AN AGRICULTURAL CHEMICAL EVALUATION AND MANAGEMENT-SYSTEM

An Agricultural Chemical Evaluation and Management System (AGCHEMS), has been developed to investigate the impact of various agricultural chemical management scenarios on the movement of these chemicals toward groundwater. AGCHEMS was developed by integrating a chemical transport model (CMLS), a weather simulation model (WGEN), and a geographical information system (GIS). AGCHEMS can evaluate the effect of chemical application rate and timing, the particular chemical used, and other management practices such as the amount and timing of irrigation water. These factors affect the time and amount of the chemical that will reach selected depths in the soil profile. The GIS allows site specific soil information to be used in the model. The GIS can also be used to prepare maps showing the vulnerability of areas to exceed selected standards of chemical movement. Uncertainty in the exact values of soil and chemical properties and variability in weather sequences can also be evaluated and maps generated showing the probability of exceeding various amounts of chemical passing preselected depths in the soil profile. The results obtained using possible and equally likely weather sequences show considerable variability in chemical movement due to weather alone. The implications of this variability upon monitoring programmes, the interpretation of model studies, and possible regulations on use of agricultural chemicals are discussed. © 1993 Silsoe Research Institute.