The consumptive use of water by cotton (G. hirsutum L.) variety 149F, sown at three dates, was calculated using Penman Et × crop factor method. The earlier the sowing date the more water evapotranspired, mainly due to differences in the length of the growing season and the amount by which it coincided with the monsoonal depression of potential evapotranspiration. An example is given of calculating the irrigation requirements of a mid-June sown cotton, accounting for average rainfall, showing that the water requirements of cotton during the early stages may be adequately met by the establishment irrigation and rains during July. Examples are cited to show that a charged profile at the beginning of the season may sustain good growth and produce satisfactory yield.

Three cultivars of Stylosanthes guyanensis, under two management regimes, were assessed for yield, quality, palatability and persistence under grazing. During the dry season progressive leaf abscission resulted in unpalatable bare stem, but both leafy stem and fallen leaf remained palatable. Between May and September there was a decline in crude protein (from 16 to 11%), phosphorus (0.22 to 0.18%) and potassium (2.3 to 1.7%), but not in digestibility (average 53%). Partial rather than total accumulation of wet season growth ensured less trampling damage, hence better persistence. Cultivar ranking for persistence and leaf yield was Schofield, Cook, Endeavour, although Cook was initially the most productive.

In trials conducted over five years, data on pest (insect, disease, bird) attack and yield of sorghum cultivar 65D were accumulated. A modified analytical method of damage assessment is described, which includes consideration of all pest occurrences and different levels and timing of pest attack. There was a positive correlation between crop yield and rainfall. The selective infestation of stronger plants, or the ability of those plants to support pest populations, is shown; thus, in most cases, yield reductions are masked. The importance of the tillering habit of 65D on yield, and its ability to compensate for pest damage by further tillering, are shown. A cultivar which does not normally tiller was tested in the final year. Effects on yield of all the pests encountered in the five years are discussed.

Studies on the effects of age on the elemental nutrients contained in Celosia argentea cultivars showed that calcium, phosphorus and potassium decreased with age, the highest content of those elements occurring in the leaves between 5 and 7 weeks after sowing. Other elements, notably manganese and magnesium, increased up to 15 weeks after sowing. An anthocyanin-pigmented cultivar contained more iron, sodium and copper than green cultivars. Breeding potentials of the cultivars in terms of elemental nutrients are discussed, and harvesting the leaves of all cultivars 5 to 9 weeks after sowing is recommended.

Two maize cvs, FARZ 23 and FARZ 25, were grown at three densities (37,000, 53,000 and 80,000 plants/ha) in 1979 and 1980. Leaf area index (LAI) increased with increase in plant population and was at a maximum at mid-silk. Grain yield was highest at 53,000 plants/ha. There was no relation between LAI and grain yield but there was a positive correlation between LAI and total dry matter yield.