| Exploring the distribution characteristics of inorganic phosphorus in typical soils in crop planting areas in northern China,and explaining that the effective performance of inorganic phosphorus forms could provide a scientific theoretical basis for the study of soil phosphorus changes in northern areas,and at the same time provide effective data support for reducing amount of phosphate fertilizer and increasing efficiency in northern agricultural areas.Therefore,in 2018,9 types of typical soils under the four systems of winter wheat-summer maize,spring maize,potato and cotton planting area in northern China were selected as the research objects.The inorganic phosphorus classification method improved by Jiang and Gu was used to determine the content of inorganic phosphorus components in soil samples.And the Olsen method was used to determine the available phosphorus content of these 9 types of soils。Additionally,the contribution of various inorganic phosphorus forms to available phosphorus(Olsen-P)was evaluated introducing correlation analysis and path analysis.Finally,the stepwise regression analysis method was used for further verification.The main results of the research were as follows:(1)The ranges of available phosphorus content in Tier soil,Cinnamon soil,Fluvo-aquic soil,Dark brown forest soil,Albic soil,Black soil,Chernozem soil,Chestnut soil and Grey desert soil were respectively 1.2～62.8、5.6～55.5、7.1～53.1、10.2～69.4、11.6～95.2、8.2～131.6、5.5～77.0、1.8～89.9 and 0.2～71.9 mg/kg.The mean values of the content were respectively 27.4、15.9、22.1、35.4、41.2、53.9、27.8、12.3 and 12.1 mg/kg。(2)In the tier soil,cinnamon soil and fluvo-aquic soil in the winter wheat-summer maize rotation planting area,the total inorganic phosphorus ranges were respectively 585.4～1513.8、360.3～919.7 and 432.6～830.5 mg/kg,The mean values of the content were respectively 983.4、513.8 and 577.9 mg/kg.Ca10-P was the main form of the inorganic phosphorus component of tier soil,accounting for 38.8%～82.9%of the total inorganic phosphorus.The order of relative content of other forms was Ca8-P(5.0%～30.7%)>O-P(6.4%～17.5%)>Al-P(1.0%～16.6%)>Fe-P(1.8%～17.2%)>Ca2-P(0.1%～4.8%).The order of the relative content of various forms of inorganic phosphorus in Cinnamon soil was Ca10-P(22.2%～48.1%)>Ca8-P(5.3%～42.9%)>O-P(13.8%～23.1%)>Al-P(9.3%～16.5%)>Fe-P(5.1%～23.2%)>Ca2-P(1.1%～9.4%).And in Fluvo-aquic soil was Ca10-P(18.9%～66.4%)>Ca8-P(11.5%～34.7%)>O-P(10.2%～24.4%)>Al-P(4.3%～18.3%)>Fe-P(2.6%～14.3%)>Ca2-P(1.2%～5.1%).The results of stepwise regression analysis also demonstrated tha Ca2-P,Ca8-P and Fe-P were the main phosphorus sources of available phosphorus in tier soil,Al-P and O-P were slow-release phosphorus sources.Ca2-P was the main phosphorus source of available phosphorus in cinnamon soil and fluvo-aquic soil,Ca8-P,Al-P,Fe-P and O-P were slow-release phosphorus sources.Ca10-P was a potential source of phosphorus in these three types of soils.(3)In the Dark brown forest soil,Albic soil,Black soil and Chernozem soil in the Spring maize monoculture planting areas were respectively 292.9～999.5、217.4～746.3、263.4～693.7 and 221.85～610.5 mg/kg,The mean values of the content were respectively 582.4、475.0、452.2 and 341.3 mg/kg.Ca10-P was the main form of the inorganic phosphorus component of Dark brown forest soil,accounting for 7.0%～59.8%of the total inorganic phosphorus.The order of relative content of other forms was O-P(17.1%～56.9%)>Fe-P(8.3%～30.2%)>Al-P(7.4%～27.9%)>Ca2-P(1.5%～9.9%)>Ca8-P(0.8%～5.9%).The order of the relative content of various forms of inorganic phosphorus in Albic soil was Fe-P(26.4%～55.2%)>O-P(11.7%～36.0%)>Ca10-P(8.9%～25.3%)>Al-P(4.6%～19.7%)>Ca2-P(2.1%～9.2%)>Ca8-P(0.3%～4.6%).In Black soil was Fe-P(15.3%～40.3%)>Ca10-P(12.0%～42.5%)>Al-P(5.0%～27.7%)>O-P(7.7%～28.8%)>Ca2-P(1.7%～25.3%)>Ca8-P(0.9%～26.4%).And in Chernozem soil was Ca10-P(18.4%～39.8%)>Fe-P(10.1%～36.0%)>Ca8-P(3.7%～47.0%)>Al-P(7.7%～18.8%)>O-P(3.0%～21.0%)>Ca2-P(0.4%～11.7%).The results of stepwise regression analysis also demonstrated that Ca2-P and Al-P were the main sources of available phosphorus in dark brown forest soil,Ca8-P and Fe-P are slow-acting phosphorus sources,and O-P was a potential source of phosphorus.Ca2-P,Al-P and Fe-P are the main phosphorus sources of available phosphorus in albic soil and black soil,and Ca8-P and O-P are slow-acting phosphorus sources.Ca2-P was the main phosphorus source of available phosphorus in chernozem,and Ca8-P,Al-P,Fe-P and O-P were slow-acting phosphorus sources.(4)The ranges of total inorganic phosphorus in Chestnut soil in the potato planting area in Inner Mongolia Autonomous Region was 163.4～1004.9 mg/kg,the mean values of the content were 456.7 mg/kg.Ca10-P was the main form of the inorganic phosphorus component of Chestnut soil,accounting for 17.5%～84.4%of the total inorganic phosphorus.The order of relative content of other forms was O-P(1.7%～33.7%)>Ca8-P(0.4%～39.9%)>Al-P(3.7%～19.6%)>Fe-P(0.8%～15.8%)>Ca2-P(0.6%～10.7%).The stepwise regression analysis also demonstrated that Ca2-P,Ca8-P and Fe-P were the main sources of available phosphorus,Al-P and O-P were slow-release phosphorus sources,while Ca10-P was a potential source of phosphorus.(5)The ranges of total inorganic phosphorus in Grey desert soil in the Cotton Planting Area in Xinjiang Uygur Autonomous Region was 617.7～1044.8 mg/kg,the mean values of the content was 826.6 mg/kg.Ca10-P was the main form of the inorganic phosphorus component of Grey desert soil,accounting for 42.6%～84.9%of the total inorganic phosphorus.The order of relative content of other forms was Ca8-P(2.2%～30.5%)>O-P(7.8%～29.3%)>Fe-P(2.0%～9.6%)>Al-P(1.0%～6.7%)>Ca2-P(0.2%～7.4%).Ca2-P was the main sources of available phosphorus.Ca8-P,Al-P,Fe-P,O-P were slow-release phosphorus sources,Ca10-P was a potential source of phosphorus. |
