关键词: 满江红, 腐解, 养分释放, 翻压量

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