Postwar Nitrogen Use Efficiency in West German Agriculture and Groundwater Quality
1997
van der Ploeg, R. R. | Ringe, H. | Machulla, Galina | Hermsmeyer, D.
Rising NO₃ concentrations in groundwater are of general concern in Germany. To estimate the role that agriculture has played in this contamination, national statistical data on fertilizer and fodder use and on agricultural productivity for 1951 to 1990 were analyzed. With use of assumptions about the N content of fertilizers, fodder, and agricultural products, an attempt was made to estimate the yearly N turnover and N-use efficiency in West German agriculture during this period. The analysis showed that from 1951 to 1990 the use of commercial N fertilizer increased from 27.4 to 107.8 kg ha⁻¹ and of N present in animal feeds from 72.4 to 158.0 kg ha⁻¹. At the same time, the estimated N content of farm produce only increased from 24.1 to 57.2 kg ha⁻¹. As a consequence, agricultural N surplus increased from 7.2 kg ha⁻¹ in 1951 to 94.6 kg ha⁻¹ in 1990. The analysis also showed that during the 1951 to 1990 period, N-use efficiency in crop production decreased from 100% in 1951 to 81.4% in 1990. Nitrogenuse efficiency in livestock production changed little and varied time-independently between 12.4 and 17.3%. For agriculture as a whole, N-use efficiency decreased from 77.0% in 1951 to 38.0% in 1990. The results indicate that low N-use efficiency in livestock production, together with an excess of farm manure, is the main reason for the NO₃ problem that Germany is facing.
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