Development of a Simple Bioponic Method Using Manure and Offering Comparable Lettuce Yield than Hydroponics

Using locally accessible organic materials as fertilizers in hydroponics can represent a sustainable alternative to the synthetic mineral fertilizers typically used. This study aimed at developing a simple bioponic method using chicken or goat manure on lettuce (Lactuca sativa var. Lucrecia) in the nutrient film technique, requiring few inputs. The first experiment compared nutrient solutions made from chicken or goat droppings and mineral fertilizers in terms of physico-chemical parameters, plant yields, and shoot mineral content. Organic solutions were produced in two main stages before being used on plants: (1) a simple manure maceration in water to produce stock solution, followed by (2) an aerobic digestion of the filtrated and diluted stock solution according to the total mineral nitrogen (TMN). The second experiment compared different concentrations of chicken manure stock solution (60, 80, 100, or 120 mg/L TMN) to a control mineral solution. In the first experiment, both organic treatments resulted in yields significantly lower than those of the control, probably due to nitrogen scarcity. In the second experiment, all organic treatments resulted in wet and dry shoot masses similar to those obtained with the inorganic control treatment. Produce quality was also improved, with lower shoot nitrate content. Important nitrogen losses occurred in the organic solutions during aerobic digestion, particularly in the goat treatment and in the highly concentrated treatments in stock solution during the 2nd experiment (~50–65% TMN losses). This was probably caused by the presence of residual organic matter, which resulted in excessive microbial development. It can be concluded that chicken and goat manure are suitable fertilizers for lettuce hydroponic production using this method; however, further research should be carried out to improve mineralization during digestion steps.