Changes in soil properties and salt tolerance of safflower in response to biochar-based metal oxide nanocomposites of magnesium and manganese

Abstract

This original research was performed to assess the possible effects of solid biochar (25 g biochar kg−1 soil) and biochar-based nanocomposites (BNCs) of magnesium oxide (25 g BNC-MgO kg−1 soil), manganese oxide (25 g BNC-MnO biochar kg−1 soil) and combined use of these nanocomposites (12.5 g BNC-MgO + 12.5 g BNC-MnO kg−1 soil) on soil properties and salinity (non-saline, 6 and 12 dSm−1) tolerance of safflower plants (Carthamus tinctorius L.). Application of biochar, particularly BNCs increased the pH and cation exchange capacity of soil, and the contents of water, potassium, calcium, magnesium, manganese, chlorophyll (a & b), nutrients uptake, water use efficiency and plant growth. Sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP) of soil, sodium absorption rate of plants and osmolyte production (soluble carbohydrates and proteins, proline and glycine betaine) under 6 and 12 dSm−1 salinities were decreased by biochar and BNCs treatments. Sodium sorption capacity of BNCs was much higher than the solid biochar, which reflected the superiority of BNCs in decreasing sodium uptake by plants. The combined application of BNC-MgO + BNC-MnO proved to be the preferable treatment for decreasing salt toxicity in safflower. Biochar and BNCs improved root and shoot growth by lowering SAR, ESP, sodium absorption rate of plants and osmotic stress under saline conditions. These results conclude that BNCs can enrich the plant cells with nutrients, increase the nutrients absorption rate and maintain the plant tissue water content at an optimum level to improve plant growth under salt stress.