The hydraulic press was compared with the dew point psychrometer and the pressure chamber methods for measuring leaf water potential (Ψ) in groundnuts (Arachis hypogaea L.). For measurements on the same leaf, regression analysis revealed that the slopes did not differ significantly from unity. An analysis of functional relations between measurements made by the press and the dew point psychrometer or the press and the pressure chamber showed that the error variance of the press was similar to those of the two other methods. Therefore, we conclude that for groundnuts the performance of the press, the dew point psychrometer and the pressure chamber are similar.

Shifting agriculture is an ancient basis for maintaining soil fertility but pressures of population have caused it to give place in most countries to rotations and bare fallows which, in turn, have had to be reduced or modified. Research on various measures to shorten the duration of fallows and increase their effectiveness is reviewed. These measures include the use of organic manures and inorganic fertilizers, green manuring, mulches and the growing of legumes and grasses, which are discussed in relation to their effects on the soil and on crop yields. The increasing use of the factorially-designed experiment is recognized as a major contributor to this research.

Mixed tree and food crop farming systems are being developed in the humid tropics. They offer one solution to the problems caused by population pressure and de-forestation, since they can provide a satisfactory income to the subsistence farmer, while adequately protecting the environment In seeking to develop optimal systems, examples and information can be drawn from traditional mixed cropping systems, from taungya systems of forestation, and from other systems developed within the commodity cropping sector. However, the full potential of mixtures involving perennials and food crops can only be realised within the limitations of local socio-economic and political circumstances.

Maturation of peas in cool temperatures (mean 17.5°C) at Dalang Maidan, Lahaul (in the Himalayas) led to the development of larger seeds in comparison to those of the same varieties which had matured in warmer temperatures (mean 24.5°C) at Delhi, India. The larger seeds from Lahaul, when sown at Delhi, gave rise to taller plants which came into flower earlier compared with those from the seeds matured at Delhi. Significant location ′ variety interactions were recorded for germination and plant height. Inherent variation in days to flowering could have been a major factor in these interactions. These data are of direct importance to breeders using seeds developed at more than a single location if environmental conditions differ appreciably.

Field experiments were done during the rainy seasons of 1980 and 1981 at Hissar, India; they studied the effects of time of weed removal on the yield of mung beans. Removing weeds at 10, 20 or 30 days after sowing led to significantly larger yields than that of the weedy check. Maximum seed yields in booth years were obtained when weeds were removed 20 days after sowing

Two sets of experiments examined the effects of weeds on maize yields using weeding methods typical of small farms in Zambia where oxen are used for cultivation. Maize yield losses of 30% due to weeds were evident with common weeding practices. A critical period of competition, during which the crop should be kept clean, was demonstrated from 10 to 30 days after emergence. This is a period of peak labour demand and the prospect of using chemical weed control to ease the situation is considered. The value of weed competition data, given its variability between sites, is discussed.

The Boro (dry) and Kharif (wet) seasons of West Bengal differ appreciably in respect of atmospheric temperature, relative humidity and hours of bright sunshine each day. Post-harvest hot temperature (31°C) either in controlled conditions (in the Kharif season) or in natural (31.5°C) conditions (in the Boro season) had a more significant effect than post-harvest cool air temperature (20.4°C) in the Kharif season on the early breaking of dormancy of paddy rice seeds. However, the pre-harvest hot air temperature (31.4°C) of the Boro season was no more effective in breaking dormancy than the pre-harvest cool air temperature (20.9°C) of the Kharif season. With a mean air temperature of 20.4°C the post-harvest exposure of the seeds to the sun from sunrise to sunset during the Kharif season was much more effective in breaking dormancy than the post-harvest mean air temperature of 31.5°C during the Boro season.

Groundnuts (Arachis hypogaea L.) are generally considered to be self-pollinated, but natural hybrids due to outcrossing have been observed in cv. Robut 33-1. Selections in segregating generations of these natural hybrids identified stable lines with large yield potentials in more than one environment. The role of natural hybrids in generating useful additonal variability is discussed.