Mineral accumulation, growth, and physiological functions in Dalbergia sissoo seedlings irrigated with different effluents.

Present study aimed to observe the mineral accumulation added through effluent application and their influence on physiological functions and growth of Dalbergia sissoo and ultimately to find out suitable combination of industrial and municipal effluent for their utilization in raising tree plantation. Dalbergia sissoo seedlings were irrigated with: canal water (T1); municipal effluent (T2); textile effluent (T3); steel effluent (T4); textile + municipal effluent in 1:1 ratio (T5); steel + municipal effluent in 1:2 ratio (T6); steel + municipal + textile in 1:2:2 ratio (T7); and steel + textile in 1:2 ratio (T8). Mineral accumulation, water relations and gas exchange, growth and biomass production were the recorded observations. Mortality occurred within a day for the seedlings in T4, 45 days in T6, and 60 days in T7 and T8 treatments. This was probably the result of high (P<0.01) Mn, Fe, Cu, and Zn and low N, P, K, Ca, and Mg concentration in different parts of the seedlings in these treatments affecting physiology and growth. Reduction in rate of photosynthesis (Pn) and transpiration (T) to the level of 90%, leaf water potential (LWP) and increased stomatal resistance (R) at two months of age is the indicator of metal toxicity in these treatments. Pn and T were 20 and 17% high in T2 treatment, respectively. However, the reduction was only 21 and 10% in Pn and 18 and 26%, respectively in the seedlings of T3 and T5 than that in T1 treatment. During nine months of observation, the seedlings of T2 and T5 maintained high LWP and same rate of Pn and T but they reduced significantly (P<0.01) in the seedlings of T3 treatment affecting biomass production. This was believed to be due to increase in Na concentration leading to decrease in Mg, Ca, Mn, Fe, Cu and Zn concentration and ratio of Mg/Na and Mg/K and increased ratio of N/Mg and K/Ca + Mg. The enhanced physiological functions in T5 treatment were probably the result of ameliorative effect of municipal effluent through increased mineral status producing biomass equivalent to that in T1 treatment at 10 months of age. The seedlings of T2 attained greater (P<0.01) height and collar diameter and produced 120g seedling(-1) of dry biomass. The study suggests that addition of excess mineral elements leads to metal toxicity that adversely affects physiology and ultimately growth and productivity of tree seedlings. Mixing of effluents to ameliorate the toxic effects could be the better management practices for their use in tree irrigation.