Abstract: To study the effect of different water and nitrogen additions on Jatropha curcas morphological characteristics and water use efficiency under salt stress, a pot experiment was conducted using three levels of salt application (S1: 0 g, S2: 3 g, S3: 6 g), three levels of irrigation (W1: 12.7 mm, W2: 25.4 mm, W3: 38.1 mm) and two levels of nitrogen supply (N1: 0, N2: 0.4 g). The results showed that with the increase of salt application, the Huber values of J. curcas increased significantly, while the total dry mass, seedling index and irrigation water use efficiency decreased significantly. With the increase of irrigation amount, the irrigation water use efficiency decreased significantly. Under salt stress of S2 and S3 treatments, the maximum total dry matter weight and seedling index and the minimum Huber values were found in W2 treatment. On each level of irrigation and salt, the total dry mass of J. curcas saplings, seedling index and irrigation water use efficiency under N treatment (N2) were significantly increased compared to the control, while the Huber value was significantly decreased. Under the intermediate salt stress (S2), compared to W3N2 treatment, the total dry mass, seedling index, and irrigation water use efficiency under W2N2 treatment were respectively significantly increased by 23.0%, 16.6% and 84.6%, the Huber value was significantly decreased by 21.1%, and the irrigation amount was saved by 33.3%. Under the high salt stress condition (S3), compared to W3N2 treatment, the total dry mass, seedling index, and irrigation water use efficiency under W2N2 treatment were respectively increased by 21.9%, 5.6% and 81.7%, the Huber value was significantly decreased by 7.3%, and the irrigation amount was saved by 33.3%. In conclusion, under salt stress, W2N2 was the best treatment for facilitating the growth and morphological characteristics of J. curcas and improving irrigation water use efficiency.

Key words: clipping, nutrient, allometry, biomass allocation, water