The strategy and associated practical details are described of a research programme which seeks to make effective use of controlled environment facilities in providing information and screening techniques useful to lentil breeders. Two principal objectives were (a) that genotypes grown in artificial climates should respond to whatever factors are being investigated in a manner which reflects their responses and relative sensitivity to different agroclimates in the field, and (b) to deploy controlled environment facilities for the longest period which is feasible during each calendar year and with maximum benefit:cost ratio.

Growth and developmental stages of Alaska peas, from planting to dry seed maturity, were examined and described. Node counts were determined by designating the cotyledonary node as 0 and counting successive nodes up the plant to the highest visible one with unexpanded stipules. Five additional nodes are already determined in the shoot apex beyond the highest one with unexpanded stipules, indicating that damage to the shoot apex would result in losses of flowers and fruits that would have developed later if damage had not occurred.

The auxin-transport-inhibiting morphactin chlorflurenolmethylester (CFM; Methyl 2-chloro-9-hydroxyfluorene-9-carboxylate) breaks the dormancy of axillary buds in young coffee plants and produces orthotropic shoots. A concentration of CFM as low as 50 mg/litre induced an average of 24 orthotropic shoots per 6-month-old seedling. This approach could provide a fast and inexpensive method of vegetative propagation for raising disease-resistant cultivars if adult clones respond similarly to the seedlings used here and the treatment does not adversely affect the propagation of induced shoots.

The nitrate–N profile of soil was studied in sole and parallel multiple-cropping systems of pigeonpea and maize and of sugarcane and blackgram. In sole cropping there was more nitrate–N in the deeper horizons because of leaching from the inter-row spaces of row crops, whereas the nitrate content was drastically reduced in parallel cropping at more than 30 cm deep as N in the inter-row spaces was better utilized by the crops. The yield of two crops, when combined, was more in parallel cropping than the sum of crops grown separately, and the Land Equivalent Ratio was higher in parallel-cropping systems than in sole cropping.

Application of zinc to six high-yielding rice varieties in calcareous soils produced significantly higher grain yield and interactions between varieties and Zn levels were significant. Yields of varieties IR 20, Jaya, Sita and Jayanti at 2.5 and 5.0 ppm Zn were similarly affected, but Archana produced significantly higher grain yield at 5 ppm Zn than at 2.5 ppm. Effects of Zn on straw yield were similar. Zn application invariably resulted in a higher Zn concentration in plants at all stages of growth and in grain in all varieties. Maximum Zn contents were observed at the tillering stage and minimum at harvest.

The response of tea shoots to temperature was studied in the field and in controlled environments. Shoot extension stopped below about 12.5°C. Shoots of mature tea took 491 day degrees above the base temperature of 12.8°C to grow to a harvestable size of 15 cm.

Temperature is the major environmental variable affecting the yield of tea, but within the framework of a temperature model shoot extension is severely depressed when daily maximum vapour pressure deficits rise above 2.3 kPa. Day length does not affect shoot extension when the nights are cool (10°C), but growth rate is depressed by short days (11 h) when nights are warm (20°C). Soil temperatures between 18–25°C do not affect shoot extension.

In two field experiments, sweet potato showed symptoms of lime deficiency, and consequently produced extremely low DM, at the natural pH of local peat (3.5–3.7). Liming to increase pH remarkably increased tuber and vine dry matter to pH 5.5 and harvest index to pH 3.8, but higher pH values decreased dry matter and harvest index. Tuber and vine yields generally decreased with continuous monocropping, probably because of increasing infestation with weevils (Cylas formicarius) and other pests, and depletion of available nutrients.

Two field experiments studied the nitrogen fertilizer requirements of guinea and napier grass on peat. Plants in the control plots, though optimally limed and fertilized with other nutrients, absorbed only 1.7 and 2.4% of total peat N in a year and N fertilization improved DM yield, with an optimum at 900 kg/ha/yr. Further positive response was not observed, probably because of a reduced ratio of N to other nutrients. Optimum N uptake, and N concentration in the DM, were achieved at 600 kg/ha/yr N but N recovery decreased linearly with increasing fertilizer N at the rate of about 2–4% per 100 kg/ha/yr N.

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.

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.