| Rice Seedling period is very important for dry nursery rice. During these times, great changes could take place in rice seedling and rice seeding may suffered by disease and chilling. Rice seedling damping-off, so-called"rice seedling blight", is a severe destroyed disease in rice dry-seeded seedling. In order to develop a more effective disease management tactic, the exogenous calcium was applied in control of this disease. In this paper, the control effect of exogenous calcium on rice seedling damping-off was evaluated.The results showed that the lime was relayed the development of rice seedling damping-off, both treated by soil and soaking. Supply of calcium from 0.6% to1.0% into soil, it could be improved resistance to chilling and the incidence of damping-off was reduced obviously. The controlling effect on YUEFU was better than on LINDAO 10. Meanwhile, the interaction effects between lime and fungicides was tested, propiconazole, humexzol and triadimefon mixed with 0.6% limewater had not synergistic activities, while mancozeb showed synergistic activities. The paper also studied effect of calcium applied into soil on the growth,absorption and accumulation of mineral nutrients in rice seedlings.The results showed that supply of calcium from 0.6% to1.0% into soil, it could increase grow significantly in shoot and improve root/shoot ratio and the content of chlorophyll in rice seedling. Further studies indicated that the different dose of calcium treatments had different influence. The effect of calcium on the total N content of rice seedlings was not distinctly. The accumulation of K was increased in seedling's shoot and the content of Ca was enhanced distinctly in both shoot and root. While the absorption and accumulation of P was inhibited obviously both in seedling's root and shoot, and the content of Fe, Mg and Zn was decreased distinctly. Consequently, supply of calcium has part of calcareous character and apply calcium at 0.6%～1.0% into soil the best concentration in cultivating rice seedling. Appling calcium oxide with 0.6~1.0% into soil could improve the ability of rice seedlings under the chilling stress. Meanwhile it had a distinct physiological effect on rice seedlings at low temperature. In comparison with the control, the height of shoot, the number of roots and leaves all increased at the application of CaO. Further studies indicated that the soil with 0.6~1.0%CaO added reduced the leakage of electrolytes and the content of MDA, increased the content of chlorophyll and enhanced the activity of peroxidase (POD) .The effects of applying calcium in rhizospere soil of rice seedling on microorganisms and enzyme activities were investigated. There was no significance effects on microbial population at dose of 0.2 %( w/w) of calcium oxide mixed in nursery soil. However, applying calcium at high rate of 1.0% and 1.5% inhibited soil microbial population significantly within 40 days, and the inhibition rate to fungi population was higher than that of bacteria and actinomycete populations. The activities of catalase, urease and invertase in rice seedling rhizospere soil treated with different dose of calcium oxide were various. When the concentration of calcium oxide was 0.2%(w/w), the catalase, urease and invertase activities were all stimulated in the first 30 days, then recoverd. But calcium applied into soil at high rate of 1.0% and 1.5%, the catalse activity was slightly stimulated at first, and then largely inhibited. The urease activity was firstly stimulated then restrained, finally recoverd when treated with high rate calcium, while the activity of invertase under the high rate treatments was largely restricted at the beginning, then recovered gradually after 30 days. It was therefore concluded that applying calcium at 0.6% may not cause significant effect on microorganism and enzyme activities after 40 days.
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