黑土有效磷阈值区间的磷形态特征及对土壤化学性质的响应

Characteristics of Phosphorus Fractions and Its Response to Soil Chemical Properties Under the Threshold Region of Olsen P in Black Soil

【目的】土壤有效磷(Olsen P)的农学阈值及环境阈值是土壤磷素管理的重要依据,但不同阈值区间磷形态学特征尚不明确。研究黑土有效磷不同阈值区间的磷形态特征及其影响因素,有助于理解土壤磷的转化过程,为优化有效磷管理和提高磷资源利用效率提供参考。【方法】采集吉林公主岭市9个有效磷含量不同(11、21、31、40、57、69、128、331、490 mg·kg-1)的农田耕层(0—20 cm)土壤,利用TIESSEN-Moir修正的HEDLEY磷分级法,对土壤无机磷和有机磷进行分级,并分析其与土壤有机质(SOM)、C/P、铁铝氧化物等土壤化学性质之间的关系,明确土壤有效磷不同阈值区间的磷形态特征及主控因素。【结果】黑土磷库以无机磷为主,占比为71.25%—96.19%,有机磷占比较小,约为3.81%—28.75%。有效磷水平低于农学阈值(7.4—13 mg·kg-1)时,活性态磷(LP)占比最小(19.89%);有效磷水平低于环境阈值(51.0—56.4 mg·kg-1)时,中活性态磷(ML-P)和稳定态磷(OP)占比接近,分别为36.03%和35.49%,均高于LP占比(28.48%);有效磷水平高于环境阈值时,LP占比最高(42.86%)。有效磷水平高于环境阈值时,土壤的LP、ML-P的含量显著高于有效磷水平低于环境阈值的土壤,树脂磷(Resin-P)是环境阈值前后区间变幅最大的磷形态。PAC、M3-Al、游离态铝(Ald)、络合态铁铝(Fep、Alp)、非晶质态铁铝(Feo、Alo)随有效磷水平的增加而显著增加,C/P随有效磷水平增加而显著降低。相关分析表明,有效磷水平低于环境阈值时,SOM和活性较高的无机态磷(Resin-P、NaHCO 3-Pi、NaOH-Pi)呈显著正相关关系;有效磷水平高于环境阈值时,Fep+Alp与无机态磷(Resin-P、NaHCO 3-Pi、NaOH-Pi、D.HCl-Pi、C.HCl-Pi)呈显著正相关关系。冗余分析结果表明,有效磷水平低于环境阈值时,SOM和M3-Fe是影响黑土磷形态变化的关键因子,分别解释了全部变异的50.2%和24.1%;有效磷水平高于环境阈值时,Fep+Alp是造成磷形态差异的关键因子,解释了全部变异的68.1%。【结论】活性态磷在有效磷水平低于农学阈值时占比最小,在有效磷水平超过环境阈值时,其占比最大,Resin-P是在环境阈值前后区间变幅最大的磷形态。SOM和M3-Fe是土壤有效磷水平低于环境阈值、Fep+Alp是高于环境阈值土壤影响磷形态变化的关键因子。

【Objective】Agronomic and environmental thresholds of Olsen phosphorus(P)are the most important parameters for soil P management,but the characteristics of phosphorus fractions under the different threshold regions are not clear.This research evaluated the characteristics of the P fraction under the different threshold regions of Olsen P and its influencing factors in black soils for enabling to understand the transformation process of soil P,so as to provide a reference for optimizing the Olsen-P management strategy and improving the efficiency of P resource utilization.【Method】9 Olsen P levels(11,21,31,40,57,69,128,331,and 490 mg·kg-1)of agricultural fields plow layer(0-20 cm)soil samples were collected in Gongzhuling,Jilin Province.TIESSEN-Moir modified HEDLEY phosphorus classification method was used to classify soil inorganic phosphorus and organic phosphorus.The relationship between the phosphorus fractions and soil chemical properties,such as soil organic matter(SOM),C/P,Fe,and Al oxides,was also analyzed to clarify the characteristics of phosphorus fractions and the main controlling factors under the different threshold regions of soil Olsen P.【Result】The P pool was dominated by Pi,accounting for 71.25%-96.19%,with Po accounting for 3.81%-28.75%.When the Olsen P level was below the agronomic threshold(7.4-13 mg·kg-1),the proportion of liable P(LP)of 19.89%was the lowest in comparation with other P fractions.When the Olsen P level was below the environmental threshold(51.0-56.4 mg·kg-1),the proportion of medium active phosphorus(ML-P)and stable phosphorus(OP)is close,36.03%and 35.49%respectively,both higher than the proportion of LP(28.48%).The highest proportion of LP(42.86%)was observed when the Olsen P level was above the environmental threshold.When the Olsen P level is higher than the environmental threshold,the content of LP and ML-P in the soil is significantly higher than that in the soil where the Olsen P level is lower than the environmental threshold,and the resin-P showed the greatest variation with Olsen P above and below the environmental threshold.The value of P activation coefficient(PAC),and the concentration of Mehlich-3 extractable aluminum(M3-Al),free Al oxide(Ald),organic-bound Fe,Al oxide(Fep,Alp),and amorphous Fe,Al oxide(Feo,Alo)increased significantly,while a significant decrease in C/P was observed with increasing Olsen P levels.The correlation analysis shows that when the Olsen P level was below the environmental threshold,the soil organic matter was positively and significantly correlated with the highly active inorganic P fractions(Resin-P,NaHCO 3-Pi,NaOH-Pi)above the environmental threshold;when the Olsen P level was above the environmental threshold,Fep+Alp showed a strong positive correlation with each inorganic P fraction blow the environmental threshold.The redundancy analysis results showed that when the Olsen P level was below the environmental threshold,SOM and M3-Fe were the key factors for affecting the change of P fractions in black soils,explaining 50.2%and 24.1%of the total variation,respectively;when the Olsen P level was above the environmental threshold,Fep+Alp was the main factor influencing the change of P fractions,explaining 68.1%of the total variation.【Conclusion】When the Olsen P level was below the agronomic threshold,the liable P accounted for the lowest proportion;however,which was the greatest proportion when the Olsen P level was above the environmental threshold.In addition,the Resin-P is the phosphorus fraction with the largest variation below and above the environmental threshold.SOM,M3-Fe,and Fep+Alp were the key factors affecting the change of P fractions below and above the environmental threshold,respectively.