Outlook on Agriculture

The present article briefly reviews the main species of aphids in Latin America which are of economic importance, or are specially noteworthy for other reasons. Various possibilities for improved control are considered. These include in particular the introduction of entomophagous insects or entomopathogens, the use of pesticides only where population densities exceed defined limits, and the use of aphicides which are either themselves selective or are used selectively.

A comprehensive enquiry into the effects of high rates of nitrogenous fertilizer applied to grassland, started at Jealott's Hill four years ago, incorporated catchment studies using automatic flow monitoring and proportional sampling techniques. Water quality studies so far indicate that nitrogen applications well in excess of present UK usage on grass pose no health problems, but more studies of this nature, linked to a national survey of nitrate concentrations in rivers, are needed.

Mai (1964) considered that there were less than 100 nematode diseases of serious proportions, but many more causing less obvious or severe damage were still unrecognized. A rather general account is here given of the role of nematodes in plant disease, using as examples nematodes and crops of economic importance–-including cyst-forming, root-knot, burrowing and reniform nematodes on crops such as potatoes, sugar beet, temperate cereals, citrus, bananas, cotton and soya beans.

During the past fifteen years–-with donations in cash and kind from the fertilizer industry, and with increasing contributions from donor governments and others–-FAO Fertilizer Programme field projects in thirty-nine developing countries have taught small farmers the efficient use of fertilizers and related inputs, prepared local extension personnel, and established pilot distribution and credit schemes. This article reviews the methods used and the results and experience gained.

Poor rainfall in 1972 and 1973 led to much of the area in the Sudan Savanna zone of Nigeria being declared a disaster area due to the widespread failures of major food crops under indigenous practices. However, in the same circumstances, a group of farmers using improved seed, fertilizer and better methods, obtained yields which were satisfactory. Crop losses from “drought” are a strong function of the cultivars grown and of the level of crop husbandry.

What is meant by “soil structure”? Microscopic examination of thin sections of soil, using such instruments as the polarising microscope, X-ray diffractometer and scanning electron microscope has enabled a classification of the components of soils and their structural types to be built up. Now with the aid of the image-analysing computer these components can be quantified rapidly, characteristics may be calculated and their behaviour under varying cultural conditions predicted.