Study On Characteristics Of Phosphate Adsorption And Desorption And Profile Distribution Of Fertility Parameters On The Foreshore Reclamation Paddy Soils

In this present study, a series of foreshore reclamation paddy soils originated from the different periods (Song dynasty,Ming dynasty,Qing dynasty and Present age) at Cixi City, Zhejiang Province were used to study the characteristics of phosphorus adsorption-desorption and soil fertility characteristics. The results obtained indicate that:Soil total K contents increased with the increase of soil profile depth, and with the increase of duration of rice - planting. Suggestion introducing rice - deep root crop rotation system for using deep layer soil K source to meet crop K demand. The top layer soil P gradually enrich with the increase of duration of rice-planting. Therefore, surface water eutrophication resulting from rice fields P transport should be paid more attention.All phosphate adsorption curves could be well described by Langmuir,Freundlich and Temkin equations with a best fitness by Freundlich equation. The maximum absorption amount of P on paddy soils tested (Q_m) showed an decreasing order as bellow: Song dynasty > Ming dynasty > Qing dynasty > Current. There was a positively relationship between Q_m and soil organic matter content (r=0.881),amounts of extractable Al (r=0.999) and Fe (r=0.930). The soil P gradually enriched at the toplayer of soil with the increase of duration of rice-planting.The value of DPS,K and MBC increased with the increase of duration of rice - planting, showed an decreasing order as bellow: Song dynasty > Ming dynasty > Qing dynasty > Current ; In contrast, the equilibrium P concentration at zero sorption (EPC₀) and RDP decreased with increasing rice cultivation time, showed an increasing order as bellow: Song dynasty < Ming dynasty < Qing dynasty < Current. Implying that the risks of P run off and leaching losses from paddy soils could decrease with increasing cultivation time.The tested soils phosphorus supply and sorption capacity had large changes after flooding 35 days. The value of DPS,K and MBC had markedly increase, however, the value of DPS,RDP,EPC₀ tended to decrease compared to non-waterlogged. These results indicated that waterlogging could decrease the risks of P runoff and leaching loss from soil due to waterlogging-induced increase of the sorption capacity of P in paddy soils. Waterlogging resulted in significantly increase of absorption amount of P, and obviously decrease of desorption P due to waterloging induced increase of unformed ferric oxide, and pH.It was observed that a part of Al-P was transformed into Fe-P in the flooded soils, Olsen-P decreased greatly after flooding in soils. These results showed that the transformation of iron oxides was important factor controlling P availability in inflooded soils.