Abstract

Onion waste of tremendous amount is produced during cultivation, after harvest, and during storage is mostly incinerated, neglected, and discarded which can rather be used as crop fertilizers with other agricultural by-products to improve both the yield and quality of crops. This study was conducted under greenhouse conditions during 2019 at Sunchon National University, South Korea to evaluate red pepper and tomato plants with liquid fertilizers made from onion and tomato by-products using fermentation, water and boiled water extraction methods. The shoots fresh weight of red pepper was 9–19, 11–31 and 34–57% greater than the control after being treated with the onion and tomato extracts using fermentation, water and boiled water extraction methods, respectively. The shoots fresh weight of tomato was 11–13, 29–54 and 36–39% greater than the control after treatments of the aforementioned fertilizers, respectively. Furthermore, the fruit number of red pepper increased by 26–156% in the tomato and onion fermentation and boiled water extracts compared to the control. The number of tomato fruits increased by 68133% after being fertilized with the tomato and onion fermentation and boiled water extracts. Generally, the shoot fresh weight of red pepper and tomato increased with increasing tomato and onion extract concentrations at 0.1, 0.5, 1 and 3%. Generally, the fermentation extracts were less effective on the shoot fresh weight, fruit number, and fruit weight of the tomato and red pepper than the water and boiled water extracts. Growth promotion of red pepper and tomato were generally more effective with twice application than that under once application. On the other hand, the growth promotion of red pepper and tomato were not consistent between the drenching application and foliar application. Generally, macroelements, such as N, P, K, Ca, Mg, and Na, in the tomato fermentation, water, and boiled water extracts were lower than in the tomato meal. In addition, the macro-elements in tomato water and boiled water extracts were higher than tomato fermentation extracts. On the other hand, tomato and onion fermentation extract levels of micro-elements such as Zn, Fe, Mn, Mo, Ni, and B were higher than both tomato and onion meals. These results suggest that extraction methods in the liquid fertilizers can result in different mineral nutrition which ultimately affect crop growth promotion levels.