Does application of cement kiln exhausts affect root nodule biochemistry and soil N-fixing microbes?

The research work carried out on cement exhausts centers mostly around vegetation and crop productivity (1-3) with little or no work on root nodulation. Soil plus foliar application of exhaust dusts did not affect soil/nodule rhizobial population, nodule initiation, and possible N-fixing capacity in Cajanus cajan, Vigna radiata, Vigna mungo, Vigna catjung, and Glycine max. The nodular biochemistry was investigated in detail. The heme protein leghemoglobin was higher compared to the control. The levels of intermediary N compounds like total ureides of the nodules, which may serve as indirect evidence of symbiotic N fixation, were higher in the treated plants. There were also increments in free proline, free amino acids, soluble proteins, soluble starch, soluble sugars, total nitrogen, and phenols in the treated plants. The levels of total nitrates, soluble sucrose, and soluble SH compounds of the nodule of the control and treated plants did not show a significant difference. The activities of ascorbate peroxidase, catalase, glutathione reductase, and Superoxide dismutase were significantly higher, possibly indicating their role in alleviation of HO and O damage by the exhausts. Enzymes like nitrate reductase, nitrite reductase, and glutamine synthetase, and also the activities of acid and alkaline phosphatases were not affected. The presence of beneficial soil microbes like Azotobacter, Azospirillum, and mycorrhizae was not affected at all. [ABSTRACT FROM AUTHOR]