Comparative evaluation of soil moisture measurement methods under crop rotation across three irrigated locations in Kano and Jigawa States, Nigeria

Abstract

Accurate soil moisture measurement is essential for efficient irrigation management and sustainable crop production. This study evaluated the performance of Time Domain Reflectometry (TDR) and a portable moisture meter relative to gravimetric method across three irrigated locations (BUK, HVIP and KRIP) during the rainy and cold dry seasons. Soil moisture data were collected under crop rotation systems, and method performance was assessed using descriptive statistics, root mean square error (RMSE) and coefficient of determination (R²). Results revealed clear seasonal and spatial variability in soil moisture. Gravimetric mean moisture content ranged from 13.9% to 23.7% during the cold dry season and from 16.7% to 21.7% during the rainy season across locations. TDR generally exhibited stronger agreement with gravimetric measurements, with R² values ranging from 0.299 to 0.844 and comparatively lower RMSE values. In contrast, the portable moisture meter showed greater variability, with weaker correlations at certain locations (R² as low as 0.042) and higher prediction errors. The findings indicate that TDR provides more reliable soil moisture estimates under the studied conditions, although sensor performance varied by location and season. Site-specific calibration is therefore recommended to improve the accuracy of electronic soil moisture monitoring tools for irrigation management.

Keywords: Soil water monitoring, Time Domain Reflectometry, Portable moisture meter, Irrigating scheduling, Gravimetric method, Sensor calibration, Seasonal variability, Irrigated agriculture