Fermented Leaf Fertilizers—Principles and Preparation

Fermented leaf fertilizers (FLF) are made of anaerobically fermented plant and/or animal re sources and principally used for foliar plant nutrition, as they provide a quick nutrient supply, especially of micronutrients. Their use is most common in horticultural production as a complementary measure to or ganic basal fertilization in the case of nutrient deficiencies. Since FLF are commonly made of farm residues, their formulation varies according to the available resources and the treated crops. The most common raw materials are cattle manure, cow milk, cane molasses, and water. Within Latin America, the production of FLF is popular with smallholders. Most of these farmers produce them on-farm using adapted plastic barrels as fermenters. Industrial production is conceivable. FLF have been successfully tested in banana, bean, broccoli, carrot, cucumber, lettuce, maize, papaya, and spinach production. This review highlights the principles of this sustainable and promising organic fertilization strategy, emphasizing the preparation of FLF.