Improvement effects of conditioners on properties of acidified-salinized soils and lettuce growth

Continuous cropping soil in the facility cultivation area causes degradation of soil properties and activation of soil-borne pathogens. To investigate the effects of conditioners (biochar and vinegar residue) on the physico-chemical properties, enzyme activities, microorganisms of acidified and salinized soils, and their effects on the growth, photosynthesis, yield, and quality of lettuce, we performed the current study. The results showed that conditioners treatments increased the pH value of acidified and salinized soils, whereas significantly reduced the EC value. Moreover, the application of conditioners enhanced the activities of catalase, sucrase, urease and phosphatase, and the number of microorganisms in the acidified and salinized soils to an extent. The conditioners also increased plant height, fresh and dry weight of lettuce. Compared with acidified and salinized soils alone, T2∼T9 treatments remarkably increased the root vitality by 49.01%, 76.68%, 51.38%, 145.06%, 110.67%, 77.87%, 30.43% and 52.96%, respectively. In addition, the net photosynthetic rate (Pn), vitamin C content, soluble sugar content and yield of lettuce treated with T5 (20 g biochar and 20 g vinegar residue) increased by 119.61%, 82.32%, 49.89%, and 64.82%, respectively, but decreased the nitrate content by 26.62%. These results indicated that the conditioners improved the physical and chemical properties of acidified-salinized soils, and increased the growth, yield, and quality of lettuce. Among the treatments, the best improvement effect was observed in T5 treatment that biochar and vinegar residue were mixed at the ratio of 1: 1 (w/w).