Effect Of Planting Density On Yield And Ecophysiological Characteristics In Different Types Of Rice With Bowl Mechanical-Transplanting Method

In order to study the impacts of planting density of nutrition bowl seedling mechanical-transplanting rice on photosynthate production and yield, a field experiment was conducted using conventional japonica rice Nanjing44, Wuyunjing24, japonica hybrid rice Yongyou8, Changyou5, and indica hybrid rice Liangyoupei9, Ⅱ you084which have been widely grown in the southern China with high, medium and low density treatments of the different hill spacings in nutrition bowl mechanical-transplanting (12cm,14cm, and16cm), and the conventional blanket seedling mechanic al-transplanting as control.The main result are as follows.1. The yield’s difference of conventional japonica rice of nutrition bowl mechanical-transplanting among different density is significant. The theoretical and practical yield of high density is highest among three densities. The practical yield of high density is2.7%and11.5%higher than medium density and low density respectively. The yields of hybrid japonica rice and hybrid indica rice are highest in medium density, and the hybrid indica rice is16.4%higher than the contrast on average, there is no difference between high density and low density but significantly higher than the contrast. The spike number of same variety decreases as the reduction of density, and is significant different among different treats. The grain number per spike presents opposite trend. The different mechanical-transplanting methods and different density have less effect to1000-grain weight and seed setting rate, and no significant difference between different treats.2. The tiller number of nutrition bowl mechanical-trans planting rice in the critical period and the declining rate of leaf area after heading decreased with the reduction of planting density, the productive tiller percen tage increased significantly, while the chlorophyll content of flag leaf and the photosynthetic parameters presented the opposite trend. The dry matter weight of sin-gle stem, the matter transportation amount in stem and leaf, and the net assimilation ra te were all the highest in the low density treatment, the medium in medium density treatment, and the lowest in high density treatment. After heading, the dry matter accu-mulation, population growth rate, photosynthetic potential and other indicators of conventional japonica rice decreased signifi-cantly with the reduction of planting density. The average dry matt er weight of population in high density treatment at maturity stage was11.8%and8.9%higher than that in medium density treatment and low density treatment re spectively, and without sig-nificant difference between the low density treatment and control. For the population growth indexes of hybrid rice, medium den-sity treatment was the highest, and there wa s no significant difference between high density treatment and low density treatments.3. Compared with control, nutrition bowl mechanical-transplanting rice plant blanket neatly, the internal temperature and humidity is reduced, which to some extent alleviate the adverse effects of high temperature and humidity on growth. The distance of leaf occiput between1st and2nd,3rd and4th leaf from top increased with the reduction of planting density, the effective leaf area ratio, high effective leaf area ratio, angle of flag leaf, length of second and third upper leaves of plants, length of panicle and uppermost two internodes increased, while the effective leaf area index and high effective leaf area index presented the opposite trend. Canopy temperature and humidity decreased with the reduction of planting density, and conventional japonica rice, japonica rice, indica hybrid rice canopy light intensity with low density, medium density, high density is the highest, respectively.