Nutrient management in calcareous soils under semi-arid environments: effects on cotton productivity and soil health

In calcareous and alkaline soils, the availability of essential nutrients is limited, leading to substantial reductions in both yield and fiber quality in cotton (Gossypium hirsutum L.) production. This study investigated the effects of different combinations of sulfur (S), zinc sulfate (ZnSO₄), potassium sulfate (K₂SO₄), and urea on cotton yield and soil health in a two-year field experiment conducted under the conditions of the Şanlıurfa–Harran (Türkiye) Plain during the 2023–2024 growing seasons. Six different treatments were applied via soil and foliar application methods, and yield parameters (seed cotton yield, boll number, SPAD value), soil properties (pH, EC, CaCO₃), and enzyme activities (catalase, urease, dehydrogenase) were evaluated. Results indicated that the combined application of elemental sulfur + ZnSO₄ + K₂SO₄ + urea increased seed cotton yield by up to 32.9% compared with the control plots, while reducing soil pH by 4.3% and CaCO₃ content by 20.8%. Moreover, catalase and urease activities exhibited changes of up to 29.7% and 15.3%, respectively. Principal Component Analysis (PCA), Partial Least Squares (PLS), and Soil Health Index (SHI) assessments revealed strong positive associations between yield, SPAD values, and microbial enzyme activities. These findings demonstrate that the integrated use of sulfur and micronutrients not only enhance cotton productivity but also contributes to improving overall soil health.