Accumulation and distribution of nitrogen,phosphorus,and potassium in Cynanchum bungei Decne and their relationships to dry matter production

Cynanchum bungei Decne is a Chinese traditional medicine and health food recorded by many ancient codices.It has beneficial effect on blood,liver,and kidney.The planting area of Cynanchum bungei Decne has been gradually increasing these years in China.However,few literatures were recorded concerning the characteristics of dry matter accumulation,and absorption and accumulation of N,P,and K,as well as their relationships of Cynanchum bungei Decne.Therefore,a field experiment was conducted to study the accumulation characteristics of dry matter,nitrogen,phosphorus and potassium of Cynanchum bungei Decne to fill up this blank.The results showed that dry matter accumulation presented a linear increase tendency with the increasing of the total accumulative amount of N,P and K,and nutrient balance index(NBI),which reached statistical significance.The absorptive capacity of nitrogen,phosphorus and potassium varied among different developing stages.The absorptive capacity of N,P and K by Cynanchum bungei Decne was comparative lower within first 60 days after transplantation,which only accounted for 16.8%,14.4%,and 15.6% of the total absorptive capacity,respectively.But it increased rapidly within 60—120 days after transplantation, which accounted for 68.7%,52.3%,and 58.2% respectively.Thereafter,it decreased.In general,the absorptive capacity of K was the highest,followed by N and P.The N∶P∶K ratio was 1∶0.8∶1.5 for whole growing stages.