Strategies to control nitrate leaching in irrigated agricultural: a meta-analysis and a case study in the Tagus river (Spain)

Séminaire FIRE, donné par Miguel Quemada. Professor on Agricultural Production. Technical University of Madrid. Spain.

Strategies to control nitrate leaching in irrigated agricultural: a meta-analysis and a case study in the Tagus river (Spain)

Nitrate leaching (NL) is an important N loss process in irrigated agriculture that imposes a cost on the farmer and the environment. While the mechanisms of NL in irrigated and rain fed agriculture are common, the strategies and options to secure ecological sustainability may differ considerably. A meta-analysis of published experimental results from agricultural irrigated systems was conducted to identify those strategies that have proven effective at reducing NL and to quantify the scale of reduction that can be achieved. Forty-four scientific articles were identified which investigated four main strategies (water and fertilizer management, use of cover crops and fertilizer technology). Management practices that adjust water application to crop needs reduced NL by a mean of 80% without a reduction in crop yield. Improved fertilizer management reduced NL by 40%, and the best relationship between yield and NL was obtained when applying the recommended fertilizer rate. Replacing a fallow with a non-legume cover crop reduced NL by 50% while using a legume did not have any effect on NL. Improved fertilizer technology also decreased NL but was the least effective of the selected strategies.

Results from a long-term experiment in Central Spain in which cover crops were used to replace the winter fallow between irrigated summer crops will be presented as a case study.