| Sumario: | 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 (De Paz et al. 2009). It is well-known
that measuring the amount of leaching and atmospheric N losses across all landscapecropping
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.
Intensive irrigated agriculture with traditionally high N fertilization dominates the
Mediterranean region of Valencian Community. Most of this region was declared a Nitrogen
Vulnerable Zone (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.
We select a study area located within a 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. Although soil texture ranges from sandy loam to
clayey soil, the area has predominantly heavy-textured clayey soils. Annual rainfall averages
500 mm, is non-uniform and has intensive rain events during autumn. Evapotranspiration
(ETo) measured with the Penman-Monteith method is 960 mm
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