Simulated nitrogen dynamics and nitrate leaching in a perennial grass ley |
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Authors: | Lars Bergström Holger Johnsson |
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Institution: | (1) Division of Water Management, Department of Soil Sciences, Swedish University of Agricultural Sciences, P.O. Box 7072, S-750 07 Uppsala, Sweden |
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Abstract: | A soil nitrogen model was used for a 4-year simulation of nitrogen dynamics and nitrate leaching, both during grass ley growth
and after ploughing a grass ley. Model results were compared with field measurements of soil mineral-N status and leaching.
A soil water and heat model provided daily values for abiotic conditions, which were used as driving variables in the nitrogen
simulation.
Simulated values for mineral-N levels in the soil agreed well with field data for the first 3 years of the simulation. During
the final year the model predicted considerably higher levels of soil mineral-N content compared with measurements. To reach
the mineral-N level measured at the time of ploughing the ley, the simulated N-uptake by plants had to be increased by 8 g
N m−2.
Simulations of nitrate leaching suggested that estimates of leaching based on measurements in tile-drained plots can be considerably
underestimated. Accurate quantification of leaching in tile-drained plots often requires additional information on water-flow
paths.
A substantial increase in simulated and measured values for the mineral-N content of the soil occurred after ploughing the
ley. In the simulation, most of the increase was due to a high crop residue input and the absence of a growing crop after
ploughing. Litter accumulations in the soil during the 4-year period contributed little to the increase in soil mineral-N. |
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Keywords: | mineralization nitrogen model N-uptake ploughing of leys water flow paths |
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