Experiments with farmers' traditional practice of growing cereals with groundnuts demonstrated that the system consistently produced greater cash returns than sole-crop groundnuts. Increasing the proportion of cereal, and incorporating maize in addition to sorghum and millet, increased cash returns even further.

The effects on local cucumbers of supplementary mineral fertilizers over an initial field dressing of 30 tonnes of poultry manure and 4 tonnes of lime/ha, were determined on tropical peat soil in Brunei. Significant yield increases were obtained with supplementary N up to 280 kg/ha but not with K/Mg above the basal rates 78/10 kg/ha. The highest yields exceeded 50 tonnes/ha of marketable fruit, obtained over a 9-week growing period.

The yield of Chipewa variety of soyabean was investigated in relation to spacing and fertilizer levels on a range of paddy soils exhibiting good, medium and poor drainage. Under good conditions of drainage optimum yield was obtained at a density of 100,000 plants/ha and a fertilizer level equivalent to N—54, P2O5—54, K2O—75 and MgO—9 kg/ha. Under poorer conditions of drainage yield continued to increase up to a density of 162,000 plants and fertilizer levels of twice the above rates. Even under sub-optimal drainage conditions, however, satisfactory yields equivalent to about 1500 kg/ha were obtained from this variety.

Measurements of the stomatal apertures of young clonal tea plants (Camellia sinensis) showed that stomata of plants irrigated during the dry seasons only were wider open than those not irrigated during both wet and dry seasons. Similarly, xylem water potential values (ψx) were always higher (less negative) in irrigated than non-irrigated plants, during both wet and dry seasons. The results suggest that more drought-susceptible clones have a greater demand for water than those less susceptible to drought.

Optimum conditions are described for the in vivo measurement of nitrate reductase activity in field-grown cotton leaves. The incubation period depended on light conditions prior to sampling. Addition of 1 mM glycolate had the effect of increasing apparent nitrate reductase activity on most days tested, and followed the general rhythmical pattern exhibited by the enzyme assayed without glycolate. While the in vivo assay appears to correlate well with soil nitrate levels, the choice of assay conditions does not appear to be absolutely critical.

In trials with Helianthus annuus in the highlands of Kenya it appeared that the major constraints for successful utilization of sunflower for forage were: high lodging susceptibility; low DM percentage of the forage; low D-value of the forage when high yielding ( = tall) cultivars are used; and poor silage making characteristics. The proportion and quality of the stem largely governed the nutritive value of the whole plant. A reduced proportion of stem would improve all four constraints, but DM yield would also be reduced. Protein yields were highest at the beginning of flowering, but DOM yields were highest about 9 days later, towards the end of flowering. DM yields were highest towards physiological maturity of the seeds.

Single-leaf net photosynthesis versus light response curves of four Hevea brasiliensis clonal seedlings showed that it was possible to divide photosynthetic rates into high and low classes.

Daily measurements of moisture by neutron probe showed an erratic pattern of ET in the Sudan Gezira, attributed to the redistribution of water and development of cracks in a drying profile. However, dividing an irrigation cycle into periods of 3–5 days revealed a unique trend of ET that was consistently low in the early period, increased to a maximum in the middle, and fell off at the end. Roots suffer from anaerobic conditions for about 5 days after flooding but subsequent drying and cracking improves soil aeration that leads to final depletion of profile moisture and depression of ET.

The nutrient composition of leaves and petioles of three yam species were studied at fortnightly intervals, and in the tubers when harvested at maturity. Highest concentrations of plant nutrients were recorded in D. alata, while D. cayenensis had the lowest. The lamina was more appropriate for determination of N and P contents, while the petiole was more satisfactory for K. Peak nutrient concentration occurred between late June and early July, suggesting that that was the period of maximum demand for nutrients. The dependence of yields on nutrients was demonstrated.

Three experiments testing the effects of nitrogen on melon showed significant varietal differences. Nitrogen increased yields by increasing fruits/plant, seeds/fruit and seed weight, had no effect on fruit weight, size and husk, and increased leaf area through leaf number and leaf size. Fruit growth coincided with a rapid decline in leaf area, indicating that the mottled green fruits contributed appreciable assimilates towards their own growth. The implications of the findings, and the inefficiency of the crop in seed formation, are discussed.

The cyanide contents were determined quantitatively of the peeled roots of 108 cassava clones, which had been previously selected as low-cyanide by the picrate leaf-test, and compared with the qualitative picrate leaf-test scores used for rapid screening. The correlation coefficient between root tuber cyanide content (dry weight basis) and leaf-test score was r = 0·36 (P < 0·01). The picrate leaf-test, while useful for screening large numbers of clones in early stages of breeding, needs augmenting by more accurate methods. There was no significant correlation between root cyanide content and dry root yield (r = 0·18). The cyanide content varied considerably between roots of the same plant; and plants of the same cultivar grown under the same conditions. Possible improvements in the effectiveness of the cyanide screening procedure are discussed.

In a field experiment to estimate water needs of intercropped sorghum and soyabeans, leaf water potential (LWP) and canopy light transmission were measured. Sorghum had 8–11% lower LWP when grown in mixture than alone, but soyabeans, shaded by sorghum had a higher LWP than in monoculture. Absolute LWP values suggest that only about 10% additional water would be required by the mixture compared with individual requirements of the aggressor species in a two-species mixture of this nature.

Three procedures for handling missing values in randomized block experiments with more than one observation per plot are examined, and their effects on the resulting expectations of mean squares in the analysis of variance studied. Using the average of the available observations in the plot in which the missing value occurs has the least effect on the validity of the tests of significance and on the estimation of variance components.

In a two-year study the yields and water use of corn were studied under four planting patterns, with different soil moisture regimes and organic (paddy straw) mulches. Normal planting and irrigation resulted in higher yields and lowest water use efficiency, while double file planting in deep furrows (rafter method) gave greatest efficiency of water use but with a slight decrease in grain yield. Mulches improved water use efficiency by 50–60% and reduced irrigation requirements by four to six irrigations. Under limited moisture conditions a combination of these practices is likely to reduce irrigation requirements by half and to double water use efficiency.

A field experiment to study the response of pop corn (Zea mays Everta) to various levels of nitrogen and plant population was undertaken at the Research Station, Bajaura (HP) during kharif 1974 and 1975. Increases in nitrogen level from 0 to 60 kg N/ha increased grain yield significantly by 54·8%, but yield differences between 60 and 90 kg N/ha were non-significant. Various plant densities did not affect yield significantly. Yield-contributory characters were significantly influenced by treatments and were interrelated with yield under the influence of nitrogen and plant population levels.