Impact of Some Pesticides on Total Counts of Soil Non-Symbiotic Nitrogen-Fixing Bacteria, Particularly Azotobacter sp

Volume 18 , Issue 1 , March 2016 , Pages 99-126

Authors

¹ Department of Environmental Science, College of Science, University of Salahaddin, Kurdistan Region, Iraq

² Department of Biology, College of Science, University of Salahaddin, Kurdistan Region, Iraq

A pot experiment was conducted to evaluate the effect of glyphosate herbicide (n-

phosphonomethyl glycine), mancozeb fungicide ([[1,2-ethanediylbis- [carbamodithioato]]

(2-)] manganese mixture with [[1,2-ethanediylbis- [carbamodithioato]]-(2- )] zinc) and

diazinon insecticide (O, O-diethyl O-[6- methyl-2- (1-methylethyl)- 4-pyrimidynyl]), three

soil orders and two soil moisture contents (50% and 100% of field capacity) and their

combinations on soil total non-symbiotic nitrogen-fixing bacteria particularly

Azotobacter sp. counts. This experiment last for two months from the 6 th of Jun until the

8 th of August 2011 with five sampling periods at biweekly intervals. Factorial experiment

(4×3×2) with Completely Randomized Design (CRD) and three replications was used

and the means were compared using Revised Least Significant Differences (R.LSD) at

the level of significant of 0.05. Significant results were obtained at the last two scheduled

period’s sampling of 4 th and 5 th , and the results showed that: Mancozeb fungicide

decreased total Azotobacter sp.; Diazinon insecticide decreased both total non-symbiotic

nitrogen-fixing bacteria and total Azotobacter sp.; Agholan soil (order Entisols) showed

the greatest increase in soil total non-symbiotic nitrogen-fixing bacteria. 50% soil

moisture content revealed the greatest reduction total Azotobacter sp. while, 100% soil

moisture content showed the greatest increase in soil total Azotobacter sp. count. The

combinations among: glyphosate, Agholan soil and 100% moisture combination showed

the greatest reduction in total non-symbiotic nitrogen-fixing bacteria and total

Azotobacter sp.

Statistics