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[Objectives] This study was conducted to construct high-yielding, high-quality, and high-light-efficiency population structures of different types of rice varieties. [ Methods] The effects of plant spacing, row spacing and seedling number allocation on stems and tillers, leaf area and dynamic traits of high-yielding rice populations (more than 9 750 kg/hm2 ) and low-yielding populations (less than 9 750 kg/hm2 ) were studied by two kinds of representative rice varieties with different tiller ability and panicle sizes in cold regions. [Results] Decreasing the plant and row spacing and increasing the number of planted seedlings per hole advanced the heading date and made the number of stems and tillers in the population increase. The impact on the super rice variety with fewer tillers and heavier panicles was greater than that of conventional variety with more tillers and lighter panicles. The stems and tillers of the high-yielding high-quality populations grew steadily in the early stage of development, until an appropriate number of panicles was reached at the critical leaf age for productive tillers (June 25 ), and the peak seedlings should appear in the jointing stage (July 9) with a small number ( that value of Longjing 21, the super rice variety with fewer tillers and heavier panicles, was about 1. 2 times the expected panicle number, and that of the conventional variety with more tillers and lighter panicles, Kongyu 131, was about 1. 1 times the expected panicle number). The populations gradually declined since then, until reaching an appropriate number of panicles at the heading stage. The high-yielding high-quality populations had a higher leaf area index at the heading stage. The value of Longjing 21, the super rice variety with fewer tiller and heavier panicles, reached about 6. 0, and that of Kongyu 131, the conventional variety with more tillers and lighter panicles, reached about 4. 5. The values decreased thereafter. At the maturation stage, the leaf area index of Longjing 21 remained above 2. 5, and that of Kongyu 131 remained above 2. 0. [Conclusions ] This study has an important guiding role and significance for their high-yielding and high-quality supporting cultivation in cold regions. [ABSTRACT FROM AUTHOR]

In order to clarify the water-saving technologies and standards in large-scale mechanized production of paddy fields, the water-saving effects and cost-benefit situations of paddy field steeping, seedling transplanting and different land preparation methods were studied. The results showed that the suitable water layer height for the closing period of mechanized operation was 10 cm, which could save water, facilitate weed control, and lead to better effect and the highest yield. The treatment with a water layer height of 1 cm(Huadashui) for the seedling planting operation achieved better quality of seedling transplanting, lower vacancy rate and higher yield and was water-saving. From the perspective of saving water and taking into account the cost of land preparation, the method of steeping and beating the field was better than the method of plowing in autumn and rotary tillage and harrowing in spring, but it was very prone to lodging. From the perspective of high yield creation, the method of plowing in autumn and rotary tillage and harrowing in spring was significantly better than the method of steeping and beating the field. In order to reduce the cost of land preparation, it is recommended to change the way of plowing in autumn and rotary tillage and hallowing in spring to plowing in autumn and rotary tillage in spring or plowing and hallowing in spring to reduce the cost of one time of rotary tillage, and to simultaneously realize deeper plough layer, which is conducive to preventing lodging and obtaining high yield. [ABSTRACT FROM AUTHOR]

[Objective] This study was conducted to construct a super-high yield population of Japnica rice in cold regions of North China and to explore its characteristics. [Method] The super rice variety Longjing 21 was selected as the experimental material. Different row spacing (two levels), plant spacing(three levels) and seedling number per hill (three levels) were designed in field trials. Then, the growth stages, dry matter accumulation, leaf area, yield and yield components of these different treatments were measured. [Result] Rice yield had significantly negative correlation with plant spacing and row spacing, but no significant correlation with seedling number per hill. Rice yield was mainly affected by plant spacing, and less affected by seedling number per hill. The best recommended specifications for plant spacing of super rice variety Longjing 21 were 24 cm for row spacing, 12 cm for plant spacing and five seedlings per hill, and the expected yield was 10 473.0 kg/hm2. The increased number of total spikelets (4.5×108hm2or more) in populations was the major reason for high yield. Super-high yield populations had fewer tillers at the early growth stage and achieved the expected number of productive tillers at critical leaf-age (June 25), and tiller number peaked at jointing stage (July 6) and was about 1.2 times of the expected number. The percentage of productive tillers in total tillers of super-high yield population was more than 85% at heading stage. At middle growth stage (from jointing to heading stage), the dry matter accumulation, leaf area index (LAI) at heading stage, effective leaf area, spikelet number of population, spikelet number per leaf area unit (cm2), and culm-sheath weight per stem of super-high yield population were significantly higher than those of other populations. At late growth stage (from heading to maturity stage), the leaf area decreasing rate of super-high yield population was significantly smaller than that of other populations. At late growth stage (from heading to maturity stage), the leaf area decreasing rate, crop growth rate, net assimilation rate, biomass accumulation, number of filled grains per leaf area unit (cm2) and grain weight per leaf area unit (cm2) of high-yield population were significantly higher than those of other populations. Output and translocation of dry matter (weight per stem and sheath and total filling rate at maturity) from heading to milky stage of super-high yield population were significantly higher than those of other populations. [Conclusion] The characteristics of superhigh yield rice in cold region of North China are enriching the amount of actual filling of sink through improving photosynthetic efficiency from heading to maturity stage on the basis of enough panicle numbers. [ABSTRACT FROM AUTHOR]

The grain-filling processes at different grain positions of curved-panicle type Longjing 29 and semi-erect-panicle type Longjing 31, two major rice (Oryza sativa L.) cultivars in Heilongjiang Province, were simulated by Richards growth equation, so as to determine the reason of great differences in head rice rate of different rice cultivar among different years and to improve the processing quality of different rice cultivar through cultivation regulation measures. The results showed that the yield of Longjing 29 was slightly higher than that of Longjing 31, but the head rice rate of Longjing 29was significantly lower than that of Longjing 31. More grains on secondary rachis branch resulted in lower plumpness, lower seed-setting rate and lower milled rice rate of Longjing 29. The grain filling rates at the six grain positions of Longjing 31 reached the peaks simultaneously, so the synchronous grain filling characteristic of Longjing 31 was more obvious. The grain-filling rate on the primary rachis branch of Longjing 31 was higher, and it reached the peak in the middle period. Although the grain-filling rate on the secondary rachis branch of Longjing 31 was lower, it early reached the peak. In addition, the middle and late filling period of Longjing 31 was longer, resulting in plump and compact grains on the secondary rachis branch of Longjing 31. After the grain-filling rate on the primary rachis branch was decreased, the grain-filling rate on the secondary rachis branch of Longjing 29 started to be increased greatly, characterized by asynchronous grain filling. In the early grain filling stage, the grains on the upper, middle and basal secondary rachis branch were all significantly suppressed by those on the primary rachis branch of Longjing 29. The initial growth potential and maximum filling rate of grains on the secondary rachis branch of Longjing 29 were all lower. The grain-filling rate on the secondary rachis branch of Longjing 29 late reached the peak. Even worse, the middle and late filling period of Longjing 29 was shorter. Therefore, the grains of Longjing 29 had poor plumpness. Synchronous grain filling led to small difference in grain quality within the same panicle, and this was also the reason for stable head rice rate of Longjing 31 among different years. In contrast, asynchronous grain filling led to great difference in grain quality within the same panicle of Longjing 29. In addition, low temperature often occurred during the fast filling of grains on the secondary rachis branch of Longjing 29. Thus, the head rice rate of Longjing 29 was decreased. [ABSTRACT FROM AUTHOR]