Determination of Some Soil Properties and Plant Nutrients in Wheat and Alfalfa Growing Areas in the Gevaş (Van) District

The purpose of this study was to evaluate the soil fertility status of wheat and alfalfa fields in the Gevaş district of Van Province. To this end, a total of 48 composite soil samples were collected from 24 fields at depths of 0-30 and 30-60 cm. Soil pH and electrical conductivity (EC) were measured in soil-water suspensions; texture, organic matter, calcium carbonate, P, N, Ca, Mg, K, Na, Fe, Cu, Zn, and Mn contents were determined using analysis methods specific to each parameter. Soil pH values ranged from 7.52 to 8.76, EC values from 0.072 to 0.450 dS m^-1, organic matter contents from 0.58% to 3.17%, and calcium carbonate contents from 3.85% to 31.03%. The observed EC values did not indicate a salinity-related concern under the adopted soil-water suspension measurement conditions; however, no formal salinity class was assigned. Of the soil samples, 81.3% were very low or low in organic matter, 77.1% were classified as highly or very highly calcareous, and 85.4% were in the very low or low class for both available P and Zn. After correcting for the false discovery rate, it was determined that the pH value at a depth of 30-60 cm was significantly higher than that at a depth of 0-30 cm (q=0.023). In contrast, no significant differences were detected between wheat and alfalfa fields for any of the measured variables (q≥0.870). In the Spearman correlation analysis, conducted separately for each depth layer and adjusted using the Benjamini-Hochberg correction, it was determined that organic matter in the 0-30 and 30-60 cm layers showed strong positive correlations with N (ρ=0.928 and 0.979) and P (ρ=0.684 and 0.818), respectively. In both depth layers, no significant correlation was found between P or Zn and pH or CaCO3 (q>0.05). The findings provide a basic dataset regarding soil fertility in wheat and alfalfa fields in the Gevaş district at both the depth and sample levels; they indicate that P, Zn, and organic matter should be prioritized in future soil fertility monitoring studies.