Compartmental model for nitrogen dynamics in citrus orchards W.A. Contreras1,2 , A. Lidón3 , D. Ginestar2 , R. Bru2
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Abstract In Valencian Community an irrigated agriculture is developed. This kind of activity is characterized by significant contributions from nitrogen in groundwater. This kind of water supplies drinking water to 54% of the population and 90% of the main cities[4] [1]. In some cases these water supply have nitrate concentrations exceeding the maximum allowed. It has been demonstrated the influence of excessive fertilization in the contamination of groundwater [3], therefore it is convenient to have different tools to make recommendations for the fertilization of trees that combine the needs of the plant and minimize the nitrate leaching. The simulation models of the movement of water and nitrogen in soil allow, once they have been calibrated to working conditions, to predict the nitrate leaching under certain growing conditions and they can be used as a tool for evaluating different situations or management strategies for fertilization and irrigation of crops. This paper presents a simple model that represents the soil nitrogen dynamics [2], consisting of several compartments of organic and inorganic nitrogen and representing the main processes that occur between each compartment of the soil column (decomposition , nitrification, mineralization, leaching, plant uptake, etc.). Some of these processes are coupled to the carbon dynamics in the soil, thus, the evolution of organic carbon in the soil has been also described in the model. The dependence of these processes with soil moisture requires the coupling of nitrogen model with a model of soil water dynamics. A compartmental model for the water has been used to simulate the dynamics of water in the root profile. The results obtained with the proposed model have been compared with those obtained with the widely used model LEACHN [5]. Both programs 1
have been used to predict the soil mineral nitrogen content and the nitrate leaching in a citrus orchard placed in the area of Valencia.
References [1] Pernía J.M., Cuesta, F., Ballesteros, B., Barba-Romero, J., García E. 1996. Los recursos hídricos de la Comunidad Valenciana. ITGME - Generalitat Valenciana, 77pp. [2] Porporato, A., P. D’Odorico, F. Laio, and I. Rodríguez-Iturbe, 2003a. Hydrologic control on soil carbon and nitrogen cycles. I. Modeling scheme. Advances in water resources, 26(1), 45-58. [3] Ramos C., Agut, A., Lidón, A.L. 2002. Nitrate leaching in important crops of the Valencian Community region (Spain). Environmental Pollution 118: 215-223. [4] Sanchis E.J. 1993. La contaminación por nitratos de las aguas subterráneas. El caso de la Comunidad Valenciana. Jornadas sobre "La contaminación por nitratos de las aguas continentales". Generalitat Valenciana, Consellería de Medi Ambient. Valencia. [5] Wagenet R.J. and Hutson, J.L. 1989. LEACHM: Leaching Estimation and Chemistry Model: A process based model of water and solute movement, transformations, plant uptake and chemical reactions in the unsaturated zone. Ver. 2. Cornell University.
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