Towards higher nitrogen efficiency in European rice cultivation : a case study for the Camargue, South of France

This study focuses on an increase in the efficiency of fertilizer nitrogen in irrigated, direct seeded rice. Three indicators for efficiency were used: agronomic efficiency, utilization efficiency and recovery. Experiments were conducted in the Camargue in the South of France, to quantify these indicators for standard non-coated prilled urea under conventional management of irrigated rice. The results were compared to those derived from data originating from other surveys within the Mediterranean rice growing countries. Additionally, the indicator values were experimentally assessed for a resin coated nitrogen fertilizer, known to be highly efficient. Those values were considered to represent the maximum attainable nitrogen efficiencies under given circumstances in the Camargue. A model was developed with which the effect of different nitrogen application strategies on crop production and fertilizer nitrogen recovery can be evaluated. With this model, 70 combinations of quantity and timing of prilled urea nitrogen were screened for 20 sets of weather data, to derive an alternative to the use of the efficient but expensive coated fertilizer. As a result of this simulation, a tailor-made application strategy for a representative medium-growth duration rice variety of the Camargue was defined.