Effects of environmental temperature on boll maturation period of cotton and the genotype response, investigated in a 3-year field experiment, showed a negative correlation between period and mean temperature and revealed genotypic differences regarding degree of temperature influence and sensibility to temperature changes. The observed genotype × temperature interactions may help cotton breeders in establishing breeding centres and in creating desirable gene combinations for wider adaptability to temperature.

The yield of cowpeas could be increased by judicious defoliation of the older leaves or by topping the growing apices at the onset of flowering. Limited defoliation at the pre-flowering stage did not reduce the yield of beans significantly but severe defoliation at any stage prior to maturity drastically reduced yield. Satisfactory yields of cowpea could be obtained by maintaining only about one-half to two-thirds of the potential leaf-area of the plants, suggesting that a reduction in the number and area of leaves, coupled with a better display of the fewer remaining leaves, could make cowpeas more productive than hitherto.

Using coffee trees sprayed with cuprous oxide and captafol it has been shown that both fungicides are redistributed within the tree canopy by rain. Under conditions of light rain fungicides are removed from upper parts of trees and redeposited at lower levels within the canopy in amounts capable of providing effective protection against coffee berry disease (CBD). With heavy rainfall, however, redeposition of fungicide at effective levels is less likely to occur. The results are discussed in relation to the success of overhead boom sprayers in controlling CBD and the observations that shoots in the upper parts of coffee trees are an important source of spores of the CBD strain of Colletotrichum coffeanum.

The nitrogen content of weeds was significantly higher than that of Dular rice-straw, but with Taichung Native I rice in winter there was no significant difference between the nitrogen in weed samples and rice plants at the tillering stage. Rice straw contained a higher proportion of nitrogen where there were three hand weedings. The total dry matter of rice was much reduced by weed competition. Weed species contained much nitrogen at the vegetative, flowering and post-flowering stages, indicating severe competition for nitrogen by weeds throughout the growth of rice under dry land conditions.

Irrigation, mulch and N-fertilizers increased the yield of fresh fruit/tree by 66 per cent due to increases of 42 per cent in the number of fruiting nodes/tree, 14 per cent in number of fruits/node and 15 per cent in fresh weight/fruit; these three yield components accounted for 42, 13 and 6 per cent of the variation in yield among all treatment combinations. Bean/fruit weight ratios and times of flowering were not affected. Correlations between yield components were positive, suggesting that still more nodes could be produced per tree and per unit area before physiological limits to yield were reached.

The leaching of boron, studied after high rates of application under different management practices, indicated that leaching was rapid and that the presence of cover crops was likely to reduce the immediate availability of boron to the main crops.

Soil analysis on samples taken from apple orchards in Khorasan and quince orchards in Esfahan, suggested that at a sampling depth of 20–45 cm., the critical soil concentration of calcium carbonate at which chlorosis might appear seems to be 14–15 per cent for apple and 39–40 per cent for quince. The incidence of lime-induced chlorosis was accompanied by lowered leaf Ca/K ratios. The application of various iron chelates to chlorotic trees not only benefited yield of apples but also exercised a residual effect in succeeding seasons.

Cynodon IB.8 was subjected to (i) various levels of N under cutting management, and (ii) various levels of K under grazing management. The results indicated significantly higher DM and CP production with 168 kg./ha. of N under cutting management, with resultant significant reduction in exchangeable and non-exchangeable soil K. Under grazing management, increased K application increased K content in the herbage, but showed a negative correlation with Ca uptake. Results indicated that the initial soil K status was adequate to supply the requirements of Cynodon, and that under grazing management the soil K status could be maintained at adequate levels to support lengthy cropping.

A method is described for estimating boron requirements of the oil palm, and factors influencing leaf boron concentration of the palm are discussed.

In a short-term competition experiment in large containers, growth of cotton planted 3 weeks after bermudagrass (Cynodon dactylon), johnsongrass (Sorghum halepense) or purple nutsedge (Cyperus rotundus), was severely reduced; after 10 weeks of competition, weedy cotton weighed only 15 per cent of the weed-free control. Cotton sown before weeds, or weeds planted before cotton, were only slightly affected by competition. Highly significant negative correlations were found between growth parameters of cotton and weeds. Inhibiting effects, and in some cases transitory stimulation, were produced on mustard seedlings by leachate from weed-infested soil and by extracts from subterranean weed parts, suggesting that the competitive effects of perennial weeds are due to nutrient depletion and to biologically active substances.

A detached-leaf technique is described for assessing susceptibility of Hevea clones to Oidium heveae, based on intensity of sporulation. This offers a rapid, systematic method of screening clones in vitro against the disease, in place of the current nursery and field methods.

Preliminary observations on tubers of yam (Dioscorea spp.) showed that there were increases in nematode populations during storage at ambient temperatures, whereas nematode counts were very low after storage at lower temperatures (12–13°C). Hot water treatments (50°C) for different lengths of time reduced the number of nematodes but damaged the tubers. Fumigation with methyl bromide, ethylene dibromide and hydrogen phosphide was not successful, as concentrations which reduced nematode numbers caused injury to the tubers. The effect of ethylene dibromide was not lasting.