Differentially improved soil microenvironment and seedling growth of Amorpha fruticosa by plastic, sand and straw mulching in a saline wasteland in northwest China

Amorpha fruticosa is often used to revegetate saline wasteland in the YinNan Irrigation Area, northwest China. However, the survival rate of transplanted A. fruticosa seedlings is constrained by its low tolerance to high soil salinity, drought, and low soil temperatures (Tsoil) at the early transplanting stage. This study aimed to evaluate the effects of three different mulches, including plastic mulch (PM), sand mulch (SM) and rice straw mulch (RSM), and control (CK) on the soil microenvironment and A. fruticosa seedling growth. The results indicated that PM (19.1-26.2 °C), followed by SM (18.6-26.1 °C), provided the highest Tsoil at 0-20 cm depth during the whole growing period, while RSM (16.5-21.5 °C) exhibited lower Tsoil than CK (15.8-22.0 °C) at all time except the later growing stage. RSM (7.1%-26.4%) retained soil water most effectively as compared to CK, followed by SM (3.2%-22.5%), and then PM (-0.6%-19.7%). PM (11.4%-18.5%) had the best performance in reduction of ECe at 0-80 cm depth, followed by RSM (10.5%-15.5%), and then SM (3.7%-7.4%). Still, PM exhibited the greatest improvement in soil structure. A. fruticosa seedlings grown in PM achieved the best stand establishment and growth characteristics, in which its root reached to 40-60 cm depth, while the counterparts in RSM showed the poorest performance in three mulching treatments. The results above suggest that PM is a promising strategy to promote the growth of transplanted halophytes in saline wasteland of the YinNan Irrigation Area and other areas with similar ecologies.