Denitrification losses from a natural grassland in the Basque Country under organic and inorganic fertilization |
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Authors: | J. M. Estavillo M. Rodriguez M. Domingo A. Muñoz-Rueda C. Gonzalez-Murua |
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Affiliation: | (1) Departamento de Biología Vegetal y Ecología, Universidad del País Vasco, Apdo. 644, 48080 Bilbao, Spain;(2) Servicio de Investigación y Mejora Agraria, Departamento de Agricultura y Pesca, Gobierno Vasco, 48016 Derio (Bizkaia), Spain |
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Abstract: | Denitrification losses from a poorly drained clayey loamy soil under natural pasture were measured over a two-year period using the acetylene inhibition technique. Plots received two different applications of fertilizer as calcium ammonium nitrate or cow slurry (a total of 145–290 kg N ha–1 in 1991 and 120–240 kg in 1992). In the first year, N losses in the mineral treatments were about 4 times greater than losses in the slurry treatments. In the second year losses in the slurry treatments increased in such a way that losses in the higher slurry application became similar to those for the two mineral treatments. Soil nitrate was the factor producing differences between treatments. In this way, N mineralization in periods between fertilizations coinciding with high soil water contents was responsible in the second year for the increase in N losses in the slurry treatments. Denitrification rates greater than 0.1 kg N ha–1 day–1 occurred at soil water contents > 33 % (air filled porosity < 26 %) and soil nitrate contents > 1 mg N kg–1 dry soil. Spring and autumn were the seasons of highest risk of denitrification because of N fertilizations coinciding with periods of soil saturation with water. Winter losses were low, but this is a period when there is a risk of denitrification in wetter seasons, particularly for a slurry application management. |
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Keywords: | acetylene-inhibition calcium ammonium nitrate cow-slurry denitrification natural prairie nitrogen losses |
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