Ebrahim Izadi; Mohammad Hassan Rashed Mohassel; Eskandar Zand; Mehdi Nassiri mohalati; Amir Lakzian
Volume 5, Issue 4 , July 2008
Abstract
Atrazine is the most important triazine herbicides with moderately persistence in soil. The objective of this investigation was to study the degradation of atrazine (50 ppm) in two soils different in texture. Experiment was conducted in completely randomized design with factorial arrangement and 3 replications. ...
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Atrazine is the most important triazine herbicides with moderately persistence in soil. The objective of this investigation was to study the degradation of atrazine (50 ppm) in two soils different in texture. Experiment was conducted in completely randomized design with factorial arrangement and 3 replications. Experimental factors included, soil texture(sandy loam and silty clay) and organic manure (0, 2 and 5 percent(w/w)). Soil samples were incubated at 30 oC and dark conditions for 0, 20, 40 and 60 days. At the end of each incubation period, atrazine residue was measured with HPLC. Data was fitted to first order kinetic equation for analysis. Results showed that soil texture and organic manure had significant effects on atrazine degradation rate. Atrazine degradation rate in clay soil with no organic amendment was 1.54 times higher than sandy soil and its half life were 138.6 and 90 days in two soil respectively. Atrazine degradation coefficient increased by 1.14 , 1.8 times in sandy loam soil and by 1.54 , 2.46 times in silty clay soil with 2 percent and 5 percent organic amendment, and the half-life decreased from 138.6, days to 121.57 and 77 days in sandy soil and from 90, days to 58.22 and 38 days in clay soil. It seems that atrazine degredation in silty clay soil is more than sandy loam soil and soil organic manure have an important role in atrazine bioremediation.
Alireza Khodashenas; Alireza Koocheki, Parviz; Parviz Rezvani Moghadam; Amir Lakzian
Volume 5, Issue 3 , April 2008
Abstract
Soil nematodes and bacteria play an important role in soil function. In order to evaluatethe effects of agricultural practices on these organisms, a study was conducted in winter wheat fields of Shirvan, Mashhad and Gonabad, three regions of Khorasan Province. In each region, high and low input fields ...
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Soil nematodes and bacteria play an important role in soil function. In order to evaluatethe effects of agricultural practices on these organisms, a study was conducted in winter wheat fields of Shirvan, Mashhad and Gonabad, three regions of Khorasan Province. In each region, high and low input fields of winter wheat were selected, along with a natural system for comparison. Use of agricultural inputs was the criterion for the selection of low and high input fields in each region. Soil sampling was undertaken on fields and natural systems. Organic matter and the number of nematodes and culturable bacteria in soil samples were measured. The percentage of soil organic matter in all systems was low but, in agro-ecosystems, it was greater than in natural systems. Results showed that organic matter, soil moisture and mean annual temperature has an affect on soil nematodes. The number of nematodes in agro-ecosystems was reater than in natural systems in all three regions. The mean number of soil nematodes in 100g dry weight of soil in the natural systems of Shirvan, Mashhad and Gonabad was 166, 184 and 132, respectively; in the low input systems of Shirvan, Mashhad and Gonabad it was 550, 459 and 1067, respectively and in the high input systems of Shirvan, Mashhad and Gonabad it was 348, 1084 and 485, respectively. Agricultural practices had no negative effects on soil bacterial numbers and the number of soil bacteria increased in some agro-ecosystems. Results showed that agro-ecosystems improved the conditions for nematodes and bacteria and increased the number of these organisms in soil.
