Abstract:Drought is one of the important factors that limits the growth of trees in the sand of old course of Yellow river area, so the black locust (Robinia pseudoacacia) has been getting attention in the last several years, for its stronger drought resistance and higher survival rate in forestation. Appropriate irrigation methods not only can promote the efficient utilization of local water resource and the growth of plants quickly, but also improve the local ecological environment. This project was held in 2012 and 2013 years, in order to find the optimal irrigation method for black locust young trees. Plants were subjected to three irrigation methods: drip irrigation (DI), furrow irrigation (FI) and hose sprinkler irrigation (HSI). The plot area of each treatment was 1334 m2, and the plant spacing was 3 m×4 m. The results showed that in different hydrological years, the net photosynthetic rate (Pn) and transpiration rate (Tr) of plants under DI both higher than that under HSI, as well as that under HSI than FI. Water use efficiency (WUE) was greatly influenced by the different hydrological years, characterized by early fall, down to the lowest in August and then slowly rose again. There were significant differences in the chlorophyll content (CC) of young trees between different treatments. The CC of plants under DI was highest, followed by which under HSI, and which under FI was minimal. For different ages, there were significant differences in plant height, ground diameter and diameter breast height of young trees between different irrigation methods. In 2011, the plant height, ground diameter and diameter breast height of young trees under DI were 23.4 cm, 0.27 cm and 0.14 cm higher than that under HSI, respectively. In 2012, the plant height, ground diameter and diameter breast height of young trees under DI were 53.7 cm, 0.61 cm and 0.54 cm separately higher than that under HSI. The annual growth of plant height, ground diameter and diameter breast height of young trees under DI were 112.1%, 107.1% and 111.8% of that under HSI, at the same time were 121.8%, 191.8% and 343.6% of that under FI, respectively. The WUE of young trees under different irrigation methods was greatly influenced by the meteorological factors of different years. DI can significantly improve photosynthetic physiological characteristics of black locust sapling, and promote the rapid growth of them.