C. R. Babu

Suitability of rhizobia-inoculated wild legumes Argyrolobium flaccidum, Astragalus graveolens, Indigofera gangetica and Lespedeza stenocarpa in providing a vegetational cover in an unreclaimed limestone quarry

Several legume-Rhizobium associations were evaluated by sowing and broadcast of seeds encapsulated with polyacrylamide-entrapped rhizobia (PER) in an opencast limestone quarry in the outer ranges of the Himalaya. Four wild legumes, Lespedeza stenocarpa, Astragalus graveolens, Argyrolobium flaccidum and Indigofera gangetica, with various rhizobial strains, showed higher seedling establishment and survival as well as higher biomass than controls (uninoculated treatments). All legumes established without aftercare. Both A. flaccidum and L. stenocarpa flowered and fruited and the self sown seeds of the experimental stands of the latter species also germinated. Within four years following seeding, many non-legumes colonized the experimental site indicating the amelioration of the derelict habitat. These results give evidence that novel, suitable wild legume-Rhizobium associations are useful in providing a vegetational cover in degraded lands, and that the ecological restoration of limestone-mined sites are possible to some extent by artificial reconstruction. Nodulation in inoculated treatments only suggests that revegetation programmes involving legumes should also include their microsymbionts. Results also suggest that the encapsulation of seeds with PER is a suitable inoculation technology for the revegetation programmes.

New nodulating papilionoid legumes of potential value for revegetation of degraded ecosystems

The north-western Himalayan ranges were surveyed for nodulating legumes that could be useful in tropical afforestation, soil amelioration and reclamation of open cast mine sites, mine spoil heaps, eroded slopes and other denuded ecosystems. Seven new nodulating papilionoid legumes were found and all of them have potential application in revegetation programmes. One new record of a non-nodulating papilionoid member is also reported. The ecological aspects of sampling sites, and habit and root characteristics of the legumes are described. The patterns of nodulation and morphology of nodules are also given. There is a substantial amount of polymorphism in nodule size and shape within a single species as well as among the species; a part of this variation is habitat induced. The nodulation occurs essentially during monsoon season. The remarkable similarity in growth form and nodulation patterns among 7 taxa is the consequence of adaptation to similar ecological conditions.