The application of organic hydroponics on homegrown urban agriculture in Taiwan

Abstract

The growing method of organic hydroponics has matured in only less than a decade. With this method, hydroponic systems can shift from a conventional approach using inorganic fertilisers, towards a more sustainable way of employing organic fertilisers that are recycled from organic wastes; and thus, fit better into urban agriculture in pursuit of sustainable development. However, the invented method requires at least several weeks for processing and pumping air, to build up enough of a concentration of nitrate in its nutrient solutions. Given that the method might be either more time- or energy-consuming than other urban farming practices, such as conventional hydroponics or organic field farming; this study aims to explore the effects on crop growth of an organic hydroponic system that omits the establishment process for nitrifying bacteria populations or with the removal of aeration in its cultivation period. We conducted hydroponic growing experiments with two variables, using organic fertilisers and giving aeration, to produce lettuce in a backyard of a private townhouse in Chiayi City, Taiwan, in autumn. Because the growth of the entire biomass in the treatment of organic fertilised material with aeration remained stagnant, lettuce were harvested and their weights recorded on the 25th day of the experiment. These experimental results showed that for the inorganic nutrient solution, the yields of the treatment with aeration are higher than those without aeration. On the contrary, for the organic nutrient solution, the yields from the treatment without aeration were higher than those with aeration. This confirms that nitrification is necessary for an organic hydroponic system.