-cropping branches were higher than those in the cropping branches, but followed the same pattern of fluctuation. In general, translocation of starch occurred rapidly throughout the tree but some exceptions to this rule were found.

Experiments involving N, P, and K fertilization, and height and frequency of cutting, were carried out on a mixed pasture of giant stargrass (Cynodon plectostachyus) and centro (Centrosema pubescens) at the University of Ibadan during the growing seasons 1951–61. For the first cut after fertilization yield responses of 17 and 24 per cent resulted from applications of 50 and 100 lb N per acre respectively in various experiments but the effect was transient and recovery of fertilizer nitrogen probably did not exceed 30 per cent. Nitrogen fertilization of sown pastures is unlikely to be an economic practice in Nigeria in the forseeable future. Yield responses of 30 per cent resulted from applications of 2½ and 5 cwt superphosphate per acre with a marked residual effect two years after application. Significantly higher concentrations of extractable inorganic soil P at the higher P fertilization rate after 2 years were largely a reflection of the levels of the iron phosphate fraction, but similar trends were evident in the aluminium and calcium phosphate fractions. No differences were found in total, organic, or residual P. The proportion of centro in one 1959 cut for the 0 and 5 cwt rates of superphosphate were 46 and 38 per cent whereas N had no effect, the reverse of the response normally encountered in a temperate mixed pasture. No response to K was obtained. Increased frequency and height of cutting both resulted in decreased yields of dry matter but cutting at 2–4 inches at 8-weekly intervals appears to be the most satisfactory method of managing this pasture for hay production, with yields of approximately 2¼ tons dry matter per acre.