CHANGES IN INORGANIC-N AND CO2 EVOLUTION IN SOIL INDUCED BY L-METHIONINE-SULFOXIMINE

Citation
L. Landi et al., CHANGES IN INORGANIC-N AND CO2 EVOLUTION IN SOIL INDUCED BY L-METHIONINE-SULFOXIMINE, Soil biology & biochemistry, 27(10), 1995, pp. 1345-1351
Citations number
31
Categorie Soggetti
Agriculture Soil Science
Journal title
ISSN journal
00380717
Volume
27
Issue
10
Year of publication
1995
Pages
1345 - 1351
Database
ISI
SICI code
0038-0717(1995)27:10<1345:CIIACE>2.0.ZU;2-L
Abstract
Short-term (up to 48 h) incubation assays were conducted in the presen ce of L-methionine-DL-sulphoximine (MSX), an inhibitor of glutamine sy nthetase, to assess its effect on exchangeable NH4+-N, NO3--N producti on, and CO2 evolution. A sandy-clay-loam (Pistoia) and a sandy (Romola ) soil were moistened and either amended with glucose (200 mu mol gluc ose-C g(-1) soil), glucose + (NH4)(2)SO4 [50 mu mol N g(-1) soil as (N H4)(2)SO4] or left unamended. In the two unamended soils, NH4+-N conce ntration was increased by the highest MSX level (1 mu mol g(-1) soil), while the lowest inhibitor concentration (0.5 mu mol g(-1) soil) had less influence. NH4+-N concentrations were higher with 1 mu mol MSX th an without the inhibitor in the glucose-only-treated Pistoia soil in t he 0-12 h period; thereafter the opposite situation was observed. Prob ably the CO2 evolution increased as a result of inhibitor mineralizati on after 12 h. In the glucose-treated Romola soil both MSX concentrati ons were generally effective in increasing NH4+-N concentrations with respect to the same amendment without the inhibitor. These increases w ere probably due to glutamine synthetase inhibition by MSX and not to the presence of mineralization of the inhibitor because CO2 evolution was only slightly increased at 48 h by MSX. Probably, as a result of t his inhibition, NO3--N was used as an alternative N source in the gluc ose-amended Romola soil. The inhibitor had no significant effect on NH 4+-N concentration when both soils were amended with glucose + (NH4)(2 )SO4 probably because, in the presence of high NH4+-N concentrations, NH3 assimilation occurred more through glutamate dehydrogenase than th rough glutamine synthetase-glutamate synthase enzymes. NO3--N concentr ations were decreased by MSX in the glucose-amended Romola but not in the glucose-amended Pistoia soil.