This study explored the complex mechanisms of methane (CH4) emissions in paddy fields, focusing on the often-overlooked role of soil texture. Through the analysis of 31 paddy soil samples, the research investigated the complex interactions among soil texture, organic carbon composition, soil nutrients, and microbial abundance in regulating CH4 emissions during the tillering stage of rice. The results revealed significant variations in CH4 emissions among different soils, which were notably associated with soil texture, organic carbon, nutrients levels, and microbial abundance. Soil texture, particularly clay content, emerged as a key factor influencing the composition of organic carbon, showing a significant positive correlation with mineral-associated organic carbon (MAOC). While organic carbon components significantly enhanced CH4 emissions, their effects were not uniform: particulate organic carbon correlated negatively with emissions, whereas MAOC showed a positive association. Soil texture also influenced nutrients availability, with clay content significantly correlated with soil nitrogen and phosphorus content, which in turn affects the abundance of functional genes. Specifically, mcrA abundance was positively correlated with available potassium, while pmoA abundance was positively correlated with available phosphorus. Additionally, dissolved organic carbon promoted pmoA abundance, although this effect was mitigated by higher clay content. Network analysis further emphasized the central role of soil texture, with clay exhibiting the highest degree and closeness centrality. In conclusion, soil texture is a fundamental and core factor influencing CH4 emissions at tillering of rice, exerting its influence through multiple pathways including modulating the composition of organic carbon, nutrient availability, and the abundance of methanogens and methanotrophs. These findings provide theoretical foundations for developing low-carbon cultivation strategies tailored to different soil textural characteristics.
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This study was conducted to research the effect of rhizosphere oxygen environment on the phosphorus uptake of rice seedlings and its physiological mechanisms, so as to provide a theoretical basis for the new cultivation measures to promote the absorption and utilization of phosphorus uptake of rice.
Two varieties, including Zhenshan 97B and Miyang 46, were cultured in nutrient solution with different oxygen content (DOC) levels (medium oxygen: DOC 2.5-3.5 mg·L-1, high oxygen: DOC>6.0 mg·L-1, continuous bubbling with atmospheric air, and normal conditions as CK) controlled by on-line dissolved oxygen meter. After different oxygen treatments, the rice seedling growth (biomass, root morphological structure), root physiology (root activity, phosphorus absorption kinetics, phosphatase activity, root secretion of organic acids, citric acid, etc.), and phosphorus absorption and accumulation were measured and analyzed.
(1) The medium oxygen treatment significantly promoted the occurrence and growth of tillers, and increased the biomass, root shoot ratio, phosphorus content and accumulation of the two tested varieties; The high oxygen treatment reduced the plant height and shoot biomass, but had no significant effect on root biomass. (2) Compared with the control, the total root length, surface area and total volume of root were significantly increased, and the average root diameter were significantly decreased after the medium oxygen treatment, while the high oxygen treatment was opposite to the medium. The medium and high oxygen treatment could promote the secretion of organic acids (the total amount of organic acids, oxalic acid, tartaric acid, and citric acid content increased), and increase the activity of acid phosphatase in leaves and roots. However, compared with high oxygen, the medium oxygen treatment significantly enhanced the activity of roots, optimized the kinetic parameters of phosphorus absorption, increased Imax, and decreased Km and Cmin. (3) The results of correlation analysis showed that the phosphorus accumulation and aboveground phosphorus content were significantly positively correlated with root morphology (total root length, root surface area, average diameter and total volume of root), root activity, absorption kinetic parameters Imax, the content of oxalic acid and tartaric acid, and negatively correlated with phosphorus absorption kinetic parameters Km and Cmin. The root phosphorus content of root was significantly positively correlated with root acid phosphatase, root activity, total organic acid and oxalic acid content, but not significantly with other indexes.
The moderate increase of dissolved oxygen concentration (medium oxygen treatment) could improve the activity of acid phosphatase in leaves and roots, root activity, the root secretion content of oxalic acid, tartaric acid and citric acid, optimize the root morphological structure (increase the root surface area) and phosphorus uptake kinetics of rice seedlings so as to increase phosphorus content and accumulation of rice. Therefore, the selecting appropriate cultivation measures could change the rhizosphere oxygen environment and improve the ability of phosphorus absorption of rice in field planting.
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