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Effect of Paraquat on Growth of Diazotrophic Strain Stenotrophomonas Maltophila in Flooded Soil

Radziah Othman
Associate Professor
Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia

Umme Aminun Naher
Principal Scientific Officer
Soil Science Division, BRRI Gazipur

Abstract/ Executive Summary:

A laboratory study was conducted at Universiti Putra Malaysia to determine the effect of commonly used herbicide Paraquat (full dose, half dose and double of the full dose) on growth of locally isolated diazotroph from paddy soil, Stenotrophomonas maltophila (Sb16), its nitrogen fixation and indoleacetic acid production in flooded soil. Recommended dose of Paraquat showed no significant effect on Sb16 population, nitrogen accumulation and indoleacetic acid (IAA) production. Populations of Sb16 in soil and soil standing water, fluctuated significantly during six weeks of sampling time. The pH of soil standing water positively correlated with the nitrogen content (2.0 %). Double doses of Paraquat significantly reduced indoleacetic acid production both in soil and standing water. Application of Paraquat at recommended dose had no adverse effect on growth and activity of diazotrophic strain Sb16 isolated from tropical soil of Malaysia.

Keywords: Diazotroph, Indoleacetic acid, Total nitrogen, Rice soil, Paraquat

Location: Universiti Putra Malaysia, Malaysia

Start Date: 01-01-2012

End Date: 30-06-2012

Program Area: Crop-Soil-Water Management

Commodity: Bio fertilizer

Objectives:

to determine the effect of different levels of Paraquat on population and phytohormone production of N?-fixing bacteria isolated from paddy soil (Inceptisol, Fluvaquentic or Typic Endoaquepts) of Malaysia.

Methodology:

This study was conducted at Soil Microbiology laboratory, Universiti Putra Malaysia, Malaysia. The diazotrophic strain used in this study was Stenotrophomonas maltophila (Sb16) isolated by Naher et al. (2009) from Tanjong Karang, rice (O. sativa L) growing area, Selangor, Malaysia. This strain have potential to fix atmospheric nitrogen (43% of rice requirement) and produce indoleacetic acid. Paraquat (dichloride-13 % w/w, perawis lengal-87 % w/w) was applied as half of the recommended rate (D1/2), recommended rate (D), and double recommended rate (D2). The study was conducted as factorial complete randomized design and the two factors were 6 incubation time and 3 doses of Paraquat. Alluvial rice soil (Inceptisol) was air dried, sieved (4 mm) and sterilized using autoclave. About 100 g of soil was placed in 250 ml conical flasks and paraquat was applied according to the treatments. Each flask was flooded with distilled water and maintained a standing water of 2.5 cm throughout the incubation period. Nitrogen fixing bacteria Sb16 which have acetylene reduction assay (ARA) of 1.4 x 10-7 μmol C2H4-1 cfu-1h-1 grown overnight in N free broth. Exactly, 10⁶ cfu ml^-1 of live cell were inoculated to each treatment. Inoculated bacterial population was determined using spread plate count method at weekly intervals for 6 weeks. Bacterial population was determined using N free media. For standing soil water, 1 ml of water sample was taken and population determined following the same procedure. The soil and pH of standing water pH (1:1) was determined at every sampling time. Kjeldahl method was used to determine total nitrogen from both soil and soil water. Indoleacetic acid concentration in soil was determined according to Sarwar et al. (1992). The experiment was laid out in a factorial completely randomized design with 4 replications. The data were analyzed using SAS (9.1 version) and treatment means were compared using Tukey’s test (P≤0.05).

Source of Information: African Journal of Microbiology Research. 6 (23):4939-4944.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The study showed that application of recommended rate of Paraquat had no adverse effect on population, nitrogen fixation and indoleacetic acid production (IAA) of Stenotrophomonas maltophila (Sb16). However, double dose of Paraquat decreased nitrogen fixation activity and IAA production.

Knowledge Management: Journal