NOTE: At the time of publication, the author David J. Wehner was affiliated with the University of Illinois at Urbana-Champaign. Currently, April 2008, he is Dean of the College of Agriculture, Food and Environmental Sciences at California Polytechnic State University - San Luis Obispo.
A microecosystem was designed to study the behavior of pesticides, fertilizers, or related compounds applied to plant stands. The system consists of three parts: a brass base that holds the plant growth media, a glass atmospheric chamber that rests on the base, and a set of analytical traps. The brass base is fitted with a porous ceramic plate so that tension can be applied to the water in the growing media. Air enters the bottom of the glass atmospheric chamber and exits through the top into appropriate trapping systems to recover volatilized pesticides, ammonia, or metabolized 14CO2 from labeled compounds. A port at the base of the chamber allows collection of leachate. The microecosystem was evaluated by applying N sources or a pesticide to intact turfgrass profiles and monitoring the fate of the applied compound. Leaching and volatilization losses of N ranged from 0 to 17% and 0.1 to 17% of the applied N, respectively, depending on N source, soil conditions, and whether tension was applied to the base of the system. Three weeks after the application of radiolabeled diazinon [O,O-diethyl-0-(2-isopropyl-4-methyl•6primidinyl) phosphorothiote] to a turf, 47% of the label remained in the form of the parent compound, 22% had been metabolized and lost as 14CO2, 1% had leached through the profile, 2% had been lost through volatilization, and 28% remained in the soil as a metabolite or in unextractable compounds. The microecosystem has proven to be an invaluable tool for turfgrass research and should be useful for fertilizer and pesticide fate studies with other crops.
Agronomy and Crop Sciences