The genus Phaseolus as currently recognized contains four pulses: common bean (P. vulgaris), runner bean (P. coccineus), lima bean (P. lunatus) and tepary bean (P. acutifolius). Although these all have their origins in tropical and sub-tropical latitudes, they have evolved in different ecological zones. The runner bean has evolved at higher altitudes, the common bean at intermediate levels and the lima bean at lower altitudes. The tepary has a specialized desert-annual life-form. The occurrence of day neutral genotypes in all species has permitted their spread into cool and worm temperate zones (the common and runner beans) and the warm temperate zone (lima bean). It is possible therefore to grow one or other Phaseolus species in most areas of the world where cultivation can be practised. The common bean has evolved the widest range of growth forms, seed and pod sizes, pod forms and textures, and seed and pod colors. World-wide an enormous primary gene pool has been produced. The common bean pool is the secondary gene pool for the runner bean and vice versa, since partially fertile interspecific species produce sterile or inviable F1 hybrids so that potential for interspecific gene transfer is limited. Thus no known secondary gene pools exist for Phaseolus species other than P. vulgaris and P. coccineus.

The development and influence of crop drought stress was examined in winter-planted small-grain cereals under Mediterranean environmental conditions. In two average or wetter than average years crop drought stress in the grain-filling period was greatly exacerbated by the addition of fertilizer (N and P) and this usually resulted in significantly lower kernel weights. Yet this reduction was not so substantial as to seriously affect crop yields. Total grain yields were largest in treatments receiving fertilizer, due to greater spike numbers and numbers of kernels per spike. But heavy nitrogen applications may promote the risk of a large proportion of small or shrivelled grains in a dry year.

Examples are taken from three biometrical texts, two unpublished experiments and Yates (1937) to illustrate quantitatively how the lay-out of the plots can affect the estimate of error variance in field experiments and how confounding of treatment and positional effects can arise. In two examples in which the plots did not run the whole length or width of the block, the estimates of error were reduced by one half and one quarter respectively by allowing for sub-blocks within blocks or for rows and columns. In split-plot experiments where the main plots were split breadthwise, the sub-plot error was about the same size as the main-plot error or larger whereas it is expected to be at most one third that of the main plots when these are split lengthwise. Serious bias can arise in the estimate of treatment effects due to confounding with positional effects; this is illustrated.

Checker-board field layouts are used to screen sorghum genotypes for resistance to Striga. A systematic check entry is used to monitor crop growth conditions and methods to analyse the results are assessed.

The relationship of leaf weight ratio (LWR), leaf area ratio (LAR), stomatal frequency and dry matter (DM) production with yield and with photosynthetic efficiency, as reflected by 14CO2 fixation rate, was studied in fox-tail millet (Setaria italica) for three consecutive years. Several genotypes were identified which combined small leaf area and/or low stomatal numbers per plant with productivity under rain-fed conditions equal to that of genotypes with large stomatal numbers. 14CO2 studies in these genotypes showed that the rate of carbon fixation by the leaves was greater, at any canopy position, than in the corresponding large LA/large DM types. Genotypes with consistently small stomatal numbers per plant, associated with good dry matter accumulation and productivity, may also show small transpirational water loss under rain-fed or drought conditions. It is concluded that such genotypes are desirable for better productivity under these conditions.

The influence of air temperature (T), vapour pressure deficit (vpd), irradiance (Q) and leaf water potential (ψ) on diurnal stomatal movement of coffee plants was examined under field and controlled environmental conditions. Leaves of plants grown under shade had larger stomatal conductance (g) values than plants grown in open sun. Stomatal responses to vpd under constant temperature conditions were very strong, indicating that ambient humidity could play a major role in controlling stomatal aperture. Changes in g as vpd increased probably contributed to observed reductions in the rate of net photosynthesis (Pn), though the effect of vpd on Pn was smaller.

Obtaining yield–density relationships for perennials is difficult. Apart from the long time span involved, problems are also posed by the different types of uncertainty associated with field experimentation. Consequently researchers have explored alternative means. This study uses survey data as an alternative. The data show sufficient variability around the density which is regarded as optimal for Typica variety of coconut (158 palms ha−1) to be of value for estimating its yield–density function. A quadratic function gives a good fit to the data. Results suggest that the yield maximizing density of variety Typica form typica is relatively insensitive to the influence of fertilizer practices adopted by farmers and to variations by agroclimatic sub-regions.

A three-year experiment examined the possibility of increasing the cropping intensity of a medium-deep Alfisol (red soil) by using sequential, relay, ratoon or intercropping systems. It was found that a short-season mungbean (Vigna radiata) crop could be taken before the commonly-grown castor crop but that castor yields were reduced by the delayed sowing. If the castor was sown after the harvest of mungbean in a sequential system the profits were less than from a sole castor system. Relay-sowing the castor 20 days before the harvest of mungbean gave 9 $US ha−1 greater profit than sole castor, but this is probably not enough to justify the more intensive double crop system. On the other hand a reasonable yield of horsegram (Macrotyloma uniflorum) could be produced after an early pearl millet crop, giving a worthwhile extra profit of 21 $US ha−1 compared with sole pearl millet. Ratooning the sorghum gave ratoon yields that averaged only 14% of the first crop, so this system was not considered suitable for these lighter Alfisols.

Intercropping systems of pearl millet/groundnut, sorghum/pigeonpea and groundnut/pigeonpea gave average yield increases of 24, 47 and 46%, respectively, compared with both component crops grown separately. Compared with growing only the higher value sole crop, increases in profits were 16, 82 and 120 $US ha−1 for the same three systems, respectively. It is concluded that intercropping systems provide the best opportunity for increasing cropping intensity on medium-deep Alfisols.

In a study of the optimum population for melon when intercropped with maize, melon at 5000, 10 000, 15 000 and 20 000 plants ha−1 was intercropped with maize at 40 000 plants ha−1. Melon biomass and seed yield increased linearly with population density in mixed and pure stands while maize yield components were virtually unaffected. Intercropping reduced melon seed yields, mainly because of a reduction in number of fruits per plant, but did not affect seed size. For good weed and erosion control and increased total yields, maize can be intercropped with up to 20 000 plants ha−1 of melon.

A two year field study designed to investigate the effect of spacing on yield of two cowpea cultivars in the savanna and forest zones of Nigeria showed that cowpea yields were larger in the savanna than in the forest zone at all spacings employed. Inter-row spacing wider than 60 cm and intra-row spacing closer than 10 cm could be used for improved seed yield in the savanna zone, while 60 × 20 cm (83 333 plants ha−1) would be optimum for cowpea production in the forest zone.