The Growth and Ion Absorption of Sesbania (<i>Sesbania cannabina)</i> and Hairy Vetch (<i>Vicia villosa</i>) in Saline Soil Under Improvement Measures

Soil salinization is a serious threat to the ecological environment and sustainable agricultural development in the arid regions of northwest China. Optimal soil salinization amelioration methods were eagerly explored under different soil salinity levels. Sesbania and hairy vetch are salt-tolerant plants, and green manure improved the saline environment. In this study, two leguminous halophytic crops, sesbania (<i>Sesbania cannabina</i>) and hairy vetch (<i>Vicia villosa</i>), were planted under different salinity levels, combined with three saline soil improvement measures, namely gravel mulching, manure application, and straw returning. No improvement measures and no salinity treatment was set as the control (CK). This study was conducted to analyze the effects of soil salinization improvement measures on the growth and ion uptake of sesbania and hairy vetch as biological measures under different soil salinity levels. Sesbania under manure application absorbed the highest soil Na⁺ (2.71 g kg⁻¹) and Cl⁻ (2.66 g kg⁻¹) amounts at a soil salinity of 3.2 g kg⁻¹, which was 14.7% and 10.95% higher than under gravel mulching and straw returning, respectively. Na⁺ and Cl⁻ absorption of hairy vetch under manure application reached the highest value of 1.39 g kg⁻¹ and 1.38 g kg⁻¹ at a soil salinity of 1.6 g kg⁻¹, which was 24.46% and 22.31% higher than under gravel mulching and straw returning, respectively. Plant height and stem diameter as well as root growth and development of sesbania and hairy vetch were limited at soil salinities greater than 1.6 g kg⁻¹ and 0.8 g kg⁻¹. Overall, sesbania and hairy vetch effectively absorbed both soil Na⁺ and Cl⁻ under manure application, thus regulating soil salinity and reducing soil salinization. However, soil salinity levels greater than 3.2 g kg⁻¹ and 1.6 g kg⁻¹ not only weakened the ionic absorption capacity but also inhibited the growth and development of sesbania and hairy vetch. This study provides evidence that soil salt ion absorption by sesbania and hairy vetch is promoted effectively, ameliorating soil salinity, under manure application as compared to under gravel mulching and straw returning.