Daisy, a flexible Soil-Plant-Atmosphere system Model

SUMMARY. Daisy is a Soil-Plant-Atmosphere system model designed to simulate water balance, heat balance, solute balance and crop production in agro-ecosystems subjected to various management strategies. The water balance model comprises a surface water balance and a soil water balance. The surface water includes a model for snow accumulation and melting, a model for interception, through-fall, and evaporation of water in the crop canopy, and a model for infiltration and surface runoff. The soil water balance includes water flow in the soil matrix as well as in macropores. Furthermore, it includes water uptake by plants and a model drainage to pipe drain. The heat balance model simulates soil temperature and freezing and melting in the soil. The solute balance model simulates transport, sorption and transformation processes. Special emphasis is put on nitrogen dynamics in agro-ecosystems. Mineralization-immobilization, nitrification and denitrification, sorption of ammonium, uptake of nitrate and ammonium, and leaching of nitrate and ammonium are simulated. Degradation, sorption, uptake and transport of agro-chemicals like pesticides are simulated. The crop production model simulates plant growth and development, including the accumulation of dry matter and nitrogen in different plant parts. Furthermore, the development of leaf area index and the distribution of root density are simulated. Competition for light, water and nitrogen between plant species are also simulated. The agricultural management model allows for building complex management scenarios. The model can work distributed with multiple soil columns. A facility to link the model to hydrological catchment models exists. This facility has been applied to link Daisy to the distributed hydrological catchment model MIKE/SHE. Furthermore, the very flexible Daisy software allows for implementation of different process descriptions of the same process. The selected process description is chosen by the model parameterization. 2 INTRODUCTION The loss of agrochemicals into aquifers and surface waters in humid regions is an inevitable consequence of intensive agriculture. In large parts of Europe, for instance, the input of nitrogen to agricultural systems and subsequent losses are so large that they constitute a threat to both the quality of surface and ground waters (EEA, 1995). In most agricultural systems the main loss of nitrogen is due to leaching of nitrate from the fields. The fact that laboratory and field measurements necessary for assessment of nitrogen leaching from agricultural fields are expensive have prompted the development of agro-ecosystem models capable of simulating the nitrogen dynamics in agricultural soils and in particular simulating the …