不同水稻栽培密度下青田稻—鱼共生系统的土壤肥力

作为联合国粮农组织的首个全球重要农业文化遗产(GIAHS)试点保护项目,青田稻—鱼共生系统以其独特的优势受到越来越多的关注。为了更好地保护这一亚洲首个GIAHS项目,实验观察了青田稻—鱼共生系统在不同水稻栽培密度下的土壤肥力情况。结果显示,调查区域稻田土壤的pH值为5.50~6.13,呈弱酸性;土壤养分(全氮、有机质、有效磷和速效钾)含量随水稻生长均呈先减少后增加趋势,且在拔节期—抽穗期达到最低值,但在水稻收割前的成熟期均能恢复至不低于初始的较高水平,表明青田田鱼的活动有助于维持土壤肥力。根据水稻产量与土壤养分的关联度分析结果,发现与水稻产量关系最密切的因子是土壤pH和速效钾;相比于含量丰富的全氮、有效磷和有机质,轻度缺乏的速效钾和较低的pH值限制了水稻的生长和最终产量。研究表明,在本季种养过程中,水稻栽插密度对稻田土壤肥力的影响不显著。

Investigation of soil fertility of Qingtian rice-fish coculture system under different rice cultivation densities

As the first pilot site of the Globally Important Agricultural Heritage System (GIAHS), Qingtian rice-fish co-culture system has attracted more and more attention due to its unique advantages. In order to better conserve the first GIAHS project in Asia, we investigated the effects of different rice planting densities on soil fertility of Qingtian rice-fish co-culture systems. The results showed that the pH value of the tested paddy soil varied between 5.50-6.13, which was weakly acidic. The contents of soil nutrients (such as the soil total nitrogen, soil organic matter, available phosphorus and available potassium) first decreased and reached the lowest values at the booting stage, then recovered to the similar higher levels with the initial before rice harvesting, indicating that the activity of the field fish and perhaps fish feces could help maintain the soil fertility. According to the results of Grey relational analysis (GRA) between rice yield and soil nutrient, it was found that soil pH and available potassium were most closely related to rice yield. Compared with the rich nitrogen, available phosphorus and soil organic matter, the less suficiently available potassium and low pH value might be responsible for the limited growth and yield of rice. Rice planting densities were not found to significantly affect soil fertility in Qingtian rice-fish co-culture system in this growing season.