Effects Of Water-nitrogen Mangement On Population Structure And Yield Formation Of Indica Hybrid Rice With Older Transplanting Seedling

Seedling age has significant effects on population quality and yield formation of rice, rice yield significantly reduced with seedling age increased. But many rice planting areas have to transplanting rice seedlings with older seedling age because of a variety of reasons. The appropriate management of water and fertilizer and cultivated density can effectively improve rice yield with older seedling age, while the study of it lack of all-around researches; and there is still not clear whether single seedling or double seedlings in a hole is better for population establishment and yield formation. So, indica hybrid rice, Fyou498, was used as test material in the two years experiments. The effects of seedling ages and nitrogen managements on spikelet differentiation and degeneration, plant type, and yield were studied in 2013 with a two-factor split plot design; and the tillering and panicle formation pattern and yield components characteristics under different seedlings per hole and different managements of water and fertilizer were laid out in a three-factor split plot design in 2014. These studies may provide theoretical and practical basis for increasing rice yield of older seedling age. The main research results are as follows:(1) The tillering capacity of the older seedling age seedlings was stronger, and the number of leaf positions with tillering and panicle formation of 65d seedling age was 25 and 31 more than 35d seedling age respectively. Primary tillers group mainly emerged from the first to eighth leaf, among which the first to seventh leaf had higher percentage of earbearing tiller of 35d seedling age; while for 65d seedling age, primary tillers group mainly emerged from the first to ninth leaf, and the second and seventh to ninth leaf had higher percentage of earbearing tiller. Second tillers group mainly emerged from the first to sixth leaf, and the first, second, seventh and eighth leaf of 35d and 65d seedling age respectively, among which the first to third leaf had higher percentage of earbearing tiller of two seedling ages, and the seventh and eighth leaf of 65d seedling age also had higher percentage of earbearing tiller too. The number of third tillers emerged of 65d seedling age was obvious more than 35d seedling age, but the percentage of earbearing tiller was still very little. Meanwhile, single seedling in a hole had higher percentage of emerging and earbearing tiller than double seedling per hole of older seedling age.(2) Contribution for yield of different tillers was primary tiller> second tiller> third tiller, and the contribution of primary tiller only 6.62% higher than second tiller for single seedling per hole. Among yield components, grain numbers per panicle and 1000-grain weight was primary tiller> second tiller> main stem, setting percentage was primary tiller> main stem> second tiller. The superior leaf positions of emerging tiller of older seedling age were the first to ninth leaf for primary tiller, the first to second and seventh to eighth leaf for second tiller; the superior leaf positions of earbearing were the second, seven to ninth leaf for primary tiller, and the first to third and seven to eighth leaf for second tiller; the superior leaf positions of yield contribution were the sixth to ninth leaf for primary tiller, the first, second and seventh leaf for second tiller. Comprehensively, the superior leaf positions of older seedling age rice were the first to second and seventh to ninth leaf, of which the total contribution to the yield nearly reached 70%. Rice yield decreased with the seedling age extended, however, single seedling per hole with 40%～60% fertilizer applied at panicle initiation stage and dry-wet alternate irrigation could get higher yield than the other treatments.(3) The number of differentiated and survived spikelets, primary and second branches increased obviously and the number of degenerated second spikelets decreased significantly with the extending of seedling age, of which the increment of second branches was the most in the basal and middle panicle and the number of differentiated and survived second spikelets increased sharply in the basal first to fifth site. The number of survived second branches,differentiated and survived second spikelets showed a trend of bimodal curve from base to top of the panicle.differentiated second branch number decreased gradually, while the degenerated number decreased first and them increased.degenerated second spikelets number was the most to the base, followed by the middle and the top of the panicle as a whole, of which the second site to the base degenerated most, and the sixth site was the least. The differentiated and degenerated number of second branch and spikelet of 65d seedling age with 40% earing fertilizer was 2～3 and 15～21 more than the other treatments. The effects of nitrogen application on the number of survived second branch and spikelet on the primary branch were approximately characterized by the 60% earing fertilizer was obvious higher than the other treatments, while the degenerated number was less than other treats.(4) The leaf area index at full heading stage decreased constantly with the seedling age extending, and the average leaf area index of 65d seedling age was significant less than 35d and 50d seedling age, but the high effective leaf area ration of 65d seedling age was significant higher than 35d and 50d seedling age because of the long and wide top three leaves. Leaf area index at full heading stage increased first and then decreased with the increase of earing fertilizer proportion, and the 40% earing fertilizer had the largest leaf area. Leaf length, width and angle of the top three leaf showed a increasing trend with the seedling age extending, while leaf mass per area was 65d> 35d>50d; the top three leaves’ angles of 65d seedling age were significant larger than 35d and 50d seedling age, and the length of the third leaf from top and the width of the top three leaves were also obvious higher than 35d seedling age. The flag leaf angle increased obviously by increasing the earing fertilizer proportion and the angle of the second and third leaf from top increased first and then decreased (40% earing fertilizer was the largest) of the 65d seedling age. The length, width, and thickness of the top three leaves were all positive correlated with grain number and weight per panicle. The plant height significantly decreased with extending seedling age and increasing earing fertilizer.In conclusion, in order to make the older seedling age rice obtain high and stable yield,dry rice-nursery, sparse sowing, and rare-planting technique should be used in production practice. Seedling age had better not exceed 65days to avoid causing a serious damage on the main stem. It should make full use of the superior leaf positions, appropriate water and fertilizer management (40%～60% earing fertilizer and dry-wet alternate irrigation), and drying paddy field timely to minimize ineffective tillers at the same tine; then coordinate the relationship between the number and weight of panicle well, and improve the percentage of earbearing tiller and lodging resistance of the superior stem to get good plant type.