Huazhong Agricultural University
The National Key Research and Development Program of China (2017YFD0200206); China Agriculture Research System of MOF and MARA (CARS-12)
明确长江流域水稻-油菜轮作种植区土壤磷（P）库现状，评估土壤磷淋失风险，以期为长江流域水稻-油菜轮作体系合理施磷提供参考。于2018年4 ~ 5月在长江流域水稻-油菜轮作典型种植区域的14个省（市/区）采集油菜收获后的耕层土壤样品247个，测定土壤全磷、有效磷（Olsen-P）和可溶性磷（CaCl2-P），参考土壤全磷和Olsen-P分级指标，明确我国长江流域水稻-油菜轮作种植区域土壤磷丰缺现状，建立Olsen-P与CaCl2-P之间的定量关系。并根据Olsen-P分级选取72个样本进行Hedley磷分级测试，分析了水稻-油菜轮作种植区域土壤磷库分布特征。结果表明：长江流域水稻-油菜轮作种植区域耕层土壤全磷、Olsen-P和CaCl2-P平均含量分别为0.62 g·kg-1、23.2 mg·kg-1和 0.49 mg·kg-1。土壤全磷在长江上、中、下游间无明显差异，区域整体48.6%处于丰富状态。土壤Olsen-P缺乏和过量的现象并存，占比分别为23.1%和31.1%，土壤Olsen-P缺乏和过量的区域分别集中在长江中游和长江下游区域。长江流域水稻-油菜轮作种植区域土壤磷库以无机磷为主，平均占比达到82.2%。H2O-Pi、NaHCO3-Pi、NaOH-Pi、HCl-Pi、NaHCO3-Po、NaOH-Po和Residual-P磷库平均含量分别为10.8、46.8、115.6、218.6、22.3、104.9和193.8 mg·kg-1。随着土壤Olsen-P水平的增加，NaHCO3-Pi和NaOH-Pi含量明显增加，稳定态磷库（HCl-Pi和Residual-P）含量相对稳定。长江流域水稻-油菜轮作种植区域耕层土壤Olsen-P和CaCl2-P的关系符合双直线模型，出现突变点时Olsen-P含量为39.9 mg·kg-1，对应的CaCl2-P含量为0.6 mg·kg-1。当土壤Olsen-P含量大于39.9 mg·kg-1时，土壤磷素淋失风险增加。整体而言，长江流域水稻-油菜轮作种植区域土壤磷含量呈上升趋势，土壤Olsen-P平均含量达到适宜养分供应水平，且存在13.0%的区域处于磷素高淋失风险状态。土壤磷素主要积累在稳定态磷库中，因此，应重视磷肥的合理施用，适当降低磷肥投入，挖掘土壤中稳定态磷库潜力。旨在减少稻-油轮作体系土壤有效磷积累和环境磷素损失，提高作物磷肥利用率。
The objective of this study was to clarify the status of soil phosphorus (P) pools in rice-oilseed rape rotation areas in the Yangtze River Basin, and assessed the risk of soil P leaching. Alse it aimed to provide a reference for reasonable phosphorus application in the rice-oilseed rape rotation system in the Yangtze River Basin. From April to May 2018, 247 soil samples of the cultivated layer after the oilseed rape harvest were collected in 14 provinces (cities/districts) around the Yangtze River Basin in typical rice-oilseed rape rotation regions to determine soil total phosphorus, available phosphorus (Olsen-P) and soluble phosphorus (CaCl2-P). With reference to soil total phosphorus and available phosphorus grading indexes, the current status of soil phosphorus abundance and deficiency in rice-oilseed rape rotation areas in the Yangtze River Basin was clarified, and the quantitative relationship between Olsen-P and CaCl2-P was established. According to the available phosphorus grading, 72 samples were selected for Hedley phosphorus fraction determination, and the distribution characteristics of soil phosphorus pool in rice-oilseed rape rotation were analyzed. The results showed that the average content of total phosphorus, available phosphorus and CaCl2-P in cultivated soils of rice-oilseed rape rotation area in the Yangtze River Basin were 0.62 g·kg-1, 23.2 mg·kg-1 and 0.49 mg·kg-1, respectively. There was no significant difference in total phosphorus between the upper, middle and lower reaches of the Yangtze River, and 48.6% of the total area was in a state of abundance. The lack and excess of soil available phosphorus coexist, accounting for 23.1% and 31.1%, respectively. The areas of soil available phosphorus deficiency and excess were concentrated in the middle and lower reaches of the Yangtze River, respectively. Also the soil phosphorus pool was dominated by inorganic phosphorus, accounting for an average of 82.2%. The average content of H2O-Pi, NaHCO3-Pi, NaOH-Pi, HCl-Pi, NaHCO3-Po, NaOH-Po and Residual-P pools were 10.8, 46.8, 115.6, 218.6, 22.3, 104.9 and 193.8 mg·kg-1, respectively. With an increase in soil available phosphorus levels, the contents of NaHCO3-Pi and NaOH-Pi increased significantly, and the stable phosphorus pools (HCl-Pi and Residual-P) were relatively stable. The relationship between Olsen-P and CaCl2-P conformed to the double-line model. When a change point appeard, the content of Olsen-P was 39.9 mg·kg-1 with a corresponding content of CaCl2-P of 0.6 mg·kg-1. Also, when the Olsen-P content was greater than 39.9 mg·kg-1, the risk of soil phosphorus leaching increased. Generally, the soil phosphorus content in the rice-oilseed rape rotation area in the Yangtze River Basin showed an upward trend and 13.0% of this area was at a high risk of phosphorus leaching. Also, the soil phosphorus mainly accumulated in stable phosphorus pools. Therefore, more attention should be paid to the rational application of phosphorus fertilizers, appropriately reduce phosphorus fertilizer input, and tap the potential of stable phosphorus pools in soils. Thus, this will reduce soil Olsen-P accumulation, environmental P loss in the rice-oilseed rape rotation system, and improve crop P fertilizer utilization.
yanjinyao, guolixuan, wangkunkun, liaoshipeng, luzhifeng, congrihuan, lixiaokun, rentao, lujianwei. Status of Soil Phosphorus Pool and Environmental Risk Assessment in Rice-Oilseed rape Rotation Area in the Yangtze River Basin[J]. Acta Pedologica Sinica,,[In Press]