Lucerne (Medicago sativa L.) is a deep-rooted perennial leguminous forage with high evapo-transpiration rate exceeding the annual precipitation in semi-arid areas of Northwest China. Groundwater might be the potential water sources of lucerne in the area with shallow groundwater table. In this study, stable isotopic compositions of oxygen and hydrogen (δ 18 O and δD) of different water sources and xylem sap were analyzed to determine the seasonal (April, June, July and August) and topographic (three slope positions) variations in water sources for lucerne growing in Ningxia eastern semi-arid area adjacent to Mu Us Desert characterized by shallow groundwater table. IsoSource software was used to calculate the probable contribution of different water sources to the total plant water uptake. Stomatal conductance, stem water potential, carbon isotope discrimination (∆ 13 C) of whole plant were also determined for evaluating the water status of lucerne growing at different slope positions. The results showed that soil water content increased as the elevation decreased. Oxygen compositions of soil water in the 0-40 cm profile fluctuated considerably. Soil water δ 18 O values in deep profile (>3.5 m) were similar to those in groundwater, implying the recharge of groundwater to this soil layer. Highest water utilization rate from deep soil profile (below 350 cm) was recorded for lucerne grown at the slope position 1 (groundwater table depth of 3.5-3.9 m) in April, June and July. The lucernes at slope position 2 (groundwater table depth of 5.8-6.4 m) and slope position 3 (groundwater table depth 7.1-8.3 m) mostly used water from deep soil layers (below 350 cm) during dry period, and turned to use water from superficial soil layer in wet period. Higher yield, ∆ 13 C value of whole plant and stomatal conductance were observed for lucerne grown at the slope position 1 than those at other slope positions. These results indicated that groundwater is a significant water source for transpiration of lucerne grown in Ningxia semi-arid area with shallow groundwater table where lucerne grassland is suggested to be established so as to obtain better yield performance.

Saline-alkali and drought stresses are one of the abiotic stress factors that limit the normal growth and development of plants. In this work, various agronomic indexes including growth physiology and yield attributes were studied under saline-alkali and drought stress treatments. It was found that the limit of plant growth and development caused by drought stress is much higher than that of saline-alkali stress (p < 0.01). Based on the comprehensive evaluation value (D value), under saline-alkali stress condition, 36 maize varieties could be divided into four groups by cluster analysis (CA): High saline-alkali tolerance (3 varieties), medium saline-alkali tolerant(10 varieties), saline-alkali sensitive (19 varieties), high saline-alkali sensitive (4 varieties). In drought stress condition, 36 maize varieties could be divided into five groups by cluster analysis (CA): High drought-tolerance (2 varieties), medium drought-tolerant (14 varieties), low drought-tolerant (15 varieties), drought-sensitive (4 varieties), high drought-sensitive (1 variety). Therefore, this study provides a comprehensive screening of maize varieties under saline-alkali and drought stresses.

To explore the intrinsic relationship of distribution of soil water and agricultural production, this paper, selecting the area of Hai River Basin in Shanxi Province as the studying district, and using the observed data of soil moisture collected in the observation stations in 1961-2005, divided the area into different regional units according to the local planting structure, and identified the main evolution trend in each unit and driving factors of soil moisture change. It shows that the fluctuation of the soil moisture is very similar with that of the antecedent precipitation and the average temperature, and the trend of the soil moisture is the same with that of the precipitation. This research could act as the reference for government in agricultural production management and drought alleviation in Hai River Basin.

Carbon isotope discrimination (Δ) has been proposed as a method for evaluating transpiration efficiency in C3 plants. It is important to study the association of Δ in different parts with the long‐term water use efficiency (WUE). In this paper, plant height, Δ in leaf water soluble carbohydrates (ΔWSC), photosynthetic gas exchange parameters, Δ in aboveground shoot (ΔAGS), stem/leaf weight ratio, aboveground biomass (AGB), evapotranspiration, and WUE were determined in a collection of 10 alfalfa (Medicago sativa L.) genotypes under three water treatments (230 [T1], 460 [T2], and 700 mm irrigation [T3]) in a Ningxia central desert steppe in 2012 and 2013. Significant interactions were found for AGB and WUE among year, treatment, and genotype, whereas significant interactions of year × treatment and year × genotype were only found for ΔAGS but not for ΔWSC. Generally, more water input increased the values of the traits tested except for WUE and single‐leaf intrinsic WUE (Pn/Gs). More irrigated water input resulted in increase in AGB, ΔAGS, and ΔWSC and decrease in Pn/Gs. The greatest WUE was recorded under T2 in 2012. Significant and positive correlations were observed between AGB and ΔAGS (r = 0.588, 0.574, and 0.386 under T1, T2, and T3, respectively). Under T2 and T3, ΔWSC correlated negatively with WUE (r = −0.383 and 0.602, respectively). Ningmu No. 1 was found to have the greatest WUE (18.34 kg ha−1 mm−1) and yield (17.71 Mg ha−1) across water treatments and years. The findings suggest that in the semiarid areas applying irrigation of 230 to 700 mm yr−1, Δ in aboveground shoots or in leaf water‐soluble carbohydrates at the flowering stage seems to be a useful indicators reflecting aboveground biomass and integrated WUE for alfalfa.