Bromide residues in vegetable crops after soil fumigation with methyl bromide

Abstract

In conjuction with the use of chemicals in agriculture, the problem of accumulation of undesirable compounds in plant arises. Soil fumigation with methyl bromive is an example, because the compound is destroyed rapidly in the soil after application, and bromide residues are taken up and accumulated in plants. Under natural conditions, landplants have a content of 1–3 ppm Br (dry matter). A higher level can be obtained in vegetable crops on intensively cultivated fields or in greenhouse plots. The contents increase up to 20–40 ppm, in single cases even reaching a concentration of 130 ppm. As a result of soil fumigation with methyl bromide (50 g/m 2), nearly 400 kg Br/ha are released. The bromide level in the soil can rise from 3 to about 50 ppm. Initially, the bromide salts are bound loosely in the soil complex and can therefore be utilzed by the plants. Depending on the plant species, the plant organs, general growth and soil conditions, the method of application and the amount of methyl bromide applied, a level of 100 ppm Br and more can be reached in fresh matter. The highest Br contents were found in foliage vegetables. The uptake of Br can be reduced by soil irrigation immediately after treatment. During harvest-time, the Br content in cucumber and tomato fruits slowly decreases.