Citation: Szekely, I.; Zeaiter, Z.; Jijakli, M.H. Development of a Simple Bioponic Method Using Manure and Offering Comparable Lettuce Yield than Hydroponics. Water 2023, 15, 2335. https://doi.org/10.3390/ w15132335 Academic Editor: Helvi Heinonen-Tanski Received: 27 April 2023 Revised: 9 June 2023 Accepted: 12 June 2023 Published: 23 June 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). water Article Development of a Simple Bioponic Method Using Manure and Offering Comparable Lettuce Yield than Hydroponics Iris Szekely, Ziad Zeaiter and M. Haissam Jijakli * Integrated and Urban Plant Pathology Laboratory, Gembloux Agro–Bio Tech, University of Liège, Passage des Déportés 2, 5030 Gembloux, Belgium * Correspondence: mh.jijakli@uliege.be Abstract: 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. Keywords: bioponics; organic hydroponics; chicken manure; goat manure; biofertilizer; low-tech 1. Introduction Hydroponics is a soilless agriculture technique in which plants extract essential nutri- ents from a nutrient solution [1]. It allows to grow year-round crops in various contexts and regions [2–4], even those with limited access to land and/or facing extreme pedo-climatic conditions, e.g., degraded, polluted, or infertile soils, water shortages, strong seasonality with periods of severe droughts or floods [5,6]. Hydroponics could therefore provide an element of response to various challenges in agriculture, such as the reduction of arable land, the increase in land cost, or the increase in frequency and intensity of extreme weather events related to climate change [3,5–7]. However, nutrient solutions in hydroponics are typically made from synthetic mineral fertilizers. Their extraction and/or manufacture cause various environmental issues [8,9]. Furthermore, they are often not accessible in developing countries or remote areas due to their high cost and/or their absence on the local market [10,11]. The development of organic hydroponics, or “bioponics”, using locally accessible organic materials as a source of fertilizer is therefore essential from a sustainability per- spective. In addition to showing positive effects on plant disease mitigation and produce Water 2023, 15, 2335. https://doi.org/10.3390/w15132335 https://www.mdpi.com/journal/water