Analysis On Ralization Of Yield Potential In Super Hybrid Rice

As world food security become a major concern for morn than half of the world's population, research on super high yielding has also attracted growing domestic and international attention. The super rice breeding progress of China is known in the world; it has released a number of super rice varieties which was accepted by farmers. These varieties showed a high yield record of 12 - 17 t·ha^-1 in small testing areas and under specific ecosystems, which demonstrate the enormous production potential. However, many of the super hybrid rice varieties also showed instability in different regional yield trials. There is a big yield gap between experimental testing plots and farmers' fields. Several field experiments were conducted to analyze how managements and climate factors affect the growth and yield of super hybrid rice. The following results were obtained:1. Yield stability and dry matter characteristics of super hybrid riceThe yield stability and dry matter production of super hybrid rice was analyzed under different fertilizer rates at different locations. Field experiments with two super hybrid rice cultivars (Zhunliangyou527 and Liangyou293) were conducted in Changsha, Guidong, Hengyang, Nanxian, and Yongzhou of Hunan province in 2004 and 2005. According to the ratio of 1N : 0.5P₂O₅ : 1K₂O, three fertilizer rates (135, 180, 225 kg N·ha^-1) were designed using randomized complete block with four replications. The results showed that the yield of super hybrid rice was highest in Guidong with significant differences among the five sites. The average yield of two years and three fertilizer rates ranged from 7 492.3-12 209.2 kg·ha^-1 for Zhunliangyou527 and from 6 984.0-11 679.5 kg·ha^-1 for Liangyou293. The regional variation of the dry matter accumulation and grain yield components showed the same tendency as the harvest yield. There were no significant differences in yield and dry matter production among the three fertilizer rates at same site. The grain yield showed significant positive correlations with productive panicles, seed setting rate and grain weight, and negative correlation with spikelet number per panicle. The fertilizer rate in the range from 135 kg N·ha^-1 to 225 kg N·ha^-1 was not the limiting factor in the yield performance. Since super hybrid rice has larger sink capacity, it is feasible to achieve high yield by increasing grain setting rate and grain weight.2. Path analysis of yield and yield components of super hybrid rice under different yield levelAnalysis were conducted of the correlation, stepwise regression and path analysis between the main yield traits and grain yield of super hybrid rice cultured in 5 different locations in Hunan province. The relative importance of 8 main yield traits contributing to the grain yield was estimated. The results showed that panicle number, spikelets per panicle, and spikelets per unit area have great effect on yield in different locations. The results suggest that the relation among all yield traits, especially between panicle number and spikelets per panicle must be assorted with each other.3. Preliminary approach on adaptability of Oryza2000 model for super rice in Hunan provinceThe ORYZA2000 model was tested and verified for super rice via field experiments conducted at 5 experiment stations in Hunan province, in 2004 to 2005. From field experiments in 2005, the developmental rates of super rice in different stages, partitioning factors of dry matter, specific leaf areas were obtained. The biomass, LAI and yield were verified using the experimental data in 2004. The slope(α), intercept(β), and determination coincident (R²) of the linear regression between simulated and measured values as well as the student's t-test assuming unequal variance and the normalized root mean square error (NRMSE) were used for the evaluating the effectiveness of ORYZA2000 model S. The results showed that ORYZA2000 model was acceptable in simulations of biomass and LAI. In general, the simulations for total biomass and panicle biomass were more accurate than that for biomass of green leaves and stem biomass. NRMSE of stem biomass, green leaves biomass, panicle biomass, total biomass and LAI, yield were 35%, 47%, 44%, 32%, and 51%, 24%, respectively. According to the results of calibration and evaluation, the authors derived the yield potential of 5 different areas in Hunan province. The result of the paper enriches the theory and practice of crop simulation and super rice cultivation, and would be an excellent reference for the development of super rice and its management. 4. Effect of light and temperature on yield and yield component of super hybrid riceThe canonical correlation analysis for super rice was tested and verified via fieldexperiments conducted at the 5 experiment stations in Hunan province, in 2004 to 2005. We analyzed the relationships between the biomass, yield components, yield of super hybrid rice and the effective accumulated temperature, extreme temperature difference, sunshine hours, daily average air temperature, minimum air daily temperature, and maximum air daily temperature during growth period of super hybrid rice. The results showed that the first, second, third, and fourth canonical correlation coefficient between the light and temperature factors with yield components of super hybrid rice were very significant. The light and temperature factors greatly affect the productive panicle number, spikelets per panicle, and spikelets per square meter area, and the resulting yield. The main affecting factors on super hybrid rice growth were not same at various growth stages. However, during the whole growth duration, the mean of minimum-daily air temperature greatly affected super hybrid growth and yield, followed by maximum-daily air temperature, and extreme temperature difference.5. Research on the optimum cultivation method of super hybrid riceField experiments with Liangyoupei9 (super hybrid rice) and Shanyou63 (CK) were conducted in Changsha from 2002 to 2004 to compare the effects of different cultivation methods on the yield performance and dry matter production of super hybrid rice. Two cultivation methods, the optimized cultivation (OM) and traditional method (TM), were compared by using randomized completely block design with 4 replications. The results showed that the two varieties yielded differently under the two kinds of cultivation methods.Liangyoupei9 yielded 8.20-10.37 t·ha^-1 under OM and significantly higher than that under TM. The yield of Shanyou63 under OM was reduced by 0.37%-8.8% compared with TM. There was a highly significant difference in the dynamics of change in tiller number per seedling between two cultivation methods. The tiller number per hill of the two varieties under OM was more than 110% than that of TM, but the tiller number per land area between two cultivation methods were not significantly different because of the different transplanting density. The plant nitrogen content of Liangyoupei9 under OM at each growth stage was not higher than that under TM.6. Uptake and utilization of nutrients by super hybrid rice under different fertilizer ratesCharacteristics of nitrogen (N), phosphorus (P) and potassium (K) uptake and their utilization in super hybrid rice were studied. Field experiments with super hybrid rice Zhunliangyou527 and Liangyou293 were conducted in five locations of Hunan province in 2004 and 2005. The following fertilizer application rates were used: low rate (135 kg N·ha^-1, 29.7 kg P·ha^-1 ,112.1 kg K·ha^-1), medium rate (180 kg N·ha^-1, 39.6 kg P·ha^-1,149.4 kg K·ha^-1) and high rate (225 kg N·ha^-1, 49.5 kg P·ha^-1,186.8 kg K·ha^-1) using randomized complete block design with 4 replications. Aboveground plants were sampled to measure the dry matter weight, NPK content, NPK uptake rate, NPK harvest index and nutrient use efficiency at heading and maturity stage. No significant differences in plant NPK content at heading and maturity stage were found between two tested varieties and among the 3 fertilizer rates. The variation in range of plant NPK content among 5 locations was relatively smaller than that of the actual yield as well as the NPK uptake rate. The differences in plant NPK uptake rates among the locations were mainly due to the differences in the dry matter production. With the increase in yield, the harvest index of NPK showed an increased tendency and the requirements for NPK nutrients to produce 1000 kg grain yield showed a decreasing tendency. The highest yield was recorded in Guidong site but the plant NPK nutrient content and their uptake rates were at the medium level among 5 locations. There were no significant differences in plant NPK content and uptake rate for super hybrid rice in the range of fertilizer rates of 135-225 kg N·ha^-1, 29.7-49.5 kg P·ha^-1, 112.1 -186.8 kg K·ha^-1. With the increase in yield of super hybrid rice, the uptake and use efficiency of fertilizer NPK nutrients increased. Therefore, the high use efficiency of fertilizer nutrients was associated with the high yield performance of super hybrid rice.7. Effect of plant-row spacing on yield and yield components of super hybrid riceThe yield performance and dry matter characteristics of super hybrid rice wereanalyzed under different plant-row spacings at different growing locations. Field experiments with three super hybrid rice cultivars (Zhunliangyou527, Liangyou293, and Yyoulhao) were conducted in Changsha, Guidong, and Yongzhou of Hunan province in 2006 and 2007. Two transplanting densities (Hd=High density, Ld=Low density) and three plant-row spacing (SQ= Square, RE= Rectangle, ST= Stripline) were designed by using randomized block with three replications. The results showed that the grain yield of ST was highest among the 3 plant-row spacing, and was significantly higher than SQ. This resulted from more spikelets per m², higher grain filling, higher grain weight, and more dry matter production after heading stage and harvest index.8. Effect of plant-row spacing on radiation and nutrient use efficiency of super hybrid riceThe radiation and nutrient use efficiency of super hybrid rice were analyzed under different plant-row spacings at different growing locations. Field experiments with three super hybrid rice cultivars (Zhunliangyou527, Liangyou293, and Yyoulhao) were conducted in Changsha, Guidong, and Yongzhou of Hunan province in 2006 and 2007. Two transplanting densities (Hd=High density, Ld=Low density) and three plant and row spacing (SQ=Square, RE=Rectangle, ST=Stripline) were designed by using randomized block with three replications. PAR value at the canopy and 10 cm above water level and NPK uptake amount at mature stage were analyzed. The results showed that there were no differences in PAR value 10 cm above water level among the different plant-row spacings with same variety in the same location. However, the PAR value at canopy level of ST treatment was significantly lower than SQ and RE. There were no differences in nutrient use efficiency or enzyme activity in leaves among the plant-row spacings in the same variety and location. The results indicated that the bottom leaves can get more radiation with stripline row spacing.