DTPA-extractable micronutrients in soils of southern Bulgaria.

A soil survey in oriental tobacco growing regions in Southern Bulgaria was carried out. One hundred thirty-one soil samples were collected. The main soil characteristics: texture, pH, and humus content were determined, as well as DTPA-extractable iron, manganese, copper, and zinc. All indices investigated show that, despite the predominant monocultural practices of growing oriental tobacco, most of the soils in the studied regions were suitable for this type of tobacco, and for obtaining a good quality of tobacco raw materials. The determined values for DTPA-extractable micronutrients were: iron ranging from 1.42 to 85.55 mg.kg-1, manganese between 7 and 212 mg.kg-1, copper from 0.35 to 12.23 mg.kg-1, and zinc from 0.59 to 11.14 mg.kg-1. The tobacco soils analyzed were characterized by very high (46%) and high content (21%) of mobile forms of iron, as well as very high content of mobile manganese – 73%. Most of the soil samples had a high to a very high content of DTPA-extractable copper – 41% and 21%, respectively. With regard to mobile zinc content, the majority of the soils were characterized by moderate levels – 63%, followed by soils with low content of the element – 23%.