La fertilisation azotée du blé en Tunisie: évolution et principaux déterminants.

Nitrogen (N) is essential for cereal production. The aim of this work is to study from the national statistics the evolution over time of nitrogen fertilizer use in wheat crop in Tunisia and to relate this consumption to wheat yields and to rainfall patterns. The results showed that wheat is the larger user of mineral nitrogen fertilizer in Tunisia with an average of 51300±19500 tons.N.yr-1 and an increase rate of 1600 tons.N.yr-1. Nitrogen is provided as diammonium phosphate (DAP) before seeding and then as ammonium nitrate during the crop cycle. The total amount of mineral nitrogen spread contributes significantly to the wheat grain yield (p<0.01). The spreading of ammonium nitrate is variable in quantity, frequency and date of application, and is highly influenced by annual climatic conditions, essentially the total amount of rainfall. A positive relationship (p<0.01) was observed between partial factor productivity for Nfertilizer and the rainfall during wheat growing cycle. [ABSTRACT FROM AUTHOR]