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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #405682

Research Project: Sustaining Productivity and Ecosystem Services of Agricultural and Horticultural Systems in the Southeastern United States

Location: Soil Dynamics Research

Title: Measuring and mapping moisture content in agricultural fields by neutron-gamma analysis

Author
item Yakubova, Galina
item Kavetskiy, Aleksandr
item Prior, Stephen
item Torbert Iii, Henry

Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2024
Publication Date: 1/10/2025
Citation: Yakubova, G.N., Kavetskiy, A.G., Prior, S.A., Torbert III, H.A. 2025. Measuring and mapping moisture content in agricultural fields by neutron-gamma analysis. Soil and Tillage Research. 248:1026444. https://doi.org/10.1016/j.still.2024.106444.
DOI: https://doi.org/10.1016/j.still.2024.106444

Interpretive Summary: Water is essential for crops and plays a critical role in sustained farm productivity to meet world food demand. Accurate monitoring and assessment of soil moisture are needed to identify best soil management practices. The present paper describes a mobile inelastic neutron scattering system (INS) for routine measurement of soil moisture in large soil volumes (~ 0.3 m3) that is fast and nondestructive. We compared INS field measurements with other standard soil moisture methods. When combined with location coordinates (via a geographical information system), INS measurement data can produce soil moisture distribution maps. These maps were quite similar to maps created using data from other methods. Thus, our mobile systems appears to be a promising map creating method for use in both agricultural practice assessments and soil science field experiments.

Technical Abstract: Pulsed fast thermal neutron analysis (PFTNA) technology for measuring and mapping soil moisture was investigated. A mobile PFTNA system was use for moisture measurements by determining hydrogen peak areas in thermal neutron capture gamma spectra acquired when scanning agricultural fields. A calibration dependency was used for converting hydrogen peak area to soil moisture content by comparing PFTNA hydrogen peak area to other soil moisture determination methods (gravimetric, time domain reflectometry, and nuclear moisture/density gauge). Moisture measurements by these different methods were in general agreement with each other (accuracy of ±4 wt%), where variability was likely related to natural changes in moisture with soil heterogeneity, and small soil volumes (1-2 dm3). In comparison, PFTNA analyzes the average soil moisture in much larger volumes (200-300 dm3 in static mode and '8 m3 in scanning mode); measurement accuracy was no worse than ±0.4 wt%. Soil moisture distribution maps can be created using PFTNA data acquired during field surveys. These maps were quite similar to moisture distribution maps created using data acquired by the other methods. While data acquired by gravimetric or instrument methods can be labor intensive and time consuming, PFTNA scanning of a 20 ha field can acquire needed mapping data in ~1 h. Thus, PFTNA scanning can be recommended as a more efficient method for measuring and mapping soil moisture in agricultural fields.