Biochar nanoparticles alleviate salt stress in tomato (Solanum lycopersicum) seedlings

Abstract

With the rapid increase in global population that is anticipated over the coming decades, more food will need to be produced to meet the increasing demand. The current agricultural production system is unable to meet this challenge, and as such, crop cultivation will need to occur under more marginal conditions. Soil salinization and the consequent salt stress on crops will become increasingly problematic. In this study, we prepared two kinds of biochar nanoparticles (NPs) (particle size 253 and 259 nm) from rice and corn straw at 350 °C and investigated their use as a soil amendment to alleviate salt stress (2000 mg kg⁻¹ biochar NPs; 1000/2000 mg kg⁻¹ NaCl) on tomato seedlings. After four weeks of growth, the biomass of tomato seedlings was reduced by 48.7% under 2000 mg kg⁻¹ NaCl treatment. With rice straw biochar NP application, the biomass increased by 13.1% over the stress controls. In addition, chlorophyll (SPAD value) was increased by 46.7% with rice straw biochar NPs. The rice straw biochar NPs inhibited the transfer of Na from roots to shoots; the Na translocation factor (TF) was 0.46, which is significantly lower than the corresponding value (0.72) for the saline stress controls. The corn straw biochar NPs also contributed to salt stress alleviation in tomato, although the effects were lower than those with rice straw biochar NPs, and there was no reduction in Na transport. However, at lower levels of salt stress with 1000 mg kg⁻¹ NaCl treatment, there was little difference in the effects of the two biochar nanoparticles. These findings suggest that straw-derived biochar may be an effective soil amendment to increase the salt stress tolerance of crop species and can serve as an effective tool to facilitate food production under marginal soil conditions.