沂北水稻主产区田间土—水磷素流失潜能

选取嘉善、余姚、德清、余杭4个具有代表性浙北水稻主产区，研究了水田土－水磷素流失潜能及环境意义。4稻区高水平磷肥投入促进了土壤高磷化，土壤Olsen-P积累的同时,相应地提高了土壤生物性有效磷、水浸提磷，并提高了土壤磷素的流失潜能。稻区土壤在富磷化过程中，存在着土壤磷素的农学意义向环境意义方向演变的趋势。在非植稻期，稻区农田水体，包括沟渠水、田表水、排渠水、暗管排水等总磷（TP）平均超过了易诱发水体富营养化临界值，其中溶解磷（DRP）占总磷40％；主要是源于绿肥田表水及部分排渠中的溶解磷对稻区外水体构成了直接危害。在非植稻期，因稻区间农耕措施的差异导致了土壤富磷水平与对应田表水磷素水平不具相关性；在植稻期，施磷措施促进水田土壤富磷，相应地提高了田表水磷素水平。

Phosphorus loss potential of soil-water in sites of the main rice-yield area in the Northern Zhejiang]

Phosphorus (P) loss potential and its environmental impact from soil-water were surveyed in Jiashan Yuyao, Deqing and Yuhang, named main rice-yield areas in Northern Zhejiang province China. High P input has resulted in soil P accumulation. Higher soil Olsen-P contributed its bio-available P, water extracted P and increased soil P loss potential. The role of P in paddy soils is of environmental rather than agronomic concern in the process of soil P build-up. During the no-rice time, total P (TP) concentration in the various water including ditch drain inside/outside field, field surface water and pipe drain et al are over the critical values associated with accelerated waters eutrophication. The average proportion of dissolved reactive P (DRP) concentration in TP was 40%, however, these current DRP levels in partly ditch drain outside field and surface or ground water in no-rice time could not caused serious impact to the outside waters nearby rice-yield agriculture area. No significant line correlation between soil P tests and P in field surface water was found in no-rice time due to differences in field tillage among rice-yield areas, while P application increased both soil P and its correspondingly field surface P level after rice was planted at the same time.