Outlook on Agriculture

The growing impact of changing agricultural practices on the environment is a matter of general concern, but it is generally supposed to date largely from the introduction of machinery and agrochemicals. In fact, the impact was substantial long before this and can, indeed, be traced back to hunter-gatherers like the Australian aborigines who, without actively cultivating the land nevertheless deliberately controlled their local environment – as by burning or simple water management – in order to conserve the wild life on which they depended.

Although the treatment of seeds to prevent disease is a practice of great antiquity, recent years have seen the advent of increasingly more sophisticated techniques. These can confer various advantages, including the production of seeds of uniform shape and size to facilitate sowing; protection against pests and diseases; control of dormancy; and enhancement of growth. Seed rather than foliar application of agrochemicals also has environmental advantages.

While grass may suffice to meet the nutritional needs of grazing ruminants in terms of carbohydrate and protein, they may not necessarily provide the minimal levels of minerals necessary to maintain health. Since, with the exception of salt, it is unusual to provide supplementary minerals it is necessary to ensure that the grazed grass is so managed that mineral levels are adequate. This article reviews the various factors that influence the mineral profiles of tropical grasses in the Caribbean, Latin America, and Africa.

By 2000 AD approximately 84 per cent of the world's arable cropland will rely on rainfall. Throughout developing countries the yields of many rain-fed farmers are falling and their ability to sustain production seems uncertain. Land degradation must be halted, security of harvests improved, and wherever necessary yields increased, crops diversified, and the area cultivated extended. For the most cultivators some form of improved rain-fed agriculture is likely to be the only practical route to such goals.

The fate of herbicides applied to the soil is a matter of great practical importance. If they disappear rapidly, for example, they may prove ineffective: if they persist unduly there may be environmental problems. Many factors contributed to the disappearance of herbicides: this article reviews the important role of soil micro-organisms.

Tea has been grown in the highlands of North Thailand for some two hundred years and has long been the most important tree crop, apart from forest products. However, there has in recent years been a change in the production pattern of the traditional ‘miang’, or pickled tea, increasingly giving way to green leaf production for black or semi-fermented tea.

Intensive research carried out over the last 20 years on the biology and control of the Australian bush fly, Musca vetustisima, a widespread and irritating pest of man in that region, has provided a wealth of information about the community relationships of fauna in the cow dung pats which provide the breeding habitat of the fly. The extension of this project to South Africa and to Southern Spain in the search for exotic dung beetles or allied controlling agents to deal with both the bush fly and the blood-sucking buffalo fly, Haematobia, has given this programme a wider significance.