Rc. Peralta et al., PREVENTING PESTICIDE CONTAMINATION OF GROUNDWATER WHILE MAXIMIZING IRRIGATED CROP YIELD, Water resources research, 30(11), 1994, pp. 3183-3193
A simulation/optimization model is developed for maximizing irrigated
crop yield while avoiding unacceptable pesticide leaching. The optimiz
ation model is designed to help managers prevent non-point source cont
amination of shallow groundwater aquifers. It computes optimal irrigat
ion amounts for given soil, crop, chemical, and weather data and irrig
ation frequencies. It directly computes the minimum irrigated crop yie
ld reduction needed to prevent groundwater contamination. Constraint e
quations used in the model maintain a layered soil moisture volume bal
ance; describe percolation, downward unsaturated zone solute transport
and pesticide degradation; and limit the amount of pesticide reaching
groundwater. Constraints are linear, piecewise linear, nonlinear, and
exponential. The problem is solved using nonlinear programming optimi
zation. The model is tested for different scenarios of irrigating corn
. The modeling approach is promising as a tool to aid in the developme
nt of environmentally sound agricultural production practices. It allo
ws direct estimation of trade-offs between crop production and groundw
ater protection for different management approaches. More frequent irr
igation tends to give better crop yield and reduce solute movement. Tr
ade-offs decrease with increasing irrigation frequency. More frequent
irrigation reduces yield loss due to moisture stress and requires less
water to fill the root zone to field capacity. This prevents the solu
te from moving to deeper soil layers. Yield-environmental quality trad
e-offs are smaller for deeper groundwater tables because deeper ground
water allows more time for chemical degradation.