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.

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.

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 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.

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.

A field experiment was conducted for two years to study the influence of type of seed bed and various mulcheson yield and nutrient uptake by pearl millet, and on moisture conservation, under the semi-arid conditions of Delhi. A flat seedbed stored more moisture, gave significantly higher yield of pearl millet, and increased the uptake of N, P and K, compared withridge and furrow beds. Mulches were effective in conserving moisture, with straw mulch significantly better than dust mulch inits effect on crop yield and nutrient uptake.

Maize yields were significantly affected by the nature of the previous crop. Maize following groundnuts significantly outyielded maize following cotton, which in turn significantly outyielded maize following sorghum or cowpeas, and this order was largely independent of the nitrogen fertilizer regime applied to the maize. Analyses of soil and crop showed that groundnuts increased nitrogen availability in the topsoil, but there was little evidence of any similar advantage after cowpeas.

The world grain situation and shortages of fertilizer place the agricultural industry even more to the forefront of policy and planning in low-income tropical farming areas. Planning must be positively directed toward eliminating the major constraint of inaccessibility to markets. The narrowing of alternative agricultural opportunities as accessibility decreases is indicated for a sample of farm-family households; low-income farmers isolated from the services sector arc particularly susceptible to the constraint of ‘scarcity of season’ which in turn is aggravated by the economic cost of ill-health when this coincides with the period of heaviest agricultural work. The problem which arises is one in which farmers rely on topping-up farm income with income from non-farm activities. Unless a two-to-threefold net income over any other combination of income-earning opportunities can be assured, small-scale producers largely persist in treating farming simply as a way of life by which the subsistence needs of the family can be met without recourse to new input forms.

Close spacing between and within rows significantly increased the biological and agricultural yields of cowpea without exerting clearly differential effects on the three test cultivars of different forms. It is suggested that low yields of cowpeas commonly observed in southern Nigeria could be due largely to low planting density. A six-fold increase in yield of beans can be achieved by halving the current spacing of 90 by 30 cm. provided the crop is protected from field pest damage.

A phenol colour reaction test was found to be useful for classifying rice varieties. The degree of colouration varied between varieties and could be explained by differences in the enzyme activity, expressed as phenoloxidase and peroxidase. Light, temperature and aeration appeared to influence colour development, but age and crop location did not. A concentration of 1.5 per cent was found to be suitable.

Availability of soil water was investigated and the methods of determining the lower limit of availability by biotic and standard 15-bar pressure were compared. Greenhouse-grown sunflower and okra were the test crops for the biotic method. The pressure membrane equipment was used for standard 15-bar moisture determination. Okra and sunflower took up water beyond the standard 15-bar tension, thus lowering the moisture content at moderate wilting below the generally accepted values. In topsoil okra wilted at very high tensions, but at somewhat lower tensions in subsoil samples, unlike sunflower which wilted at higher tensions in subsoil samples. An equation is given which may be used to estimate the moisture content at the moderate wilting point of plants with known wilting tensions.

The effects of three irrigation regimes on growth, yield and quality of cotton were investigated for two seasons in relation to earliness, quality and water-use efficiency, expressed as m. of water/kg. cotton produced. Light irrigations of cotton, at 75 mm. per irrigation every ten days, were economically better than the traditionally-accepted practice of irrigating every 14 days, and markedly better than prolonging the irrigation cycle to 20 days, mainly due to increased market value of the crop. The results also showed that irrigation intervals of 20 days, besides depressing yield, had a deleterious effect on fibre strength, though the different water regimes did not seem to affect other quality tests.