Exploring a low-cost turbidimetric sensor for available potassium determination in soil

Area of Science:

• Agricultural Chemistry
• Soil Science
• Analytical Chemistry

Background:

• Potassium (K) is an essential macronutrient for crop production, absorbed by plant roots from soil solution.
• Accurate assessment of available soil K is crucial for effective fertilizer management.
• Limited literature exists on turbidimetric methods for K determination, especially in soil samples.

Purpose of the Study:

• To evaluate a portable, low-cost system for the turbidimetric determination of available K in soil.
• To optimize conditions for K extraction and turbidimetric measurement.

Main Methods:

• A turbidimetric method involving K precipitation with sodium tetraphenylborate (NaTPB).
• Evaluation of extraction solutions (Mehlich-1, diluted Mehlich-1, water), extraction time, pH, NaTPB volume, and sensor signal stability.
• Comparison of results with Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) and Multi-Pixel Array Charge-Coupled Device (MP-AES) using Mehlich-1 extraction.

Main Results:

• Optimized conditions yielded excellent sensor calibration linearity (r² = 0.9982).
• The method demonstrated low limits of detection (0.1 mg L⁻¹) and quantification (0.3 mg L⁻¹).
• No significant differences were found between the turbidimetric sensor and MP-AES/ICP OES methods for K determination.

Conclusions:

• A portable, low-cost turbidimetric system can accurately measure available soil K in field conditions.
• The method utilizes minimal reagents, enhancing accessibility for soil K analysis.
• This approach offers a practical alternative for on-site soil nutrient monitoring.