Trials were conducted for three seasons at a range of altitudes in Tanzania to investigate the effect of plant populations and levels of applied nitrogen and phosphate on the performance of maize varieties. Increasing population to 47,500 plants per hectare gave increased yields even though cob size and number of cobs per 100 plants showed considerable reductions, but 72,000 plants/ha. is probably too many for late maturing varieties. Sites over 900 m. showed good response to applied fertilizer, but below 900 m. response was much smaller or absent. Cob height was increased by fertilizer but hardly affected by spacing, no treatment made any appreciable difference to days to 50 per cent pollen shed, and lodging increased with closer spacing.

When wetted overnight by dew, dye spots on a cone-shaped paper ‘sensor’ will spread to an extent which depends on both the duration and the intensity of dewfall. Results from such a sensor have been compared with those from the de Wit recorder. Although only a qualitative assessment of surface wetness is obtained, the paper sensors are cheap and easily replicated, they can be stored for assessment later and they can be made in sizes to suit any particular situation in the field.

Effects of moisture stress during different stages of cotton development were examined in two experiments when temperatures were mild and evapotranspiration less than 6 mm./day. Two varieties of upland cotton, Acala 4–42 and Deltapine Smoothleaf, were affected similarly. Moisture stress at the beginning of flowering reduced growth rate and the numbers of flowers and bolls. During the second half of the flowering period it reduced the percentage of boll retention, boll number, boll weight, seed index, lint index and lint length. Stress during boll development had similar effects and caused earlier maturity. Lint yield was reduced significantly by moisture stress during each of the periods but tensile strength of lint was not affected. Three irrigations, if properly timed so that no appreciable moisture stress occurred, were sufficient for high yields and good quality of lint, and the first could be postponed until after flowering began without any loss in yield.

The effects of moisture stress at various stages of development were studied on two varieties of cotton in the arid Negev region of Israel. Experiments over two years indicated that the stage at which moisture stress occurred determined its effect: when at the beginning of flowering, yield was considerably reduced; at the peak of flowering there was a less pronounced effect; and when stress occurred during boll development it had an effect in only one year, when reserves of moisture in the deep soil layers were low. Lint yield ranged from 380 kg./ha. without irrigation to 2150 kg./ha. with five irrigations. Effects on lint length and lint strength were also studied. Two physiological indices, stomatal aperture and refractive index of leaf sap, were used to determine the onset of moisture stress.

Under the three levels of submergence (0, 5 and 10 cm. depths), water requirement of rice was maximum at 10 cm. but crop performance was similar to that at 5 cm. With medium and high levels of fertilization the crop had a higher water requirement than under low level, for ‘aus’ and ‘aman’ crops. Compacted soil compared well with puddled soil, but water requirement was appreciably higher with shallow puddling. In the two seasons water requirement, transpiration, evaporation and percolation losses were greater under submergence, and only transpiration was greater under higher levels of fertilization. Transpiration was maximum at flowering stage.

Data of uniformity trials on apple in farmers' gardens showed large localized and genetic variation, indicating that larger plots could be used with advantage. Formation of blocks on the basis of uniformity trials can be expected to increase block efficiency considerably. With only four to six years for experiments it was found better to use trunk girth as a calibrating variate for forming plots and blocks instead of losing two years for a uniformity trial. The minimum number of replications needed to obtain estimates of treatment effects with a given standard error has been calculated. There was a pronounced biennial swing in the yields as reflected by the intra-tree correlation.

Thirty one soils from the Savanna Zone of Nigeria were low in exchangeable potassium, ΔK°, and ΔK°° and had very low potassium buffer capacities. The soils were low in clay, which was kaolinitic. Two soils high in 2:1 layer clay minerals contained higher quantities of labile potassium. Total potassium varied with parent material. Release of non-exchangeable potassium was low. After cropping, wet/dry cycles released exchangeable potassium. Potassium deficiency is expected to occur commonly with intensive cropping in the field.