Growth and biomass production in Azadirachta indica seedlings in response to nutrients (N and P) and moisture stress

Production of quality seedlings is an important aspect of successful tree p lanting. No information is available on the effect of nutrients and water o n the growth and development of the seedlings of neem (Azadirachta indica A . Juss), an important component of many tropical agroforestry systems. In a n experiment in central India, the growth and nutrient-use efficiency of ne em seedlings grown at various levels of light, nutrients (N and P), and wat er stress were determined. Seedlings were given light (diffused and complet e) and nutrient (N and P) treatments comprising either high N-high P, high N-low P, low N-high P, or low N-low P. Seedlings grown in complete light (8 00 mu mol/m(2)/s) had four times more biomass than those grown in diffused light (200 mu mol/m(2)/s). Significant increase in seedling biomass was obs erved with nitrogen application, while phosphorus had no effect on biomass. Leaves contributed maximum biomass, followed by roots and stem. Nutrient u se efficiency decreased with an increase in the supply of nutrients. In ano ther experiment, containerized and bare-root seedlings were subjected to fi ve watering treatments, viz., watering twice a week, watering weekly, water ing every alternate week, watering every third week, and natural precipitat ion. Plant moisture stress affected both growth and survival of neem seedli ngs. Only 50 per cent of seedlings survived in severe drought treatment (no . 4) whereas 90 to 95 per cent seedlings showed growth in all other treatme nts. Plant moisture stress in severe drought treatment averaged -21 bar whi le in other treatments it ranged from -9 to -12 bar. Shoot- root ratio was high in bare-root seedlings as compared to containerized seedlings. Contain erized seedlings had shown better endurance against drought than the bare-r oot seedlings. The results suggest that neem seedlings adjust their nutrien t use efficiency and can be grown even under limited available resources. I t is also inferred that the species can tolerate soil resource depletion ca used by competitor species.