多年冬种紫云英对两种典型双季稻田土壤肥力及硝化特征的影响

Fertility and nitrification characteristics of two typical paddy soils after application of milk vetch(Astragalus sinicus) for 8 years

以湖南紫潮泥和江西黄泥田两种典型稻田下的绿肥定位试验为依托,分析了晚稻收获后两种土壤的养分性状、硝化强度、硝化势及氨氧化细菌(AOB)和氨氧化古菌(AOA)的amoA基因丰度,探讨多年冬种紫云英对两类稻田土壤肥力、硝化作用及氨氧化微生物的影响。两地试验处理一致,包括:1)不施肥不种紫云英(CK);2)冬种紫云英不施化肥(GM);3)不种紫云英单施化肥(CF);4)冬种紫云英配施化肥(GM+CF)。结果表明,冬种紫云英可以改善两种典型稻田土壤pH,即提高江西酸性土壤pH、降低湖南碱性土壤pH;提高土壤全氮、有机质、无机氮和有效磷含量。两种典型水稻土的硝化能力不同,江西黄泥田的硝化强度及硝化势均明显低于湖南紫潮泥。在湖南紫潮泥中,各处理硝化强度在0.269~0.325μg/(g·h)之间,处理间差异不显著;硝化势在培养第5周达到10.25%,紫云英配施化肥在一定程度上抑制了紫潮泥的硝化作用。江西黄泥田中,各处理硝化强度在0.010~0.021μg/(g·h)之间,硝化势从培养第3周开始上升,在培养第5周达到5.41%;单独种植翻压紫云英相对于不施肥对照提高了土壤硝化强度及硝化势,与施用化肥处理效果相当,绿肥配施化肥对硝化作用的促进最强。AOA在紫潮泥和黄泥田中均占优势地位,紫潮泥中AOA-amoA基因丰度显著高于黄泥田,冬种紫云英对紫潮泥中AOA-amoA和AOB-amoA基因丰度均无明显影响,而显著提高了黄泥田中AOA-amoA和AOB-amoA基因丰度,与冬种紫云英对硝化强度和硝化势的影响一致。

Two green manure experiments in Hunan and Jiangxi provinces were conducted in this study.The soil types at the two experimental sites were purple alluvial soil in Hunan and yellow clayey soil in Jiangxi.Soil properties,nitrification activity,potential nitrification rate,and the abundance of AOA（ammonia-oxidizing archaea）and AOB（ammonia-oxidizing bacteria）amoAgene transcripts were determined to evaluate the effects of application of milk vetch for 8 years on soil fertility,nitrification characteristics,and ammonia oxidizers.The two experiments had the same treatments：1）no fertilizer and milk vetch（CK）;2）milk vetch but no chemical fertilizer（GM）;3）chemical fertilizer but no milk vetch（CF）;4）chemical fertilizer and milk vetch（GM＋CF）.The results showed that the application of milk vetch improved the pH of both the paddy soils;i.e.,the pH of acidic soil in Jiangxi was increased and that of alkaline soil in Hunan was decreased.Application of milk vetch increased the soil organic matter,total nitrogen,ammonium nitrogen,and available phosphorus.The two paddy soils had different nitrification abilities,both the nitrification activity and potential nitrification rate were much higher in purple alluvial soil than in yellow clayey soil.In purple alluvial soil in Hunan,the nitrification activity ranged from 0.269 to 0.325μg/（g·h）in all the treatments,and there was no significant difference among the treatments.The potential nitrification rate in purple alluvial soil reached 10.25% at the fifth week of incubation,and the GM＋CF treatment inhibited nitrification ability to some extent.In yellow clayey soil in Jiangxi,the nitrification activity ranged from 0.010 to 0.021μg/（g·h）in all the treatments.The potential nitrification rate in yellow clayey soil increased after the third week of incubation and reached 5.41% by the fifth week.Compared with the control,winter green manuring improved the soil nitrification activity and potential nitrification rate,and had almost the same effects as the CF treatment.The GM＋CF treatment had the strongest effect to promote the nitrification ability of yellow clayey soil.Transcripts of AOA were predominant in both purple alluvial soil and yellow clayey soil,and the abundance of AOA-amoAtranscripts was significantly higher in purple alluvial soil than in yellow clayey soil.The application of milk vetch did not significantly affect the abundance of AOA-amoAand AOB-amoAtranscripts in purple alluvial soil,but increased their abundance in yellow clayey soil,similar to the effects of milk vetch to promote nitrification activity and the potential nitrification rate.