| Summary: |
Phosphorus (P) loss potential of agricultural soils is one of the limiting factors of water-body eutrophication, while inappropriate P fertilization could increase this potential. In the Liaohe River Plain of Northeast China, lowland rice soil has been applied with chemical P fertilizer at a rate of 50 kg P hm-2 for a longer time. To approach whether a long-term P fertilization with this rate could increase the P loss potential of this soil, a field experiment with three treatments, i.e., no P fertilization (P0), P fertilization at a rate of 50 kg P hm-2 (P50, routine), and at a rate of 250 kg P hm-2 (P250, simulation of a longer-term P fertilization with 50 kg P hm-2 per year), was conducted at a representative site in the lower reaches of the plain. Basal application of chemical P fertilizer in-creased the total dissolved P (TDP) concentration in soil surface water and in the soil leachate down to a depth of 60 cm during the early growth period of lowland rice, especially at its turning green stage. This TDP concentration was higher than the critical value for eutrophication, suggesting that the soil surface water run-off and soil leaching in this growth period could cause soil P loss, and threaten the quality of the water-bodies nearby. The Olsen-P and CaCl2-P in surface soil layer had significant positive correlations with the TDP, suggesting their great contributions to the TDP, and the Olsen-P content was much higher than the CaCl2-P content, illustrating its more important role in the TDP storage. There was a significant difference in the surface soil Olsen-P content among the treatments, being the highest in P250, followed by P50, and P0, while less difference was observed in the CaCl2-P content, indicating that P fertilization mainly affected soil Olsen-P. In the lower reaches of Liaohe River Plain, a long- term fertilization with 50 kg P hm-2 could increase the P loss potential of lowland rice soil. |