Nitrogen (N) deficiency remains a critical constraint in cotton production, reducing photosynthetic efficiency, limiting biomass accumulation, and triggering metabolic shifts that alter the emission of volatile organic compounds (VOCs). These VOCs offer early indication of plant physiological stress, yet existing diagnostic tools such as tissue analysis, gas chromatography, and remote sensing are costly, time-intensive, and not suited for continuous, in-situ monitoring and early stress identification. To address this gap, we developed and evaluated a low-cost dual-sensor VOCs monitoring platform capable of real-time detection of methanol and terpene (specifically α-pinene), two volatiles closely linked to cell wall remodeling and defensive signaling during nutrient stress. The system integrates a metal oxide-nanoparticle methanol sensor and a molecularly imprinted polymer-based α-pinene sensor within a compact enclosure designed for VOCs monitoring and portable field deployment. Cotton plants were grown under two nitrogen regimes (no N and high N), enabling assessment of treatment-dependent emission patterns. Across replicates, N-deficient plants consistently exhibited elevated release of VOCs, with methanol concentrations averaging 17.65 ppm under N stress versus 3.81 ppm under high N, and α-pinene concentrations averaging 1217.49 ppb versus 529.82 ppb, respectively. These trends align with established links between nutrient stress and increased emission of VOCs, confirming that the platform successfully captures physiologically meaningful metabolic responses without reliance on laboratory-based instrumentation. This study demonstrates that low-cost, in-situ VOCs sensing can provide sensitive and non-invasive detection of N stress in cotton. By enabling continuous monitoring of plant metabolic dynamics, the dual-sensor platform offers a scalable and field-deployable tool for integrating VOCs-based diagnostics into precision agriculture, supporting earlier stress detection, improved nutrient management, and more sustainable cotton production.