Abstract: In order to compare the effects of different irrigating regimes on the validity of nodule bacteria of alfalfa and discuss the effect of intermittent drought on nodule formation of alfalfa in cold and arid area,drying-wetting courses with different intensities of field soil were simulated.The results show that intermittent drought affected the normal growth of alfalfa nodule;the longer the drying period,the bigger it influenced the validity of nodule bacteria.Regardless of the soil water status,nodules transferred from taproot to side-root along with the growth of alfalfa.Higher noduling ability was maintained under two irrigating models when soil holding capacity was 32.7%: irrigating to 80% of soil holding capacity and intermittent drying interval was 20 days and 30 days;irrigating to 50% of soil holding capacity and intermittent drying interval was 20 days.

Key words: Alfalfa, Intermittent drought, Nodule bacteria, Noduling ability

摘要： 模拟田间土壤干湿交替及其强度,研究灌溉模式对苜蓿(Medicago sativa L.)根瘤菌有效性的影响,以及间歇性干旱对寒旱区苜蓿根瘤形成的影响。结果表明:间歇性干旱将影响苜蓿根瘤的正常发育,且周期越长,对根瘤菌的有效性影响越大;不论土壤是否缺水,根瘤均随着生长期的延长不断向侧根转移;当土壤持水量为32.7%,一次灌水达土壤持水量的80%,间歇干旱20 d、30 d和一次灌水达土壤持水量的50%,间歇干旱20 d两种水分控制模式均可保持根瘤菌较高的结瘤能力。

关键词: 苜蓿, 间歇性干旱, 根瘤菌, 结瘤能力