pH Tolerance of Sal (Shorea robusta) Seedlings

Pot experiments using soil-sand medium and water culture solution were conducted in the laboratory to determine the range of pH tolerated by sal seedlings for their growth. The results obtained in the soil-sand medium indicated that sal seedlings grow freely and luxuriantly in the range of pH 5.6-7.8 and fail to survive beyond this range. However, owing to the large quantities of acid and alkali needed to accomplish the extreme pH values in the soil medium, on the acidic and alkaline side, it is not safe to define exactly the critical pH values unless confirmed by further experiments. It is suggested that while assessing the precise role of pH values in governing the growth and distribution of sal in the field a great consideration should also be given to other soil factors like cation exchange capacity, cationic equilibrium, organic matter content, available nutrients, moisture regime, texture, etc. In water culture experiment, the profuse development of white slimy growth on the ischolar_main system resulted in the early death of sal seedlings in spite of treating the ischolar_mains with copper sulphate solution and providing adequate aeration throughout. It is, therefore, concluded that sal seedlings are particularly susceptible to slimy growth under excessive water accumulation, as in the case during peak rainy season (Aug. & Sept.), and this extraneous growth is primarily responsible for destroying ischolar_main hairs and thus causing the death of plants. Carbon dioxide accumulation in soil water is only the secondary cause in the process of such mortality.