Variation in the Properties of the Arable Horizons of Chernozems in the Moderately Arid Steppes of the Kostanay Region, Republic of Kazakhstan

The spatial variation in acidity, organic matter, nitrate nitrogen, and mobile forms of phosphorus and potassium in the arable horizon (0–20 cm) of southern chernozems was studied in the Fedorovsky, Denisovsky, Altynsarin, and Karasu districts of the Kostanay region. The arable horizons were predominantly alkaline (pH (H2O) 7.6–8.0) to strongly alkaline (pH (H2O) above 8.0); organic matter content was low (2–4%); nitrate nitrogen (N-NO3) and mobile P2O5 were very low (less than 10 mg/kg), and mobile K2O was high (400–700 mg/kg). The spatial distributions of pH (H2O), organic matter, and K2O were normal, whereas those of N-NO3 and P2O5 were lognormal. Hierarchical analysis of variance showed that variability within plots of 0.5 km2 accounted for a significant proportion of the total variance of the soil properties. Variation between fields (1–3 km2) within farms (10–40 km2) was most pronounced for nitrate nitrogen and mobile phosphorus, whereas for pH (H2O) and mobile potassium the differences between districts (1000–7500 km2) prevailed. Significant correlations between the soil properties and their dependence on the latitude and longitude of the sampling points were revealed in the moderately arid steppes of the Kostanay region.