Estimating Nutrient Balances in Agro-Ecosystems at Different Spatial Scales

Research on soil nutrients is going through a development process away from agricultural production per se towards sustainable production. Not so long ago, the research focus was largely on empirical point models, enabling the prediction of crop yields as a function of soil chemical properties and fertilizer application. These models often related to just one nutrient, and were valid only for the site where the experiment was located. Of late, the attention has shifted from nutrient stocks to nutrient flows. It is no longer soil fertility per se that hits the headlines, but rather imbalances between nutrient inputs and outputs, their agronomic and environmental consequences, and “integrated nutrient management” as the commonly perceived though open-ended solution. Although the problems in northern and southern countries of nutrient imbalances differ by 180° (e.g., Aarts et al., 1992; Smaling, 1993), they both perfectly fit the message of this chapter.