Ecology of Earthworms under the ‘Haughley Experiment’ of Organic and Conventional Management Regimes

Summary

Significant differences in earthworm populations and soil properties were found in three sections of a farm at Haughley in Suffolk that, since 1939, had either an organic, a mixed conventional, or a stockless intensive arable regime. Compared with the mean earthworm population of a 1,000 year old permanent pasture of 424.0 m-2; an organic field had 178.6 m-2; a mixed field 97.5 m-2; and a stockless field 100.0 m-2. Species recorded were: Allolobophora chlorotica, accounting for most of the increase in the organic section; Aporrectodea caliginosa, dominant in the stockless section; Aporrectodea icterica; Ap. longa; Ap. nocturna; Ap. rosea; and Lumbricus terrestris.
Soil analyses showed the organic soil had higher moisture, organic C, and mineral N, P, K, and S compared with soil from the stockless field. The organic soil also had lower bulk density and good crumb structure whereas the stockless soil was cloddy and subject to puddling. The properties of the mixed field soil were intermediate to the others. Winter wheat (Triticum aestivum) 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 fields, respectively.
Choice chambers offering the three field soils, with and without organic amendments, showed an earthworm preference for the organic soil (total 96 headcounts) 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 distributions in the laboratory.