| The double-rice planting is an important crop systems in the South rice zones, which was unique significance to food safety and society economy in our country. Early-rice production is easy to fluctuate in the double-rice planting, thus, steadily obtaining its high- or superhigh-yield was not only an very important production questions for discussion but also was of important significance to stabilitate double-rice areas, improve rice compositive productivities and increase peasant's incomes. In recent years, due to many benefit policies to farming and new super early-rice varieties, the yields of the double early rice improved year after year, furthermore, there appeared many models of high- and superhigh-yield. But compared to the middle or late rice, there were disadvantages such as low and unsteady yields, unknown laws for superhigh yields and characteristics, uncertain quantitative technologies and planting, bad repeating high- yield experiments and so on. Therefore, from 2006 to 2009, in Ganzhou, Yuanzhou, Fengxing and Poyang zones in Jiangxi province, the rice varieties, Jingyou463, Xiannong31, Xinfenyou22, Lulianyou28, YouI458 were used to study the characteristics of yield formation, material production and N absorption by building middle-, high- and superhigh colony with many combining technologies of different sow period, basic seedling and N application; The topic experiments about different seeding ages, basic seeding, N amounts and management were done to study and build key technologies of calculating basic seedling and precise and quantitative N in early rice in the double-cropping system. The results were as follows:1.The averagely spike number per ha. was 3,391,000 in super high-yield colony, which was higher notably than that in high- and middle-yield colony, improved at 13.5%, 25.7% respectively;The total grain number per spike was averagely 120.3, which was equal to that high- and middle colony;The colony floret number was averagely 4.19×108 , which was higher notably than that in high- and middle-yield colony, improved at 14.5%, 31.8%, respectively; The seed-setting rate was averagely 84.1%, which was about equal to that in high-yield, but higher notably than that in middle-yield colony; The 1000-grain weight was averagely 27.0g, which was not notably difference to that in high- and middle-yield. Among the yield factors, the spike number was the most important to the yield, the next was grain number and seed-setting rate, but there was not notably differences; Seed-setting rate was the most important to net contribution of yield, the next was spike and grain number, but there was not notably difference.The basic characteristics of superhigh-yield formation in early rice in the double-cropping system were more and bigger spikes, enough floret number and substantial ratio. The proper component factors of early rice super high-yield were as follows: effective spikes were 339.14±26.34×104.hm-2, total grain number per spike was 120.31±8.48, seed-setting rate was 84.11±2.35%, 1000-grain weight was 27.03±0.42g.2.The colony leaf area of super high-yield early rice at jointing stage was lower than that of high- and middle colony, but it was higher at N-n+1 leaf age, heading and maturity stage; Its growth rate of leaf area was lower from N-n+1 leaf age to jointing stage, but higher from jointing stage to heading stage; Its decreased rate of leaf area after heading was lower than that of high- and middle colony;Its photosynthesis potential was higher notably than that of high- and middle colony from heading stage to maturity stage; Its colony growth ratio was also higher notably.The proper LAI of superhigh-yield early rice at main stages were as follows: 1.5～2.0 at critical stage of effective tiller emergence(N-n+1), 4.5 at jointing stage; 6.5 at heading stage, 2.5～3.0 at maturity, respectively. The effective and high leaf proportions were 85%, 65%, respectively. The proper photosynthesis potential of super high-yield early rice in main growth stage were as follows: 1.4～1.6 from transplanting to N-n+1 stage, 2.5～3.0 from N-n+1 to jointing stage, 7.0～7.5 from jointing to heading stage, 9～10 from heading to maturity stage. The growth rate of super high-yield early rice in main growth stage were as follows: 8.0～10.0 from transplanting to N-n+1 stage, 16～18 from N-n+1 to jointing stage, 25～30 from jointing to heading stage, more than 20 from heading to maturity stage.3.The dry material accumulations of super high-yield early rice were higher notably than those of high- and middle colony in main growth stage except from N-n+1 to jointing stage; Its economic yield had a notably parabola correlativity with dry material accumulations at heading stage, and a notably positive correlativity with dry material accumulations at maturity stage or from heading to maturity phases, but economy index was not significant to yield.The dry material accumulations of super high-yield early rice in main growth stage were as follows:2100 at N-n+1 leaf age, 4300 at jointing stage, 9500～10500 at heading stage, over 15750 at maturity stage, the ratio of dry material accumulation from heading to maturity phase to total dry material accumulations was over 40%.4.The materials export amounts from stem of super high-yield early rice were notably higher than those in high- and middle colony, but its leaf material export amounts, apparent export ratio in the stem after heading and their yield contributions were lower. Its apparent export ratio in the stem after heading was 20%～22%, the apparent export materials contribution ratio for yield was 19%～20%.5. At (N-n+1) leaf stage and elongation stage, the plant nitrogen content in super high yield population was similar with that in high yield and middle yield population, but was higher at heading and maturity stage. The amount of N accumulation, stage N accumulation and the N absorption intensity at (N-n+1) leaf stage and elongation stage were slightly higher than that in high yield population, and significantly higher than that in middle yield population, but significantly higher than that at heading and maturity stage. At maturity stage, the percentage of panicle N accumulation, N absorption per 100 Kg grains and nitrogen use efficiency in super high yield population were higher than that in high and middle yield population, while the N harvest index, N agricultural efficiency and N physiological efficiency were similar with that in high yield population, but higher than that in middle yield population. On the other hand, the N dry matter producing efficiency and N apparent productivity were significantly lower than that in high yield population.The characters of N uptake in super high yield population were as follows: (1) The plant N content was about 2.7(2.5～3.0)at (N-n+1) leaf stage, about 2.0(1.8～2.2)at elongation stage, about 1.3(1.0～1.5)at heading stage and about 1.0(0.8～1.3)at maturity stage. (2) The plant N absorption amoun(tKg.hm-2)was about 50 at (N-n+1) leaf stage, about 90 at elongation stage, about 136.5 at heading stage, and above 160 at maturity stage. The percentage of plant N accumulation at (N-n+1) leaf stage to total N accumulation was about 30%, at elongation to heading stage it was about 25%~30%, while at heading to maturity stage it was about 20%, and the percentage of panicle N accumulation to total N accumulation was about 75%. (3) The N harvest index was about 70%, the N agricultural efficiency was more than 18 Kg·Kg-1, the N physiological efficiency was more than 46 Kg·Kg-1, and the N use efficiency was more than 40%.6. The basic seedling formula of double crop early rice for super high yield could be simplified as X = Y/ (1 + t1 ) [ 1 + ( N﹣n﹣SN﹣bn﹣α) r1 ], and the key parameters for the formula were definite. Among the formula, the earbearing tiller percentage(s1)of tillers with more than 3 leaves was averagely 98.1%(94.2%～100%), and the survival rate of tillers with less than 2 leaves was averagely 11%(8.3%～13.4%). The tiller formation percentage (r) in productive tillering sites was averagely 72.9%(70.2%～76.2%), and the amount of tiller absent when transplanting (bn) was 0.6~1.0 leaves, averagely 0.8 leaves. And the properly leaf stage to enough tillers was 8.5~9.2, averagely 8.8, the correctional coefficient (a) was -0.5~-1.2. When calculating the amount of basic seedling with this simplified formula for super high yield cultivating, the practical parameters were as follows: Y was the proper panicles number for the target yield, t1 was the number of tillers with more than 3 leaves when transplanting, and SN was the leaf stage when transplanting, and N=12, n=4, r1=0.7, bn=0.8,α=-1.The above simplified formula and the key parameters were used in Yuanzhou, Yugan, Boyang, Jiangxi Province, where located the testing and demonstrating area of double crop early rice for super high yield cultivating. The seedlings were transplanted with 5~6 leaves, every seedling had 1~2 tillers with more than 3 leaves. After calculating with the formula, the amount of needed seedlings was 45~60×104, which was 20%～30% higher than large scale cultivation, and the leaf stage to enough tillers was the 9th stage, 0.5~1.0 leaf stage earlier than large scale cultivation. Furthermore, the final yield was above 9000 Kg.hm-2, 20%~50% higher than large scale cultivation.7. It was definite for the calculation of N application and the parameters in double crop early rice with the Stanford formula. The basic yield in non-N soil and the N supply of soil (amount of N accumulation in non-N soil) had remarkably positive correlation with the yield from normally N application area, but the content of soil organic matter, alkali-hydrolyzed N were not obviously correlated with N supply of soil. On the other hand, the N demand per 100 Kg grains in non-N soil was remarkably positively correlated with the basic yield. The basic yield in non-N soil was averagely 4881.5 kg.hm-2 (4575.9～5193.0 kg·hm-2), and the N demand per 100 Kg grains in non-N soil was averagely 1.53 kg (1.45～1.64 kg), while the N supply of soil was averagely 74.79 kg·hm-2(66.35～85.17 kg.hm-2). In N application area, the N demand per 100 Kg grains was remarkably correlated with yield, which showed as quadratic equation, and the N demand per 100 Kg grains for super high yield was 1.75～1.95 kg, especially between 1.75 kg and 1.85 kg, the optimal regressed value was 1.83 kg. The total N demand was 157.5～166.5 kg·hm-2, which the optimal regressed value was 163.8 kg·hm-2. In addition, the yield was promoted with the increase of N use efficiency, that was, the N use efficiency for super high yield was 37.4～47.8%, averagely 43.2%. So the 40% of N use efficiency was the critical target for super high yield in double crop early rice.As for the double crop early rice, the parameters of the Stanford formula for calculating the accurate N application were as follows: The N demand per 100 Kg grains was 1.5 kg when the basic yield was 4500～4875 kg.hm-2, and 1.6 kg when the basic yield reached 4875～5250 kg.hm-2. In N application area, the N demand per 100 Kg grains for super high yield was 1.8 kg, and the N use efficiency was 43%.The above parameters were used in the testing and demonstrating area in Yuanzhou, Yugan, Boyang, the pure N application was 202.5～225 kg.hm-2, which was 37.5～60 kg.hm-2 (27.8%～36.4%) higher than large scale cultivation. The real yield reached 9000 kg.hm-2, which was 3300 kg.hm-2 (57.9%) higher, and the N use efficiency was 41%~46%, 15% higher.8. The yield and N use efficiency were apparently influenced by the proportion of base-tiller fertilizer and panicle fertilizer, as well as the application stage of panicle fertilizer. The yield and N use efficiency with 7:3 and 6:4 of the proportion of base-tiller and panicle fertilizer were remarkably higher than that with 8:2 and 9:1, which the yield with 7:3 was 6.88% and 10.43% higher than that with 8:2 and 9:1 respectively, and the N use efficiency was 21.46% and 33.13% higher. Similarly, the yield with 6:4 was 4.41% and 7.87% higher than that with 8:2 and 9:1 respectively, and the N use efficiency was 17.52% and 28.8% higher. There was no difference of the yield between 7:3 and 6:4. Furthermore, there was the highest yield (9229.2 kg.hm-2) when applied with panicle fertilizer at top third leaf stage, which was not apparently different with the yield when applied at top second leaf stage, but significantly higher (8.67%) than applied at top fourth leaf stage, and remarkably higher (22.43% and 47.41% each) than applied at top leaf stage and none panicle fertilizer. When applied with panicle fertilizer at top third leaf stage, the N use efficiency and N agricultural efficiency were the highest, 45.11% and 20.79 kg.kg -1 respectively, which were 9.14% and 10.6% higher than applied at top second leaf stage, and remarkably higher than other treatments. The 7:3 and 6:4 of the proportion of base-tiller and panicle fertilizer, and panicle fertilizer applied at top third or second leaf stage, were the key factors to get super high yield in double crop early rice.The results show that our technology could increase 729～1503 kg.hm-2, 8.1～16.7%, than the technology currently used in large scale cultivation (10:0 or 9:1), and the N use efficiency improved 15.4%～31.8%.
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