| It’s very important to explore high yield and good grain quality of mechanical transplanting rice for ensuring food security and promoting the whole mechanization of rice. For now, mechanical transplanting rice is the limiting factor to realize the whole mechanization of rice. The main reason is that carpet seedling mechanical transplanting rice has some problems which needing to solve. The problem is that the row space of mechanically transplanted carpet seedling could not match the characteristic of different typed cultivars, namely there is no clear high cultivation specification for different typed cultivars. The another problem is that mechanical transplanting rice has lower yield, due to seedling weaken and plant injury in field and later tillering because of specific raising seedling and specific plant method. Therefore, it’s essential to explore the new mechanical transplanting method in rice, that is mechanically transplanted pot seedling rice. But there is no clear of high-yielding plant density of different tpyed rice of mechanically transplanted pot seedling rice, which characteristic and superiority of high-yielding formation need to clarify. To solve these problems, we conducted the experiment which set different mechanical transplanted methods and different plant density for applying reasonable panicle typed cultivar and adopting suitable plant density of different mechanically transplanted rice, and clarifying high-yield formation and its physiological and ecological characteristics of different panicle typed rice in different mechanically transplanted methods. The experiment was conducted in Xinghua test point of Yangzhou university during 2013 and 2014. Three panicle typed rice including large panicle type (LPT, Yongyou 2640 and Yongyou 8) and medium panicle type (MPT, Wuyunjing 24 and Ningjing 3) and small panicle type (SPT, Huaidao 5 and Huaidao 10) were field-grown. We compared three mechanically transplanted methods including mechanically transplanted pot seedling (PS) in row spacing of 33 cm (A), mechanically transplanted carpeted seedling (CS) in row spacing of 30 cm (B), mechanically transplanted carpeted seedling (CS)in row spacing of 25 cm (C), and set different plant density in A, B,C methods, which included three plant spacing of 12 cm、14 cm、16 cm (mark, as 1,2,3) in A method and five plant spacing of 10 cm、11.7 cm、13.3 cm、14.8 cm、16 cm (mark as 1,2,3,4, 5) in B and C methods. Yield and yield formation, panicle traits, dynamic of stem and tiller, photosynthesis matter production, plant type, lodging-resistant, nitrogen absorption and utilization, rice quality were investigated. The main results were as follows:1. About yield and its formation:(1) For PS, with plant density reduced, yield of LPT increased and then reduced, which was highest in A2 treatment; yield of MPT and SPT reduced, which was highest in Al treatment. For CS, with plant density reduced, yield of LPT increased and then reduced in B method, which was highest in B4 treatment, yield of LPT increased in C method, which was highest in C5 treatment; yield of MPT increased and then reduced in B and C methods, which were highest respectively in B3 and C4 treatment; yield of SPT reduced in B method, which was highest in B1 treatment, yield of SPT increased and then reduced, which was highest in C2 treatment. In the same plant density, yield of PS was higher significantly than mechanically transplanted carpet seedling, the range of increased yield showed LPT>MPT> SPT, there was no difference in B method and C method. For B method and C method, in the same plant spacing, yield of LPT was higher in B method than C method; yield of MPT was higher in B method than C method in plant spacing of 10 cm、11.7 cm、13.3 cm, but it was opposite in plant spacing of 14.8 cm、16 cm; yield of SPT was higher in C method than B method in plant spacing of 11.7 cm、13.3 cm、14.8 cm、16 cm. (2) With plant density reduced, panicles reduced and spikelets per panicle increased in different panicle typed rice of different mechanically transplanted methods. In the same plant density, there was no difference in panicle, grain filled percentage and 1000-grain weight in different mechanically transplanted methods, but spikelets per panicle was higher significantly in A method than B or C method, which range was LPT>MPT>SPT. For B method and C method, number of panicle was lower in B method than in C method, but it was opposite in spikelets per panicle. (3) Panicle length, grain density, grain weight per panicle, number of first and second branches, number of grains of first and second branches were increased with plant density reduced, it was opposite in the ratio of No. of branches of primary branch to No. of branches of secondary branch and Ratio of No. of grains of primary branch to No. of grains of secondary branch. In the same plant density, Panicle length, grain density, grain weight per panicle, number of first and second branches, number of grains of first and second branches in A method than in B or C method.2. About dry matter accumulation and photosynthetic production:(1) For dynamic of stem and tiller, the number of stem and tiller of three panicle type rice cultivars at the mid-tiller stage, jointing, heading and maturity were reduced in different mechanically transplanted method with plant density decreased. Compared CS, PS showed earlier tiller establishment after transplanting, and had more number of tiller at productive tiller stage and had peak seedling at jointing, which number of population tiller reduced slowly after jointing, finally, the productive tiller percentage was higher. (2) For biomass production, with plant density decreased, dry matter weight of three panicle typed rice cultivars before jointing reduced in different mechanically transplanted method, but biomass production at middle and last growth period showed different response. For PS, which LPT applied medium plant density and MPT and SPT applied high plant density could be beneficial to increase biomass production at middle and last growth period. For CS, LPT applied lower plant density and MPT applied medium plant density and SPT applied higher plant density, which could increase biomass production at middle and last growth period. Compared CS, PS had more dry matter accumulation at middle tiller stage, and increased significantly dry matter accumulation after jointing. (3) For photosynthetic production, with plant density decreased, leaf area index, crop growth rate and net assimilation rate before jointing of three panicle type rice cultivars reduced in different mechanically transplanted methods. During middle and last growth period, for PS, LPT adopted medium plant density, MPT and SPT adopted high plant density, which could enhance photosynthetic production; for CS, LPT adopted lower plant density and MPT adopted medium plant density and SPT adopted high plant density, which could increase photosynthetic production. Compared CS, PS had higher LAI at middle tiller stage and greater photosynthetic potential from sowing to middle tiller stage, and had higher LAI after jointing and greater photosynthetic potential at the last growth period, which crop growth rate and net assimilation rate showed smaller before jointing, better at the middle growth stage and higher at the last growth stage.3. About plant type:With plant density decreased, length and width of top three leaf, specific leaf weight, leaf basal angle, leaf open angle and leaf drooping angle of rice increased in different mechanically transplanted method, and the same as spad value after heading and light transmittance. Compared CS, PS had greater in length and width of top three leaf, specific leaf weight, spad value after heading and light transmittance, but it was opposite as leaf basal angle, leaf open angle and leaf drooping angle. Correlation analysis showed that there were significant or very significant positive correlation relationship between length and width of top three leaf and spikelets per panicle of different panicle typed rice cultivar, and as same as yield of LPT and MPT, but it was opposite as yield of SPT. Meanwhile, there were negative correlation relationship between leaf drooping angle of top three leaf and yield of different panicle typed rice. Therefore, different mechanically transplanted rice reduced plant density which could increase length and width of top three leaf, specific leaf weight and enhance appropriately leaf angle, which increased yield of LPT and MPT; but for SPT, reduced length and width of top three leaf and leaf angle could increased yield. Compared CS, PS had some advantage that it had tight plant type, higher quality and larger leaf area of canopy leaf, and greater spad value after heading and light transmittance.4. About the trait of stem and lodging-resitance:(1)With plant density decreased, breaking resistance and bending moment of different panicle rice cultivar increased in different mechanically transplanted method, which lodging index reduced due to higher breaking resistance than bending moment. In the same plant density, compared to CS, PS had greater breaking resistance and bending moment, but had lower lodging index, which there was significant difference in the internode of N2 and N3. but there was no difference in breaking resistance and bending moment and lodging index between B method and C method. (2)With plant density decreased, internode length of N1, N2 and N3 of different panicle type rice reduced in different mechanically transplanted method, which neck internode length and stalk length and plant height increased as same as culm diameter, culm wall thickness and dry weight of unit internode of N1, N2 and N3. In the same plant density, compared to that of CS, PS had higher plant height and gravity center height, but had lower relative gravity center height; meanwhile, PS had shorter internode of N1, N2 and N3, but which neck internode length and stalk length and plant height increased. For B method and C method, there was no difference in index of plant stalk. (3) Correlation analysis showed that there were significantly or very significantly positive correlation relationship between lodging index and internode length of basal internode of N1, N2 and N3, but it was opposite as culm diameter, culm wall thickness and dry weight of unit internode. Therefore, different mechanically transplanted rice reduced plant density which could shorten length of basal internodes and increase culm diameter, culm wall thickness and dry weight of unit internode to the benefit of enhancing breaking resistance and bending moment and decreasing lodging index, strengthen lodging-resistance capability. PS had shorter basal internode length and thicker clum of internode than those of CS, which could increase breaking resistance and reduce lodging index.5. About nitrogen uptake and utilization:(1) With plant density decreased, nitrogen content at middle tiller stage, jointing, heading and maturity of different panicle type rice cultivar showed increase tendency. In the same plant density, compared to those of CS, PS had higher nitrogen content at middle tiller stage, jointing, heading and maturity, but there was no difference between B method and C method. (2) With plant density decreased, nitrogen uptake at middle tiller stage and jointing of three panicle typed rice reduced in different mechanically transplanted method; For heading and maturity, nitrogen uptake of LPT in A and B method increased and then reduced, but which of C method increased, nitrogen uptake of MPT in A method decreased, which of B and C method increased and then reduced, nitrogen uptake of SPT in different panicle typed cultivar all decreased. In the same plant density, compared to those of CS, PS had greater nitrogen uptake at middle tiller stage, heading and maturity, but there was no difference between B method and C method. (3) With plant density decreased, nitrogen accumulation and its ratio and nitrogen uptake rate during transplanting to middle tiller stage reduced; there was no difference in nitrogen accumulation and nitrogen uptake rate during middle tiller stage to jointing; during jointing to heading and heading to maturity, nitrogen accumulation and nitrogen uptake rate of LPT in A method and B method increased and then reduced, which of C method increased, for MPT and SPT, which of A method reduced, and which of B method and C method increased and then reduced. (4) With plant density decreased, nitrogen agronomic efficiency(NAE), nitrogen recovery efficiency(NRE), nitrogen physiological efficiency(NPE) and partial factor productivity of applied nitrogen(PFN) of LPT increased and then decreased in A and B method, which of C method increased; NAE, NRE, NPE and PFN of MPT decreased in A method, and which of B and C method increased and then decreased; NAE, NRE, NPE and PFN of SPT decreased in A and B method, which of C method increased and then decreased. In the same plant density, compared to those of CS, NAE, NRE, NPE and PFN of PS increased significantly, but there was no difference between B and C method. Therefore, when applied to PS, LPT should reduced appropriately plant density and MPT and SPT should increased plant density, which could be beneficial to increase nitrogen uptake at maturity and enhance nitrogen use efficiency. When applied to CS, LPT should reduced plant density and MPT should adopt medium plant density and SPT should adopt high plant density, which could be beneficial to increase nitrogen uptake at maturity and enhance nitrogen use efficiency. Compared to those of CS, PS increased nitrogen uptake at middle tiller stage, heading and maturity, and enhanced nitrogen use efficiency.6. About rice quality:(1) With plant density decreased, brown rice rate, milled rice rate and head rice rate of LPT and MPT increased and milled rice rate and head rice rate of SPT increased in different mechanically transplanted method; chalky grain rate, chalkiness degree, amylose content and protein content of three panicle typed rice cultivar showed decline trend, but it was opposite in Gel consistency. Therefore, which rice plant density decreased in different mechanically transplanted method could be contribute to improve process quality and appearance quality and cooking and eating quality, but decreased nutritional quality. In the same plant density, compared to those of CS, brown rice rate, milled rice rate and head rice rate of PS increased, but chalky grain rate, chalkiness degree, amylose content and protein content decreased, there was no difference between B and C method. Therefore, PS had better process quality and appearance quality and cooking and eating quality than those of CS. (2) The results of starch RVA were analysed, with plant density decreased, for LPT, peak viscosity and breakdown increased and setback decreased in different mechanically transplanted method; for MPT, peak viscosity and breakdown increased and then decreased in A and B method, but which of C method increased, setback decreased and then increased in A and B method, which of C method showed decline trend; for SPT, peak viscosity and breakdown increased and then decreased in A, B and C method, but setback decreased and then increased. Therefore, LPT should reduce plant density and MPT and SPT could adopt medium plant density, all of which could be contribute to increase peak viscosity and breakdown and decrease setback, which improving cooking and eating quality of rice. In the same plant density, PS had greater peak viscosity and breakdown and lower setback than those of CS, but there was no difference between B and C method in peak viscosity, breakdown, setback. Therefore, PS had better cooking and eating quality than those of CS.Above all, When applied LPT, mechanically transplanted pot seedling could configure medium density, it was beneficial to enlarge panicle type and increased total spikelets and yield; when used MPT and SPT, it could adopt higher density to increase panicles and spikelets per panicle for high yield, Which high yield were due to greater dry matter accumulation and nitrogen uptake during the medium and late growth period, and higher total dry matter weight and total nitrogen uptake. For mechanically transplanted carpet seedling, when applied LPT, it could adopt B method and increase plant spacing to expand panicle type and acquire higher yield; when applied MPT, it could adopt B method and configure medium density to coordinate panicle and spikelets per panicle for increasing total spikelets; when applied SPT, it could adopt C method and decrease plant spacing to increase significantly number of panicle for high yield. The reason of high-yielding of CS was the same as PS. Rice of different mechanical tansplanting methods reduced properly plant density which could improve canopy leaf quality at heading and increase spad value of flag leaf and light transmittance after heading, and enlarge leaf drooping angle, which could shorten length of basal internode and increase culm diameter and culm wall thickness and dry weight of unit internode, thereby enhance breaking resistance and bending moment and decrease lodging index, which could improve process quality and appearance quality and cooking and eating quality. In the same plant density, compared to those of CS, PS had more greater yield, which increasing range was LPT> MPT> SPT. The reason of high yield of PS was that PS had enough panicles and greater spikelets per panicle and normal filled grain percentage and 1000-grain weight. The physiological basis of high-yielding in PS was that:After transplanting, there had strong seedling, earlier seedling establishment, faster tillering, more tillers of low postion, lower peak seedlings, tiller slowly reduced after jointing, finaly higher productive tiller percentage; After jointing, there had greater dry matter production and nitrogen uptake; PS had better plant type at heading and greater light transmittance and spad value of flag leaf after heading which increasing photosynthetic matter production and enhancing total dry matter accumulation and total nitrogen uptake; After heading, there had more greater lodging-resitance of stem which was benefit to improve grain filling.These results could provide references in rice production that different mechanical transplanted methods applied reasonably different panicle typed cultivar and matched high-yielding plant density. Meanwhile, by analyzing different plant density treatment, we revealed further the characteristic of physiology and ecology of high-yielding formation of different panicle typed cultivar in different mechanical transplanted methods, and illuminated the advantage and characteristic of high-yielding and high quality formation of PS. These results enriched the theory and techniques of high-yielding formation of mechanically transplanted rice, which could popularize and apply quickly mechanically transplanted rice. |
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