Biochar amendment ameliorates soil properties and promotes Miscanthus growth in a coastal saline-alkali soil

Biochar amendment has been proposed to be as a promising means to improve soil properties and enhance plant productivity in different types of soils. However, biochar application in the improvement of plant productivity in saline-alkali soils has received less attention. In the present study, we carried out a pot experiment in greenhouse to evaluate the effect of biochar amendment on the growth of Miscanthus lutarioriparius, a promising bioenergy crop, in a coastal saline-alkali soil during a 92-day growth period. The biochar was added at 0, 1.0%, 2.0%, 2.5%, 5.0%, and 10.0% (w/w) levels in a random block design with three replicates. The results showed that biochar applications at 2.0% and 2.5% levels significantly promoted Miscanthus growth by ameliorating the physicochemical and biological properties of the saline-alkali soil. The soil moisture, soil organic matter (SOM), nitrate nitrogen (NO3−-N), available phosphorus (Olsen-P), and concentrations of potassium (K+), calcium (Ca2+) and magnesium (Mg2+) ions were significantly increased, while soil pH, bulk density, ammonium nitrogen (NH4+-N), sodium (Na+) ion, and exchangeable sodium percentage (ESP) contents were substantially reduced. In addition, the soil bacterial community structure and diversity were substantially shifted after the biochar amendment, which in turn affected soil N and P cycling and improved soil physicochemical properties. Meanwhile, biochar application considerably mitigated the salinity stress to Miscanthus plants by activating anti-oxidative enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), therefore enhancing the scavenging capability of reactive oxygen species (ROS). Together, our results indicated that biochar amendment effectively promoted Miscanthus growth by ameliorating soil physical, chemical and biological properties, and alleviated salt stress injuries to plants in a coastal saline-alkali soil.