干湿交替条件下稻田土壤氧气和水分变化规律研究

Change in soil oxygen and water contents under alternate wetting and drying in paddy fields

  • 摘要: 在水稻高产栽培技术中, 为合理利用水资源, 改良土壤通气性, 干湿交替灌溉技术已广泛应用。干湿交替灌溉技术的核心是协调土壤水分与氧气之间的平衡。本研究采用大田试验, 在水稻生育后期进行干湿交替处理, 同步监测稻田5 cm土层土壤氧气、水分及温度的变化, 以探讨稻田土壤氧气和水分运移变化规律及其互作关系, 为进一步揭示干湿交替灌溉技术的内在生理机制奠定基础。研究结果表明, 干湿交替条件下, 稻田土壤含水量处于饱和状态时, 基本监测不到土壤含氧量; 而稻田土壤在慢慢变干的过程中, 5 cm土层土壤体积水分含量逐渐降低, 土壤氧气含量逐渐升高。在花后19 d、24 d、29 d, 当5 cm土层土壤体积含水量分别下降为25.4%、25.1%、24.7%时, 土壤含氧量则分别上升到17.5%、17.4%、17.4%。在水稻生育后期不同阶段, 土壤氧气含量的日变化呈现先降低再升高的趋势, 谷值一般出现在14:00-15:00之间; 土壤含水量随时间呈波动式逐渐降低的变化趋势; 土壤温度呈现先升高后降低的趋势, 峰值一般出现在15:00-16:00之间。从上午8:00到下午17:59, 当土壤温度升至峰值时, 土壤水分含量较低, 而土壤含氧量开始升高。水稻开花期、灌浆期和成熟期的土壤氧气含量与土壤含水量均表现出极显著负相关关系, 土壤温度与土壤水分间呈显著负相关关系, 而土壤氧气与土壤温度之间无显著相关关系。说明干湿交替条件下, 水稻生育后期稻田土壤中的水分和氧气含量存在一定的此消彼长的关系。因此, 通过适度的干湿交替管理措施, 可在一定程度上调节水稻根系周围的土壤水分和氧气的平衡。

     

    Abstract: Alternate wetting and drying technique at late growth stage of rice has been widely used in high-yield cultivation techniques to increase water use efficiency, improve soil aeration and enhance root growth in paddy fields. The aim of alternate wetting and drying technique was to coordinate and balance soil water and soil oxygen, making the technique typically different from traditional rice cultivation techniques. To further enhance production under high-yield cultivation techniques like alternate wetting and drying technique, change in soil oxygen and soil water contents were investigated in a paddy field in Sanya, Hainan Province. A field experiment was carried out with alternate wetting and drying treatments at the late growth stage (February to April) of rice in 2013. The aim of the experiment was to develop a novel strategy for further research on physiological mechanism of rice with alternate wetting and drying technique. Soil oxygen content, soil water content and soil temperature at 5 cm soil depth in the studied paddy filed were synchronously monitored from 8:00 to 17:59 every day from heading to maturity stage of rice. While the soil was saturated with water under alternate wetting and drying, soil oxygen was almost impossibly detected by Firesting O2. While soil water content at the 5 cm soil depth decreased gradually as soil slowly dried up, soil oxygen content increased. On the 19th, 24th and 29th day of post-anthesis, soil water content decreased to 25.4%, 25.1% and 24.7% while soil oxygen content increased to 17.5%, 17.4% and 17.4%, respectively. During flowering, grain-filling and maturity stages of rice, daily soil oxygen content initially decreased and then increased later in the day, with the lowest value generally appearing at 14:00 15:00. Soil water content fluctuated but gradually decreased during the day. Soil temperature increased initially and then decreased later in the day, with peak value generally appearing at 15:00 16:00. When soil temperature was the highest during 8:00 17:59, soil water content was lower while soil oxygen content increased. At flowering, grain-filling and maturity stages, a significantly negative correlation was noted between soil oxygen content and soil water content. Although soil water content was negatively influenced by soil temperature, the correlation between soil oxygen content and soil temperature was insignificant. Under alternate wetting and drying cultivation, a reciprocal relationship existed between soil oxygen content and water content in paddy fields during late growth stages of rice. Thus through moderate alternate dry-wet management measure, soil water and soil oxygen balance in root-zone soil layer was adjusted to some extent.

     

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