Articles
THE DEVELOPMENT OF METHODS TO DETERMINE WEED SEED CONTAMINATION IN MUNICIPAL COMPOSTS
Article number
469_17
Pages
179 – 186
Language
Abstract
Weed seeds can be a serious contaminant of compost derived from green municipal waste.
Estimation of the number and species content of weed seeds and weed propagules in mineral soil uses an established technique of sieving and flotation from small representative soil samples.
The high organic matter content of compost impedes this technique.
Successful estimation of weed seed contamination in compost is further complicated by the low numbers of seeds compared to that of arable soils, making sampling and detection inherently more difficult.
The weed seed content of compost can be determined by germination methods, however these would give less immediate results.
In order to identify improvements in the physical extraction technique for composts, an experiment was devised to determine the effect of different modifications made to the component stages in the extraction process.
Three representative composts (a sewage/coir mix, and two green wastes) were mixed with known numbers of contrasting seeds from a range of weed species.
The seeds were classified as to whether they were large, small, dark or bright in appearance.
Different combinations of sieve sizes and washing time, all had significant effects on the number and type of weed seeds recovered.
However, all three composts differed in the combination of the modifications that proved the most effective for seed extraction.
The most consistent improvement in the technique for all three composts was that of reducing the sample size.
The results gave a comprehensive measure of the effect of variations from the standard method, in the recovery of different classes of weed seeds from compost.
Estimation of the number and species content of weed seeds and weed propagules in mineral soil uses an established technique of sieving and flotation from small representative soil samples.
The high organic matter content of compost impedes this technique.
Successful estimation of weed seed contamination in compost is further complicated by the low numbers of seeds compared to that of arable soils, making sampling and detection inherently more difficult.
The weed seed content of compost can be determined by germination methods, however these would give less immediate results.
In order to identify improvements in the physical extraction technique for composts, an experiment was devised to determine the effect of different modifications made to the component stages in the extraction process.
Three representative composts (a sewage/coir mix, and two green wastes) were mixed with known numbers of contrasting seeds from a range of weed species.
The seeds were classified as to whether they were large, small, dark or bright in appearance.
Different combinations of sieve sizes and washing time, all had significant effects on the number and type of weed seeds recovered.
However, all three composts differed in the combination of the modifications that proved the most effective for seed extraction.
The most consistent improvement in the technique for all three composts was that of reducing the sample size.
The results gave a comprehensive measure of the effect of variations from the standard method, in the recovery of different classes of weed seeds from compost.
Authors
Andrea C. Grundy, J. M. Green, B. Bond, S. Burston, M. Lennartsson
Keywords
flotation, sieving, germination, sample volume, Calcium chloride
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