Earthworm community response to tillage and residue management on different soil types in southern Finland

Earthworm communities were studied in a factorial experiment in which spring cereals were grown in autumn mouldboard ploughed, autumn stubble cultivated and spring stubble cultivated soils where straw residue was either chopped and left or removed. The experiment was conducted on different soil types in southern Finland. Samples were taken in the eighth and ninth autumn of the experiment. In silty clay the abundance of earthworms was lowest in ploughed soil, the total number in spring stubble cultivated soil being on average 1.9 times, and the total dry weight 5 times, higher than in ploughed soil. In silty clay loam tillage did not affect the total number but the total dry weight in autumn stubble cultivated soil was 2.6 times higher than in ploughed soil. In sandy loam the total number in ploughed soil was 1.5–2 times higher than in stubble cultivated soils while the total dry weights did not differ. Handling of straw had a discernible effect only in silty clay, where leaving the straw in the field on average doubled the total dry weight. Interaction between tillage and handling of straw was not statistically discernible at any locality. The total abundances were low in 1987, which was related to the harshness of the preceding winter. There was no consistent evidence for interaction between the factors and the time of sampling. The number of species was two in silty clay, where no epigeic species were found, four in silty clay loam and six in sandy loam, where three epigeic species were found. The endogeic (Aporrectodea caliginosa (Sav.) usually formed the bulk of the total dry weight. It was not consistently affected by the treatments. The anecic Lumbricus terrestris L.) was clearly associated with reduced tillage. In sandy loam its densities were low and it was absent from two out of the six experimental fields. The epigeic Dendrodrilus rubidus, (Sav.), present in sandy loam, generally increased under reduced tillage and straw residue. The reasons for the observed patterns, their implications to soil conditions and the problem in deducing from the results to treatment effects in field scale cultivation are discussed.