Antecedent soil moisture is a critical driver of hydrological and erosive processes, directly affecting runoff generation and soil loss. An accurate assessment of soil water content (SWC) variability is therefore essential for sustainable land and water management, particularly in arid and semiarid regions. This study explores the use of two emerging nuclear techniques, cosmic ray neutron sensors (CRNS) and proximal gamma ray spectroscopy (PGRS), to monitor SWC at the field scale in a semiarid agricultural field in NE Spain. Changes in soil moisture induced by a 16 mm rainfall event were monitored to evaluate the sensitivity and response of both techniques under dry and wet conditions. A stationary CRNS, located in the centre of the study field, recorded neutron counts at hourly intervals over a two-week period. Complementary PGRS surveys were conducted before and after the rainfall event, including (i) stationary measurements at the four corners of a 20 x 20 m plot, and (ii) mobile stop-and-go measurements along ten transects across the plot, with a spatial resolution of one metre. The results captured clear temporal dynamics in SWC, inferred from neutron count variations, as well as significant differences in 40K (cps) measurements, between dry and wet conditions. These differences were observed when comparing the data from both stationary and mobile surveys conducted before and after the event. The integration of CRNS and PGRS offers complementary insights into scale, temporal dynamics and spatial variability, validating and highlighting the potential of these sensors for soil moisture monitoring. Both techniques demonstrated high sensitivity to variations in soil water content, and their complementary capabilities offer a robust, multi-scale approach with clear applications for precision agriculture and soil conservation.