This chapter shows how organic fertilizers can provide essential nutrients soluble to plants, so as to be used in hydroponic systems in its various forms. Such materials are an important source of macro- and micronutrients. This form of plant nutrition can contribute to the sustainable production of food, both in developed and developing countries. Nutrient solutions can be formulated when soluble nutrients are extracted from the solid phase of organic manure. In some vegetables, equal yields, or sometimes higher, have been obtained in nutritive solutions formulated with synthetic chemical fertilizers. It has also been documented that the resulting edible products can be of a better nutraceutical quality. Ions can be obtained by means of preparations based on teas, extracts, leachates, digestate, urine, aquaculture, etc. Subsequently they must be diluted in water until reaching a level of electrical conductivity according to the tolerance levels of the crop to be established. The heterogeneity of the chemical composition of the solutions obtained is the main point that must be attended with the greatest possible precision to formulate the nutritive solutions and obtain satisfactory results. Therefore, it is necessary to measure the concentration of macro- and micronutrients (NO3−, NH4+, SO4=, H2PO4−, K+, Ca++, Mg++, Fe+++, Cu++, Mn++, Zn++, Cl−) as well as the Na+ ion (which is usually at high levels); it will also be necessary to adjust the pH. In addition, the chapter presents a broad overview and a series of research results in recent years: composition of solutions, nutrient supplements, substrates, and floating root trials in tomato, lettuce, cantaloupe melon, and green fodder. The environmental implications of inappropriate formulations are also analyzed. The nutritious solution, formulated from organic fertilizers, is not only an alternative for the nutrition of agricultural crops, but it also represents a more efficient way to use these resources.
Part of the book: Urban Horticulture