Abstract: We explored the characteristics of inorganic phosphorus fractions and influencing factors in saline-alkali soils in North China, by analyzing soil samples from eight land use types, including pepper field, mildly saline-alkali corn field, heavily saline-alkali corn field, sunflower field, Leymus chinensis grassland, Chloris virgata grassland, Suaeda glauca grassland, and bare land. The results showed that the proportion of Ca_10-P in soil inorganic phosphorus fractions of saline-alkali soil was the highest, and the proportions of other phosphorus fractions were following an order of Ca_8-P>Al-P>O-P>Fe-P>Ca_2-P. The results of redundancy analysis and correlation analysis showed that Ca_2-P and Ca_8-P were significantly negatively correlated with soil pH, electrical conductivity, and sodium adsorption ratio (P<0.05), but significantly positively correlated with available phosphorus, available nitrogen, and available potassium (P<0.05). Soil physicochemical factors explained 36.03% of the variations of inorganic phosphorus fractions. Ca_2-P and Ca_8-P of saline-alkali soil were the key fractions of soil phosphorus, and mainly affected by soil pH, electrical conductivity, and sodium adsorption ratio. According to the differences of phosphorus fractions and physicochemical properties of the eight land use types, pepper and sunflower can be used as the preferred crops for the improvement and utilization of mildly and severely saline-alkali land, respectively. L. chinensis can be used as a grassland species for ecological restoration of saline-alkali land. In addition, soil phosphorus availability in saline-alkali lands can be enhanced by improving soil physicochemical properties such as pH, electrical conductivity, sodium adsorption ratio, and organic matter.

Key words: saline-alkali soil, land use type, inorganic phosphorus fraction, soil physicochemical property.