The effects of populations of 33,000–250,000 plants/ha on growth and grain yield of two cowpea genotypes of bush growth habit was studied in lowland Papua New Guinea. The optimum economic seed rate seems to be 100,000 plants/ha; increasing the plant population decreased pods/plant and lateral branch development, but increased seed number/pod. Genotype UV.53 yielded more than UV.19 due to a combination of all three yield components, and a large dry weight. Growth analysis showed that treatment effects were mediated by differences in growth between 8 weeks and harvest.

The effect of split application of N on the uptake of N by wheat from N15 labelled ammonium nitrate and urea was studied in the field. Nitrogen fertilizers were applied at 120 kg N/ha in a single application (at seeding); two split applications (at seeding and tillering); and six split applications (at seeding, tillering, boot, heading, flowering and the milky stage). Nitrogen applied in two splits was most productive for grain yield for both the N sources, but six split applications significantly increased the protein content in grain compared with single or two split applications. The utilization of N from ammonium nitrate in grain was significantly higher than from urea when applied in six split applications.

Mean yields and average trends with time are given for cotton, finger millet and groundnuts grown in a rotational experiment during the period 1936–64. The experiment, which ran for five cycles, involved a five-year rotation with three different resting periods, five types of resting cover, and farmyard manure at three levels. Yield trends differed from crop to crop, and a critical level of total soil nitrogen is suggested in partial explanation. Responses to farmyard manure in most crops increased over die years, with increasingly marked negative curvature in a pattern that showed most strongly in cotton crops immediately following the application of manure.

The effects of frequency of potash fertilizer application and of different rates on sweet potato yields were studied in three different cropping systems on Njala upland soils. Fertilizers containing higher K rates (448 kg/ha sulphate of potash) and an N/K ratio of 3:4, gave maximum tuber and low vine yields with low vine/tuber ratios on intensively cropped areas, whereas fertilizers containing lower K rates (112 kg/ha sulphate of potash) and an N/K ratio of 3:1 gave maximum but relatively low tuber and relatively high vine yields, with relatively high vine/tuber ratios on newly cropped areas after seven years bush fallow. Two equal split applications of fertilizer is recommended under the weather conditions prevailing in this part of Sierra Leone.

Phenotypic correlation coefficients of flag leaf blade length, breadth and sheath length with plant height, grain yield and its components were computed in four wheat varieties and their ten F2 crosses. Flag leaf sheath length was positively related to plant height, grain yield and its components in almost all the populations, but little or no such relation occurred with flag leaf blade length and breadth in most cases. The data suggested the possibility of selecting plants with longer flag leaf sheaths, with obvious yield advantage.

One ppm molybdenum produced the greatest height, fresh and dry weight per plant; number, fresh and dry weight of leaves; diameter, length, fresh and dry weight of stem; length, fresh and dry weight of roots; yield and yield-attributing characters (height, diameter, fresh and dry weight of curd), and N content of component parts of cauliflower plants (curd, leaf, stem and root). The lowest values for these characters were obtained in the control (nil Mo). Reducing and non-reducing sugars and vitamin C (ascorbic acid) were favourably enhanced (0·5 ppm Mo). The lowest values for sugars and ascorbic acid were observed under 1·0 ppm and nil Mo respectively. The quadratic response curve was drawn in terms of fresh weight of curd and rates of molybdenum application.

Studies of seed pelleting and liming for legume establishment at initial low pH levels in prepared seedbed and natural pasture situations were conducted in 1971 and 1972 at Rio Grande do Sul, Brazil. Lime-pelleted seed often improved establishment and increased subsequent dry matter herbage yield of soybeans, greenleaf desmodium, and perennial soybeans at low pH levels (4·8 and 4·9) and low lime rates. Applying agricultural lime at rates up to 6 t/ha generally improved legume establishment and herbage yields on prepared land or in disked natural grass sod, compared to unlimed areas.

Post-anthesis trends in yield and forage quality of dry matter in components of the maize shoot were studied in experiments with barren and fertile plants grown at 10 plants/m2. In fertile plants, which had a maximum shoot DW 6 or 7% higher than barren ones, the stems (including leaf sheaths) yielded 5 t/ha (42% shoot DW) 30 days after flowering, declining to 3·5 t/ha (26% DW) at final harvest 60 days later. During this period the ear increased by more than 4 t/ha, from 23 to 50% of shoot DW, whereas in barren plants there was little change in DM distribution, with the stem representing about 48% shoot DW, leaf and husk together 40–45% and the ear (rachis only) less than 10%. DM percentage of shoots was similar in barren and fertile plants until maximum DW was attained about 60 days after flowering, after which fertile plants dried more rapidly. In vitro dry matter digestibility was as high in barren as in fertile plants, and the analytical data on forage quality do not suggest that it was positively associated with grain content.