Effects Of Water Management On Rice Photosynthetic Carbon And Its Rhizosphere Stimulating Effect

The paddy soil ecosystem is both a carbon source and a carbon sink,and plays an irreplaceable role in controlling greenhouse gas emissions（CO₂,CH₄）and increasing terrestrial carbon fixation.Paddy soils are concerned with the characteristics of dry soil for their special field water management.Under different water management conditions,the physical,chemical properties and microbial community structure of paddy soil may change,which affects photosynthetic carbon.Distribution and transformation in the“rice-soil”system.Therefore,under the different water management conditions,the relationship between carbon turn over in rice fields and its stimulating effects and microbial community structure is explored in the exploration of soil carbon sequestration potential,promotion of rice yield increase,mitigation of greenhouse gas emissions and water saving measures in agriculture.And sustainable development is of great significance.In this paper,the subtropical red paddy soil was taken as the research object,and the carbon mineralization transformation process in the“plant-soil-microbial”system was taken as the entry point to explore the mechanism of water management and its effect on the distribution of photosynthetic carbon in rice and its rhizosphere stimulating effect.Mechanism of action.Using stable isotope and phospholipid fatty acid（PLFAs）technology,combined with pot experiment,¹³C continuous labeling of rice during the whole growth period was carried out to explore the mechanism of water management on the distribution of rice photosynthetic carbon and the direction and size of rhizosphere stimulating effect.Reveal the mechanism of action of microorganisms.Through research,the main conclusions are as follows:（1）Water management significantly affected the distribution of photosynthetic carbon in the“rice-soil”system.Compared with continuous flooding treatment,the dry-wet alternation increased the biomass of aboveground and roots by 223.60 kg·hm^-2 and 77.04 kg·hm^-2,respectively,so that 4%and 26%of photosynthetic carbon was preserved and fixed on the ground.In the roots and roots,the root-to-shoot ratio was significantly reduced.About 43%of photosynthetic carbon in rice photosynthetic ¹³C is distributed in rice plants.Continuously transferred to the lower part（roots and soil）,13%to 144%of photosynthetic ¹³C is secreted from the roots and deposited into the soil.The dry-wet alternation and continuous flooding treatment also increased the proportion of photosynthetic carbon in roots and soils,which were 4%～34%and15%～42%,respectively,increasing the input of photosynthetic carbon to soil and the deposition of rhizosphere carbon.（2）Water management not only significantly affected the input of photosynthetic carbon to the absolute and relative proportion of rhizosphere carbon,but also affected the composition and structure of soil microbial community.Mainly manifested in:under continuous flooding conditions,soil rhizosphere carbon input is low,microbial turnover rate is slow,accompanied by lower ¹³C-MBC content(0.73～4.44 mg·pot^-1)and total ¹³C-PLFAs content(25.18～89.43μg·C·kg^-1),gram-negative bacteria play an important role in carbon turnover.In contrast,microbial turnover is faster under dry and wet conditions,and ¹³C-PLFAs are abundant in fungi and actinomycetes,which are about 9.05～23.72μg·C·kg^-1 and 0.39～5.28μg·C·kg^-1,increased soil carbon retention.（3）Water management significantly affected the CO₂ and CH₄ emissions in paddy fields.With the increase of rice cultivation time,under the two water management conditions,the effects of CO₂ and CH₄ emission fluxes on soil organic matter decomposition and mineralization were different.The two water management methods have significant effects on the rhizosphere stimulating effects of CO₂ and CH₄.Compared with continuous flooding treatment,the dry-wet treatment promoted CO₂emissions 50 days before rice transplanting,and the CO₂ emission was 0.57～2.26mg·C·kg·h^-1,during the whole growth period of rice.The CH₄ emission was suppressed,and the CH₄ emission was between 0.34 and 16.93μg·C·kg·h^-1.The above results indicated that the water-saving management of dry and wet alternates maintained a similar SOC content to the traditional continuous flooding through the 61day ¹³C continuous labeling rice pot experiment,and the SOC content was 15.40～16.09 g·kg^-1.Under water-saving management,the input of rice photosynthetic carbon to the underground increased,which not only promoted the stable growth of rice plants,but also increased the rhizosphere carbon retention of paddy soil.Compared with continuous flooding treatment,the wet and dry alternate water management method reduced emissions from 94%to 99%CH₄.The dry and wet alternate water management method is an effective measure to further improve and improve the quantity and quality of SOM in rice fields,and provide data support for the implementation of water saving measures in agriculture.