MONITORING OF THE GROUNDWATER BROMINE CONTENT AND PLANT RESIDUES IN METHYL BROMIDE FUMIGATED GLASSHOUSES

Each fortnight from September 1986 to August 1988 the level of the groundwater table was measured, the water was sampled, where possible samples of crops were taken and analyzed on their bromine content using X-ray fluorescence spectrometry.

When the deeper soil layers contained more clay, the bromine content of the groundwater after fumigation and leaching was still relatively high but decreased with time; in dry periods the groundwater table sank beneath the drainage tubes but showed higher bromine content; in wet periods the effect of dilution was clear. In one glasshouse, the installation of a new drainage system resulted in lower soil bromine residues after fumigation and leaching.

Bromine contents of crops were more difficult to interpret, however the following trend could be derived :

With nearly equal soil types, bromine residues depended on the type of crop, the soil bromine content, the time between culture and fumigation and the culturing techniques. Higher soil bromine contents resulted in higher bromine residues in crops but decreased with increasing time between culture and fumigation. The bromine content of tomatoes showed to be reduced when the plant roots were continuously supplied with nutrient solution as is usual in culturing techniques on substrates.

Download Adobe Acrobat Reader (free software to read PDF files)