Effect of blending level of wastewater-fresh water on yield and water use efficiency of three eucalyptus species

Sewage and wastewater are extensive sources of water in the suburbs of many cities of the country. In many parts of the world, treated sewage and wastewater have been successfully used for the irrigation, and many researchers have recognized its benefits. In arid and semi-arid regions have provided good conditions for planting of susceptible species by irrigation with sewage or wastewater for development of green cover and economic exploitation such as wood production. Different eucalyptus species are prepared for planting by irrigation with industrial and household sewage and wastewater, because they have high growth rate and high resistance to biotic and non-biotic stresses and they have high product of wood too. In this regard, a study was conducted by measurements of yield, water use efficiency and some performance indicators in three eucalyptus species that they were planted in drainage lysimeters and they were irrigated with wastewater. This experimental was carried out in Yazd city and greenhouse condition. The research was conducted by factorial experiment in completely randomized design and three replications. Two main treatments were applied: Irrigation with wastewater in three levels (control or without wastewater, 50% water and 50% wastewater, 100% wastewater) and eucalyptus species in three levels (Eucalyptus microtheca, Eucalyptus camaldulensis and Eucalyptus rubida). Each treatment was applied to tow eucalyptus trees or two pot. Annual seedlings planted in drainage lysimeters or pot with 7 liters capacity and they were kept for four months. The soil of the experimental pot was a soil field, with loamy sand texture (76% sand, 20% silt and 4% clay). Wastewater that was used from the wastewater treatment plant of Yazd city was prepared. Wastewater samples were taken during the irrigation period and examined for mineral, bio materials and biological. The chemical and biological analyses of the wastewater were according to standard methods. We studied the influence of irrigation with wastewater on high and diameter of trees, length and wide of leaves, leaf surface, dry mass of leaves, stem and root, specific leaf area, shoot and root dry mass, chlorophyll content and water use efficiency (WUE). The significance of differences between mean values was determined by one-way analysis of variance. Duncan’s multiple range test was used to compare the means. The use of tree plantations for the renovation of wastewater and the simultaneous production of forest produce is now being widely studied. In the condition of wastewater use, the presence of nutrients and organic matter in the wastewater will help to growth and water use efficiency in some plant species. However, reclaimed sewage or wastewater application may create undesirable effects in soils and plants with direct effects on soil suitability for cultivation and water resources availability. The use of wastewater for irrigation of fast growing trees it can be useful. They can use to excessive fertility elements in the wastewater. Irrigation with wastewater can cause increase of number of leaves, length and width of leaves in plants. Increase of leaves number and leaves area will make the absorption of solar energy better and enhance the efficiency of photosynthesis. Irrigation with wastewater can accelerate the flowering of plants and the seeds produced are also healthier. All of this factors can improve water use efficiency in plant. The results show that the potential for utilizing tree plantations in wastewater management. The results showed that there was a significant difference between irrigation treatments at 1% level (p <0.001) on morphological characters such as height and diameter of trees, length, width and leaf area. Specific leaf area, leaf water content, chlorophyll content also increased with increasing of wastewater concentration and we absorbed significant different at 1% level (p <0.001) between of different irrigation treatments. In 100% treatment wastewater, chlorophyll content increased up to three times than control treatment. Shoot dry weight and water use efficiency were increased with increasing of wastewater concentration that in subject can be due to the high levels of fertilizer elements in the wastewater. The results showed that there was significant difference between trees species in a number of morphological and physiological characteristics. By increasing the amount of wastewater concentration, these characteristics improved in three species experimented. The E. camaldulensis had higher growth and water use efficiency than other species. This species has a high growth rate and therefore its can use good wastewater conditions. We suggested that for economic use of wastewater for wood producing, E. camaldulensis than other species in this experiment is suitable and its can be used.