| Effect of different organo-mineral complexes on desorption characteristic of phosphorus on sandy soil was investigated by batch experiment of equilibrium desorption. Results indicated that desorption ratio increased dramatically after humus was removed by H2O2（Dr=0.99）, and desorption hysteresis index decreased simultaneously（TⅡ＝0.02）. Organo-mineral complex was a main influencing factor in fixed and maintained characteristic of phosphorus on sandy soil. On the one hand, the irreversible transformation of aggregate structure on Fe/Al-bound or Ca-bound complex was the fundamental reason of desorption ratio decreasing and hysteresis index increasing. On the other hand, fixed and maintained capacity of Fe/Al-bound complex（Dr=0.35、TⅡ＝0.44） was higher than Ca-bound complex（Dr=0.62、TⅡ＝0.28）. Trivalent iron ion was more favorable for complex structure formation than divalent calcium ion; Besides Fe/Al-bound complex had a great effect upon aggregate structure formation, there was a Fe/Al oxide or hydration oxide coordination sorption（chemical sorption） of phosphorus on sandy soil. Taking into account desorption characteristic was not only humus content, but also compound state of humus, it was also an important factor. When sorption capacity was regarded as a basic standard, releasing flux of adsorption state phosphorus on Ca-bound complex and Fe/Al-bound complex were also estimated in accordance with 62% and 35%. |
