应用电导法实时测定磷酸氢二铵和氯化钾混合肥液浓度

【目的】通过电导率(EC)准确反应水肥一体化条件下磷酸氢二铵和氯化钾不同配比值的肥液质量浓度。【方法】测定了一定质量浓度范围(2～10 g/L)和温度范围(20～45℃)内不同磷酸氢二铵和氯化钾配比混合肥液的EC值,并基于灰色关联分析(GRA)法研究了质量浓度rf、温度T和配比值rv对磷酸氢二铵、氯化钾混合溶液电导率的影响。【结果】磷酸氢二铵、氯化钾混合肥液电导率(EC)随质量浓度rf和温度T的升高而增大,随配比值rv的增大而减小;3个因素对混合液EC影响的大小顺序为:质量浓度rf温度T配比值rv;基于拟合优度评价指标对比3次样条插值和3次B样条插值后的数据分别优选混合溶液质量浓度-EC、温度-EC、配比值-EC单因素曲线模型,构建了以磷酸氢二铵、氯化钾混合肥液EC、温度T、配比值rv为自变量的质量浓度预测模型。【结论】该模型预测精度为97.53%,满足实际使用要求,可用于水肥一体化灌溉过程中的肥液浓度的实时监测。

Electrical Conductivity Method for Measuring Concentrations of Diammonium Hydrogen Phosphate and Potassium Chloride in Their Mixed Solution

【Background】 Integrating fertilization and irrigation is a potential agricultural management technology and its success depends on accurately real-time monitoring the change in fertilizers concentration. The existing electric conductivity(EC) method is only able to detect concentration of single fertilizer, and developing simple and cheap device to accurately real-time monitor concentration of mixed fertilizers solution is hence needed.【Objective】The purpose of this paper is to study the feasibility and accuracy of an electric conductivity method to real-time monitor the concentrations of diammonium hydrogen phosphate and potassium chloride at in their mixed solution.【Method】We first measured the EC of the mixture of diammonium phosphate and potassium chloride at different concentrations ranging from 2 g/L to 10 g/L and different temperatures ranging from 20 ℃ to 45 ℃, and then analyzed the change in EC with temperature, concentration and ratios of the two fertilizers using the grey correlation analysis(GRA).【Result】The EC of the mixed solution increased with its concentration and temperature and decreased as the ratio(n) of diammonium hydrogen phosphate to potassium chloride increased. It was also found that the factors affecting the EC of the mixed solution was ranked in the descending order of concentration > temperature > n. Based on goodness of the fitting, the evaluation index of the GRA was compared with the measured data after cubic spline interpolation and cubic B-spline interpolation, from which we obtained pairwise models for concentration-EC, temperature-EC and n-EC relationships, respectively. These enabled us to derive a model to predict the concentration of each fertilizer in their mixed solution based on EC, temperature, and the ratio n.【Conclusion】Testing against measured data showed that the model accuracy was 97.53%, meeting the requirement in practical application. The method can thus be used for real-time monitoring concentration of mixed fertilizers solution in integrated irrigation and fertilization.