Cascante, Marvin D.Marvin D.CascanteWu, Po-HuiPo-HuiWuAsio, Victor B.Victor B.AsioYanai, JuntaJuntaYanaiHseu, Zeng-YeiZeng-YeiHseu2026-01-162026-01-162025-12https://www.scopus.com/pages/publications/105019083057?origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/735438Article number 100208In humid tropical regions, highly weathered soils are widely distributed in most of the developing countries, but are often under-monitored due to the high cost and logistical demands of conventional soil analysis. This systematic review evaluates the application of two cheap NixPro color sensor and KT10 magnetic susceptibility (κ) meter for assessing soil organic carbon (OC) and potentially toxic metals (PTMs) in these soils. Following systematic literature review (SLR) with standard protocols, 1419 records from five major academic databases were screened, with eight empirical studies meeting inclusion criteria. The NixPro color sensor showed more acceptable accuracy for OC prediction in air-dried surface soils (R2 up to 0.80 and achieved a lower RMSE by up to 0.43 %) but declined in moist and heterogeneous conditions. The KT10 κ meter needs to be complemented with other sensors to perform better for OC (SMLR: R2 ≤ 0.67) but reliably detected PTMs, particularly Fe (R2 up to 0.79), due to its sensitivity to magnetic minerals. Both sensors are limited by shallow sensing depth, moisture sensitivity, and poor model transferability. However, their combined use by integrating optical and magnetic data enhances prediction accuracy, especially when paired with machine learning, preprocessing techniques, and sensor fusion. Within the soil security framework, they contribute to all five dimensions: condition, capacity, capital, codification, and connectivity. These sensors offer a scalable and affordable solution for OC and PTM monitoring in resource-constrained tropical environments.trueColor sensorMagnetic susceptibilityProximal sensorsSoil securityjournal article10.1016/j.soisec.2025.1002082-s2.0-105019083057