Zinc bioavailability in semiarid agricultural regions: a soil property-based assessment

Zinc concentration in soils can cause both nutritional deficiency and toxicity in plants. Therefore, both the concentration and availability of Zn, especially in semiarid soils, are critical for agriculture and the environment. This study was carried out to determine the relationship between Zn concentrations and some soil properties in semiarid agricultural areas of Türkiye and to create spatial distribution maps. For this purpose, 1529 surface soil samples (0-30 cm) were taken from the 8687 km² study area and organic matter (OM), calcium carbonate (CaCO₃), pH, available phosphorus (AP), available Zn (AZn) and total Zn (TZn) analyses were carried out. In addition, the Zn availability ratio (Zn-AR) was calculated by the ratio of AZn to TZn concentration. The results indicated that AZn and TZn had high coefficients of variation (> 45%) due to the high heterogeneity of agricultural soils in the study area. Total Zn concentration ranged from 11.74 to 276.45 mg kg^-1 and only 11.8% of the soil samples for TZn were found to exceed the upper continental crust value (67 mg kg^-1), indicating low Zn accumulation in the study area. Similarly, none of the samples for TZn exceeded the maximum permissible concentration in soils. However, AZn deficiency was determined in 55% of the samples. Correlation analysis showed that AZn had significant positive correlations with TZn, AP and OM (p < 0.01). Spatial distribution maps showed that there were some differences in distribution trends of TZn and AZn concentrations. Total Zn concentrations were higher in the northern and northwestern regions of the study area, while AZn concentrations were higher in the western region. The zinc availability ratio (Zn-AR) showed higher values in the western and southeastern regions of the study area. Soil properties influencing the spatial distribution of Zn availability were AZn, AP and OM.