Biological improvement is a sustainable approach for saline–alkali land amelioration and utilization. Echinochloa frumentacea (Roxb.) link is a salt-tolerant gramineous forage, which plays an important role in improving saline–alkali land. The Hetao Ningxia Plain is located in the upper–middle reaches of the Yellow River with a large area of saline–alkali soil, where E. frumentacea has potential applications for improving saline–alkali land. Three experiments were conducted on saline–alkali land in Pingluo County, Ningxia, including soil-leaching experiments in pots as well as monoculture or intercropping experiments involving E. frumentacea in fields. The results showed that: (1) E. frumentacea had a strong leaching ability of Na⁺ and SO₄²⁻ in saline–alkali soil. (2) The planting of E. frumentacea decreased soil pH and total salt; enhanced the available N, P and K; and increased plant height, stem thickness and yields compared with the control. (3) The diversity of soil bacteria and land use efficiency could be improved by the intercropping of E. frumentacea with legume forages. Overall, E. frumentacea is an important pioneer species of biological improvement for the sustainable utilization of secondary saline–alkali land produced by irrigation around the world.

The relationships between carbon isotope discrimination (?) and some morphophysiological traits such as specific leaf dry weight (SLDW), gas exchange parameters, and relative water content (RWC) were studied in a collection of 20 bread wheat cultivars (landraces, released cultivars and advanced lines) in three locations of the Ningxia region (North-East China), i.e. Yinchuan (limited irrigation conditions), Huinong (limited irrigation conditions + salinity) and Guyuan (rain-fed conditions). Relationships between ?, grain yield (GY), and harvest index (HI) and above-ground biomass (AGB) were also analysed. Differences in the measured traits between different locations were highly related to the variation in water availability. Positive correlations were noted between ? and HI and grain yield. Flag leaf ? was positively correlated with RWC at anthesis, and negatively associated with SLDW at grain filling. Significant and negative correlations between ? and dry matter weight per plant at anthesis and biomass at maturity were noted. Leaf temperature (LT) was found to be negatively correlated with ? and gs. The findings suggest that ? may be a useful indicator reflecting wheat yield, harvest index, and water status under irrigation and rain-fed conditions in the Ningxia region.

Carbon isotope discrimination (?) in flag leaf, grain and basal stem, grain yield (GY), and harvest index (HI), were determined in a collection of 20 bread wheat cultivars (landraces, released cultivars and advanced lines) in Yinchuan, located in the central region of the Ningxia region (North-west of China), in 2007 and 2008. In 2008, specific stem DW (SSDW) and carbohydrates, including water-soluble carbohydrate (WSC), non-water-soluble carbohydrates (NWSC) and total non-structural carbohydrate (TNSC) in stem were also measured. Relationships between GY, HI, SSDW, accumulation and mobilisation of stem carbohydrates and ? were analysed. There were positive and significant correlations between grain ?, basal stem ? and GY in 2007 and 2008. A significant and positive correlation between ? and HI was found. In 2008, positive correlations were recorded between stem WSC concentration, SSDW sampled 7 days after anthesis and ?. Carbon isotope discrimination was associated positively with remobilisation efficiency of stem WSC and TNSC. While negative relationships were noted between ? and SSDW at maturity, stronger association was noted between ?, carbohydrate concentration, accumulation and mobilisation efficiencies on stem length basis than on stem DW basis. In conclusion, there is a good relationship between ? and carbohydrate in stem of wheat when irrigation does not meet the crop’s water requirement and wheat experiences a slight water stress after anthesis.

Carbon isotope discrimination (Δ) has been proposed as a method for evaluating transpiration efficiency in C₃plants. 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 (Δ_WSC), photosynthetic gas exchange parameters, Δ in aboveground shoot (Δ_AGS), stem/leaf weight ratio, aboveground biomass (AGB), evapotranspiration, and WUE were determined in a collection of 10 alfalfa (Medicago sativaL.) 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 Δ_AGSbut not for Δ_WSC. Generally, more water input increased the values of the traits tested except for WUE and single‐leaf intrinsic WUE (P_n/G_s). More irrigated water input resulted in increase in AGB, Δ_AGS, and Δ_WSCand decrease inP_n/G_s. The greatest WUE was recorded under T₂in 2012. Significant and positive correlations were observed between AGB and Δ_AGS(r= 0.588, 0.574, and 0.386 under T₁, T₂, and T₃, respectively). Under T₂and T₃, Δ_WSCcorrelated negatively with WUE (r= −0.383 and 0.602, respectively). Ningmu No. 1 was found to have the greatest WUE (18.34 kg ha⁻¹mm⁻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.

Soil salinization is detrimental to crop growth, agricultural yields, and environmental protection. Echinochloa frumentacea (Roxb.) Link is a pioneer species for the alteration of saline–alkali lands. In this paper, we examined the effects of intercropping between E. frumentacea and leguminous forages on saline land improvement in the saline–alkali soil of the Hetao-Ningxia Plain, China. We found that intercropping increased the diversity and richness of the arbuscular mycorrhizal fungi (AMF) community in the rhizosphere soil of E. frumentacea. Glomus was the dominant genus in the saline–alkali soil of the Hetao-Ningxia Plain, where Glomeraceae, VTX00067, VTX000193, and VTX000165 were the dominant species. Intercropping improved the activities of soil urease, sucrase, alkaline phosphatase, and catalase. The hay yields of E. frumentacea were correlated positively with soil enzyme activities, Chao1 index, and ACE index, and negatively with total water-soluble salt content. Together, intercropping between E. frumentacea and leguminous forages enhances AMF diversity and soil enzyme activities, which provides an agricultural practice for improving sustainability of the agro-ecosystem in saline–alkali areas.