ABSTRACT

Increasing carbon storage in soil is a potential measure against global warming, but the mechanisms of carbon accumulation in soil are not well understood. Clarifying the mechanism would help in the development of new methods for soil carbon storage, such as in agricultural systems. We grew high-biomass forage rice cultivars for 11 years under conditions of potassium and silicic acid deficiency. Rice cultivars were healthy, without signs of potassium or silicic acid deficiency. The quantities of potassium and silicic acid absorbed by the rice plants were greater than those of available forms in the soil, fertilizer, and irrigation water, indicating that mineral weathering promoted the release of potassium, silicic acid, and aluminum from primary minerals. Furthermore, the carbon bound to active aluminum increased by 69.4 kg C ha⁻¹ year⁻¹ during 11 years of paddy rice cultivation. Although organic acids secreted by rice roots have been expected to be a factor in the strong mineral weathering effect in the rhizosphere, an only extremely small amount of organic acids were detected from rice roots. Therefore, organic acids are not a factor in promoting mineral weathering. On the other hand, leaching of potassium and silicic acid is observed in the contact reaction between the mineral powder and the cell wall prepared from rice root. These findings show that the primary minerals could be reacted with chelating sites on the cell wall of the rice root surface to dissolve potassium, aluminum, and silicic acid. The rice plants absorb potassium and a large amount of silicic acid under potassium and silicic acid deficient conditions. Then, the highly active aluminum remained in the rhizosphere, where it bound to organic matter, producing persistent soil carbon. Plants that can absorb silicic acid vigorously have a role of increasing active aluminum through mineral weathering, resulting contribute to carbon accumulation in soil.

摘要

增加土壤中碳的储存量可能是应对全球变暖的一种潜在措施，但人们对土壤中碳累积的机理还不甚了解。澄清机制将有助于开发土壤碳储存的新方法，例如在农业系统中。在钾和硅酸缺乏的条件下，我们将高生物量的饲草水稻品种种植了11年。水稻品种健康，没有钾或硅酸缺乏的迹象。水稻植物吸收的钾和硅酸的量大于土壤，肥料和灌溉水中可用形式的钾和硅酸的量，这表明矿物风化促进了钾，硅酸和铝从主要矿物中的释放。此外，与活性铝结合的碳增加了69.4 kg C ha^-1年^-1水稻种植11年期间。尽管已经预计稻根分泌的有机酸是根际中强烈的矿物风化作用的一个因素，但从稻根中仅检测到极少量的有机酸。因此，有机酸不是促进矿物风化的因素。另一方面，在矿物粉和由稻根制成的细胞壁之间的接触反应中观察到钾和硅酸的浸出。这些发现表明，主要矿物质可以与稻根表面细胞壁上的螯合位点发生反应，从而溶解钾，铝和硅酸。水稻在钾和硅酸缺乏的条件下吸收钾和大量硅酸。然后，高活性铝保留在根际中，与有机物结合，产生持久的土壤碳。可以强烈吸收硅酸的植物具有通过矿物风化增加活性铝的作用，从而促进了土壤中碳的积累。