The ecological background of food production.

In the industrialized countries dramatic decreases in the number of people employed in agriculture have been made possible by a rise in soil and labour productivity. There is scope for these to improve further, particularly in developing countries. Potential yields are determined by the characteristics of the crop, local temperature and sunlight. Because the availability of nutrients and that of water are limiting for at least part of the growing season in most agricultural lands, attainable yields are lower than potential yields. Proper management of nutrient inputs, such that optimum use is made of each, can reduce this gap without causing negative environmental side-effects. Actual yields are lower than attainable yields because of growth-reducing factors, such as pests, diseases and weeds. For sustainable agriculture these should be controlled mainly by biological measures. There are many possibilities for this, thus biocides may be used as a last resort not as preventive insurance. Potential yields of rice and sugarcane can reach 30,000 kg ha-1 per year of consumable organic matter, sufficient to feed 120 people. Such yields cannot be achieved on all agricultural land, but it is estimated that world food production could support a population of 80 thousand million, if they were all vegetarian and required only 1500 m2 for non-food-related purposes. The green revolutions that occurred in the Western industrialized countries in the late 1940s and early 1950s and in Asia in the late 1960s and early 1970s need to be followed by a similar increase in agricultural productivity in Africa and West Asia to feed their rapidly growing populations. Better use of fertilizers and good water management require well-educated farmers with the financial means to implement long-term strategies. If these developments are managed properly, food production for the ever-increasing human population can be guaranteed and the burden on the environment and natural habitats reduced, enabling the development of sustainable agricultural systems.