SUNDIAL: A PC-based system for simulating nitrogen dynamics in arable land

SUNDIAL (SimUlation of Nitrogen Dynamics In Arable Land) is a user-friendly, PC-based version of the Rothamsted Nitrogen Turnover Model. It comprises a menu-driven system that allows agricultural advisers, even with minimal computing experience, to enter details of a particular held or farm and simulate N turnover, The processes involved are described by a set of parameterized zero and first-order equations. The addition of a novel facility for calculating crop parameters enables instantaneous estimation of parameters for rough but immediate simulations of a new crop, graphical visualization of the expressions used in SUNDIAL, comparison of the parameterized expressions with experimental measurements, and further refinement of parameters by fitting individual expressions to measured data or by iteratively adjusting parameters to improve the fit of simulated results to soil and crop N and N-15 measurements. The facilities in SUNDIAL for displaying the various outputs in graphical form make it particularly useful for examining the impact of different management strategies on the N cycle in arable agriculture. Graphical facilities include balance sheets, graphical plots, pie charts, and flow diagrams.