Micronutrient and Sulfur Status of Typical Sierozems Formed on Neogene Deposits and Cotton Response to Fertilization

Micronutrient availability in carbonate-rich sierozems of dissected foothill landscapes is controlled by both vertical profile differentiation and lateral redistribution of soil material along erosion-deposition catenas. This study aimed to characterize the radial and lateral distribution of Cu, Zn, Mn, B, and S in non-eroded upper-slope, moderately eroded midslope, and depositional footslope typical sierozems formed on Neogene deposits and to evaluate cotton responses to mineral, sulfur-containing, micronutrient, and organomineral fertilization. Total and mobile forms of the elements were determined in successive soil horizons, whereas cotton biomass, element uptake, and raw cotton yield were assessed in vegetation and lysimetric experiments. Soil pH ranged from 7.4 to 7.8, while CO2-carbonate contents across the studied profiles ranged from 6.21 to 9.55%, corresponding to approximately 14.1–21.7% CaCO3 equivalent. In the upper horizons, mobile Zn concentrations were 0.8–1.0, 0.3–0.6, and 1.0–1.2 mg kg–1, while mobile S concentrations were 7.1–8.0, 4.9–6.0, and 8.9–9.2 mg kg–1 in the non-eroded, moderately eroded, and depositional soils, respectively. For the mobile forms, the upper-horizon-to-parent-material concentration ratios were 3.0–3.5 for Cu, 2.3–2.6 for Zn, 1.5–1.6 for Mn, 1.9–2.4 for B, and 1.5–1.8 for S. Among the reported mobile forms, the moderately eroded midslope soil had the lowest upper-horizon concentrations of Zn, Mn, B, and S, whereas the depositional soil generally showed higher values. This pattern may reflect the combined influence of downslope redistribution, parent-material heterogeneity, soil texture, and carbonate distribution. Cotton S concentration increased from 0.13% in the control to 0.25–0.27% under the application of 20–40 kg S ha–1. Raw cotton yield increased numerically from 16.9 to 52.9 g plant–1 in the non-eroded soil and from 14.7 to 51.0 g plant–1 in the moderately eroded soil, with the highest values recorded under NPK + manure. The study is limited by the absence of replicate-level data for statistical testing and by the inability to separate the effects of erosion from differences in parent material and management history.