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    Population dynamics of earthworms (Lumbricidae) and their role in nitrogen turnover in wheat and wheatclover cropping systems

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    Summary
    The temporal dynamics of earthworm populations were studied for three years in two farm-scale winter wheat production systems, conventionally monocropped wheat and low-input, direct-drilled wheat intercropped with white clover. Populations were estimated by soil sorting monthly in the first two cropping cycles and bimonthly in the third cycle. Earthworm population dynamics were strongly related to changes in soil moisture, with low population levels coinciding with low moisture content. Populations in conventional wheat were generally quite stable but showed a sharp drop after autumn ploughing followed by a marked recovery in the first two cropping cycles. In wheat–clover, drought conditions during the first summer probably disrupted population build-up. Population levels in the two systems diverged in the second cropping cycle and were widely separated in the third cycle when 319 individuals m—2 (55 g biomass m—2) were found in conventional wheat and 1160 individuals m—2 (175 g biomass m—2) in wheatclover. Nine earthworm species were present in both cropping systems and shifts in species composition were relatively small. Murchieona minuscula, a little known endogeic species previously unreported from Ireland, was abundant in both systems and appeared to benefit from annual ploughing.
    Earthworm tissue production was estimated to be 81–209 g m—2 in conventional wheat and 122–552 g m—2 in wheatclover, while N output resulting from mortality was calculated at 0.75–4.24 g m—2 in wheat and 1.16–10.61 g m—2 in wheatclover. N output via excretion and mucus was estimated to account for a further 2.93–3.65 g m—2 in the wheat and 4.98–10.69 g m—2 in the wheatclover crop.

     

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    作者:Schmidt, Olaf,Curry, James P. 来源:Elsevier 发布时间:2011年07月12日