施用聚磷酸铵的紫色土壤对磷的吸附-解吸特征

Adsorption⁃desorption characteristics of phosphorus in purple soils applied with ammonium polyphosphate

【目的】探讨施用不同聚合度分布的聚磷酸铵(APP)土壤对磷的吸附-解吸特征及其与施用传统正磷酸盐磷酸一铵(MAP)和磷酸二铵(DAP)土壤的差异,为APP的高效利用提供理论依据。【方法】分别以3种APP(18-58-APP、16-60-APP和11-37-APP,N-P2O5-K2O分别为18-58-0、16-60-0和11-37-0,聚合度分布分别为1-2、1-4和1-7)、MAP和DAP为供试肥料,在石灰性和酸性紫色土壤进行56 d培养,测定各处理土壤磷的吸附-解吸特征和土壤理化性质。【结果】Langmuir和Freundlich方程均能很好地拟合两种紫色土壤对磷的吸附特征(R2=0.825~0.997)。在石灰性紫色土壤中,与施用MAP和DAP土壤相比,施用APP土壤对磷的吸附率降低15.1%~20.7%,解吸率提高4.5%~164.9%;施用APP土壤的Langmuir KL值、吸附自由能(|ΔG|)和Freundlich KF值分别降低20.4%~54.0%、3.3%~10.6%和23.8%~43.8%,土壤对磷的吸附结合力减弱,其中施用11-37-APP土壤相应值的变幅最大(KL、|ΔG|和KF值分别降低40.8%~54.0%、7.2%~10.6%和43.6%~43.8%)。在酸性紫色土壤中,施用不同磷肥对土壤磷的吸附-解吸特征影响不显著,但施用APP土壤较施用MAP和DAP土壤表现出降低磷吸附和促进磷解吸的趋势。相关分析表明,土壤pH、铁铝氧化物和土壤有效磷(Olsen-P)含量与石灰性紫色土壤磷素吸附参数显著相关;土壤Olsen-P与酸性紫色土壤磷素吸附参数显著相关。施用APP石灰性紫色土壤中络合态铁铝氧化物降低,游离态铁铝氧化物增加,对磷的吸附降低且解吸增加。与石灰性土壤相比,酸性紫色土壤的有效磷含量更低,对磷的吸附能力更强,使得其吸附-解吸特征在短期内受不同磷肥影响差异不明显。【结论】施用APP紫色土壤磷的吸附-解吸特征受土壤性质和自身聚和度分布的影响,在石灰性紫色土壤中变化显著,且以聚合度分布更广泛的11-37-APP对土壤磷素吸附-解吸特征的影响更显著。

【Objective】The study aimed to investigate the adsorption⁃desorption characteristics of phosphorus(P)in soils applied with ammo⁃nium polyphosphates(APPs)of different polymerization distribution,and to compare these characteristics with those of soils applied with tra⁃ditional orthophosphates(Monoammonium phosphate,MAP;Diammonium phosphate,DAP).It can provide a theoretical basis for the efficient use of APP.【Method】Three kinds of APP(18⁃58⁃APP,16⁃60⁃APP and 11⁃37⁃APP,whose N⁃P2 O5⁃K2 O were 18⁃58⁃0,16⁃60⁃0 and 11⁃37⁃0,and the distribution of polymerization degree were 1⁃2,1⁃4 and 1⁃7,respectively),MAP and DAP were used as test fertilizers.The fertiliz⁃ers were applied to calcareous and acid purple soils and then were incubated for 56 days.The adsorption⁃desorption characteristics of P and the physicochemical properties of the soils were determined.【Result】Both Langmuir and Freundlich equations fit the adsorption characteris⁃tics of P in the two purple soils well(R2=0.825-0.997).In the calcareous purple soil,compared with MAP⁃and DAP⁃treated soils,the APP⁃treated soil showed a 15.1%-20.7%decrease in P adsorption rate and a 4.5%-164.9%increase in desorption rate.The Langmuir KL,adsorption free energy(|ΔG|),and Freundlich KF values of the APP⁃treated soil decreased by 20.4%-54.0%,3.3%-10.6%,and 23.8%-43.8%,respectively,indicating a reduction in the binding force of soil for P.The 11⁃37⁃APP treated soil showed the largest chan⁃ges in these values(KL,|ΔG|and KF values were reduced by 40.8%-54.0%,7.2%-10.6%and 43.6%-43.8%,respectively).In acid purple soil,the impact of different P fertilizers on the adsorption⁃desoprtion characteristics of P was not significant,but APP⁃treated soil tended to reduce P adsorption and promote P desorption.Correlation analysis showed that pH,iron and aluminum oxides,and Olsen⁃P were significantly correlated with P adsorption parameters in calcareous purple soil and soil Olsen⁃P was significantly correlated with P adsorption parameters in acid purple soil.APP application in calcareous purple soil decreased complexed iron and aluminum oxides while increased free iron and aluminum oxides,resulting in decreased P adsorption and increased desorption.Compared to calcareous soil,acid purple soil had a lower available P content and a stronger adsorption capacity,making the adsorption⁃desorption characteristics less susceptible to the influence of different P fertilizers in the short term.【Conclusion】The adsorption⁃desorption characteristics of P in APP⁃treated purple soils are influ⁃enced by the soil properties and the APP’s polymerization distribution.The significant changes are observed in calcareous purple soil,espe⁃cially for 11⁃37⁃APP with a broader polymerization distribution.