Reclamation of ‘Usar’ Lands in India through Blue-green Algæ

Abstract

WHILE other plants, including crops, fail to grow on the alkaline ‘Usar’ lands of northern India, blue-green algae form a thick stratum on the surface of the soil during the rainy season (from July to September) and during the retreating monsoon (December–January). The most important algae are species of Nostoc (N. commune, N. muscorum, N. punctiforme), Scytonema (S. ocellatum, S. javanicum), Microcoleus (M. chthonoplastes, M. vaginatus), Porphyrosiphon (P. Notarisii), Camptylonema (C. lahorense), and Cylindrospermum (C. licheniforme, C. muscicola). In later stages, when the soil is waterlogged, forms like Aulosira fertilissima, various species of Anabœna, Cylindrospermum gorakhporense and Wollea Bharadwajœ make their appearance. Nostoc commune, which covers many miles, fulfils an especially striking role. The annual addition of organic matter to the soil is of the order of 36.5–59.7 per cent and that of nitrogen, 30–38.4 per cent. Although the nitrogen-fixing capacity of Nostoc commune and of other species is still being investigated in bacteria-free cultures, results so far obtained suggest such fixation, which has already been established in certain forms1–4. The numbers of Azotobacter appear to be considerably reduced in these soils.