Use of mixed solid waste as a soil amendment for saline-sodic soil remediation and oat seedling growth improvement

Soil salinization has become a worldwide problem that imposes restrictions on crop production and food quality. This study utilizes a soil column experiment to address the potential of using mixed solid waste (vinegar residue, fly ash, and sewage sludge) as soil amendment to ameliorate saline-sodic soil and enhance crop growth. Mixed solid waste with vinegar residue content ranging from 60-90 %, sewage sludge of 8.7-30 %, and fly ash of 1.3-10 % was added to saline-sodic soil (electrical conductivity (EC_1:5) = 1.83 dS m^-1, sodium adsorption ratio (SAR_1:5) = 129.3 (mmol_c L^-1)^1/2, pH = 9.73) at rates of 0 (control), 130, 260, and 650 kg ha^-1. Results showed that the application of waste amendment significantly reduced SAR, while increasing soil soluble K⁺, Ca²⁺, and Mg²⁺, at a dose of 650 kg ha^-1. The wet stability of macro-aggregates (>1 mm) was improved 90.7-133.7 % when the application rate of amendment was greater than 260 kg ha^-1. The application of this amendment significantly reduced soil pH. Germination rates and plant heights of oats were improved with the increasing rate of application. There was a positive correlation between the percentage of vinegar residue and the K/Na ratio in the soil solutions and roots. These findings suggest that applying a mixed waste amendment (vinegar residue, fly ash, and sewage sludge) could be a cost-effective method for the reclamation of saline-sodic soil and the improvement of the growth of salt-tolerant plants.