CHLORPYRIFOS SOIL AND PLANT METABOLISMS IN CAULIFLOWER CROPS GROWN ON COW MANURE AND COMPOSTS SOIL FERTILIZED FIELDS

Several cauliflower crops were grown on fields located in different regions. Cauliflower plants were treated against the root fly by applying, some days after planting, chlorpyrifos onto the soil around the stem of the plant. Fields were divided into plots. Either one or 3.5 months before planting, one of the organic fertilizers city refuse compost, or mushroom cultivation compost, or cow manure was incorporated into the soil of each plot; there were also soil unamended control plots. The rates of chlorpyrifos soil metabolism were smaller in the organic fertilizers amended plots, than what they were in the unamended plots. In the summer cauliflower crop made on loamy sand soil, the chlorpyrifos soil half-lives were 41, 44, 53 and 25 days, respectively in the plots amended either with the city refuse compost, or cow manure, or the mushroom cultivation compost, and in the unamended plots. The organic fertilizers effects were slightly greater when the amendments had been soil incorporated 3.5 months before planting, instead of 1 month before it. The chlorpyrifos transport from soil into the plant foliage was also greater in the soil organic fertilizers amended plots, than in the control plots. During the final crop period, the rates of chlorpyrifos soil metabolism increased; the organic fertilizers effects were levelled off, and the chlorpyrifos soil residues at harvest were similar in all the amended and unamended plots. During the first main crop period, to the greater chlorpyrifos soil residues—due to the soil organic fertilizers—should correspond a better insecticide protection efficiency against the soil insects, relative to the soil unamended plots. No chlorpyrifos, nor its metabolites were detected at harvest in the ‘flower’ of cauliflower of all the trials plots. © 1991, Taylor & Francis Group, LLC. All rights reserved.