Isotope-Aided Micronutrient Studies in Rice Production with Special Reference to Zinc Deficiency (I) -Efficiency of $^{65}Zn$ labelled fertilizers under flooded so il condition-

Using tracer technique of $^{65}Zn$, a field experiment has been carried out to evaluate the efficiency of zinc fertilizer by rice plant grown under flooded conditions. The treatments include zinc slufate mixed throughout the soil with and without organic matter, combined urea-zinc fertilizer (N: 37.7%, Zn: 3.1%), and surface application at transplaning and two weeks after transplanting at the rate of 5kg Zn/ha respectively. Other treatments were zinc sulfate mixed throughout the soil at the rate of 10 kg and 20 kg Zn/ha respectively. Root dipping in 2 % ZnO suspension, only organic matter added, and control were also included. There was not much difference in rough grain yield between zinc levels and different application methods, but the highest yield was obtained from the treatment of the root dipping in 2% ZnO suspension. Among the 5kg Zn/ha treatments, the highest total zinc yield was observed from the zinc mixed throughout the soil. The organic matter treatment seemed to reduce the zinc fertilizer efficiency. In case of the zinc fertilizer levels, 5kg Zn/ha mixed throughout the soil showed the highest zinc fertilizer efficiency as compared with 10kg and 20kg Zn/ha treatments.

담수(湛水) 상태에서 수도(水稻)에 의한 아연비료의 이용율을 평가하기 위해서 $^{65}Zn$ 표지아연비료를 사용하여 포장(圃場) 실험을 했다. 처리방법은 유기물 시용(施用)과 무시용 상태에서 $ZnSO_4$ (5 kg Zn/ha) 전층시비, 이앙(移映)시와 이앙 2 주후 $ZnSO_4$(5 kg Zn/ha ) 표층(表層) 시비, $ZnSO_4$ 다량(10 kg Zn/ha, 20kg Zn/ha) 전층시비, 2 % ZnO용액에의 묘(苗) 뿌리침적, 유기물과 대조구로 하였다. 수량은 2 % ZnO용액에의 묘 뿌리침적후 이앙한 것이 가장 많았다. 기타처리에서는 아연 시비량과 시비방법에 따른 수량차는 크지 않았다. 아연흡수량은 $ZnSO_4$ 5kg Zn/ha 전층시비에서 가장 많았다. 유기물 시용은 아연비료의 이용율을 저하시키는 것 같았다. 아연비료 이용율은 5 kg Zn/ha 전층시비가 다량 전층시비보다 높았다.