1.College of Resource and Environment, Hunan Agricultural University;2.National Field Observation and Research Station of Farmland Ecosystem in Qiyang, Hunan Province/Hengyang Red Soil Experimental Station, Chinese Academy of Agricultural Sciences
Supported by the Science and Technology Innovation Program of Hunan Province, China (No. 2021RC2081), the Key Research and Development Project of Hunan Province, China (No. S2021GCZDYF0345) and China Agriculture Research System (No.CARS-22)
冬季复种绿肥是我国南方稻区传统的培肥增产模式，探究长期冬种绿肥下光合碳在水稻-土壤系统中的分配规律，对深入解析稻田土壤碳循环、充分发挥绿肥的生态功能具有重要意义。基于稻-稻-绿肥复种长期定位试验（38年），针对稻-稻-紫云英、稻-稻-油菜和稻-稻-休闲三种处理，采用13C-CO2脉冲标记技术，研究长期冬季复种绿肥下光合碳在早稻季分蘖期水稻-土壤系统中的分配特征。结果表明，与冬季休闲处理相比，复种紫云英和油菜处理使早稻地上部13C-光合碳积累量分别增加每穴19.9 mg和80.6 mg；复种紫云英处理使早稻地下部13C-光合碳积累量每穴降低2.7 mg，而复种油菜处理对早稻地下部13C-光合碳积累量无显著影响。同时，冬季复种紫云英和油菜减少了早稻13C-光合碳向土壤的分配，积累量每穴分别降低7.6 mg和7.8 mg；复种紫云英处理对水稻13C-光合碳在土壤颗粒有机碳（POC）和矿物结合态有机碳的分配比例无显著影响，复种油菜处理促进了水稻13C-光合碳向土壤POC中的分配，使13C-POC的占比增加35.3%。综上，长期复种绿肥促进了水稻分蘖期光合碳在水稻-土壤系统中的积累，与冬季休闲处理相比，冬季复种绿肥使光合碳在水稻-土壤系统中积累量增加3.7%~28.0%；增加了光合碳向水稻地上部的分配，减少了其向水稻地下部及土壤中的分配比例；且复种油菜处理减弱了土壤中水稻光合碳的稳定性。
【Objective】Winter multiple cropping of green manures such as Chinese milk vetch and rapeseed is a traditional system for improving soil fertility and crop yield in the rice field in southern China. Thus, it is of great importance to analyze the soil carbon (C) cycle and the ecological functions of green manure by exploring the distribution of photosynthetic C in a rice-soil system under long-term winter cropping of green manure. 【Method】In this study, based on a 38-year rice-rice-green manure cropping experiment, the 13C-CO2 pulsing labeling technology was used to study the distribution characteristics of photosynthetic C in a rice-soil system at the tillering stage of early rice season under long-term green manure (Chinese milk vetch, rapeseed and winter fallow). At the same time, the stability of 13C-photosynthetic C in soil was studied by measuring the content and distribution ratio of 13C in particulate organic carbon (POC) and mineral associated-organic carbon (MAOC). 【Result】The results showed that the biomass of rice at the tillering stage was not significantly changed but the root/shoot ratio was decreased by 12.6%-19.4% with the long-term multiple cropping of green manure. Compared with winter fallow treatment, the cropping of green manure promoted the distribution of 13C-photosynthetic C in the shoot of early rice, and the accumulation of 13C-photosynthetic C was increased by 19.9 mg·plant-1 and 80.6 mg·plant-1 in cropping of Chinese vetch and rapeseed treatments, respectively. The 13C-photosynthetic C accumulation in the root of early rice was decreased by 2.7 mg·plant-1 under Chinese milk vetch treatment, while it was not significantly affected by rapeseed treatment. This result infers that long-term multiple cropping of green manure increased soil nutrient supply and reduced the ratio of root to shoot of early rice, which allows the rice to distribute more biomass to the shoot. Meanwhile, the cropping of Chinese vetch and rapeseed treatments reduced the distribution of 13C-photosynthetic C in the soil by 7.6 mg·plant-1 and 7.8 mg·plant-1 respectively. The proportions of rice 13C-photosynthetic C to POC and MAOC were not significantly affected by the cropping of Chinese milk vetch, but the proportion of 13C-photosynthetic C in POC was increased by 35.3% with multiple cropping of rapeseed. 【Conclusion】The long-term multiple cropping of green manure promoted the accumulation of rice photosynthetic C in the plant-soil system. Compared with winter fallow treatment, the accumulation of photosynthetic C in the rice-soil system increased by 3.7%-28.0% in cropping of Chinese vetch and rapeseed treatments. On the other hand, the long-term multiple cropping of green manure increased the distribution of photosynthetic C to the shoot of rice and reduced the proportion of photosynthetic C to the root of rice and soil. Moreover, the stability of rice photosynthetic C in soil was weakened by multiple cropping of rapeseed treatments.
LIU Weimin, SHU Yeqin, XIA Yinhang, XIANG Hongkun, GAO Peng, ZHAO Ziwei, HUANG Jing, GAO Jusheng, ZHANG Zhenhua. Distribution and Stabilization of Photosynthetic Carbon in Rice-soil System under Long-term Multiple Cropping of Green Manure[J]. Acta Pedologica Sinica,,[In Press]