Research on Cereal Nitrogen Fixation at ICRISAT

Wani, S P (1986) Research on Cereal Nitrogen Fixation at ICRISAT. In: Cereal nitrogen fixation. Proceedings of the Working Group Meeting, 9-12 Oct 1984, ICRISAT Center, Patancheru, India.

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Abstract

The acetylene-reduction assay for nitrogenase activity has shown that the roots ofsorghum and pearl millet stimulate N,jixation. A soil-core assay usedfor measuring nitrogenase activity of field-grown plants showed large planHo-plant variability. An improved core assay (planted core assay) developed at ICRISAT Center showed higher activity than that recorded by regular core assay. In greenhouse assay methods plants with shoots sustained higher activity than the ones whose tops were cut before the assay. Nitrogen(Jse activity varied throughout the day, as well as over the season. Activity was maximum at the lateflowering or early grain:/illing stage and it was related to the ontogenetic development of the plant. Activity was favored in moist, warm (ca 35° C) soil and decreased with high levels of fertilizer N. Genotypic variation in sorghum and pearl millet lines for stimulating rhizospheric nitrogenase activity was observed. Out of 184 pearl millet lines tested, 18 lines stimulated high nitrogenase activity (> 460 nmol C2H4 h-I 15 em diam core-I) in the rhizosphere. Two lines, Gam 73 and J 1407, were consistently active over several seasons. Similarly, 28 of 334 sorghum lines tested had high nitrogenase activity (>460 nmol C2H4 h-I 15 cm diam core-I). At ICRISAT Center, pot-culture experiments with sorghum and pearl millet grown in a low-fertility Alflsol, or in unsterilized washed vermiculite, showed substantial positive balances for N. Long-term N balance studies .in, 'the field with sorghum and pearl millet cultivars are continuing. Using IS N2 it has been shown that 10-days-old sorghum seedlingsfix N2 in the rhizosphere, and part of it is taken up by the plant within 3 days after exposure. The 15 N isotope dilution technz'que has been evaluated for studying genotypic variation in sorghum and pearl millet cultivars for N2 fixation. Many different kinds of bacteria closely associated with the roots of sorghum and pearl millet plants show nitrogenase activity. Responses to inoculation in terms of increased dry-matter production and N uptake have been observed in pot experiments with sorghum and pearl millet grown in Alfisols and vermiculite. In five out of nine field trials with pearl millet cultivars, inoculations with N2:/ixing bacteria significantly increased the grain and plant dry-matter yields in all the cultivars.

Item Type:	Conference or Workshop Item (Paper)
Divisions:	UNSPECIFIED
CRP:	UNSPECIFIED
Subjects:	Mandate crops > Millets Mandate crops > Sorghum Others > Soil Science
Depositing User:	Mr Sanat Kumar Behera
Date Deposited:	05 Nov 2011 05:01
Last Modified:	05 Nov 2011 05:01
URI:	http://oar.icrisat.org/id/eprint/3675
Acknowledgement:	UNSPECIFIED
Links:	Author

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