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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVING SOIL AND NUTRIENT MANAGEMENT SYSTEMS FOR SUSTAINED PRODUCTIVITY AND ENVIRONMENTAL QUALITY Title: Nleap-Gis Modeling in a Mediterranean Region of Spain

Authors
item DE Paz, J -
item Albert, C -
item Delgado, Jorge

Submitted to: Nitrogen Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 30, 2009
Publication Date: June 28, 2009
Citation: De Paz, J.M., Albert, C., Delgado, J.A. 2009. NLEAP-GIS Modeling in a Mediterranean Region of Spain. Nitrogen Workshop. "Connecting Different Scales of Nitrogen Use in Agriculture". Grignani C., Acutis M, Zavattaro L., Bechini L., Bertota C., Gallina P., Sacco D (edds). Turin, Italy, June 28-July 1, 2009.

Interpretive Summary: We select a study area located within a Nitrogen Vulnerable Zone (NVZ), to evaluate the management practices with NLEAP-GIS. This area, covers 6300 ha, with citrus and vegetables being the main crops grown under drip and surface irrigation. Intensive irrigated agriculture with traditionally high N fertilization dominates the Mediterranean region of Valencian Community. Most of this region was declared a NVZ following European directives. The goal of this paper was to use the Nitrogen Losses and Environmental Assessment Package, which has GIS integration capabilities (NLEAP-GIS v4.2) to assess the effects of management on regional N losses. NLEAP was previously calibrated and validated with data from experimental plots with several crops and N management. The upscaled NO3 leaching assessment based on calibration and validation results and regional NO3 leaching map was used to assess the effects of management practices spatially across the region. We found that the areas closer to the shoreline where the vegetables are grown have the highest risk of NO3 leaching and denitrification. The main NO3 leaching events occur during the intensive rainfall of October-November, when 56% of nitrate leaching losses occur. We also found that the soils close to a wetland area have high concentrations of organic matter, restricted water drainage due to clayey textures, and a shallow water-table. This area showed the highest denitrification rates with losses as high as 166 kg N ha-1 y-1. We found that nearly 50% of the total denitrification occurred during the summer time when soil temperatures were the highest. The highest monthly denitrification rate, 13 kg N ha-1 y-1, was observed in August.

Technical Abstract: Several nitrogen (N) models have been developed to assess the effects of management practices on N losses from agricultural systems. These N tools range from very complex N models useful in research to simple N index tools that can be use for a quick assessment of management practices on N losses to the environment. It is well-known that measuring the amount of leaching and atmospheric N losses across all landscape-cropping system combinations is difficult, so calibration and validation of models are used to obtain estimations of N losses. Some N models can help us to identify hot spots across fields, facilitating the implementation of precise conservation practices in crop production. These models in combination with Geographical Information Systems (GIS) help us to upscale the assessment from plot research to a regional scale. We select a study area located within a Nitrogen Vulnerable Zone (NVZ), to evaluate the management practices with NLEAP-GIS. This area, covers 6300 ha, with citrus and vegetables being the main crops grown under drip and surface irrigation. Intensive irrigated agriculture with traditionally high N fertilization dominates the Mediterranean region of Valencian Community. Most of this region was declared a NVZ following European directives. The goal of this paper was to use the Nitrogen Losses and Environmental Assessment Package, which has GIS integration capabilities (NLEAP-GIS v4.2) to assess the effects of management on regional N losses. This assessment of N practices across the NVZ of the Mediterranean region found that use of fertigation, or splitting N applications in several events, in addition to adjusting the N fertilizer rates to those recommended by the Code of Good Management Practices, reduces the risk of NO3 leaching. It also avoids leaving high N residues on the soil during winter that can be leached by intensive rainfall.

Last Modified: 12/28/2014