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Agricultural Productivity Threatened by Over-fertilization


farmsoildeteAs agricultural practices become more advanced, and different types of fertilizers flood the market, it is almost inevitable to assume that soils no longer determine the agricultural productivity.

Stephen Porder, an assistant professor of biology in the Department of Ecology and Evolutionary Biology is a co-author of a study about to be published in the January 2013 edition of BioScience. Together with a team of scientists from BrownUniversity, Porder highlighted the importance of phosphorus as a fertilizer requirement.

What the team points out is that although phosphorus concentrations in soils determine crop production, overuse of the element in fertilizers poses even bigger problem- algal blooms in nearby water bodies.

As part of the study, the team analyzed the production of soybeans in three different areas- Iowa in the United States, Mato Grosso in Brazil, and Buenos Aires in Argentina. One of the key findings is that although the crop that is produced is the same, the type and amount of fertilizer, and consequently the impact it has on the environment, is completely different.

As stated by lead author of the study Shelby Riskin of Brown University and the Marine Biological Laboratory, the amount of fertilizer used in Brazil is much higher than anywhere else. The researchers estimated that 31 kg phosphorus per hectare is added to the soils per year.

In Iowa the runoff from agricultural fields causes extensive algal blooms in rivers and lakes. Although farmers in Iowa have significantly reduced the amount of used fertilizer since 1995, phosphorus is still clearing from the soils into the big rivers and lakes.

According to the authors, over-fertilization might be one of the biggest challenges in future. In addition, the authors suggest that considering the current trend of increasing population sizes, more agricultural production will be needed in the coming decades, so we should start reducing the environmental cost as soon as possible.

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