Abstract: Azolla is a genus of small floating aquatic ferns,which can be used as green manure and feed in the southern rice cropping system.Among them,Azolla filiculoides is one of the species widely used in actual production.To reveal the decomposition and nutrient release characteristics of Azolla filiculoides under different manuring doses in non-flooded soil,a 60-day simulation trial was carried out using the method of combining glass fiber filter paper with nylon mesh bags.Three manuring doses treatments were set up in this experiment,including the mass ratios of 5 g·kg^-1(low),10 g·kg^-1(medium) and 15 g·kg^-1(high)Azolla-soil,respectively.The results showed the same general rules of decomposition and nutrient release under different manuring doses in A. filiculoides.The decomposition and nutrient release was fast in the early stage (0~10 d) and became slow in the later stage (20~60 d).After 60 days of manure application,the dry matter decomposition rate of A. filiculoides was 36.1%~47.6%.The nutrient release rates of C,N,P,and K were 47.12%~57.4%,47.2%~56.7%,68.5%~75.2% and 53.5%~61.3%,respectively.The final (after 60 d) decomposition rate and nutrient release rate decreased with the increase of manuring dose,but the short-term (60 d) nutrient release amount of carbon,nitrogen,phosphorus,and potassium increased.The final nutrient elements release rates were P>K>C>N in all treatments.The functional relationships between nutrient release rate (y),nutrient release speed (v) and decomposition time (x) under different treatments were fitted by power function y=ax^b(P<0.001) and exponential decay model v=v_oe^-kx(P<0.05),respectively.The regression analysis showed that the increasing manuring doses delayed the release of nutrients,and the delay effect of complete release of nitrogen was the largest (435 to 1749 d),followed by carbon (200 to 607 d),potassium (52 to 131 d) and phosphorus (32 to 98 d).With the increase of manuring dose,the maximum release rate of each nutrient increased significantly,but the decay rate of the rate also increased.It indicated that increasing the manuring dose could not increase the ability of continuous nutrient supply.Therefore,the suitable manuring amount should be determined based on the fertilizer requirements of the subsequent crops to avoid nutrient waste caused by excessive manuring in actual application.This study provided a theoretical basis for the scientific utilization of A. filiculoides in single-season rice mode,rice-fishing mode,rice-tobacco (vegetable) and other paddy-upland rotations models or upland crop systems.

Key words: Azolla, Decomposition, Nutrient release, Manuring dose

摘要： 为明确不同翻压量细叶满江红(Azolla filiculoides)在非淹水土壤中的腐解过程差异,以玻璃纤维滤纸与尼龙网袋结合的方法开展翻压模拟试验,研究了3个翻压量(萍土质量比为5 g·kg^-1,10 g·kg^-1和15 g·kg^-1)下细叶满江红的腐解及养分释放特征。结果表明:不同翻压量细叶满江红的腐解及养分释放规律均为前期(0~10 d)快、后期(20~60 d)慢,最终(60 d后)的腐解率和养分释放率随翻压量的增加而降低,但养分释放总量随之增加,各翻压量养分释放率均为磷>钾>碳>氮。养分释放率(y)和释放速率(v)与腐解时间(x)的关系分别符合幂函数y=ax^b (P<0.001)和指数衰减模型v=v_oe^-kx(P<0.05)。回归分析表明,增加翻压量可延缓细叶满江红养分的释放,且延缓效果为氮>碳>钾>磷;随着翻压量的增加,各养分的最大释放速率均显著提升(P<0.05),但速率衰减速度也随之加快。可见,增加细叶满江红翻压量并不能增加养分持续供应能力,实际应用时应结合后茬作物的需肥特性选择适宜的还田翻压量,避免过量翻压造成养分浪费。

关键词: 满江红, 腐解, 养分释放, 翻压量