KC, B.Chau, HenryMohssen, Magdy A. W.Cameron, Keith C.Safa, MajeedMcIndoe, IanRutter, H.Lee, MinaPandey, V. P.Schultz, B.Prasad, K.2019-09-292019-09-01https://hdl.handle.net/10182/10976Estimation of soil moisture (SM) is an essential component of effective agricultural water management practices. However, subtle spatial variations in SM across a farm are often overlooked as standard irrigation planning practices in New Zealand generally rely upon SM data derived from a single monitoring location. The current study had two objectives:1) to understand spatio-temporal variability of SM measurements using multiple length Time Domain Reflectometry (TDR) probes and Aquaflex soil moisture sensors (Aquaflex); and (2) coupled TDR and Aquaflex SM readings to improve SM determination in non-weighing lysimeters for improving crop coefficient (Kc) estimation. Twenty non-weighing lysimeters and an Aquaflex located within different soil types were utilized for the study. TDR probes with 200, 500 and 900 mm lengths were installed vertically adjacent to an Aquaflex and the lysimeters for monitoring SM contents. Both TDR and Aquaflex responded to wetting and drying events, with varying SM measurements both vertically and horizontally, due to variations in soil types at different locations. The amplitudes of the daily fluctuations in SM measurements were noticeably higher for the 200 mm TDR and the Aquaflex top sensor, with slightly lower fluctuation for the 500 mm TDR and the Aquaflex bottom sensors. However, the 900 mm TDR showed only minor fluctuations in average SM values indicating that pasture water uptake dominates in the top 500 mm soil profile. These results indicate the importance of multiple lengths TDR to assess root water uptake for improving irrigation management. When the same Aquaflex soil moisture values were used in the water budget equations for data from all lysimeters, the coefficient of determination (R2) for the Kc – h relationship was 0.43, which increased to 0.66 when Aquaflex SM values were adjusted for each lysimeter using corresponding TDR readings. This implies that SM monitoring at different locations in the farm is essential for improving water budget studies aimed at quantifying actual irrigation requirements.ensoil moistureTime Domain ReflectometryAquaflexlysimetercrop coefficientOral Presentation