Nitrogen fixation (C₂H₂reduction) in the rice rhizosphere soil as influenced by pesticides and methods of their application

Abstract

The effect of pesticides on nitrogenase activity in rhizosphere soil from rice fields was investigated. The differential response of insecticides on nitrogenase depended on the method of field application. Results also showed that the differential response to the pesticides of. specific groups of nitrogen-fixing micro-organisms depended upon the method of application.Soil incorporation of carbofuran stimulated the rhizosphere nitrogenase, while endosulfan and hexachlorocyclohexane inhibited it. Carbofuran and hexachlorocyclohexane stimulated nitrogenase when applied to the standing water. Seedling root dips of isofenphos stimulated nitrogenase, while endosulfan, BPMC and carbaryl showed a variable effect. Quinalphos inhibited nitrogenase irrespective of method of application.

Production and Metabolism of Indole Acetic Acid in Root Nodules and Symbiont (Rhizobium undicola) Isolated from Root Nodule of Aquatic Medicinal LegumeNeptunia oleraceaLour.

“…The N37 strain and Rhizobium sp. P2 strain (HNO56031) (as positive control) are grown in nitrogen-free CS7 medium [35] and E. coli (as negative control) is grown in nutrient agar medium; the nitrogenase was estimated by acetylene reduction test using gas chromatography (VARIAN CP3800) fitted with flame ionization detector (FID) [36]. Extracellular polysaccharide of the cell-free supernatant was estimated by phenolsulphuric acid method, following Dubois et al [37].…”

Studies on Non-Symbiotic Diazotrophic Bacterial Populations of Coastal Arable Saline Soils of India

“…After visible growth was observed, cotton plugs were aseptically exchanged with rubber stoppers and the headspace air was replaced with 10% (by volume) of high purity C 2 H 2 gas by hypodermic syringe. The C 2 H 4 production was measured after 72 h incubation of the tubes in dark at 29°C [14]. Tubes without C 2 H 2 served as control.…”

Nitrogen fixation as influenced by pesticides and rice straw in paddy soils

“…Similarly, the addition of rice straw and soil type also affected N 2 fixation. In rice cultivation water management and water requirement play an important role and pesticides applied in these conditions can affect the non-target processes of importance to soil fertility (Rao et al 1983). Further evidence was provided for a uniform stimulatory effect of carbofuran irrespective of soil type, water regime, organic amendment and pesticide combination at least in the three soils tested.…”

“…The influence of several pesticides on growth and N 2 fixation was investigated in pure cultures (Mackenzie & MacRae, 1972;Charyulu & Rao, 1978;Tu, 1978). Few data are available on the effect of pesticides on N 2 fixation in paddy soils although these are employed extensively in practice ' (Nayak & Rao, 1980, 1982Rao, Pasalu & Rao, 1983). In view of the positive effect of organic matter in improving fertility status and N 2 fixation, application of organic matter to paddy soils has been recommended.…”