Response of dry matter and water use efficiency of alfalfa to water and salinity stress in arid and semiarid regions of Northwest China

As the planting acreage has been expanding on salinized soils of arid and semiarid regions of Northwest China, it is important to understand how alfalfa dry matter (DM) and water use efficiency (WUE) respond to soil salinity stress under deficit irrigation. A test pit experiment with a total of twelve treatments combing three water levels of full (W1), medium (W2), and low irrigation (W3) and four salinity levels was conducted in Northwest China in 2016 and 2017. For salinity treatments, salt addition rate was 0, 2, 4, and 6 & permil; of 0-60 cm soil dry weight, referred as S0 - S3, respectively. Soil water content (SWC) and soil electrical conductivity (ECe) were measured regularly during the growth period, and DM and WUE for cut 2 and cut 3 of each year were presented. For alfalfa DM and WUE for both individual cut and the combination of the two cuts each year, both water and salinity stress were found significant while the interaction was consistently insignificant. Dry matter and WUE decreased continuously with less irrigation water and greater salinity stress in both years. On average, DM reduction was about 20%, 30%, and 58%, for S1, S2, and S3, respectively, relative to S0, while the reduction was 21% and 34% for W2 and W2, relative to W1. Simultaneous water and salinity stress had more negative effects on DM and WUE than a single stress. Total alfalfa DM was found linearly correlated with average ECe over the growth period with R2 larger than 0.8, suggesting that ECe is an effective predictor for estimating alfalfa yield on saline soils in the area. The results are valuable in evaluating the productivity of saline soils in the region, and the performance of some remedy measures.

Automated summary

The study found that alfalfa dry matter and water use efficiency decreased significantly when under water and salinity stress, with simultaneous stress having a more severe impact. Soil electrical conductivity is an effective indicator for predicting alfalfa yield on saline soils.