本研究在臺北市臺灣大學試驗農場進行，分別於三、五、九與十一月自試驗水稻田區逢機採取50個5.5公分直徑17公分深圓筒土樣，進行土中鴨舌草種子數目估算。每田區530平方公尺，計有四重複。估算方法結合分離法與發芽法。種子在30/25℃及缺氧的最適環境下能發芽者視為無休眠種子；不能發芽的種子再經一個月冷層積處理後，在最適環境下可以發芽者，視為休眠種子。結果顯示鴨舌草在水田形成持續性種子庫，十一月土樣中種子最高，每平方公尺12,922粒。三月及五月種子數目略有遞減，但差異未達5%顯著水準。九月份種子數目顯著地最少，僅有5,014粒。十一月土樣中種子約有20%為具休眠種子，九月份約0.4%，三、五月份則全無休眠種子。

Seasonal changes in the seed bank of Monochoria vaginalis (Burm.f.) Presl var. plantaginea Solms were estimated from the paddy soil collected in National Taiwan University Experimental Farm. The experimental field was divided into four plots with an area of 530 m2 for each plot. On each sampling date, 50 sets of soil per plot in Taipei were sampled randomly using soil sample cylinders, which were 5.5 cm in diameter and 17 cm in depth. Sampling time was in September (booting stage of the 2nd crop) and November (grain maturation stage of the 2nd crop) of 1995, and in March (after soil preparation for the planting of the 1st rice crop) and May (booting stage of the 1st crop) of 1996. Seeds were extracted from the soil sample and were germinated under favorite environment, i.e. 30/25℃ room temperature and anaerobic condition. Seeds thus germinated were counted as non-dormant. Seeds not germinated were cold stratified for one month and tested again. Seeds thus germinated were counted as dormant. It showed that Monochoria vaginalis var. plantaginea constituted a persistent seed bank in paddy soil. The highest seed number was found in November (12,922 seeds m-2), less but not significant in March and May, and the lowest in September (5,014 seeds m-2). In November there were 20 % of seeds classified as dormant. It was 0.4% in September, yet no dormant seeds were found in March and May.