The vernalization and photoperiodic response of six locally adapted bread wheat cultivars grown under natural daylength conditions during the summer or winter months was examined in glasshouse experiments. The wheat was vernalized by chilling imbibed grains at 2 ± 1°C for 0, 15 or 45 days. Vernalization for 45 days followed by long summer days led to floral initiation in all cultivars within 28 days but vernalization for 0 or 15 days only led to floral initiation in one cultivar. Vernalization followed by long days reduced the time from transplanting to anthesis, resulting in early ear emergence. Vernalization followed by short days accelerated the development of all the cultivars, but normal development could also occur without vernalization at this time of year. Apical differentiation of the primary shoot and its length and development gave the most reliable information on the period of vernalization required.

In sub-tropical India where 70% of the country's sugarcane is grown, companion cropping of wheat in autumn-planted sugarcane is beneficial. However, because the yield of sugarcane is reduced, farmers there are reluctant to adopt this cropping system in spite of the greater monetary gains compared with wheat-sugarcane sequential cropping. Application of 200 kg nitrogen ha−1 to sugarcane in two doses, two-thirds immediately after the wheat harvest and the remainder a month later, combined with irrigation at 75% available soil moisture during the summer months (April–June), produced cane yields similar to those from sole autumn-planted sugarcane, with an additional 4.8 t ha−1 of wheat.

Yield stability in beans from diverse sources in Malawi was estimated using the statistical parameters of genotype X environment variance, slope and standard error from regression. The heterozygous F2 and the most complex synthetic mixture were very stable, although not significantly different from some pure genotypes. The mean yields of most mixtures were marginally higher than the average of their components. There was a linear relationship between magnitude of diversity and stability. Evidence for heterozygote advantage was demonstrated.

The soil physical properties of tied ridges were measured in a trial, established in 1983, comparing three treatments: handhoe cultivation and planting on the flat; planting directly without any cultivation on tied ridges constructed the previous year; and handhoe cultivation and remoulding of tied ridges constructed the previous year. Two maize varieties and two management levels were used. The soil properties monitored were particle size distribution, penetro-meter resistance in the surface 20 mm, bulk density, water infiltration, soil water retention and soil temperature.

Soil physical properties were affected mainly by the type of seedbed. Clay content in the surface 0.05 m was greater with tied ridging, with that in the furrows being higher than that in the ridge slopes. Daily maximum soil temperature was greatest in the flat planted plots and in the ridge slopes of the tied ridged plots. Penetrometer resistance at a soil water content of 0.05 kg kg−1 was greater in the tied ridged plots. Cumulative infiltration after 2 h was greatest with flat planting. The bulk density of ridge slopes in tied ridged plots was less than that in the furrows and in the flat planted plots. Soil water retention was greatest in the furrows of the tied ridged plots. Clay content was the major factor determining all the soil physical properties measured.

Field experiments were carried out during the rainy seasons of 1985 and 1986 to examine the frequency of weeding necessary for the optimum growth and yield of okra in Nigeria. Weed removal within 12 weeks of sowing generally resulted in significantly better crop growth and yield than that in the weedy check. Weeding once as early as four weeks was as beneficial to okra growth and yield as two or three weedings later in the 12 week period. Weed removal four times at 3, 6, 9 and 12 weeks significantly enhanced crop growth and pod yield over all other treatments. For good pod yields, protection from weed competition over most of the duration of crop growth is therefore essential. Such weed removal may enhance crop yield partly by increasing aeration and water movement in the soil.

Field experiments were performed in 1981 and 1982 on the cotton cultivar Giza 75 to determine the effect of different concentrations and application dates of the defoliant Harvade on the lint, seed, protein and oil yields, and oil properties of cottonseed. Defoliant concentrations of 240, 360 and 480 ml ha−1 increased lint yield per plant but tended to decrease seed index. Cottonseed yield per hectare, seed oil and protein percentage and yield, oil refractive index, free fatty acids, saponification and iodine values were not significantly affected by the defoliant. Late application increased lint yield per plant and cottonseed, oil and protein yield per hectare. Date of application had no effect on seed index, seed oil and protein percentage and oil properties.

Rice, pigeonpea and rice + pigeonpea systems (in the row proportions of 1:2 and 2:5) were compared. Soil water depletion and percolation were determined during selected dry spells and yields ascertained after harvest. The mean evapotranspiration rates of rice, pigeonpea, rice + pigeonpea (1:2) and rice + pigeonpea (2:5) were 0.28, 0.79, 0.40 and 0.35 cm d−1, respectively, during a dry spell around 60 days after sowing. In general low rainfall intensity and frequent dry spells in the growing season increased pigeonpea yield but depressed that of rice. Intercropping thus ensured yield stability and hence the profitability of the system as a whole.

Evaluation of the yield stability of a group of CIMMYT tropical maize populations across international environments, measured by the performance of varieties derived from them, showed that the populations Mezcla Tropical Blanca, La Posta and Amarillo Dentado produced the most stable varieties across environments. Mezcla Tropical Blanco and Amarillo Dentado produced selections with good stability in both low and high yielding environments while La Posta produced varieties with better performance in favourable environments. ‘Across-site’ varieties were not consistently more effective than ‘site-specific’ varieties in improving yield stability. Varieties selected for some specific population-environment combinations have been very stable in other areas of the world.