Abstract:

Soil moisture deficit is a key factor restricting agricultural production and establishment of grassland vegetation in Ningxia， China. The identification of drought-resistant pasture species is of great significance to the region’s agricultural and pastoral production and ecological restoration of grassland vegetation. This research evaluated the growth performance and feed quality of seven Poaceous forages to determine drought resistance in arid areas. The grass species and lines evaluated were： Agropyron mongolicum-Ningxia， Agropyron mongolicum-Inner Mongolia， Agropyron desertorum， Agropyron cristatum， Agropyron trachycaulum， Bouteloua gracilis and Elymus sibiricus. The trade-off between seven agronomic traits （including green leaf number and plant height） and soil water content was quantitatively analyzed， using the root mean square deviation and soil water content as model variables. In this way， the soil water content needed to maintain normal plant growth was determined by quantile regression. A multivariate score derived from physiological indexes of plants under drought stress was used to evaluate the drought resistance of the tested forages. It was found that： 1） The higher the degree of drought stress， the greater the negative impact on the chlorophyll and plant height of forage； 2） The degree of tolerance to drought stress and the response range differed for different grass forages. In particular， the soil water content thresholds for adequate green leaf number in A. trachycaulum and B.gracilis were 9.1% and 9.7%， respectively. The soil water contents for which maintaining normal plant height growth attained the threshold for A. trachycaulum， B. gracilis and A. mongolicum-Ningxia were， respectively， 4.6%， 5.6% and 13.0%. The quantile regression models of other forages failed to pass the significance test. 3） Through evaluation and analysis of the seven physiological indexes， the drought resistance of the seven tested perennial grasses was ranked as follows： A. mongolicum-Ningxia>B. gracilis>A. trachycaulum>A. mongolicum-Inner Mongolia>A. desertorum>A. cristatum>E. sibiricus. Based on their multivariate score for drought resistance traits and tolerance threshold to soil moisture deficit， A. trachycaulum and B. gracilis were selected as recommended forages in moderately arid areas.

Key words: drought-resistant pasture, soil water content, response threshold, physiological index