Soil salinization is a major problem in irrigated agriculture. A field study was conducted in the Sariosiyo district in the Surkhandarya region of southeast Uzbekistan to evaluate soil nitrogenase activity and nitrogen-fixing bacteria populations in saline serozem soils under wheat, maize, and alfalfa, as well as from adjacent fallow land. | Turk J Biol 32 (2008) 85-90 © TÜB‹TAK Cropping Effects on Microbial Population and Nitrogenase Activity in Saline Arid Soil Dilfuza EGAMBERDIEVA, Zulfiya KUCHAROVA Department of Biotechnology and Microbiology, National University of Uzbekistan, Vuzgorodok, Tashkent 100174 - UZBEKISTAN Received: Abstract: Soil salinization is a major problem in irrigated agriculture. A field study was conducted in the Sariosiyo district in the Surkhandarya region of southeast Uzbekistan to evaluate soil nitrogenase activity and nitrogen-fixing bacteria populations in saline serozem soils under wheat, maize, and alfalfa, as well as from adjacent fallow land. Composite soil samples were randomly collected from depths of 0-10, 10-20, and 20-30 cm in autumn, winter, spring, and summer, which were then 2-mm sieved and subjected to selected microbial population analysis and enzymatic studies. The results showed that alfalfa contributed both to high nitrogenase activity and to a large nitrogen-fixing bacteria population. The fallow soil had a lower nitrogenase activity and bacterial population. The nitrogenase activity was higher in the soil from a depth of 10-20 cm in spring. Results suggest that cropping, especially suitable crop rotation, is essential to support greater microbial biomass population and nitrogenase activity for improving the biological fertility of saline and nitrogen-poor calcareous arid soils. Key Words: Irrigated agriculture, salinity, season, soil depth, nitrogenase activity, microbial population Tuzlu ve Kurak Topraklarda Mikrobiyal Populasyon ve Nitrojenaz Aktivitesi Üzerine Tar›m›n Etkisi Özet: Toprak tuzlulu¤u sulu tar›mda en önemli problemdir. Özbekistan’›n güney do¤usunda Surkhandarya bölgesinde Sariosiyo’da bu¤day, m›s›r, alfalfa tar›m› yap›lan serozem topraklarda nitrojenaz aktivitesi, nitrojeni fikse eden bakteri populasyonunu araflt›ran bir arazi çal›flmas› yap›lm›flt›r. Kompozit toprak örnekleri 0-10, 10-20, ve 20-30 cm derinlikte sonbahar, .
