Daisy: Model Use, Calibration, and Validation

Abstract

Daisy is a soil-plant-atmosphere system model focusing on agro-ecosystems. It simulates water, heat, carbon, and nitrogen balances as well as crop production and pesticide fate in agro-ecosystems subjected to various management strategies. The basic scale of application is the field (management unit), which may be simulated in one or two dimensions. Daisy allows several different process descriptions for water flow, evapotranspiration, crop growth, and solute transport. Furthermore, it can operate in a distributed mode (several fields) and link up with distributed hydrological models. In this case, statistical and remote sensing data are relevant. Considerations concerning the objective of a given study and available data determine the choice of process descriptions. All applications require information concerning weather (at minimum, daily values of solar radiation, air temperature, and precipitation), soil (texture, organic matter, hydraulic parameters, etc.), location of groundwater, and vegetation cover. Applications that focus on nitrogen dynamics require a description of crop rotation, tillage, use of fertilizer and manure, irrigation, sowing, harvesting, and organic matter turnover in the soil. In carbon and nitrogen balance simulations, the uncertainty associated with crop growth is particularly important because Daisy only considers water and nitrogen stress. Dry matter and nitrogen yield may require calibration. Uncertainty associated with initialization of the organic matter pools and the parameterization of organic fertilizers is considered to be of major importance. For pesticide transport calculations, descriptions of macroporosity and hydraulic conditions close to the surface are critical. Daisy has been validated in several international comparative validation studies.