Effects Of Ecological Conditions And Transplanting Density On The Rice Population Characteristics, Yield And Quality

The formation of rice yield and quality was determined by the combined effects of rice genetic characteristics, ecological conditions and cultivation practices; transplanting density was an important cultivation practices which regulate the growth and population structure of rice; it had important practical significance for the promotion of rice quality, high yield, efficient production to study effect of transplanting density on rice yield and quality under different ecological conditions. In this study, ten different types of rice was used as material to carry on field experiment in Xichang and Ya’an from2008to2009in order to discover rice quality and yield formation rule of the different types and effect of transplanting density on rice yield and quality under the two different ecological conditions. The results were as follows:1. Rice yield, yield components and the main direction of yield in both ecological conditions was different.The rice yield in Xichang which was an area of high altitude, strong light, the large temperature difference were higher than in Ya’an which located in the mid-to-low elevation, rainy and humid regions except that yield of two Japonica rice varieties including Xudao3and Mianjing147was low because suited to ecological conditions of Xichang. Performance of different varieties in the two places had some differences; increase of Hexi39yield in Xichang in2008and2009was the highest, followed by the Japonica hybrid rice Jiuyou418; either in Xichang of in Ya’an, hybrid Indica rice Jinyou527showed a certain degree of heterosis and its yield increased significantly compared with inbred Indica rice Changmi011. The yield of hybrid Japonica rice Jiuyou418showed strong heterosis significantly increased compared with inbred Japonica rice Hexi39in Ya’an, but the advantage was not obvious in Xichang in2009, and the yield difference between Jiuyou418and Hexi39was not significant. Correlation and path analysis showed that it had a longer tillering stage and more effective panicles but a small number of grains per ear and lower1000-grain weight in Xichang;1000-grain weight and grains per ear had the greatest contribution to yield; it should be to improve1000-grain weight and grains per ear on the basis of sufficient panicles in Xichang. The lack of effective panicles was the biggest factor restricting the yield increase which had the greatest contribution to yield; it should be to improve the number of panicles in production in Ya’an.2. There were significant differences in the characteristics of rice plant type and population structure features in the two ecological conditions. Rice plant growth was suppressed to a certain extent in Xichang, due to its high altitude, adequate light and strong ultraviolet radiation; a large difference in morphology between the two ecological conditions was formed and better growth and development characteristics was produced in Xichang. The plant height and ear length in Xichang were significantly lower than in Ya’an, respectively,16.1%and6.3%(2009); the leaves of rice in Xichang compared with Ya’an was short, narrow, thick and erect, and the leaf patterns was upright more compact which laid the foundation for the close planting and larger tassel capacity with the better field ventilation and higher photosynthetic efficiency. On the stem, the basal internodes in Xichang was shorter than in Ya’an, but its lodging capacity was significantly enhanced; the bending moment of the base Ⅰ, base Ⅱ and Ⅲ section in Xichang was lower than Ya’an,41.8%42.8%and48.4respectively; the break variable torque of the base Ⅰ, base Ⅱ and Ⅲ section were higher17.5%,11.2%and4.4%and the lodging index was than Ya’an54.0%,53.1%and53.6%, respectively. The rice roots in Xichang was more developed than Ya’an, the average group total root number in Xichang was more than18.3%in Ya’an, the average group total root length was13.8%larger, the average root dry weight of the single-stem was91.4%larger, and well-developed root system had laid a good foundation for the absorption of nutrients.3. Effect of planting density on the rice population characteristics and yield formation in the two ecological conditions was demonstrated.The change of planting density changed the space of individual growth and affected the morphological characteristics of the plants and their corresponding properties firstly. As the density increased, the reduction of individual nutrition space inhibited plant growth, and the leaves especially in the upper was short and narrow; Leaf area and LAI increased, but the field light transmittance decreased, the blade thickness and specific leaf weight reduced. With the increase of planting density, the base angle of flag leaf in the two experimental places was smaller, the curvature of the flag leaf and the second leaf in Xichang showed an increase trend but the flag leaf, the second leaf and three-leafs curvature in Ya’an showed an decrease trend. Effect of planting density on the leaf curvature in Ya’an was greater than in Xichang, which may be related to the different light conditions of the two places.Planting density had a significant effect on the basal internodes length and plant height in Ya’an, but there was not significant effect in Xichang; there were an increase of16.5%,7.4%,12.0%and5.3%respectively on the base I, base II and III section length and plant height under the high-density conditions contrasted the rare-planting density; with the increase of planting density, the basal internodes width decreased, the bending moment, the break variable torque and the resistance to lodging reduced and the lodging index increased, but the degree of influence of the density on the breaking moment and lodging index in Ya’an was far greater than in Xichang. With the increase in planting density, the root number, root length and root weight of single-stem reduced, but the root number root length and root weight of the group increased, uptake of nitrogen, phosphorus and potassium increased accordingly, but the use efficiency of nutrition decreased both in Xichang and Ya’an.The rice yield improved with increase in planting density in Xichang and Ya’an, especially Japonica rice and inbred Indica rice. The suitable selection order of four rice varieties in Xichang as follows:the hybrid Indica rice Jinyou527>the hybrid Japonica rice Jiuyou418>the inbred Japonica rice Hexi39>the inbred Indica rice Changmi011; Jinyou527, Changmi011and Jiuyou418was suitable for the medium-density and high-density planting, and Hexi39was suitable for the high-density planting. The suitable selection order of four rice varieties in Ya’an as follows:the hybrid Indica rice Jinyou527> the hybrid Japonica rice Jiuyou418>the inbred Indica rice ChangmiOll>the inbred Japonica rice Hexi39; Jinyou527and Hexi39was suitable for the medium-density and high-density planting, Jiuyou418and Changmi011was suitable for the high-density planting.4. Effect of planting density on the rice qualities in the two ecological conditions was demonstrated.Rice integrated quality in Xichang was better than Ya’an. Percentage of chalky grain and chalkiness had little difference in the two ecological conditions except for the individual species. Except that alkali digestion value of Jiuyou418, Hexi39and Mianjing147in Xichang was significantly greater than for Ya’an, seven other varieties’ alkali spreading value in the two ecological conditions showed no significant difference. Gel consistency of Japonica rice varieties in Xichang was significantly greater than Ya’an; the average content of crude protein of rice in Xichang was greater than Ya’an too.Planting density had great effect on brown rice rate, milled rice rate, chalky grain rate, alkali spreading value and gel consistency in Xichang; brown rice rate, milled rice rate in the rare-density planting was significantly lower than the medium-density and high-density which adversely affected the rice milling quality; chalky grain in the high-density planting was significantly higher than the rare-density and medium-density, which adversely affected the rice appearance quality; the rice qualities was best when in the medium-density planting.Planting density had great effect on brown rice rate, chalky grain rate, alkali spreading value, gel consistency and crude protein; brown rice rate in the rare-density and medium-density was significantly lower than the high-density which adversely affected the rice milling quality; chalky grain rate was higher than the high-density, which adversely affected the rice appearance quality; by comprehensive judgment, the cultivation density in Ya’an was suitable to the medium to ensure the quality of rice.5. Effect of planting density on dry matter accumulation and nutrient characteristics in the two ecological conditions was demonstrated.The dry matter accumulation and harvest index at tillering stage, jointing stage, booting stage, full heading stage and maturity stage in Xichang were significantly higher than Ya’an; With the increase in planting density, dry matter accumulation at tillering stage, jointing stage, booting stage, full heading stage and maturity stage in two test points increased too, and there are significant differences in the rare-density, medium-density, high-density. For dry matter at maturity stage, Jingyou527and Jiuyou418were decided by ecological conditions and planting density, and Changmi011and Hexi39was mainly affected by planting density.Except for the total nitrogen accumulation at maturity (TNA), nitrogen harvest index (NHI), nitrogen transport rate (NTR), contribution rate of translocated nitrogen to grain (CRN), nitrogen use efficiency for grain production (NGPE), nitrogen use efficiency for biomass production (NDMPE) of Xichang was significantly higher than the performance of Ya’an. The total phosphorus accumulation at maturity (TPA) in Xichang was less than Ya’an, but the phosphorus use efficiency for grain production (PGPE) was significantly higher than Ya’an. The total potassium accumulation at maturity (TKA) in Xichang was slightly higher than Ya’an, but the potassium use efficiency for grain production (KGPE) was significantly higher than Ya’an. Overall, the use efficiency of nitrogen, phosphorus and potassium in Xichang was better than Ya’an.With the planting density increased, the total accumulation of NPK increased at mature stage. TNA in the rare-planting density was significantly lower than medium-density and high-density, but NHI, NTR, CRN and NGPE decreased with the increase of planting density; NDMPE had no significant difference in different densities. Planting density had a significant impact on TPA, and phosphorus harvest index (PHI), phosphorus use efficiency for grain production (PGPE) and phosphorus use efficiency for biomass production (PDMPE) decreased with the increase of planting density; TKA in the high-density was significantly higher than in the rare-planting density and medium-density; potassium harvest index (KHI), potassium use efficiency for grain production (KGPE) and potassium use efficiency for biomass production (KDMPE) decreased with the increase of planting density.