The development of models simulating nitrogen transport in soil and manure S. HENGNIRUN, S. BARRINGTON, S.O. PRASHER and D. LYEW Department of Agricultural and Biosystems Engineering, Macdonald Campus of McGill University, 21111 Lakeshore Road, Ste Anne-de-Bellevue, QC, Canada H9X 3V9. Received 10 June 1998: accepted 4 February 1999. OofcUlDalo MElEO.DAT BAR.DAT ROOTWAT.DAT NIV1C>L MCPROFIL.DAT TEMPPROF.DAT MElEO.DAT BAR.DAT VOLAT ROOTWAT.DAT """INER MCPRORL.DAT MElEO.DAT DENITRI Del'aUt0at0 UPTAKE SURFACEN.DAT II NMOL biological and chemical processes affecting nitrogenous components in the manure and soil, and the transport of nitrogenous compounds through the system. MANIMEA is a dynamic model which considers temporal and spatial changes in environmental factors. It also considers the manure as a separate component prior to its incorporation into the soil. Consequently, MANIMEA should provide a more realistic simulation of the manure-soil system. The objective of this paper is to present the development of three submodels ofMANIMEA which simulate solute transport in the manure-amended soils system, namely RUNOFF, LEACH, and ADSORP. Nitrogen losses in surface runoff were evaluated by RUNOFF, nitrogen movement and loss through the soil profile were simulated by LEACH, and the retention of charged species of nitrogen solutes moving through the soil was simulated by ADSORP coupled to LEACH. The effects of micropores and macropores on the transport of nitrogenous compounds in the soil were taken into account in the development of LEACH and ADSORP. These submodels were run using two scenarios: manure that was surface applied and left for a period before incorporation into the soil; and manure that was injected into the soil. Hengnirun, S., Barrington, S., Prasher, S.O. and Lyew, D. 1999. The development of models simulating nitrogen transport in soil and manure. Can. Agric. Eng. 41:035-045. Three submodels were developed for simulating the transport of nitrogen in a manure- amended soil. RUNOFF and LEACH are the submodels for simulating nitrogen losses by runoff after a rainfall and for leaching into the subsoil. The effects of soil adsorption and the presence of both micro- and macropores were considered in the development of LEACH. The simulation of adsorption was accomplished by a third model called ADSORP which was coupled with LEACH. The consideration of macropores in addition to micropores contributed towards a more realistic simulation of leaching and adsorption in the soil. The three submodels were integrated into a model called MANIMEA (Manurial Nitrogen Management: Environmental Aspects). The MANIMEA model simulated the transformation and transport processes affecting nitrogen in a manure-soil system for a specified soil and meteorological conditions so as to predict the fate and distribution of nitrogen in this system. Such a model is a useful tool in the management of manure application so as to lessen the environmental impact of this manure. The integration of RUNOFF, LEACH, and ADSORP into MANIMEA was successfully realized. The simulation results indicated that the submodels were able to generate results that fell within reasonable limits. Trois sous-modeles furent developpes pour simuler les mecanismes de transport de l' azote dans un sol amende avec des engrais organiques (fumier) et inorganiques. RUNOFF et LEACH sont les sous-modeles qui simulent les pertes d'azote par ruissellement et par lessivage dans Ie sous sol. Les effets de l'absorption du sol et de la presence de micro et macropores dans Ie sols furent consideres dans Ie sous-modele LEACH. La simulation de l'adsorption fut realisee par Ie sous-modele ADSORP qui fut accouple au sous-modele LEACH. La consideration des macropores du sol fait en sorte que Ie modele est plus realiste lors de la simulation de l'adsorption et du lessivage dans Ie sol. Les trois sous-modeles furent integres dans Ie modele MANIMEA (Gestion de I' azote des fumiers: aspects environnementaux). Le modele MANIMEA simule la transformation et Ie transport de l'azote dans tout systeme constitue de fumier et de sol, pour des conditions specifiques de c1imat et de sol. Ce modele fut developpe dans Ie but d' offrir un outil de gestion des fumiers en tenant compte des aspects environnementaux et agronomiques. L' integration des sous-modeles RUNOFF, LEACH et ADSORP avec MANIMEA fut realisee avec succes car les donnees calculees sont realistes. INTRODUCTION Fig. 1. Structure and organization of MANIMEA. The MANIMEA model simulates the fate of nitrogen in manure-amended soils (Hengnirun et al. 1995). The MANIMEA model is modular in structure and is presently comprised of 11 submodels (Fig. 1) to simulate the environmental conditions of the manure-soil system, the MODEL DEVELOPMENT Manure and soil N in the form of NH 4 + is generally bound to organic matter and the soil minerals, while N0 3 - and N0 2 - are CANADIAN AGRICULTURAL ENGINEERING Vol. 41. No.1 JanuarylFebruary/March 1999 35