Abstract
This study compares the aquaponics Nile tilapia (Oreochromis niloticus)—pak choi (Brassica chinensis) system with and without a bacterial biofilter (BF and NBF) in a tropical location. The aim was to determine whether a semi-intensive aquaponics system NBF could offer a production alternative for small-scale farmers in this region, both technically and biologically. The Tilapia aquaponics culture was continuously recirculated and water was added (influent) and removed (effluent) from the plant aquaponics culture every 24 h. Total ammonia nitrogen (TAN) and nitrite nitrogen (NO2−-N) were analysed in the plant aquaponics culture influent and effluent. At the end of the experiment the individual fresh total weight, dry total weight, edible weight, height and diameter of the pak choi plants were measured. None of the pak choi variables showed significant differences between treatments. TAN and NO2−-N were higher in the NBF influent than in the BF influent. TAN and NO2−-N in the effluent of both treatments were similar and lower than in the influent. The plant aquaponics culture therefore works as a biofilter and the NBF aquaponics system could be used for small-scale farmers in the tropics, with easier management and less costs than a BF aquaponics system.
Highlights
The rural population is highest in countries in intertropical regions [1], and most of them are in the categories of developing economies and least developed countries [2]
Pak choi plants attained commercial size in both treatments and all growth parameters showed no significant difference between treatments, F1,6 = 1.08 × 10−3, p = 0.97 for final fresh weight; H4,4 = 0.08, p = 0.89 for final dry weight; H4,4 = 1.33, p = 0.34 for moisture; F1,6 = 0.03, p = 0.87 for fresh weight edible portion; F1,6 = 0.49, p = 0.51 for average leaf height and F1,6 = 0.04, p = 0.84 for average stem basal diameter (Table 1)
Small (s) and large (b) fish, a higher value of specific growth rate (SGR) and lower feed conversion ratio (FCR) value were obtained in the BF treatment compared to NBF (Table 2)
Summary
The rural population is highest in countries in intertropical regions [1], and most of them are in the categories of developing economies and least developed countries [2]. For these populations, agriculture is the main source of income and employment. Eco-efficiency in the simplest of terms is about achieving more with less [4], by using the available resources more efficiently in order to improve sustainable productivity and increase the food available [5]. Eco-efficiency can be increased either by altering the management of an individual crop and livestock enterprise or by altering the land-use system [6], for example, diversifying farm production. According to Tscharntke et al [7] the agriculture practiced under smallholder farmer-dominated landscapes, rather than large-scale farming, is the backbone of global food security in the developing world
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