Abstract:

【Objective】The Chinese milk vetch (Astragalus sinicus L.) is an important green manure in the winter fallow of double-cropping rice system. The long-term returning of Chinese milk vetch to the field could achieve both soil fertility improvement and higher rice yield. However, it is still unclear that the key factors among many soil physical and chemical indicators, which drives the change of rice yield in turnover of Chinese milk vetch for different years. 【Method】 Five treatments with 0, 3, 5, 10, and 15 (G0, G3, G5, G10, and G15) turnover years of Chinese milk vetch were selected in Yujiang District of Jiangxi Province, China, the traditional planting area of Chinese milk vetch. The soil aggregates, organic matter, nitrogen, phosphorus, potassium contents and soil acidification characteristics were analyzed. Furthermore, the relationship between soil indicators and yield of early rice was explored. 【Result】The proportions of > 2 mm aggregate in G5, G10 and G15 were significantly increased. The longer turnover years of Chinese milk vetch led to the higher contents of soil organic matter, total nitrogen and phosphorus, available nitrogen, phosphorus, potassium, and readily available potassium. Compared with G0, the soil pH values in G10 and G15 were increased by 0.83 and 0.65 units. Moreover, the contents of exchangeable acid, hydrogen, and aluminum in G15 were significantly decreased as compared with those in G0. The comparison of correlation coefficients indicated that the proportion of >2 mm aggregate, soil organic matter, available nitrogen had higher interrelation with the grain yield (R²> 0.80, P<0.01). In addition, it was found that the turnover years of Chinese milk vetch significantly affected the soil aggregates, organic matter, and nutrient indicators, leading to the change of rice yield. 【Conclusion】In the double-cropping rice system, long-term turnover of Chinese milk vetch could be the main pattern to achieve higher soil fertility and rice yield. The soil acidification can be alleviated when more than 10 years turnover of Chinese milk vetch. The macro-aggregate content was more sensitive to different turnover years of Chinese milk vetch. It suggested that soil organic matter and available nitrogen were the key factors to the change of rice yield.

Key words: Chinese milk vetch, different years, aggregates, soil acidification, grain yield, early rice

摘要：

【目的】紫云英(Astragalus sinicus L.)是双季稻冬闲期重要的绿肥作物,长期进行紫云英翻压还田可以实现土壤培肥和水稻增产的双重目标。但是,在众多的土壤理化指标中,有关紫云英不同翻压年限下驱动水稻产量变化的关键因子还不明确。【方法】本研究在紫云英传统种植区(江西省余江区),选择紫云英翻压时间为0、3、5、10和15年(G0、G3、G5、G10和G15)的稻田,分析了土壤团聚体、有机质、氮磷钾养分含量和土壤酸化特征,并进一步探讨了土壤理化指标与早稻产量的相关关系。【结果】G5、G10和G15处理下,>2 mm团聚体组分的比例显著高于G0和G3处理。紫云英翻压年限越长,土壤有机质、全氮磷和速效氮磷钾及缓效钾含量越高。与G0处理相比,G10和G15处理下土壤pH提高了0.83和0.65个单位,且G15处理下土壤交换性酸/氢铝含量均显著低于G0处理。比较相关系数,在所有指标中,>2 mm团聚体组分的比例、土壤有机质、速效氮含量与籽粒产量的相关性较高(R²均大于0.8,P<0.01)。通径分析结果表明,紫云英翻压年限显著影响团聚体和有机质及养分指标,进而影响水稻产量。【结论】在双季稻区,长期紫云英翻压还田是实现土壤培肥和早稻增产的关键途径。紫云英翻压达到10年以上时,稻田土壤酸化得到明显改善。翻压年限对土壤大团聚体组分的影响程度较高,而土壤有机质和速效氮含量则是调控水稻产量变化的关键因素。

关键词: 紫云英, 不同年限, 团聚体, 土壤酸化, 产量, 早稻