Dynamics of Soil and Fertiliser Nitrogen in Arable Systems

Keywords: annual crop, ¹⁵N tracing, fertilisation, microbial immobilisation, N use efficiency, wheat.

The research done over the past few years on the use of nitrogen (N) fertilisers on crops in the intensively farmed areas of Northern Europe, has attempted to improve the efficiency of N uptake by crops, and to identify and quantify the "unused" N. This unused N can have several effects on the environment depending on the processes involved. To follow the fate of N in soil-plant systems, 15N-enriched substrates have been widely used in many studies. The findings are used here to examine i) the availability of inorganic N in soil after fertiliser-N application in time and space, ii) the short-term competition between plant uptake and other soil processes, iii) the interactions between added N and the soil N mineralisation-immobilisation turnover (M.I.T.) with respect to carbon (C) dynamics, and their short and long term consequences.

Dr Sylvie Recous, I.N.R.A Unité d’Agronomie, 02007 Laon Cedex, France.

16 pages, 2 figures, 1 table, 39 refs.