The effect of Delijan reclaimed wastewater and well water on soil carbon sequestration and growth of hard wood trees

The reclaimed wastewater can be used as tool for compensation of water scarcity and control and reduce harvesting from deep and semi deep wells. Investigation on the effect of irrigation with Delijan reclaimed wastewater and well water for 5 years on soil carbon sequestration and growth of 7 hard woods trees species was the purpose of this study.

In the present study, seedlings were cultivated after ground preparing as a group at 3 × 3 m. spacing based on a randomized complete block design with three replications in March 2011. For determination of the effect irrigation type on soil carbon sequestration, in the fifth year, soil sampling was taken by drilling at soil five profiles from tree consecutive depths (0-30, 30-60 and 60-90 cm) under the crown of the trees. In evaluating the growth of hardwood tree species at the end of the fifth year, characteristics of height, collar diameter, canopy diameter, canopy cover area, percentage of survival and percentage of vitality were measured.

The results of the study on the amount of soil carbon sequestration in different depths showed that irrigation with reclaimed wastewater increased the organic carbon content of the soil, which it’s the highest content is in the depth of 60-90 cm of soil. Among the species planted, in irrigation with well water, the highest height was in species of Ailanthus altissima and collar diameter, canopy diameter, canopy cover area, and percentage of vitality were in species of Melia azedarach. In irrigation with reclaimed wastewater, there were the highest height in species of Robinia pseudoacacia, diameter of collar in species of Elaeagnus angustifolia, canopy cover diameter and canopy cover area in species of M. azedarach and vitality in two species of M. azedarach and Celtis australis. There were the lowest percentage of survival in species of Acer negundo in both of irrigation system.

The main effect of irrigation type did not show significant statistical difference. Species of A. negundo was more susceptible to water supply and soil conditions and was not suitable for planting in this area. Species of M. azedarach is the most consistent in the present study.