IRRIGATION VOLUME AND FERTILIZER CONCENTRATION EFFECTS ON LEACHING AND GROWTH OF PETUNIA
Excessive irrigation in greenhouse production causes leaching of water with dissolved nutrients. This leaching causes a direct economic loss to growers by removing fertilizer from the pots and potentially causes environmental pollution. Improving irrigation efficiency can reduce leaching, decrease the amount of fertilizer needed and improve both economic and environmental sustainability. Our objective was to quantify the interactive effect of fertilizer concentration and irrigation volume on leaching and growth of petunia (Petunia × hybrid) and determine whether growers can use less fertilizer if they irrigate more efficiently. Petunia seedlings were grown to a salable size in 15-cm pots filled with peat:perlite (80:20) substrate using two concentrations of N (at 100 and 200 mg∙L-1) of water soluble fertilizer (15N2.2P12.5K) injected into a drip irrigation system resulting in an EC of 1.12 and 2.45 dS∙m-1 respectively. An automated irrigation system opened a solenoid valve to drip irrigate the plants when substrate moisture content (θ) dropped below 0.45 m3m-3. To achieve a range of leaching volumes, different amounts of water were applied at each irrigation event; 11, 121, 244 and 488 mL for the control (efficient irrigation), low, medium, and high irrigation volumes respectively. The total leaching volume after three weeks (end of experiment) in the 100 mg∙L-1 N treatments was 384, 661, 982, and 2,910 mL/pot in the control, low, medium, and high irrigation and 1,128, 1,568, 2,030, and 3064 mL/pot in the control, low, medium, and high irrigation in the 200 mg∙L-1 N treatments, respectively. Shoot dry mass more than doubled as fertilizer concentration increased from 100 to 200 mg∙L-1 N, regardless of the irrigation volume. No difference in shoot dry mass was observed among the irrigation treatments. The 200 mg∙L-1 N concentration resulted in more leaching than the 100 mg∙L-1 N. Because the plants grown with 200 mg∙L-1 N were larger and needed more water to sustain their growth, they were irrigated more often, resulting in larger leaching volumes. Contrary to our hypothesis, this study provided no proof that fertilizer rates can be reduced when more efficient irrigation practices are used. However, even reducing just the volume of irrigation water applied, without decreasing the fertilizer concentration, will reduce the amount of fertilizer applied, thus reducing production costs and decreasing the risk of environmental pollution.
Alem, P.O., Thomas, P.A. and van Iersel, M.W. (2014). IRRIGATION VOLUME AND FERTILIZER CONCENTRATION EFFECTS ON LEACHING AND GROWTH OF PETUNIA . Acta Hortic. 1034, 143-148
Petunia × hybrid, drip irrigation, leachate, soil moisture sensors, substrate moisture content