This chapter examines the changes that have occurred in farming over the past 10,000 years and which continue today. Agriculture and food play an important role in the economic systems of all countries and regions. Indeed, crop and animal domestication — integral to the practices of farming — were essential for the development of human civilizations. Agricultural systems in different regions of the world differ in their productivity, and in the modern world, scientific and technological discoveries are responsible for many of those differences. Whereas modern science-driven agriculture is highly productive, especially in developed countries, a billion smallholder farmers in developing countries are confined to small farms where productivity is low and where they produce just enough food to supply themselves with the bare essentials of life.
Chapter
A Changing Global Food System
One Hundred Centuries of Agriculture
H. Maelor Davies and Paul Gepts
Chapter
Soil Ecosystems,Plant Nutrition, and Nutrient Cycling
Eric M. Engstrom
This chapter studies soil ecosystems, plant nutrition, and nutrient cycling. Soils are complex ecosystems where changes in one soil variable are likely to affect multiple other variables, often in ways that are difficult to predict accurately. Chemical elements cycle within the ecosystem. Chemical transformations occur continuously, fueled by biological and physical processes. Agricultural systems are inherently different from natural ecosystems in that soil nutrients are regularly removed from agricultural systems and must be replaced. In addition, agricultural ecosystems, which often encompass only one crop, have almost no aboveground biodiversity. The chapter then looks at the roles of soil nutrients, soil organic matter, and plant roots. It also considers plant nutrients such as nitrogen and phosphorus, before discussing mycorrhizae.
