| Paddy field drainage degrees in controlling tiller, panicle nitrogen fertilizer management are important factors to affect yield and nitrogen utilization of rice, and there is a great significance in improving fertilizer efficient utilization and yields of rice, by the study on optimization panicle nitrogen fertilizer management under different paddy field drainage degrees, and the differences and characteristics between rice genotypes with different N use efficiency. The effects of different paddy field drainage degrees including three soil water content level (In2011:0-20cm soil relative water content was controlled at80%±5%,60%±5%, and40%±5%, named W1, W2, and W3respectively; in2012:0-20cm soil volumetric water content ontrolled at80%±5%,60%±5%, and40%±5%, named M1, M2, and M3, respectively) and three panicle nitrogen fertilizer managements (In2011:the first panicle nitrogen fertilizer was applied on the1st,8th, and15th days after rewatering, named SI, S2, and S3, respectively, the second panicle nitrogen fertilizer was applied at leaf age of15; in2012:the panicle nitrogen fertilizer was applied on the1st,8th, and15th days after rewatering, named N1, N2, and N3, respectively) on photosynthetic productivity during filling stage, nitrogen accumulation and utilization, dry matter accumulation, key enzyme of carbon and nitrogen metabolism and yield of rice were investigated using medium hybrid rice Ⅱ you498at2011, nitrogen efficient varieties (De xiang4103) and nitrogen-inefficient varieties (Yi xiang3724) at2012. The main results are follows:Total amount of spikelets, effective panicle numbers and yield were increased by suitable paddy field drainage degree and panicle nitrogen fertilizer managements. There are higher total amount of spikelets, effective panicle number, number of filled grains, seed setting rate and spike rate under the treatment with much higher yield. The yield of the treatment of W2S1reached10.96t ha-1by applying the first panicle nitrogen fertilizer on the Ist day after rewatering under the treatment W2which0-20cm soil relative water content ontrolled at60%±5%; the highest yield of De xiang4103was the treatment of M1S3which reached10.07t ha-1by applying the first panicle nitrogen fertilizer on the15th day after rewatering under the treatment W2which0±20cm soil volumetric water content ontrolled at80%±5%; the highest yield of Yi xiang3724was the treatment of M2S2which reached8.80t ha-1by applying the first panicle nitrogen fertilizer on the8th day after rewatering under the treatment W2which0-20cm soil volumetric water content ontrolled at60%±5%.Photosynthetic rate in flag leaves, dry matter accumulation, harvest index, nitrogen accumulation, translocation and utilization were increased by suitable paddy field drainage degrees and panicle nitrogen fertilizer managements. Comparing with nitrogen-inefficient varieties, there are much higher dry matter translocation, harvest index, nitrogen translocation and utilization for nitrogen efficient varieties after heading. For Ⅱ498, at Maturity total nitrogen accumulation of W2is22.29kg hm-2higher than W1and11.31kg hm-2higher than W3, and total nitrogen accumulation of S1is4.61kg hm-2higher than S2and9.25kg hm-2higher than S3. Nitrogen apparent efficiency of W2is6.10%higher than Wi and12.38%higher than W3, and nitrogen apparent efficiency of S2is5.14%higher than S3and2.58%higher than S1; for De Xiang4103, at maturity total nitrogen accumulation of M2is18.10kg hm-2higher than M1and18.85kg hm-2higher than M3, and total nitrogen accumulation of N3is19.25kg hm-2higher than N1and13.17kg hm-2higher than N2. Nitrogen apparent efficiency of M2is10.12%higher than M1and15.97%higher than M3, and nitrogen apparent efficiency of N3is8.95%higher than N2and12.94%higher than S1; for Yi Xiang3724, there is no significant effect on total nitrogen accumulation at maturity under paddy field drainage degrees, and total nitrogen accumulation of N3is3.99kg hm-2higher than Ni and12.50kg hm-2higher than N2. Nitrogen apparent efficiency of M3is14.20%higher than M1and17.01%higher than M2, and nitrogen apparent efficiency of N3is2.65%higher than Si and8.13%higher than S2.The activity of carbon and nitrogen metabolism enzymes can be improved by suitable paddy field drainage degree, and its peaks and troughs would be early or delay by suitable panicle nitrogen fertilizer managements, meanwhile the cycle of GS/GOGAT for nitrogen in leaves was improved. During the study of2012, the reasonable paddy field drainage degrees could improve carbon and nitrogen Metabolism in leaves of rice. By the process of paddy field drainage, the activities of NR, GS, GOGAT, GDH, SS and SPS in fully expanded leaves of De xiang4103in drainage treatments are higher than the submergence treatments and the activity of GOGAT, NR and SS in fully expanded leaves of Yi xiang3724in drainage treatments are higher than the submergence treatments. Meanwhile the activity of GS in fully expanded leaves of Yi xiang3724in drainage treatments are higher than the submergence treatments under M1and, and the activity of SPS in fully expanded leaves of Yi xiang3724in drainage treatments are higher than the submergence treatments under M2and M3. With interaction of paddy field drainage degrees and panicle nitrogen fertilizer management the activity of.NR, GS, GOGAT, GDH, SS and SPS in fully expanded leaves of De xiang4103is higher than Yi xiang3724overall before heading, but there were differences in key enzyme of carbon and nitrogen metabolism in flag leaves between De xiang4103and Yi xiang31724from heading stage to20days after heading. From the comprehensive analysis and comparison, nitrogen utilization and yield all were improved under the optimum combination for moderate paddy field drainage degree and panicle nitrogen fertilizer management. |
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