聚磷酸铵对砖红壤和石灰性土壤上磷素吸附解吸行为的影响

以砖红壤和石灰性土壤为供试土壤,探索不同聚磷酸铵(APP)对土壤中磷吸附解吸的影响,为评价磷的有效性提供数据参考。在等磷等氮条件下,分别以APP1(以中聚为主)、APP2(以低聚为主)、APP3(聚合度分布均匀且高聚含量高)、MAP(磷酸一铵)、A-M(APP3和MAP以P₂O₅质量比1∶1的比例混合)、CK(空白对照)为供试材料,设置6个处理(各处理名同所用材料),在砖红壤和石灰性土壤上进行50 d的培养,测定各处理下磷的吸附解吸特性。结果显示,在石灰性土壤和砖红壤上,朗缪尔(Langmuir)方程、弗罗因德利希(Freundlich)方程和Temkin方程均可很好地拟合土壤中磷的等温吸附特征,且以Freundlich方程的拟合效果最好(相关系数在0.86~0.98)。在石灰性土壤上,除CK外,以APP1处理下土壤对磷的吸附性最强,A-M处理下土壤对磷的吸附性最弱,磷解吸量最大,磷解吸率最高;在砖红壤上,除CK外,以APP1处理下土壤对磷的吸附性最强,APP2处理下土壤对磷的吸附性最弱,磷解吸量最大,磷解吸率最高。结果表明,聚合度分布均匀且高聚含量高的APP配施MAP可减少石灰性土壤对磷的吸附,提高磷的有效性;而以低聚为主的APP可减少砖红壤对磷的吸附,保持土壤磷的平衡和供磷能力。

Effect of ammonium polyphosphate on phosphorus adsorption and desorption in laterite and calcareous soil

In the present study, the soil culture experiments were conducted to study the adsorption and desorption behaviors of ammonium polyphosphate (APP) and monoammonium phosphate (MAP) in calcareous soil and laterite, to provide theoretical reference for the evaluation of phosphorus availability. Six treatments were introduced in this work according to the materials used: APP1 (mainly high polymer), APP2 (mainly oligomeric), APP3 (mainly low, medium, and high polymer), MAP, A-M (APP3 and MAP mixed with the ratio of 1∶1 based on the content of P₂O₅), and CK (blank control). All the treatments set the same rate of nitrogen and phosphorus except CK. After 50 days of soil cultivation, the adsorption and desorption characteristics of phosphorus were measured. The results showed that the equations of Langmuir, Freundlich, and Temkin could well fit the adsorption characteristics of soil phosphorus in different soils, and the Freundlich equation had the best fitting effect with a correlation coefficient of 0.86-0.98. In calcareous soil (except CK), the soil with APP1 had the strongest adsorption capacity, while the soil with A-M had the weakest adsorption capacity, the largest phosphorus desorption, and the highest phosphorus desorption rate. In laterite (except CK), the soil with APP1 showed the strongest adsorption capacity, and the soil with APP2 showed the weakest adsorption, the largest phosphorus desorption, and the highest phosphorus desorption rate. The results indicated that the application of MAP with APP with uniform polymerization degree distribution and high aggregate content could reduce the adsorption of phosphorus in calcareous soil to improve the availability of phosphorus. While APP with low polymerization degree could lower the adsorption of phosphorus by laterite, and maintain the balance of phosphorus.