There is a prevailing view that global food and ﬁber production will continue to expand because of modern agricultural management systems with improved cultivars and intensive chemical inputs dominated by synthetic ammoniacal fertilizers. The use of these fertilizers has led to concerns regarding water and air pollution but is generally perceived to play an essential role for sustaining agricultural productivity, not only by supplying the most important nutrient for cereal production but also by increasing the input of crop residues for building soil organic matter. The scientiﬁc soundness of the buildup concept has yet to be substantiated empirically using baseline data sets from long-term cropping experiments. The present paper and a companion study by Khan et al. (2007) provide many such data sets that encompass a variety of cereal cropping and management systems in diﬀerent parts of the world. Overwhelmingly, the evidence is diametrically opposed to the buildup concept and instead corroborates a view elaborated long ago by White (1927) and Albrecht (1938) that fertilizer N depletes soil organic matter by promoting microbial C utilization and N mineralization. An inexorable conclusion can be drawn: The scientiﬁc basis for input-intensive cereal production is seriously ﬂawed. The long-term consequences of continued reliance on current production practices will be a decline in soil productivity that increases the need for synthetic N fertilization, threatens food security, and exacerbates environmental degradation [Mulvaney 2009: 2308].
Mulvaney R. L., S. A. Khan, & T. R. Ellsworth, 2009, Synthetic Nitrogen Fertilizers Deplete Soil Nitrogen: A Global Dilemma for Sustainable Cereal Production, Journal of Environmental Quality 38, 2295-2314: http://www.mudcitypress.com/PDF/mulvaney.pdf