Instruments and techniques are described for measuring the interception of light by the canopy of a crop, the CO2 exchange of individual leaves, leaf extension rate, and root distribution. Suitable systems for recording are also reviewed. Names and addresses of manufacturers are cited for a few representative models.

Minimal competition was observed between adjacent plots of climbing bean varieties and maize in association, but there was a large head border effect which was not uniform among varieties. Head borders of 1 m at each end of the plot are recommended and a net plot size of 11 m2 with 3 replications for climbing bean varieties associated with maize was found to be adequate to detect significant differences in yield of beans of 24% of the mean. For climbing beans in monoculture a somewhat smaller plot (8 m2) would achieve the same level of precision. Larger plot sizes in general were needed for maize comparisons, especially in association.

Twelve varieties of sugar-cane grown in Barbados, West Indies, during the past 40 years are compared with respect to cane yield performance in trials and in agriculture. Comparisons are based on data-pairs matched for site, season and crop, using both means and variety-on-variety regressions. Conclusions are that: trials greatly over-estimate mean agricultural differences between varieties; variety-on-variety regressions reveal numerous GE effects and account for much variance, but agree poorly as between trials and agriculture and are not useful in improving prediction; in view of the universal use of trials for prediction and decision-making, it is a matter of some practical importance that their validity should be tested in other crops.

An account is given of large-scale trials of the use of saline water for the trickle irrigation of forest trees in the desert areas of Abu Dhabi, in eastern Arabia. Water of salinities up to an equivalent of 16,000 ppm have been used on Casuarine glauca and Eucalyptus camaldulensis. Growth rates ranged from 1.7 m in 7 years on salinities of 16,000 ppm to 10–12 m in 8 years on salinities of 2000–2500 ppm. Trickle irrigation appears to allow the use of more saline water than can be used with other systems, perhaps because plant roots are not subject to the fluctuations in moisture stress that occur under all other systems.

The ‘banjhi’ or dormancy cycle in free-growing tea trees appears to be the result of an endogenous rhythm. However, in harvested tea apical dominance causes dormant shoots to be produced under conditions favourable to growth, and the synchronized flushing cycle causes periods of apical shoot (active terminal bud) and secondary shoot (dormant terminal bud) production.

A field experiment evaluating criteria for scheduling wheat irrigation was conducted from 1975 to 1977 in a sandy loam soil with treatments scheduled according to physiological stages, soil moisture conditions, pan evaporation and leaf water potential. Grain and straw yields, spikes/m, fertile spikelets/spike and number and weight of grains/spike were significantly influenced by treatments. Irrigation based on leaf water potential was as good as when based on physiological stages or soil moisture, and the use of pan evaporation was no better than other methods of scheduling.

In three field experiments, peat pH increased in parabolic relation to liming at the rate of 0.0544 pH unit/t/ha between 0–40 t/ha lime, but only 0.0224/t/ha between 40–72 t/ha. Groundnut and sorghum seed yield and crop residue also showed parabolic responses to peat pH and liming, but groundnut seed yield correlated poorly with soil pH (r2 = 0.38, P = 0.05), compared with its crop residue as well as with sorghum seed and residue (r2 = 0.75, 0.76 and 0.79, respectively, P = 0.01). Groundnut was generally more tolerant of peat acidity (pH 3.35–3.65) than sorghum, giving higher plant survival in unlimed plots, optimum seed and residue at pH 4.60 compared with 5.70 for sorghum, and reduced responsiveness to pH increase. Seed and residue of both crops decreased with continuous cropping, probably because of increasing pest and disease incidence and depletion of available soil nutrients.

In three field experiments studying the liming needs of cassava on peat, optimum tuber DM was obtained at pH 3.8 and optimum top DM at pH 4.2; liming to higher pH values decreased tuber DM while maintaining top DM. Consequently, the Harvest Index decreased over the whole range of soil pH studied (3.49–5.50). Increases in tuber DM per hectare with liming, and with an increasing growth period, were associated with mean tuber weight (r = 0.86) and with Harvest Index (r = 0.65) rather than with tuber number (r = 0.37).

Inoculating Zea mays (three cultivars), Sorghum bicolor, Panicum miliaceum and Setaria italica with nitrogen-fixing bacteria of the genus Azospirillum in Northern Negev and Bet Shean Valley field experiments resulted in significant increases in yield of grain and foliage of commercial value. It was concluded that inoculating summer cereal crops in Israel may save valuable nitrogen fertilizer.

An experiment was conducted during the 1978/79 summer at the Central Cotton Research Institute, Multan-Pakistan to evaluate the crop production patterns of two cultivars of cotton (G. hirsutum L.) differing in their reaction to heat-induced sterility. Boll set in variety ST3 amounted to 7.7% of the total fruiting points, from flowers opening during the hottest months of June, July and early August, while almost all the fruiting points produced by cultivar B557 during the same period were shed and no bolls were set. Of the flowers examined during July, 83.3% in B557 contained non-dehiscent anthers against 6.7% in ST3.

Considerable variation in seedling vigour was observed among 36 maize populations; genotypic variances were generally high for emergence percentage (E%), emergence index (EI), dry-matter accumulation and relative growth rate (RGR). Broadsense heritability values and environmental variances indicated that E% and EI would be more reliable indices for seedling vigour than emergence rate index (ERI). The expression of growth rate (GR) was influenced more by the environment than the genetic constitution of seedlings; GR was not therefore an effective indicator for seedling vigour, and RGR would be preferred because it was more heritable and less influenced by the environment.

Results from field experiments showed that number of mature grains per plant was related to the plant growth rate during the pre-flowering period. This relation was further improved when growth rate was expressed relative to the rate of plant development. This evidence supports the theory that grain abortion is linked with assimilate production.

Mesquite (Prosopis spp) is a nitrogen-fixing and drought-resistant leguminous tree which exists in many of the semi-arid regions of the world but little has been done to develop its potential for wood, nitrogen fixation or pod yield. We report field and greenhouse cultural practices for mesquite and the results of a field screening trial for biomass production of 32 accessions, representing North and South American and African germplasm. Non-destructive biomass estimates, derived from height and stem diameter measurements, had a 180-fold range; the preponderance of slow-growing accessions were from the rangelands of southwestern USA.