Objective  The effects of different soil modified materials on the adsorption, desorption and forms of phosphorus (P) in soda alkaline soil were studied in order to provide a theoretical basis for the scientific improvement of soda alkaline soil.

  Methods  Taking soda alkaline soil in Songnen Plain of Northeast China as the research object, six treatments were arranged, including control (CK), organic fertilizer (M), aluminum sulfate (Al), gypsum (Ca), aluminum sulfate + organic fertilizer (Al + M) and gypsum + organic fertilizer (Ca + M).

  Results  M treatment could reduce the P adsorption and increase the P desorption of soda alkaline soil, but the other four treatments could increase the P adsorption and reduce the P desorption. Among them, there was a significant difference between Al and Al + M treatment. The contents of soil inorganic P in different soil modified materials increased in varying degrees. Among them, M, Ca and Ca + M treatments significantly increased the contents of soil Ca₂-P (P < 0.05), and the largest was in Ca + M treatment (21.43%). The additions of different soil modified materials could increase the contents of slow acting P (Ca₈-P, Al-P and Fe-P), with the increase of 1.00% - 112.03%. Among them, the treatments of Ca, Al, Ca + M and Al + M could significantly increase the contents of Al-P and Ca₈-P, with the increases of 66.37% - 250.1% and 18.06% - 74.36%. Compared with Ca treatment, Ca + M treatment significantly increased the content of Ca₂-P (P < 0.05) and significantly decreased the contents of Al-P and O-P (P < 0.05).

  Conclusion  The combined application of gypsum and organic fertilizer in soda alkaline soil can reduce the adsorption of gypsum on phosphorus in soil and increase the content of available phosphorus in soil. It is the best measure to improve the availability of phosphorus in soda alkaline soil.