Comparative study on growth, yield and carbon content in Pongamia pinnata under water stress and urea supplementation

The growth, yield, and carbon content of eight-month old seedlings of Pongamia pinnata were compared under water and urea supplementation. One set of plants were subjected to water stress condition (WS), whereas the other supplied with 2 g of urea (WS+U) under WS. Both the experimental set ups were exposed to varying treatment levels which include full irrigation (100%, control) followed by 75% (T1), 50% (T2), 25% (T3) and 12.5% (T4). The growth, leaf area and relative water content were maximum under WS when compared to WS+U (p < 0.001). The maximum biomass was produced in the seedlings under WS in control (1.68 g) followed by T1 (1.38 g), T2 (1.53 g), T3 (0.93 g) and T4 (0.73 g). A significant (p < 0.001) reduction in biomass production was observed in WS+U in control (1.28 g), T1 (0.66 g), T2 (1.13 g) and T3 (0.44 g). T4 of WS+U showed similar biomass (0.73 g) as that of T4 of WS. Under WS, the highest biomass allocation was recorded in shoots followed by leaves and roots. Similar trend was observed in WS+U. However, the percentage of allocation was more in the roots of WS+U (27.2%) when compared to WS (22.24 %). The highest amount of carbon content was observed in control plants treated under WS (9.59 g) followed by control plants of WS+U (7.31 g) (p < 0.001). The results of the preliminary study clearly indicated that P. pinnata seedlings were able to cope-up with water stress conditions without urea application and can perform well in 50% water availability and is best suited for the plantation programs in the semi-arid ecosystems.