Growth and Biomass Responses of Cotton to Nitrogen and Molybdenum Applied via Seed, Foliar, and Soil Pathways

This study aimed to evaluate the effects of different molybdenum (Mo) doses and nitrogen (N) levels, applied using various application methods, on the physiological, morphological, and biochemical responses of cotton plants, as well as on soil biochemical properties. Mo (25 and 50 µg kg⁻¹) was applied as seed coating, foliar spraying, and soil drenching, and each Mo dose was combined with two N levels (15 and 30 kg ha⁻¹). Plant growth parameters, stomatal conductance, SPAD values, leaf N content, and biomass were measured. Soil pH, EC, and enzyme activities (catalase, urease, and dehydrogenase) were also analyzed. Combined N-Mo applications significantly improved plant height, root length, leaf area, SPAD values, leaf N content, and both shoot and root biomass. Stomatal conductance decreased, thereby improving water use efficiency. Soil pH decreased while EC increased in all treatments compared to the control. Soil enzyme activities increased markedly across all Mo–N treatments, reflecting enhanced soil biochemical functioning. The Mo–N interaction positively influenced cotton physiology by enhancing photosynthetic performance, root development, nitrogen assimilation, and enzymatic antioxidant activity. Mo applications combined with appropriate N levels improved plant performance and offer a promising strategy for strengthening cotton productivity under diverse soil conditions.