Multi-Element Analysis of Farmland Soil Extracts Using ICPE-9820 and a Multi-Component Extraction Method

Importance of the Topic

The chemical composition of farmland soil governs crop productivity and quality. Rapid multi-element soil analysis supports efficient fertilizer management and sustainable agriculture. Combining a multi-component extraction with simultaneous ICP-AES detection streamlines routine soil testing by reducing the number of individual assays and minimizing sample handling.

Objectives and Study Overview

This study evaluates the Shimadzu ICPE-9820 inductively coupled plasma atomic emission spectrometer coupled with a multi-component extraction protocol from the Tokyo University of Agriculture Soil Diagnostic System. Two farmland soil types (high-humic cumulic andosol TUAS-1 and sand-dune regosol TUAS-4) were extracted and analyzed for:

• Exchangeable cations and anions (Al, Ca, K, Mg, Mn, P, S)
• Available boron
• Available trace elements (Co, Cu, Fe, Mn, Ni, Zn)

Validation included spike recovery and dilution tests to confirm method accuracy and precision.

Methodology and Instrumentation

Extraction conditions:

• Exchangeable constituents: 1 mol/L NaCl at soil:reagent ratio 1:20, 5× dilution for analysis
• Available boron: 0.01 mol/L CaCl2 at 1:2
• Available trace elements: 5 mmol/L DTPA + 0.1 mol/L TEA + 0.01 mol/L CaCl2 at 1:2

ICP-AES analysis:

• Instrument: Shimadzu ICPE-9820 with AS-10 autosampler
• Nebulizer: 10UES; spray chamber: twister cyclonic; torch: high-salt solution; water bubbler to handle complex matrices
• Viewing orientation: axial for low-level analytes (higher sensitivity), radial for major constituents (reduced ionization interferences)
• Plasma conditions: RF power 1.20 kW, plasma gas 15.0 L/min, auxiliary gas 1.20 L/min, carrier gas 0.70 L/min

Main Results and Discussion

Limits of quantitation spanned 0.0003 mg/L (Mn) to 0.2 mg/L (S). Calibration curves were linear up to standards equivalent to soil concentrations of 10–400 mg/kg or 0.1–1 000 mg/100 g, depending on the analyte. Recovery from 10-fold dilutions and spiked samples fell within 94–104%, demonstrating accuracy. Calculated soil oxide contents for TUAS-1 included CaO 986 mg/100 g, MgO 126 mg/100 g and K2O 75.3 mg/100 g; trace metals in the range 0.05–38.6 mg/kg.

Benefits and Practical Applications

This integrated method offers:

• Simultaneous determination of multiple soil constituents in a single extract
• Capability to analyze high-salt matrices without extensive sample dilution
• High throughput for routine soil fertility assessment and quality control in agricultural laboratories

Future Trends and Potential Applications

Further developments may include automation of extraction and data processing, application to saline or contaminated soils, extension to on-site or portable systems for near-real-time soil monitoring, and integration with precision agriculture platforms.

Conclusion

The combination of a multi-component extraction method and the Shimadzu ICPE-9820 ICP-AES enabled precise, accurate, and efficient multi-element analysis of farmland soil extracts. This approach reduces analytical time and improves data consistency, supporting optimized fertilization strategies and agronomic research.

Instrumentation Used

• Shimadzu ICPE-9820 inductively coupled plasma atomic emission spectrometer
• AS-10 autosampler
• Nebulizer 10UES, twister cyclonic spray chamber, high-salt torch, water bubbler