Abstract Leguminous green manure crops are important for accumulating nitrogen by means of biological nitrogen fixation and for building up soil fertility in organic arable cropping systems. Whole-year green manure crops are also known to deplete the soil weed seed bank, e.g. by decaying and predation, but there is uncertainty about the magnitude of the legacy effect after termination of the green manure crop. This study sampled soil for weed seed bank assessment upon termination of a two-year leguminous green manure crop and then one, two and three years afterwards. The samples were taken from two five-year crop rotations (2011–2015) in a long-term organic crop rotation experiment in Denmark. One rotation (O2) had a two-year green manure crop followed by three years of annual cash crops, and the other rotation (O4) consisted only of annual cash crops, with four crop sequences in both rotations represented every year. In general, the weed seed bank of rotation O2 was 54 % lower than O4, with 5475 seeds m−2 versus 11,967 seeds m−2. Similarly the aboveground amount of weed biomass in O2 was lower than in O4 over the course of the five years. The legacy effect of the green manure crop showed a negative exponential rise in weed seed numbers with the increase in years after termination of the green manure crop. A biennial leguminous green manure crop can mitigate weed problems in organic annual crops. This effect adds to the benefits of including nitrogen fixing leys in crop rotations with limited access to animal manures.

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豆科绿肥作物对有机轮作杂草种子库的影响

摘要 豆科绿肥作物对于通过生物固氮积累氮和在有机耕作系统中建立土壤肥力很重要。众所周知，全年绿肥作物也会耗尽土壤杂草种子库，例如通过腐烂和捕食，但绿肥作物终止后遗留效应的程度尚不确定。本研究在两年豆科绿肥作物终止后以及之后的一年、两年和三年对土壤进行采样以评估杂草种子库。样本来自丹麦长期有机作物轮作试验中的两次五年轮作（2011-2015）。一次轮作 (O2) 种植两年绿肥作物，然后种植三年一年生经济作物，另一个轮作（O4）仅由一年生经济作物组成，两个轮作中每年都有四种作物序列。一般来说，轮作的杂草种子库 O2 比 O4 低 54%，5475 粒种子 m-2 对 11,967 粒种子 m-2。同样，在过去的五年中，O2 中的地上杂草生物量低于 O4。绿肥作物的遗留效应表明，随着绿肥作物终止后年数的增加，杂草种子数量呈负指数增长。两年生豆科绿肥作物可以缓解有机一年生作物的杂草问题。这种效果增加了在作物轮作中包含固氮地的好处，而动物粪便的获取有限。杂草种子库 O2 比 O4 低 54%，5475 粒种子 m-2 与 11,967 粒种子 m-2。同样，在过去五年中，O2 中的地上杂草生物量低于 O4。绿肥作物的遗留效应表明，随着绿肥作物终止后年数的增加，杂草种子数量呈负指数增长。两年生豆科绿肥作物可以缓解有机一年生作物的杂草问题。这种效果增加了在作物轮作中包含固氮地的好处，而动物粪便的获取有限。杂草种子库 O2 比 O4 低 54%，5475 粒种子 m-2 与 11,967 粒种子 m-2。同样，在过去五年中，O2 中的地上杂草生物量低于 O4。绿肥作物的遗留效应表明，随着绿肥作物终止后年数的增加，杂草种子数量呈负指数增长。两年生豆科绿肥作物可以缓解有机一年生作物的杂草问题。这种效果增加了在作物轮作中包含固氮地的好处，而动物粪便的获取有限。绿肥作物的遗留效应表明，随着绿肥作物终止后年数的增加，杂草种子数量呈负指数增长。两年生豆科绿肥作物可以缓解有机一年生作物的杂草问题。这种效果增加了在作物轮作中包含固氮地的好处，而动物粪便的获取有限。绿肥作物的遗留效应表明，随着绿肥作物终止后年数的增加，杂草种子数量呈负指数增长。两年生豆科绿肥作物可以缓解有机一年生作物的杂草问题。这种效果增加了在作物轮作中包含固氮地的好处，而动物粪便的获取有限。