| In order to understand the characteristics and genotypical differences of grain yield and its components, biomass production, and nitrogen (N), phosphorus (P), potassium (K) uptake and accumulation in super hybrid rice under different ecological conditions, field experiments with 8 representative varieties of super hybrid rice (Liangyoupeijiu, Zhongzheyou 1,Ⅱ-you 084, Ⅱ-youhang-1,Y-liangyou 1, Zhunliangyou 527, D-you527, Neiliangyou 6) and with the check varities of a common hybrid rice (Shanyou 63) and a super inbred rice (Shengtai 1) were conducted in Guidong county, Changsha city and Nanxian county of Hunan province from 2007 to 2009. Meanwhile, field experiments with super hybrid rice (Liangyoupeijiu and Y-Liangyou-1) and inbred rice (Huanghuazhan and Yuxiangyouzhan) were conducted under different N application conditions (0,113～176, 225 kg/hm2) in five locations (Chengmai county of Hainan Province, Huaiji county of Guangdong Province, Binyang county of Guangxi Province, Changsha city of Hunan Province and Xingyi city of Guizhou Province) from 2011 to 2013. Yield and its components, dry matter production and distribution, NPK uptake and accumulation patterns, and soil-based yield were determined. In addition, the data of soil-based yield in related litertures were also extracted to discuss the theory and method for determining the target yield of super rice. The main results were summarized as follows:1. The genotypical differences of grain yield and its components and biomass production of super hybrid rice grown in different locations. The average yield of 8 tested varieties of super hybrid rice was significantly higher than the check varieties of Shanyou 63 and Shengtai 1. The average yield of the super rice was up to 8.56～10.06 t/hm2 in 2007, 9.07～10.39 t/hm2 in 2008 and 9.74～10.54 t/hm2 in 2009 and increased by 4.0%～22.2%, 2.3%～17.1%,2.5%a～10.9% and by 10.0%～29.3%,6.1%～21.5%,4.3%～12.8% compared with Shanyou 63 and Shengtai 1,respectively. The highest yield was up to 11.45±1.08 t/hm2 in Guidong site due to the higher panicle number and higher setting grain rate. The yield components of super hybrid rice performed as the multiple types of greater panicle size, higher panicle number and bigger grains, but no matter that their yield component type, the panicle number per unit area showed the greatest contribution to the grain yield, and next the spikelets number per panicle, of which their path coefficients were 0.734～0.925 and 0.308-0.546, respectively. It is concluded that the yield contraction of the panicle number and panicle size is coordinated in super hybrid rice. The dry matter production of 8 tested varieties of super hybrid rice reached to 16.93～ 18.67 t/hm2 at the maturity stage and was significantly higher than that of Shanyou-63 and Shengtai no 1. The highest dry matter production was commonly found in Guidong site and reached to 12.05-14.26 t/hm2 at heading stage and 19.14-21.59 t/hm2 at maturity stage, which were significantly higher than those in both Changsha and Nanxian sites. There were no significant differences of the dry matter accumulation percentage of to the total during different growth periods among locations or varieties, of which was up to 5.5%～12.2% at mid-tillering stage,23.5%～29.1% at panicle initiation stage,61.2%～66.6% at heading stage, and reached to 33.4%～38.8% from heading stage to maturity stage. Compared with the check varieties, the ratio of the dry matter production after heading stage increased by 2.5～4.2 with the percentage points, but the translocation rate and the contribution rate of the dry matter at heading stage was not obviously different. As a result, super hybrid rice showed the characteristics higher dry matter production than common hybrid rice and inbred rice, especially after heading stage.2. The variation characteristics of NPK uptake and accumulation of super hybrid rice grown in different locations. The results showed that the grain yield and NPK uptake and accumulation of super hybrid rice had significantly genetic differences among varieties, different locations regional and years. The nutrient uptake rate appeared as N 177.7～189.1 kg/hm2, P 36.9～39.8 kg/hm2 and K 153.4～165.4 kg/hm2, of which 61.2%～65.3% of N and 67.6%～74.4% of P accumulated in rice grains and 86.9%～89.6% of K accumulated in rice straw. The percentage of N uptake rate to the total was about 20% until to mid-tillering stage (20 d after transplanting),25%～30% from the mid-tillering stage to the panicle initiation stage,30%～40% from panicle initiation stage to heading stage and about 20% after heading, and the percentage of P was 15%,20%～30%,40%～45% and 10%～20% respectively, and the percentage of K was 15%～20%,25%～35%,30%～40% and 15%～ 20% respectively. The nutrient need appeared as N 18.0～19.3 kg/hm2, P 3.8～4.6 kg/hm2 and K 15.9～17.4 kg/hm2. It is concluded that super hybrid rice displayed the high absorption capacity of NPK nutrients after heading and was beneficial to coordinate the relationship between the highest yielding and the efficient utilization of NPK nutrients.3. Comparison of yield formation and nutrient uptake and utilization between super hybrid rice and conventional rice under different N application conditions. The results showed that super hybrid rice yielded in average 9.55～9.57 t/hm2 rice grains, produced averagely 18.05～18.25 t/hm2 dry matter and assimilated averagely 189.5～191.9 kg/hm2 N at maturity stage, of which increased significantly by 6.03%～9.44%, by 10.67%～7.72% and by 5.49%～2.25% compared with conventional rice, respectively. Both super hybrid rice and conventional rice showed the nonlinear relationship of quadratic function between the grain yield and the NPK uptake rates and the multiple correlation coefficient was significant. Requirements for N, P and K of super hybrid rice were up to 19.8-20.1 kg,3.9～4.1 kg, 20.6-22.4 kg, respectively, of which was significantly lower than that of conventional varieties. Under the condition of nitrogen application, there was a significantly linear correlation between the grain yield and the NPK nutrient requirements. Nitrogen recovery efficiency and its partial productivity showed the significant difference among tested varieties, but the agronomy efficiency and physiological utilization efficiency did not show the significant difference among the varieties. Nitrogen harvest index of super hybrid rice was as high as 68.6%～69.1% and significantly higher than that of conventional rice (62.7%-64.0%), but no significant difference of N grain production efficiency was observed among the varieties.4. The theory and methods for determining the target yield in super rice production based on the soil-based yield. The field experiments showed that yield performance of even the same rice variety existed significant or extremely significant difference among the five locations. Under N application conditions (moderate and high N rates), Xingyi had the highest average yield (Liangyoupeijiu:13.20～13.54 t/hm2, Y-liangyou 1:13.50～13.78 t/hm2, Huanghuazhan:11.26～11.42 t/hm2, Yuxiangyouzhan:11.32～11.45 t/hm2), followed by Changsha, Chengmai and Binyang, and Huaiji had the lowest average yield (Liangyoupeijiu: 6.66～6.71 t/hm2, Y-liangyou 1:6.96～7.20 t/hm2, Huanghuazhan:6.96～7.11 t/hm2, Yuxiangyouzhan:7.35～6.86 t/hm2). Similarly, the highest average soil-based yield (yield of no N application treatment) was recorded in Xingyi (10.52 t/hm2), followed by that in Changsha, Chengmai and Binyang, and the lowest average soil-based yield was recorded in Huaiji (4.53 t/hm2). Rice yield under fertilized conditions (namely fertilized yield) (YF) depended extremely significantly on the soil-based yield (FS). The regression equations under moderate and high N rates were YF= 0.814Ys+3.337 (R2= 0.824) and YF= 0.864Ys+ 3.094 (R2=0.839), respectively. The contributions of the soil-based yield (the percentage of the soil-based yield in the fertilized yield) ranged from 64.8% to 85.5% on the average of five locations and from 72.7% to 79.3% on the average of four varieties. The analysis of the data (n= 315) collected from previous studies also indicated that there was a significant positive linear significant relationship between the soil-based yield and the fertilized yield (YF=1.031 YS+2.421, R2=0.523), and the average contribution of soil-based yield was 67.7%. In addition, the results showed that yield increased by fertilization was tightly negatively related with soil-based yield contribution; grain yield was significantly quadratically related to plant N uptake and N application rate. |
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