Investigations on Non-functioning of Podzolisation in Darjeeling Region of Himalayas

The soils of Darjeeling Himalayan region occurring in the high altitude zones under different coniferous vegetations were studied for their pedogenesis through study of the physico-chemical characteristics, the translocation and deposition of Fe, Al and humus in the B-illuvial horizons. The soils were extremely acid (pH-3.7) to very strongly acid (pH-5.0) in reaction with the organic carbon varying from 26.7 to 58.8 g kg⁻¹ in surface mineral horizon and 3.9 to 44.2 g kg⁻¹ in deeper horizons. The total N of soils varied from 0.01 to 0.41% and the C/N ratio narrowed down with depth. Exchangeable cations were present in the order Ca⁺⁺ > Mg⁺⁺ > K⁺ > Na⁺ reflecting the decreasing energy of adsorption by the complex and increasing mobility of ions. The distribution of dithionite and pyrophosphate extractable Fe and Al showed no zone of marked accumulation of these constituents in any of the six pedons. The same was true in case of humus also. There was limited migration of Fe and Al bound with humus as evidenced by pyrophosphate extraction. However, the ratio of per cent Fep and Alp to per cent clay was less than 0.2 or % (Fe_p + Al_p) to % (Fe_d + Al_d) slightly less than 0.5, thereby confirming the absence of spodic horizon. The study revealed that pedons showed limited downward migration of Fe and Al along with humus and the process of podzolisation was in juvenile stage. The soils were podzolic in nature on account of limited migration of Fe-Al and humus. The soils were classified as Humic Dystrudepts, Humic Pachic Dystrudepts and Typic Haplohumults.