Factors Affecting Micronutrient Availability in Calcareous Soils of Southern Iran

The present research was conducted to determine iron, manganese, zinc, and copper availability in 59 calcareous soils of southern Iran; to find relationships between micronutrient availability and some major soil properties; and to predict the micronutrient availability of soils from physiographic position, soil development, and climatic condition. Experiments were done by equilibration of 10g soil sample with 20ml DTPA extractant for 2h. Results indicated that DTPA-extractable Fe, Mn, Zn, and Cu in the soils ranged 2.290.0, 0.615.4, 0.212.2, and 0.65.4mgkg(1), respectively. Generally, Zn deficiency was more widespread, followed by Fe deficiency, but Cu and Mn contents in nearly all soils were sufficient. Micronutrient availability was significantly correlated with some soil properties including pH, organic matter (OM), clay, and cation exchange capacity (CEC). Soil development, physiographic condition, and soil moisture and temperature regimes had significant effects on the micronutrient distribution and availability. The highest amount of micronutrients (except Mn) was found in Histosols, lowland soils, and soils with aquic moisture and mesic temperature regimes. On the other hand, the lowest value was measured for Aridisols and soils with aridic and ustic moisture and hyperthermic temperature regimes. It is concluded that these factors may affect soil properties such as clay, pH, CEC, OM, and calcium carbonate equivalent and thereby micronutrient cycling and distribution in the soils.