Abstract

Boron is an essential micronutrient required for plant growth. Soil microorganisms directly influence boron content of soil as maximum boron release corresponds with the highest microbial activity. The objective of this study is to determine the effects of different levels of boron fertilizer on microbial population, microbial respiration and soil enzyme activities in different soil depths in cultivated wheat soils. A randomized block design with three replications was used in this experiment. Field experiments were conducted to evaluate the effects of B levels (0, 1, 3, 6 and 9 kg ha^–1 B) on soil microbial population in cultivated wheat (Triticum vulgare cultivar Dogu-88) soils.  Statistical results showed a significant (p < 0.01) differences between B applications and microbial population and between B applications and microbial respiration in 0 to 30 and 30 to 60 cm soil depths. The highest population of bacteria, fungi, actinomycetes and CO₂-C production were observed at 3 kg ha^-1 B level in different growing periods of the plant and in different soil depths. Urease, phosphatase and dehydrogenase enzyme activities showed a significant (p < 0.01) positive correlation with B applications. The highest urease activity was observed in 6 kg ha^-1 B level and the highest phosphatase and dehydrogenase enzyme activities were observed in 3 kg ha^-1 B level in harvest period in both soil depths.

Key words: Boron management, soil microbial population, urease activity, phosphatase activity, dehydrogenase activity.

Abbreviation

IAA, Indole acetic acid; loss-on-ignition; DTPA,diethylenetriaminepentaacetic acid; SEA, soil extract agar; DPA, dextrose-peptone agar; RBME, rose bengal-malt extract agar; CFU, colony forming units; ODE, oven-dried equivalent; BR, basal respiration; WFP, water-filled porosity; UE, urease enzyme; Alk-P, alkaline phosphatase; pNPP, para-nitrophenyl phosphate; DH,dehydrogenase; TTC, tetrazolium chloride; IAA, indole acetic acid; PBS, phosphate buffered saline; TPF, triphenyl formazone.