Phosphorus Concentration and Forms in Surface and Subsurface Drainage Water from Wetland Rice Fields in the Shaoxing Plain

ZHANG MINGKUI; JIANG HONG; LIU XINGMEI

摘要

Phosphorus (P) is the limiting factor for eutrophication in most freshwater ecosystems. In China, Ptransported from intensively cultivated land has been reported as an important source of P in surface waters.In this study, we investigated P concentration and forms in surface and subsurface drainage from wetland ricefields in the Shaoxing plain, Zhejiang Province, China. From selected rice fields, surface drainage sampleswere collected at rice-growing, non-growing and fertilization periods, and subsurface drainage samples atdrought and rewetting (irrigation or precipitation after 5～10 d drought period in the surface soils) and wet(drainage under long-term wet soil condition) periods. Water samples were characterized for their totalreactive P (TRP), dissolved reactive P (DRP) and particulate reactive P (PRP). Concentrations of the TRPand DRP in the surface drainage ranged from 0.08 to 1.50 and 0.06 to 1.27 mg L-1, respectively. The TRPand DRP were dependent on field operation activities, and decreased in the order of fertilization period ＞rice-growing period ＞ non-growing period. Phosphorus concentration of runoff receiving P fertilizer can bean environmental concern. The PRP concentration in the surface drainage, ranging from 0.01 to 0.57 mgL-1, accounted for 8%～78% of the TRP. Concentration of the TRP in the subsurface drainage was from0.026 to 0.090 mg L-1, consisting of 29%～90 % of the DRP and 10%～71% of the PRP. In the droughtand rewetting period, the PRP accounted for, on average, 63% of the TRP, much higher than in the wetperiod (23%), suggesting that there was transport of P in preferential flow during drainage events after ashort-term drought period in the surface soils. Therefore, P losses in particulate form may be importantin the subsurface drainage from rice fields when surface soils form cracks and favor rapid flow downwardthrough the soil profiles, suggesting the important role of water-dispersible colloid particles in mediating andco-transporting P in the subsurface drainage of rice fields.

机译：磷是大多数淡水生态系统中富营养化的限制因素。在中国，从集约化耕地运来的磷已被报告为地表水中P的重要来源。在这项研究中，我们调查了中国浙江绍兴平原湿地稻田中地表和地下排水中的P浓度和形态。从选定的稻田中，在水稻生长，非生长和施肥时期收集地表排水样品，在干旱和重湿（表层土壤中5〜10 d后灌溉或降水）和湿润（长期排水）下收集地下排水样品。长期湿土条件）期。对水样品的总反应性P（TRP），溶解性反应性P（DRP）和颗粒反应性P（PRP）进行了表征。地表排水中TRP和DRP的浓度分别为0.08至1.50和0.06至1.27 mg L-1。 TRP和DRP取决于田间作业活动，并以施肥期＞水稻生长期＞非生长期的顺序降低。接受磷肥的径流中磷的浓度会影响环境。地表排水中的PRP浓度为0.01〜0.57 mgL-1，约占TRP的8％〜78％。地下排水中TRP的浓度为0.026至0.090 mg L-1，由DRP的29％〜90％和PRP的10％〜71％组成。在干旱和再湿润时期，PRP平均占TRP的63％，远高于在湿润时期（23％），这表明在短期干旱后的排水事件中，优先流中存在P的运移。在表层土壤中。因此，当表层土壤形成裂缝并促进土壤剖面向下快速流动时，颗粒形式的P损失可能在稻田地下排水中很重要，这表明水分散性胶体颗粒在地下排水中介导和共运P的重要作用。的稻田。

Phosphorus Concentration and Forms in Surface and Subsurface Drainage Water from Wetland Rice Fields in the Shaoxing Plain

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