Lunchtalk by Holger Brück
(Yara International, Research Center Hanninghof, Hanninghof 35, D-48249 Dülmen, Germany)

Title: “Impact of Crop Nutrition on the Water Footprint of Agricultural Production”

Abstract of the presentation:

The projected increase in food demand requires an intensification of cropping systems in order to avoid massive expansion of agriculture into natural ecosystems. Increased resource input (irrigation water) and inefficient farming practices (fertilizer doses and timing), however, currently present a burden to the environment because of regional exhaustion of freshwater reserves or non-point pollution of ground- and surface waters. Therefore, agriculture has to adopt measures to reduce the environmental impact which are qualitatively and quantitatively described by several ecological indicators such as the carbon or water footprint and the nutrient use efficiency.

The recently suggested water footprint is a quantitative indicator of water appropriation in the food sector. It enables policy makers, enterprises and stakeholders in the food and water sector to compare food production systems in terms of efficiency of water use and the impact on regional freshwater resources within a watershed.

The presentation will illustrate, based on case study data, the relationship between mineral N fertilizer application and grain yield of winter wheat (Germany) and the related grey water demand. The economic optimum N application rate is generally similar to the ecological optimum N application rate in terms of grey water demand. This indicates that there is not necessarily a trade-off of between best-practice intensive agriculture and freshwater protection goals. However, economic and ecological optimum N application rates differ substantially between locations and from year to year, underlining the relevance of precision farming and site-specific nutrient management. N application above the economic N application rate induces a severe increase in the grey water demand making grey water demand ultimately to the most relevant item in the water footprint. Such inappropriate use of fertilizer increases not only the water footprint but at the same time it decreases fertilizer use efficiency.