Organic amendments affect phosphorus sorption characteristics in a paddy soil

Abstract Continuous excessive application of phosphorus (P) fertilizer and/or manure in areas with intensive agriculture can lead to an accumulation of P in soils and progressive saturation of soil sorption capacities, thus resulting in increased P loss from soil to aquatic ecosystem. An 8-year field experiment with four fertilization patterns (chemical fertilizer only, fertilizer plus straw, fertilizer plus 7.5 t ha −1 manure, and fertilizer plus 15 t ha −1 manure) was conducted in the Taihu Lake region of eastern China to investigate the effects of incorporation of straw and manure on P accumulation and the changes of P sorption capacity of a paddy soil. Degrees of P saturation, contents of Olsen-P and total P in manure treated soils were significantly higher than those treated with fertilizers alone or with straw retention ( P S max ) ranged from 24.7 mmol kg −1 to 43.2 mmol kg −1 , and was highly correlated with oxalate extractable Al (Al ox , r  = 0.85) and Fe (Fe ox , r  = 0.79). Moreover, path analysis showed that the direct effect of Al ox on S max was significant ( P ox on S max was insignificant; and that Al ox could also exert influence on S max via its indirect effect through Fe ox and organic matter. Thus, Al was the most important soil property associated with S max in the paddy soil based on path analysis results.