In a 4 × 4 × 4 NPK field experiment with coconut on a sandy soil, N increased girth, height and leaf production during the pre-bearing period, but phosphorus (up to 6½ years) and K (up to 3½ years) had no effect on any vegetative growth parameters. The rates of fertilizers for optimum copra and nut yield (13 to 16 years) were 0.35, 0.73 and 0.64 kg N, PO and KO/palm/ year respectively. The high P requirement was due to the low solubility of the saphos phosphate in these sandy soils. A positive N × P interaction was also observed.

Line sowing of jute has been advocated by some workers for the past 40 years as being more productive than the traditional broadcast method. But most cultivators still prefer broadcast sowing. A comparative study employing identical management practices showed that there is no significant difference in fibre yield per unit area between the two sowing methods. Under similar population pressures self-thinning is greater in line sown than in broadcast crops. Thus, provided similar seed rates and cultural conditions are maintained, farmers may use either sowing method.

P. Palit, A. C Bhattacharyya y B. K. Samanta: Re-evaluación de los efectos de la siembra al voleo y en lineas sobre el rendimiento defibra del yute.

The perennial grass Pennisetum polystachyon was grown alone or in mixture with the indigenous legumes Atylosia scarabaeoidesand Clitoria ternata and the exotic species Calopogonium mucunoides, Centrosema pubescens and Stylosanthes gracilis. Only the last two persisted for more than one or two years. Mean annual yield from the mixture containing Centrosema was 61 to 65 q./ha., of which 20 per cent was legume herbage. The protein content of grass was about 3 to 6 per cent and of legumes 10 to 14 per cent. Mixed swards produced as much protein as in a previous experiment where pure swards of Pennisetum polystachyon received 44. kg./ha. of nitrogen in fertilizer form. Soil nitrogen increased under the Centrosema mixture and yields from the mixture increased during the experiment. Yields of grass herbage from the mixtures were generally lower than those of the grass swards. The reduction in yield of grass grown in mixed swards was mostly due to decreases in the area of foliage rather than to reductions in net assimilation rate.

Banana packing systems rely on floating the fruit in water in order to remove latex produced at the cut surfaces of the crown. At some periods of the year up to 5% of the fruit sinks and rolls along the bottom of the tanks, resulting in heavy scarring of the peel. Potassium content of buoyant fruit exceeded 1·3% dry weight in the pulp and 6·0% in the peel, but in one investigation the sinker fruit had 36 and 20% less than these levels respectively. Application of potassium fertilizer in the field greatly reduced the amount of sinker fruit.

A simple yet effective field screening technique for estimating drought tolerance is described. It involves growing plants in sloping plots which are opposite each other and connected to sub-channels lined with polyethylene sheet. The slopes are designed to achieve instant surface run-off and the sub-channels connected to a main channel for rapid drainage of rain-water. Stress is created at different stages of crop growth by manipulating the timing of irrigation and covering the soil surface with polyethylene sheeting. The technique proved effective even in the monsoon season which is characterized by irregular intensity and distribution of rainfall. Data on six characters for 80 genotypes of pearl millet grown in six artificially created environments representing different levels of moisture stress are discussed. The ‘slope’ technique was effective in creating different levels of moisture stress at various stages of crop growth and in distinguishing categories of genotypes by their relative drought tolerance.

The change in seed oil percentage and 100-seed weight of Brassica juncea Varuna was studied as the crop matured during rabi 1977–78. Statistically, the oil percentage reached its highest value at 55 days from flowering, whereas the 100-seed weight was highest about 20 days later, when the pods were fully yellow. Oil yield (the product of oil percentage and seed weight) also reached its highest value when the pods were fully yellow. This information should enable the crop to be harvested at the proper physiological stage (yellow-podded) for maximum oil yield.

The response of Italian ryegrass (IRG) to nitrogen fertilization, irrigation frequency and harvest interval indicated that management of nitrogen and water is the determinant of productivity under semi-arid northern Mexican conditions. Where water is non-limiting the effects of harvest interval can be eliminated. A soil moisture balance model indicated the inadvisability of seeding IRG in sandy soils if water is a scarce resource because of the high frequency of irrigation that would be required. The seeding (September) and late production (April) periods were identified as critical in regard to irrigation need and limiting in terms of the area that it would be possible to seed.

The West and Central Africa Collaborative Maize Research Network (WECAMAN) was established in 1987 to strengthen the capacity and capability of national programmes of West and Central Africa (WCA) to tackle regional constraints to maize production. The Network created several mechanisms for implementing, monitoring and evaluating maize research and development activities, including research project development and implementation, attendance and quality of paper presentation at technical conferences organized by the Network, scientific monitoring tours, consultation visits, mid-term reviews, and end-of-project reviews and impact assessment. WECAMAN's approach to the system of allocating research responsibilities and competitive grants resulted in increased research efficiency and the generation of sustainable technologies that have catalysed increased maize production in the region.

Genotypic correlations and path coefficients were used to determine the importance of various characters as components of yield in castorbean. Number of primary branches per plant and 100-seed weight had high positive correlations with yield per plant and with each other. Oil content was significantly and positively correlated with 100-seed weight. The path analysis revealed that number of clusters per plant, number of branches, height at maturity and yield of the first spike had the highest direct effect on yield per plant. Sixteen selection indices were constructed using these four yield components, the index combining all four being about 54 per cent more efficient than straight selection based on yield alone.

Variety, spacing and harvesting date trials with fodder beet were carried out in Cyprus under rainfed conditions. The variety Polyrossa gave the highest dry matter (DM) yield, 12,906 kg/ha. Yield of DM increased linearly with population density to an optimum spacing of 45 × 20 cm. Yields of beet decreased slightly when harvested after 15 June and significantly when harvested after 29 August. Irrigation with saline water increased DM yields.

Dry weight, stem and branch length and node number, and flower and fruit number where appropriate, were recorded through the season on cotton, groundnuts, kenaf and sesame in the central rainlands of the Sudan in 1965. For each sampling date variation within plots and betweenreplicate plots within blocks and treatment x block interaction have been studied, together with the effect of these components on the magnitude of the residual root mean square in the analysis of treatments x blocks. The main components were usually within plot and between replicate plots within block errors. Uncontrolled variation was unacceptably great, and was thought to be in large part the result of irregular surface drainage conditions. It seems more likely to be useful to include surface drainage contrasts in field experiments subject to high intensity rainfall on this impermeable clay soil than to attempt to increase precision alone.