This study was conducted to investigate the application effects of controlled release fertilizer (CRF) treated in seedling tray on the changes of growth, nutrient dissolving rate and fertilizer efficiency under different rice ecotypes. The results are summarized as follows.

1. CRF capsule coated with biodegradable resin is 100% naturally decomposition and does not likely cause environmental risks.

2. The result of dissolution in formulations 2 and formulation 3 is 9.1% and 6.1% for 30 days at 20℃, respectively. This result indicates that CRF could be used in the seedling tray.

3. For the seedling-raising period, The treatments of 500g and 600g of CRF per tray was tended to be somewhat higher compared to the control in plant height, number of leaves and nutrient content.

4. Rice growth of early maturing cultivar and mid-late maturing cultivar increased according to application rate of CRF. Up to 60 days after transplanting, CRF 400g, CRF 500g and control treatment of 3 element fertilizer were similar in plant height, number of tillers and yield.

5. In the rice cultivation of early maturing and mid-late maturing cultivar, NH4+-N content in the soil was decreased as the more time elapsed and was lower in the CRF treatments than the control. Av.P2O5 and Ex-K content was somewhat lower in the CRF treatments than the control. pH in the flooded water was higher in the CRF treatments than the control, and EC, NH4+-N, NO3-N, PO43-P and K+ contents of CRF treated plots were lower than the control.

6. Because of fast fertilizer dissolution by late transplanting (June 11), Rice growth of double cropping (barley-rice) at 30 days after transplanting (DAT) increased higher than control in the CRF treatments but was similar in plant height, tillering number since 60DAT. The yield of rice was decreased by CRF 300g treatment and similar in CRF 400g, 500g compared to control (4.21Mg ha-1).

7. In the rice cultivation of double cropping (barley-rice), NH4+-N content in the soil increased according to application rate of CRF and was lower in CRF treatments than the control. Av.P2O5 and Ex-K content was somewhat lower in the CRF treatments than the control. pH in the flooded water was higher in the CRF treatments than the control, and EC, NH4+-N, NO3-N, PO43-P and K+ contents of CRF were lower than the control.

8. In the case of nitrogen use efficiency of early maturing cultivar, mid-late maturing cultivar and double cropping (barley-rice), the CRF treatments were higher than control treatments in the harvest stage.