The Synergistic Effect of Biochar and Poly(2-ethyl-2-oxazoline)/poly(2- hydroxyethylmethacarylate)/Chitosan) Hydrogels on Saline Soil Properties and Carrot Productivity

Background: Soil Salinity is one of the most important factors limiting crop production. Moreover, with the increasing population and saline soil worldwide there is no choice but to use saline soil to increase the agricultural area. Therefore, to increase carrot productivity under saline conditions, it's necessary to provide good management such as applying hydrogels and biochar for improving soil properties. Methodology Hydrogels (PEtOx-HEMA-CS) were prepared from poly (2-ethyl-2-oxazoline), chitosan (CS), and 2-hydroxyethyl methacrylate (HEMA as crosslinker), by exposure those to gamma irradiation at range from 0–50 kGy with 0.9 kGy/h, and obtained three types of hydrogels according to concentration of chitosan. The PEtOx-HEMA-CS hydrogels were prepared for enhanced water holding capacity for agriculture purposes. The chemical structures of those were investigated by FTIR, XRD and SEM. Biochar (BC) as an active substance was physically mixed with those hydrogels at different ratios (0/100, 0.5/99.5, 1/99 and 100/0 (g/g) biochar/hydrogels). BC, PEtOx-HEMA-CS and the mixture of PEtOx-HEMA-CS-BC were mixed with saline soil at ratio 0.05 and 0.1% w/w of prepared materials/soil. Pot agriculture carrot experiments were conducted to mitigate the salinity hazards by using biochar with and without hydrogels. Findings The obtained data referred that there is a significant decrease in soil salinity and exchangeable sodium percentage and increase in organic matter, cation exchange capacity, field capacity, permanent wilting point and available water especially at (PEtOx-HEMA-CS5)0.1-BC1. The highest increment percentage of NP and K were 36.36, 70 and 72%, respectively. Also, the relative increase of carrot productivity was 49.63% at the highest rates of biochar and hydrogels. However, the highest value of water use efficiency was observed at the mixture of biochar and hydrogels at (PEtOx-HEMA-CS5)0.1-BC1. Conclusion Finally, applying biochar combined with (PEtOx-HEMA-CS5) could be recommended as a good approach to enhance carrot productivity and water use efficiency under saline soil conditions.