At Pantnagar, India, linear response in maize to nitrogen application was observed up to 150 kg. of N/ha. with some of the most promising hybrids and composites released by the All India Co-ordinated Maize Improvement Programme. Increase in grain yield, and total nitrogen accumulation in grain, were substantially more in Ganga 2 than in the local cultivar or the composites, at higher rates of N application. In absolute terms, the local cultivar accumulated more nitrogen in its grain, but the relative amounts declined at higher rates of N application. Among the yield components influencing ultimate grain yield, barrenness exerted a negative influence on grain yield through the number of cobs per plot. Among cob characters, such as thousand grain weight and number of grains per cob, the former exerted a substantial influence on grain yield.

Various sequences of different daylength regimes were given to five potentially tropically-adapted soyabean and three cowpea cultivars, to establish the duration of the photoinductive period which is necessary for their subsequent satisfactory development for experimental trials in the U.K. in long summer days. Genotypic differences in response to photoperiodic delay of flowering were clearly distinguished, but unless these soyabean and cowpea cultivars were kept in short photoperiods for at least 49 days, flower retention and pod development were adversely affected when they were subsequently planted in natural U.K. long summer days. The developmental stages from juvenility to flowering are discussed.

The response of six cane varieties to nitrogen fertilization (0, 70 and 140 kg. N/ha.) has been studied. Results of three ratoon crops from 23 trials on representative sites throughout Mauritius indicate that optimum fertilization is around 70 kg. N/ha. Three levels for optimum nitrogen in the third leaf blade have been established, namely 1·93, 2·05 and 2·22 per cent corresponding roughly to the sub-humid, humid and super-humid areas of Mauritius.

The results of a three-year water conservation trial in the Zambezi Valley of Zambia are reported, for an area characterized by high temperatures and low, often poorly distributed, rainfall, with low infiltration and high evapotranspiration rates. As a result of these conditions local farmers often produce grain crops yielding as little as 200–300 kg./ha., though considerable increases could be obtained by simple water conservation methods. Of four treatments, tieridges made before the start of the first rains consistently gave the heaviest yields. Mean yields of the three crops under trial (maize, sorghum and bulrush millet) were higher on tie-ridges than on conventionally prepared seedbeds by 168, 159 and 17 per cent in the 1968–69 to 1970–71 seasons respectively.

Application of dimecron to cowpea plants increased grain yield, its effect being more pronounced in widely spaced plants and those planted in March. Dimecron increased grain yield by encouraging greater leaf area development, by increasing the number of flowering inflorescences and the number of pods set per inflorescence, and by decreasing the number of shrivelled pods. March planting encouraged greater dry matter production than January and May planting. Dimecron application decreased the number of Ootheca beningseni, reduced the proportion of leaf damaged by these insects, and reduced the number of plants infested with aphids and Acidodis larvae.

Root measurements on three Malayan varieties of tapioca (high, medium and low-yielding clones) showed that the onset of tuberization brings about a slowing-down or cessation of growth in root length, but no changes in stem growth rate were associated with the onset of tuber growth. High yield was associated with high tuber weight rather than with tuber number, which could be related to the size of storage tissue cells formed by the root cambium. The process of tuberization in tapioca is discussed generally.

Sources of variation in the leaf area of rice were examined from 11,356 sample leaves. The three major sources of variability, in decreasing order, were variation among leaves within tillers, variation among tillers within hills, and variation among hills within plots. Within the same tiller upper leaves were larger than the lower ones, except for the flag leaf. Larger leaves were also associated with the taller tillers in a hill. For assessing leaf areas of rice in experimental plots, it is suggested that all leaves from the middle tiller of each sample hill be measured. Furthermore, to avoid border effects, at least two outermost rows on each side of a plot should be excluded from leaf area determinations.

Analysis of a 4-parent diallel cross showed marked heterosis for yield and its components in two crosses (Mexipak × Dirk and C273 × AU49) under irrigation, while little or negative heterosis occurred under moisture stress. A large part of the genetic variation among crosses for yield, and most components of yield, was attributed to the general combining ability, indicating that the additive effects were important. Reciprocal effects and various interactions were insignificant except for kernel weight, which suggests that effective selection could be made under irrigation of genotypes adaptable to moisture stress.

The effects of plant population on yield and its components were investigated in three experiments in 1969, 1970 and 1971. Increasing populations from 9000 to 36,000 plants/ha. increased yield linearly. The number of tubers produced per plant was not affected by population, but an increase in plant density decreased average tuber weights. Increasing sett weight from 203 to 608 gm increased tuber yields/ha. and the number of tubers per plant but did not affect average tuber weights in two experiments. In 1971 compound fertilizers increased yield up to the highest rates of 90 kg./ha. each of N, P2O5 and K2O respectively.

Simple, partial and multiple correlations, as well as regression coefficients, were worked out for 14 quantitative characters in a collection of 42 sesame varieties grown for two consecutive seasons. Total number of seeds per plant, number of pods per plant, plant height, height to the first pod and days to flowering and maturity, gave positive and highly significant correlation coefficients with yield and with one another. Partial regression and partial correlations indicated that the number of pods per plant and plant height are important yield-contributing characters.

Two weeks after irrigation there was a temporary water-table between 30 and 127 cm. below the soil surface in four different parts of a grapefruit orchard. As the temporary water-table rose closer to the soil surface the percentage of soil water in the root zone increased and tree size, number of leaves per branch, and leaf size all decreased. Shallow water-tables also induced more die-back and reduced yields significantly. Analyses of soils at various sites indicated that there was no problem of salinity or alkalinity, but physical soil analyses showed that the percentage of clay increased with increased shallowness of the water-table, in line with the soil moisture characteristic curves.

The effects of plant population on the yields of four commercially important Malawian groundnut cultivars have been investigated. Pod number per plant was found to be the most variable component, bearing an inverse relationship to plant density. Kernel weight and shelling percentage were low at reduced populations, and yields and kernel size declined at very high populations. The effect of plant habit upon spacing requirement is discussed and recommendations are made.

Substantial improvement is reported in a quality measure, large seed size, after only one generation of mass selection from a bulk ‘Chalimbana’ population of Zambian land races of the inbred species Arachis hypogaea L. There were large positive correlations between seed size as planted and the subsequent mean size harvested. Large seed also tended to produce an increased proportion of 2- rather than 3-seeded pods, further improving both crop uniformity and quality. Total yield was unaffected, or possibly even slightly enhanced, by planting larger kernels. The circumstantial advantages of mass as opposed to pedigree selection methods are discussed.

Two years study was made on variability in 42 indigenous and exotic varieties of sesame. With very few exceptions, highly significant differences were found between the varieties for the 15 characters investigated. A wide range of phenotypic and genotypic variability was exhibited by all characters except oil, protein and moisture, and 9 out of 15 characters gave heritability estimates exceeding 80 per cent. To relate heritability values to other genetic parameters, a ‘rank procedure’ showed that the characters followed one another in a definite order.

The genotypic and phenotypic correlations and path-coefficients were studied in two different environments, using twenty fodder genotypes of cowpeas. Among quantitative characters, leaves/plant, branches/plant and stem girth were highly correlated with both green and dry matter yield, whereas among quality characters, total protein (per cent) showed significant association with digestibility (per cent). Based on path-coefficient analysis, leaves/plant and protein (per cent) were found to be the most important component characters. These two characters were also highly correlated at both the genotypic and phenotypic level and, therefore, selection based on leaves/plant is likely to be useful for simultaneous improvements in yield and quality of fodder in cowpeas.

The application of molybdenum, as ammonium molybdate at 40 gm./ha. as a foliar spray, alone or in combination with 400 kg./ha. of N, as ammonium sulphate, significantly increased total and soluble nitrogen in the leaves, stem and grains of the high-yielding rice cultivar IR8. The significant increase in protein content of grains was associated with a corresponding increase in most of the protein-bound amino acids, viz. leucine, phenylalanine, methionine and valine, alanine, threonine, glutamic acid, serine and glycine, aspartic acid, lysine, arginine and histidine, asparagine and proline. Nitrogen itself considerably increased the protein content, but nitrogen in combination with molybdenum was more effective.

The sugar cane ripener Mon O45, tested on three commercial sugar cane varieties, showed responses depending on variety, time of application, dosage rate and the interval between application and harvest. Age of crop at application appeared to have little influence on the response. The chemical was also shown to have growth inhibiting properties. The possible use of this chemical to increase sugar produced per unit area is discussed.

Thirteen cultivars of cassava were planted, widely spaced, and harvested after two, three, five and seven months. Differences in root yield after seven months were caused by variations in rate of root bulking, and were not associated with differences in onset of root bulking, which occurred during the second month of growth in all varieties that produced thickened roots.

Effects of cutting lengths on tuber yields and vine production of Missus and Madam sweet potatoes, as influenced by two different fertilizer regimes, were studied on Njala upland soils of Sierra Leone. Cuttings 61 cm. long gave significantly the highest tuber yields for both early-maturing cultivars when fertilized with 336 kg. sulphate of ammonia, 112 kg. basic slag, 448 kg. sulphate of potash, 841 kg. lime and 340 kg. sulphate of magnesium per ha. in two split applications a month apart. Fertilized with 502 kg./ha. sulphate of ammonia per application for 4 applications, 61 cm. long cuttings again gave the highest vine production. The lower the vine/tuber ratio, the higher the tuber yield.

Field experiments conducted over 2 years to evaluate the merits of fractional application of N to hybrid maize unequivocally established its utility in circumventing leaching losses and consequently boosting grain yield. Combinations of fractional application need to be phased to minimize leaching losses and also to correspond to crop needs. Fractional application improved yields even in years when the incident rainfall was evenly distributed.