Abstract
The response of earthworms to soil application of boardmill waste sludge was quantified in field and laboratory experiments. The influence of one application of 6×104 tonnes ha−1 of unamended sludge was tested against no application on silty-clay arable soil. After 2 years, results in stubble-cultivated soil showed a 1.7 times lower density of earthworms where sludge was added, whereas there was no difference in average earthworm fresh weight. In direct-drilled soil, there was an indication of lower average numbers of Lumbricus terrestris middens when sludge was applied. Negative impacts in the field may have been due to indirect negative effects of the sludge application. In the laboratory, habitat choice tests were undertaken with two common species from the field site using sludge-based mulch and fertiliser products. Aporrectodea caliginosa showed no discernible preference between soil and soil mixed with unamended sludge (mulch), but favoured soil over soil mixed with sludge and chicken manure (fertiliser). Tests with L. terrestris showed a similar pattern. The preference of L. terrestris for the two products was compared with that for chopped barley straw by direct observation of foraging behaviour. Differences in foraging time of L. terrestris for different feeds were not significant, but mass of straw collected was significantly greater compared with either type of sludge treatment.
Published Version
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