Monitoring Irrigation in Small Orchards with Cosmic-Ray Neutron Sensors

Area of Science:

• Environmental Science
• Agricultural Science
• Geophysics

Background:

• Cosmic-ray neutron sensors (CRNSs) offer unique capabilities for soil moisture (SM) monitoring in agriculture.
• Existing methods struggle to monitor small, irrigated fields effectively due to CRNS sensing volume limitations.

Purpose of the Study:

• To assess the feasibility of using CRNSs for continuous SM monitoring in small (~1.2 ha) irrigated apple orchards.
• To develop and validate a correction method for improving CRNS-derived SM accuracy in irrigated areas.

Main Methods:

• Continuous SM monitoring using CRNSs in two irrigated apple orchards.
• Comparison of CRNS-derived SM with a reference SM from a dense sensor network.
• Application of a novel correction method based on neutron transport simulations and data from a non-irrigated site.

Main Results:

• In 2021, CRNSs primarily captured irrigation event timing, with limited accuracy improvements post-calibration.
• In 2022, the proposed correction significantly enhanced CRNS SM accuracy (RMSE reduced from 0.052 to 0.031).
• The corrected method enabled quantitative monitoring of SM dynamics influenced by irrigation.

Conclusions:

• CRNSs, with appropriate corrections, can effectively monitor soil moisture in small irrigated fields.
• This advancement supports the use of CRNSs as a decision support tool for optimizing irrigation management.
• Improved SM monitoring contributes to more efficient water resource utilization in agriculture.