Ecology of earthworms under the 'Haughley experiment' of organic and conventional management regimes

Significant differences in earthworm populations and soil properties were f ound in three sections of a farm at Haughley in Suffolk that, since 1939, h ad either an organic, a mixed conventional, or a stockless intensive arable regime. Compared with the mean earthworm population of a 1,000 year old pe rmanent pasture of 424.0 m(-2); an organic field had 178.6 m(-2); a mixed f ield 97.5 nra; and a stockless field 100.0 m(-2). Species recorded were: Al lolobophora chlorotica, accounting for most of the increase in the organic section; Aporrectodea caliginosa, dominant in the stockless section; Aporre ctodea icterica; Ap. longa; Ap. nocturna; Ap. rosea; and Lumbricus terrestr is. Soil analyses showed the organic soil had higher moisture, organic C, and m ineral N, P, K, and S compared with soil from the stockless field. The orga nic soil also bad lower bulk density and good crumb structure whereas the s tockless soil was cloddy and subject to puddling. The properties of the mix ed field soil were intermediate to the others. Winter wheat (Triticum aesti vum) in the organic field had significantly longer shoots (by 11.3% and 13. 9%) and roots (by 5.4% and 10.8%) compared with the mixed and stockless fie lds, respectively. Choice chambers offering the three field soils, with and without organic am endments, showed an earthworm preference for the organic soil (total 96 hea dcounts) compared to the mixed and stockless soils (75 and 73 headcounts). Adding organic matter tended to override this trend and indicated that food supply was an important determinant in earthworm distribution in the labor atory.