CONSTRUCTING A NITROGEN-FERTILIZER RECOMMENDATION SYSTEM USING A DYNAMIC-MODEL - WHAT DO FARMERS WANT

An effective fertilizer recommendation system requires information on seasonal, soil-related and cultural variations in soil mineral nitroge n (N) and nutrient requirements of the crop. This can be provided by d ynamic N turnover models, such as listed by Plentinger & Penning De Vr ies (1996). In this paper, we describe a survey of farmer opinion desi gned to ascertain what farmers want from such a decision support syste m. Over 100 farmers were surveyed. Surveyed farmers requested that def ault values be available for all model inputs. Inputs should be entere d both by windows-based menu (for clarity) and tabular format (for spe ed), have user-selected units, and be fully supported by context-sensi tive help. The system should have a hierarchical structure allowing ac cess to fixed parameters, and be compatible with commonly used farm re cording packages. Recommendations should be provided both for the fiel d (single and optional application rates), and in tabular format acros s the whole farm. Simulations should be easily rerun using more recent crop and weather data. Turnover processes underlying recommendations should be illustrated by flow diagrams of flux between pools, pie char ts of fertilizer fate, bar charts of movement down the soil profile an d graphical plots of changes in N status against time.