Ecological intensification of cereal production systems: yield potential, soil quality, and precision agriculture

Abstract

Wheat (Triticum aestivum L.), rice (Oryza sativa L.), and maize (Zea mays L.) provide about two-thirds of all energy in human diets, and four major cropping systems in which these cereals are grown represent the foundation of human food supply. Yield per unit time and land has increased markedly during the past 30 years in these systems, a result of intensified crop management involving improved germplasm, greater inputs of fertilizer, production of two or more crops per year on the same piece of land, and irrigation. Meeting future food demand while minimizing expansion of cultivated area primarily will depend on continued intensification of these same four systems. The manner in which further intensification is achieved, however, will differ markedly from the past because the exploitable gap between average farm yields and genetic yield potential is closing. At present, the rate of increase in yield potential is much less than the expected increase in demand. Hence, average farm yields must reach 70-80% of the yield potential ceiling within 30 years in each of these major cereal systems. Achieving consistent production at these high levels without causing environmental damage requires improvements in soil quality and precise management of all production factors in time and space. The scope of the scientific challenge related to these objectives is discussed. It is concluded that major scientific breakthroughs must occur in basic plant physiology, ecophysiology, agroecology, and soil science to achieve the ecological intensification that is needed to meet the expected increase in food demand.

Figure 1

National average rice yields from 1967 to 1997 in three Asian countries (http://apps.fao.org).

Figure 2

Yield trends from 1968 to 1990 of the highest yielding rice cultivars and IR8 in a long-term continuous cropping experiment at the International Rice Research Institute in the Philippines. Reproduced from ref. with permission of John Wiley & Sons, Ltd., London.

Figure 3

Conceptual model illustrating the relationship between crop yields and input requirements as influenced by soil quality. A decrease in soil quality from an initial state (curve A) can result in the need for greater inputs of energy, nutrients, water, seed, and pest control measures to achieve the same yield. The slope and asymptote of the shifted response (shown by curves B, C, and D) depend on the type of soil degradation and can result in a reduction in input use efficiency, yield potential, or both.

Figure 4

Frequency distribution of rice grain yield without nitrogen fertilizer application in 42 different farmer’s fields in the Guimba Municipality, Central Luzon, Philippines. Reprinted from ref. with permission from Elsevier Science.