Abstract
Rhizospheric soils from 13 nodulated legume species were collected at two contrasting savanna sites. Site 1 (S-1) was characterized by 2.6 µg available P g–1 soil, 2.5% Al saturation and a pH of 5.9. Site 2 (S-2) presented a pH of 4.0, 1.0 µg available P g–1 soil and 40% Al saturation. For all legume species and at both sites, acid phosphatase (AP) and dehydrogenase (Dh) activities were significantly higher in rhizospheric than in non-rhizospheric soils. Between sites, the highest significant rhizospheric and non-rhizospheric AP and Dh activities were recorded at S-1, indicating a negative effect of S-2 properties on soil enzymatic activity. Among species, the highest significant AP activity was detected in the rhizosphere of Aeschynomene hystrix at S-1 and Galactia jussieuana and Mimosa pudica at S-2. The Dh activity was significantly higher in the rhizosphere of Calopogonium mucunoides at S-1 and Chamaecrista flexuosa and G. jussieuana in S-2. Dh activity was below detectable values in the rhizosphere of Chamaecrista rotundifolia, C. mucunoides and Phaseolus gracilis at S-2. Glucose amendment (GA) of soils did not enhance AP activity in all rhizospheric and non-rhizospheric S-1 and S-2 soils. In contrast, GA increased the Dh activity in all soils, regardless of the site and legume species. Nevertheless, Dh activity in GA S-2 rhizospheric and non-rhizospheric soils did not reach the values detected in non-amended rhizospheric and non-rhizospheric S-1 soils, respectively. The non-response of AP to glucose amendment can be considered as an indicator of its plant origin.
Published Version
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