Latex flow can be stimulated by bark scraping and by the application of vegetable oils, auxins and some other substances to the bark, either above or below the tapping cut. Auxin preparations are now widely used in commercial rubber production, 2,4–D and 2,4–5–T being the most common. The response obtained depends upon the formulation, on the method of application, and on other factors such as the age and condition of the tree and the tapping system employed. The effect of stimulation is considered to be due to a dilution of the latex and an increased rate of flow. A larger area of bark is drained, and the duration of flow is prolonged, because plugging of the latex vessels is delayed. In young trees, the conflict between increased latex production and active tree growth requires the development of different and less intensive techniques.

Mature lucerne on shallow granite sand was irrigated at different intervals, determined by four factors, 0·4, 0·6, 0·8 and 1·0, applied to daily evaporation (E0) as measured by a USWB Class A pan. Moisture balances were calculated for each treatment, and when the accumulated sum of daily evaporation, multiplied by the appropriate factor, reached 1·2 inches, which was about 50 per cent of the available moisture in the top 2 feet of soil, this amount of water was applied to the plots of the treatment concerned. Irrigation on the basis of 0·8 E0 gave the but overall results, although the highest yield from a single cut was obtained with the irrigation frequency defined by 1·0 E0. During the rainy season yields from all treatments declined markedly, those from the most frequently irrigated treatment showing the greatest drop. The lucerne under the irrigation regimes defined by 0·4 and 0·6 E0, although subjected to considerable moisture stress in the dry weather, suffered no lasting ill effects and yielded well during the rains. The experimental area was almost certainly subject to advective energy but the results are considered valid for local conditions.

An experiment in which irrigation intervals for lucerne were dictated by four factors applied to daily evaporation from a Class A pan has been reported by Landsberg (1966). This paper discusses data from a number of subsidiary measurements made during that experiment. An extensive soil sampling programme yielded data on the effects of treatments on soil moisture content, and plant height and per cent ground cover measurements enabled detailed evaluations to be made of crop responses. Both height and ground cover were decreased by soil moisture stress. Relative turgidity was closely related to soil moisture content in the early morning, dry treatments showing more rapid recovery of turgor than those where water was kept at more adequate levels. Radiation utilization by the crop was affected by soil moisture conditions, and also apparently by temperature.

As part of a programme to improve production of the main food crops of Northern Nigeria, trials were carried out to investigate the effect of nitrogen and phosphate fertilizer on the grain yield of sorghum. Five fertilizer response areas have been defined and estimates have been made of the most profitable combinations and levels of phosphorus and nitrogen to use in each area. Fertilizers produced the greatest increase in yield in the two response areas which cover the north of the country.

An early upright-bunch variety of groundnut, Barberton, and a medium-late spreading-bunch variety, Ashford, were compared at 7·5, 15·0 and 30·0 cm. intra-row spacings planted at one and two kernels per hill on 60 cm. ridges in the irrigated heavy clay soil of the Sudan Gezira in 1963 and 1964. Barberton was harvested on days 95, 110 and 125, and Ashford on days 125, 140 and 155 after planting in July–August. Ashford outyielded Barberton at the lower densities, and the best pod yields were obtained on day 125 harvest at a population of 55,000–60,000 plants per acre. A higher plant population depressed the yield of Ashford while the increased pod yield of Barberton was not significant. Field germination of kernels increased more in Barberton with delay in harvest and with decrease in plant population than in Ashford. Mean pod and kernel weights and shelling out-turn of Barberton increased with delay in harvest. Barberton gave higher oil content and shelling out-turn, and lower proportion of pods with single kernels than Ashford. The highest population of Barberton gave the best oil content in early harvests. In general, the arrangement of plants within rows at similar populations had only small effects except on the quality of nuts, which was improved by planting single kernels at close spacing (7·5 cm.) with the variety Barberton and two kernels at wide spacing (15·0 cm.) with Ashford, at optimum plant populations.

This paper summarizes the results of a series of NPK experiments conducted in the past on mature tea in north-east India.

The failure of overdrilling techniques to improve poor pasture and the development of the dipyridylium herbicides, particularly paraquat, for controlling grass species, prompted research into oversowing techniques in 1963 and 1964. Rotary cultivation, although giving better establishment than any other oversowing technique, did not always reduce the more persistent weed grasses such as Agrostis spp., and so failed to produce a perennial rye-grass dominant sward. This was believed to be due to various factors such as unsatisfactory herbicide pre-treatments, the interval between spraying and cultivation, the high moisture content of the soil when cultivated, as well as the greater resistance of rhizomatous grass species to paraquat. In the absence of paraquat, rotary cultivation was able to establish a satisfactory number of seedlings. In both experiments, however, the subsequent botanical composition was considerably influenced by pasture management.

Two types of design are described, in which the number of plants per unit area varies systematically within any one plot in the field, the plant arrangement being held constant. Any desired range of spacing can be covered in either design and the calculations necessary to establish specific sets of dimensions are given. In addition descriptions are given of the laying-out, planting (or sowing), management and recording of experiments using these designs.