"Aquaponics an excellent tool for recycling phosphorus"
A study was carried out to quantify a P flow, P mass balance, and evaluate P removal efficiency by hydroponic lettuce integrated with tilapia aquaculture. Also, a phosphorus dynamics simulation model was developed to be a decision support system for phosphorus management.
15 tilapia juveniles (20 g) and four 15-day-old lettuce seedlings comprised each aquaponics experimental unit (n = 3). At days 0, 7, 14, 21 and 28 after transplanting, water samples were taken from each aquaponics biofilter to determine the reactive and total concentration of phosphorus. The P dynamics model was validated by comparing predicted to observed values of dissolved P over time. The linear regression equations between predicted and measured values were compared with the 1:1 line for statistically significant differences (p < 0.05) in slope and intercept values. The adequacy of the model was determined by testing if intercept equals zero and slope equals one separately using the one sample Student t-test.
Comparison of simulated and measured values of dissolved P dynamics showed a good fit around the 1:1 line with the slope (b = 1.005) and intercept values (a = 0.0189) being not statistically different (p > 0.05) from 1.0 and 0, respectively. The assimilation of P in the fish and plant components comprised 71.7% of the total P input, indicating high P utilization by the system.
The P dynamics model predicted the behavior of dissolved phosphorus in aquaponics systems, which can be used to determine adequate fish:plant ratios, maximize P use efficiency and minimize waste. The overall high P utilization by fish and plants identified in this study showed that aquaponics is an excellent tool for recycling phosphorus while yielding a high-quality crop.
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