Some early attempts to graft black pepper are described. Good unions have formed between different clones of Piper nigrum L., and between different species of Piper grown in a glasshouse in the United Kingdom. The structure of pepper stems is considered in relation to the apparent impermanence, in the tropics, of unions that initially appear to be successful.

The effect of four crops of maize on the distribution of organic nitrogen in ten West Indian soils, given either lime, P, K, Mg and trace elements or no fertilizers, was studied in a greenhouse experiment. The soils were also analysed for ‘available N’ by incubation and chemical methods. Variations in the redistribution of organic N fractions during the greenhouse experiment did not permit conclusions to be drawn on the source of N used by the maize, although the amount of hydrolysable N, particularly hexosamine, amino and hydroxy-amino N, in the initial samples was closely related to N uptake. Part of the chemically stable, non-hydrolysable organic N was broken down by soil organisms during the experiment; this was increased by liming acid soils.

An experiment was conducted on peanut inoculation with Rhizobium inoculum, introduced below the planting level at three different soil depths (8, 12 and 15 cm.), to ensure more favourable moisture conditions for proliferation of the root nodule bacteria, and to obviate the need for frequent irrigation. Inoculation on both sides of the peanut rows, after the plants had emerged, was also tested. The number and weight of nodules per plant decreased with increase in placement depth. Side inoculation after emergence of the plants resulted in significantly less plant infection than placement of the inoculum at 8 and 12 cm. depths. Peanut yield and quality after inoculation at 15 cm. depth were significantly lower than at 8 cm. inoculation.

In a second stock-scion trial with mango in Israel the influence of five rootstocks was investigated. In our first trial, two rootstocks—Sabre and 14·12—had been found suitable and unsuitable respectively. In the second trial, 14·6 and 14·7 were found to be not significantly different from Sabre, 3·2 was found to be somewhat inferior and 14·12 was again unsuitable. The important characters of the 22 varieties grown are described, and an evaluation is attempted of their yield and marketability.

Soil inoculation was tried in field experiments during two seasons using different concentrations and amounts of bacterial suspension and compared with direct seed inoculation of chemically protected and unprotected peanut seed. Soil inoculation gave significantly better results than direct inoculation of chemically protected or unprotected seed.

Large yields of high quality peanuts, which compared favourably with highly nitrogen-fertilized peanuts, were obtained after the application of relatively small amounts (10–40 gm.) of enriched peat inoculant in 5 litres of water per dunam (1/10 ha).

Cross-inoculation tests, based on nodule formation and nitrogen fixation, were made on 21 species of legumes commonly found in the Sudan. The results showed that they may be grouped according to the accepted system of classification, but there were some important inconsistencies in the cowpea group. For instance, Arachis hypogaea and Acacia spp. have their own strains of Rhizobium. The cultural and physiological characters of the rhizobia studied were generally similar to those known for other species of the organisms.

The polyphagous nature of the dark-headed rice stem borer, Chilotraea polychrysa (Meyr.), may contribute greatly to its ability to survive periods of food shortage when rice plants are scarce. Investigations on the preference and survival of C. polychrysa on seven selected hosts belonging to the Gramineae revealed that it oviposited on all the hosts tested, but showed a marked preference for its normal host, rice (Oryza sativa). Survival rates on rice and the alternate hosts did not differ significantly. The percentage of larvae surviving to the adult stage was generally low because of the high rate of mortality from larval to pupal stage, irrespective of host species. In rice, there was distinct ovipositional preference for plants at the maximum vegetative stage rather than for younger plants. The larval survival rate increased with the age of the host from 35 to 65 days, but dropped sharply when infestation occurred on plants 80 days old, by which time the inflorescence is beginning to emerge.

Leucaena leucocephala (Lam.) de Wit. failed to nodulate with 94 of the 99 strains of Rhizobium tested, representing the seven recognized cross-inoculation groups of nodule bacteria. A group of legumes including L. leucocephala, Mimosa invisa Mart., M. pudica L., Acacia farnesiana (L.) Willd. and Sesbania spp. showed the properties of a cross-inoculation group of plants. Rhizobia isolated from these legumes were all fast-growers and nodulate L. leucocephala, often effectively, and also many other tropical legumes, including Vigna sinensis (L.) Savi ex Hassk., which are usually nodulated effectively with slow-growing root-nodule bacteria. The taxonomic significance of the results is discussed.

Fourteen out of 43 fungicides were selected, after laboratory screening, for field trials against coffee berry disease. Each fungicide was compared with a commercial cuprous oxide formulation and an unsprayed control, by assessing conidial production of bearing coffee branches and by recording the percentage of healthy ripe berries picked. In assessments of fungicidal efficiency, healthy ripe berry counts gave more consistent results than those obtained by measuring conidial production. The results from berry counts indicate that in these experiments Ortho Difolatan (BSI ‘Captafol’) was equal, but not significantly superior, to the standard formulation used in estate spraying. The annual rhythm of conidial production seems to have changed over the past five years. The significance of this is discussed in relation to the control of coffee berry disease.