Following preliminary work in the previous year, further field trials were carried out with strains of the pearl lupin (Lupinus mutabilis Sweet) at Oxford, England. Two strains originating in Argentina and one in Bolivia were considered to show promise for development as crop plants in England if toxic alkaloids can be bred out of them. The seeds harvested had a crude protein content from 38·6 to 41·8% and an oil content from 13·1 to 14·4%. Advice is given, based on these trials, on sowing date and spacing.

The rapid post-harvest deterioration of cassava roots, which usually prevents their storage in the fresh state for more than a few days, is poorly understood. Two types of deterioration are defined, namely primary, shown by internal root discoloration, and secondary, caused largely by wound pathogens. Information is presented on the influence of such factors as mechanical damage and plant cultivar upon the development of the two types. Control of primary, and a reduction in secondary, deterioration is achieved during a curing process, but none of the chemical treatments examined gave consistent practical control of deterioration.

Herbicides tested at Kenana Agricultural Research Station (K.A.R.S.) from 1968 to 1972 showed that pre-emergence application of oxadiazon, nitrofen, linuron, phenobenzuron, prometryne, nitralin, diuron and fluorodifen gave satisfactory weed control. Applications of oxadiazon at 2·38 kg/ha, fluorodifen at 7·14 kg, nitrofen at 4·76 kg and nitralin at 3·8 kg had no adverse effect on growth of groundnuts, but prometryne, diuron, phenobenzuron and linuron at relatively lower rates caused phytotoxicity symptoms. Residues from treatment with 7·14 kg fluorodifen, 2·38 kg oxadiazon and 4·76 kg alachlor did not injure test crops, but growth of sorghum and maize was reduced 9 months after applying 3·8 kg nitralin. Phenobenzuron was persistent in soil and most test crops were injured following an application of only 1·9 kg.

Ureaform, applied twice a year, in early spring and late summer, was compared with poultry manure and (NH4)2SO4 top dressings as nitrogen suppliers in a banana plantation. No significant differences between the treatments were obtained in any of the plant criteria, but nitrate concentrations in the soil were higher in the ureaform treatment at the standard nitrogen level than in the standard treatment, within the root zone as well as below it. The spring application of ureaform affected the nitrate concentration in soil for 8 months and was better utilized by the crop than the autumn application, which left a greater residual effect. It therefore seemed that one spring application might be sufficient to meet the banana's nitrogen requirement.

A study was made of the effect of micronutrients such as boron, copper, zinc, manganese and iron, applied as foliar spray or directly to peat soil, on growth and yields of pepper under greenhouse and field conditions. Combinations of micronutrients were applied in two forms, as salts or as chelates. Results showed positive effects on yield and quality of red pepper, and soil chemical tests substantiated the results.

Forty different cultivars of cassava were grown in unreplicated plots at a plant population of 20,000 plants/ha in fertile soil. Harvests were taken at 4, 6, 8, 10 and 12 months after planting 18 varieties. The characteristics of the two highest yielding varieties, M Colombia 113 (66 t/ha) and M Colombia 22 (32 t/ha), were compared with the other types. M Colombia 22 is an early type (25 t/ha after 6 months) with a very high harvest index; M Colombia 113 yields little better than average 6 months after planting. High yield is associated with a balance between leaf production and root production, so that leaf area index does not decline excessively in the later growth stages. Changing canopy structure is unlikely to increase yields.

The efficiency of the randomized complete block design, relative to the completely randomized design, is linearly expressed as: Relative efficiency=A+CF, where A and C are constants determined by the number of treatments (t) and blocks (b) and F=calculated F value for blocks in the ANOVA table. For values of t and b ranging from 2 to 10 the constants A and C are estimated. Curves of relative efficiency are given when o≤F≤10 for t values ranging from 2 to 10 when b=4, 6 and 8.

The design of field trials sometimes raises queries (which often go unanswered) about alternative designs and the best ways of allowing for environmental variation in the area allotted to the experiment. It is shown how recent developments in iterative methods for working out analyses of variance make possible the determination of error for systems of blocks other than the one actually used, and also for the row-and-column case. Some suggestions are also made for judging the error to be expected if plots were made larger.

Trials are described comparing the effects of applying four, eight and 12 sprays of various insecticides on control of Heliothis armigera Hub, and Earias biplaga Wlk., and the consequent effect on yield and quality of seed cotton produced. Yields of unsprayed cotton ranged from 300–900 kg/ha, while four sprays of DDT gave 1000–1200 kg/ha. Increasing the number of sprays to 12, using three insecticides (DDT, endosulfan and carbaryl) gave increments of 300–600 kg/ha over the standard four spray treatment. Eight sprays gave smaller but significant yield increases, and endosulfan, dicrotophos and carbaryl were particularly promising in such regimes. A mixed DDT/phenthoate spray was not superior to DDT used alone. Spraying reduced the percentage of stained cotton.

Since 1970 the University College of North Wales, in co-operation with the Saudi Arabian Ministry of Agriculture and Water, has been investigating the potential for forage production in all-year-round irrigated conditions in Saudi Arabia, and the principal results of the first 4 years of field experiments are discussed. Both temperate and tropical annual forages as well as perennial species were tested, and generally produced high yields with high nutritional value. Fertilizer responses and different management practices were evaluated and their relevance to the development of systems of forage production are discussed.

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.

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.