Screening of pretreatment parameters for novel solid-state ISE-based soil extractable potassium detection

Soil potassium testing plays an important role in soil fertilizer recommendation and site-specific fertilization. Conventional detection methods, including soil sampling, sample pretreatment and nutrient determination, are time-consuming and expensive. Ion-selective electrode (ISE) shows great potential in soil macronutrient detection because of its obvious advantages on rapid response, inexpensive cost, simple use and easy integration. In this paper, preliminary experiments were conducted to evaluate the feasibility of self-designed all-solid-state potassium ISE for soil extractable potassium detection with an automatic detection platform. The influences of soil pretreatment parameters, especially the extraction parameters, were discussed. Testing results indicated that NH₄ cation existing in 1 mol/L NH₄OAc extracting solution were too high to greatly degrade the potassium ISE performance. The optimized soil pretreatment parameters to obtain soil potassium extracts for ISE method was shaking 2.5g soil with 25mL Kelowna solution (soil-to-solution ratio 1:10) for 15 minutes. Under these optimized pretreatment parameters, the range of such potassium ISE could detect was from 4.8mg/L to 370.0mg/L. And there were good consistency and correlation between the results determined by potassium ISE and conventional method. It indicted that self-designed all-solid-state potassium ISE combined with the automatic detection platform could basically meet the need of soil extractable potassium rapid detection.