| Potassium is one of the most important macronutrients for rice. It has a visible promotional action in the rice growth and development, and it takes part in the processes of plant physiological and biochemical reaction, including the activation of various enzymes, physical synthesis, assimilate transport, water metabolism, photosynthesis and ion balance. Thus, it plays a very important role in improving the nutrient utilization efficiency, increasing production and improving quality of rice. Under field and pot experiment conditions, through different potassium management methods of basal dressing, panicle dressing and fore-and-aft operation, the influences of potassium application rates on the nutrient absorption, transportation and use efficiency, photosynthetic physiology and defense systems, culm biomechanics and mechanical strength, rice quality and yields of different types of rice were analyzed, the plant potassium distribution character of the tiller stage and panicle stage and their correlation separately to percentage of tiller occured, yield composition were revealed. The results were as follows:1. Both rice yield and harvest index were increased with the proper potassium application under the condition of soil potassium deficiency, the range of yield increase rate was4.56-14.77%. Potassium application improved rice milling qualities, appearance qualities, eaten qualities and nutrition qualities of different types of rice. Potassium application increased brown rice rate, head rice rate, rice protein content and starch characteristic values of R.VA, reduced rice amylase content. Rice yield and quality were declined with a less or excessive potassium application. In addition, potassium application at basal dressing and panicle dressing relative to only basal dressing can further reduce the chalkiness rate and amylose content, increase gel consistency, and improved the quality of rice.2. Plant potassium content and accumulation at different growth stages were raised by potassium application. Plant potassium accumulation amount and absorption percentage reached the biggest from elongation stage to heading stage, which was further increased by potassium application in this stage. A larger percentage of the potassium absorption before elongation stage occurred at control experiment (no potassium application) and excessive potassium application, thereby suppressed tillering occurrence. The average and maximal rates of potassium speediness accumulation period under potassium application were increasing, but starting to terminating date and duration date of potassium speediness accumulation period were the opposite. Potassium application promoted potassium distribution amount in leaf, culm and sheath, panicle, and distribution percentage of culm and sheath, whereas reduced distribution percentage of leaf. The variation of potassium distribution amount in culm and sheath were larger than others. With the increment of potassium application rates, rice potassium recovery efficiency, plant potassium productivity and potassium utilization index decreased, while potassium agronomy efficiency, physiology efficiency and physiology index increased at first and then decreased. Among these estimation indexes, potassium physiology index and physiology efficiency correlate more to yield. Proper potassium application can significantly improve the utilization efficiency of rice. In addition, potassium application at basal dressing and panicle dressing relative to only basal dressing can significantly increased the amount and proportion of potassium absorption during elongation stage and heading stag, improve filled grains per panicle, setting panicle rate and grain yield.3. Potassium application increased nitrogen accumulation during growth stages, with the maximum from elongation stage to heading stage, but nitrogen uptake ratio decreased. Potassium application enhanced nitrogen transport amount and percentage after anthesis, as well as nitrogen accumulation in different rice organs, nitrogen distribution percentage in leaves and panicles, whereas reduced nitrogen distribution percentage in culm and sheath. Nitrogen absorption from fertilizer, basic nitrogen recovery efficiency before elongation stage, nitrogen recovery efficiency during the whole growing stage, and nitrogen harvest index were raised significantly, but plant nitrogen productivity was the opposite. Under the condition of soil potassium deficiency, nitrogen accumulation, nitrogen translocation amount and percentage after anthesis, and nitrogen distribution in different rice organs reached maximum at K2O application rate of12kg/667m2, as well as nitrogen absorption from fertilizer, basic nitrogen recovery efficiency before elongation stage, nitrogen recovery efficiency during the whole growing stage. However, nitrogen absorption percentage from elongation stage to heading stage, nitrogen distribution percentage in culm and sheath, and plant nitrogen productivity decreased to the minimum.4. Potassium application increased SPAD of high efficient leaf, net photosynthetic rate and stomatal conductance20days after heading stage, enhanced leaf chlorophyll fluorescence parameters, including leaf Fv/Fm, Fo, OPS Ⅱ, qP and so on. At the same time, Potassium application increased the activity of the key photosynthetic enzyme (RuBPCase) and the activity of antioxidant system (SOD and POD), reduced the MDA content in leaves. Leaf photosynthetic characteristics were strongest at K2O application rate of12kg/667m2.5. Potassium application increased the plant height, clum length, single clum weight, and clum strength, reduced clum length of the basal internode. Potassium application increased thickness of the basal internode, dry matter weight and internode substantial degree, and section modulus, cross-sectional area, thickness of culm wall, area of culm wall, number and area of large and small vascular bundle of the basal internode, as well as the clum of bending moment, bending stress, mechanical strength and clum type index, reduced clum coefficient and lodging index. Furthermore, potassium application also increased the soluble sugar, starch, cellulose, lignin content of the basal internode and plant C/N. As for the same type of rice, clum resistant press was positively correlated with clum length, thickness, single clum weight, culm substantial degree, and internode physical properties, biomechanics, carbohydrate content, and was negatively correlated with the basal internode length, clum coefficient, and lodging index. Under the condition of soil potassium deficiency, clum strength was biggest while lodging index was smallest at K2O application rate of12kg/667m2.6. Potassium application of basal dressing increased leaf, leaf sheath and plant shoot K content and K/N under the condition of soil potassium deficiency, while leaf sheath had the maximal potassium content, and K/N variance. Potassium application of basal dressing increased improved K content and K/N of different position leaf and leaf sheath, While3rd leaf sheath from the top had the maximal variance of potassium and K/N. The K/N of plant tiller germination required also increased with the leaf ages, proper potassium application of basal dressing promoted plant percentage of tiller occured, but a less or excessive potassium application reduced percentage of tiller occurred. Potassium application of panicle dressing also increased leaf, leaf sheath and plant shoot K content and K/N, thereinto, leaf sheath had the maximal variance of potassium content and K/N. K content and K/N of different position leaf and leaf sheath increased with Potassium application of panicle dressing, among these organs,3rd leaf sheath from the top had the maximal variance of potassium and K/N. Rice spikelets, filled grains per panicle and yield were also increased at first and then decreased with the K/N ratio of leaf, leaf sheath and plant shoot. Within different positions and organs, leaf sheath and3rd leaf sheath from the top correlate most with the yields.7. For the same potassium application of different types of rice, yield, plant potassium absorption percentage from elongation stage to maturing stage, starting to terminating date and duration date of potassium speediness accumulation period, potassium physiology efficiency, potassium physiology index, plant potassium productivity of conventional japonica rice were higher than those of hybrid japonica rice, but population potassium absorption, the average and maximal rate of potassium speediness accumulation period, the amount and proportion of potassium distribution percentage of clum and sheath, potassium recovery efficiency of conventional japonica rice were lower than those of hybrid japonica rice. Nitrogen use efficiency and photosynthetic effect after heading stage of conventional japonica rice was greater than that of hybrid japonica rice. Moreover, basal internode length, thickness, section modulus, cross-sectional area, thickness of culm wall, area of culm wall, mechanical strength and carbohydrate content of conventional japonica rice were lower than those of hybrid japonica rice, but the substantial degree of basal internode, clum type index and clum coefficient of of conventional japonica rice were higher than those of hybrid japonica rice. |
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