In the cultivation of amaryllis (Hippeastrum) every year about 350 m3/ha of rinsing water is released during the regeneration (flushing) of the substrate during crop interchange. This rinsing water contains on average 75 kg N/ha/year and is therewith higher than current emission standards for nitrogen. Three solution approaches were studied to decrease the emitted amount of nitrogen: 1. Prevention/decrease emission of rinsing water; 2. Reuse of rinsing water during cultivation; 3. Decrease nitrogen in rinsing water. Most important bottlenecks are protection against bulb scale mite, the low uptake of sodium by the crop and the low tolerance towards sodium in the nutrient solution. By endless reuse of the substrate and zero liquid discharge during cultivation, the only discharge of sodium is via the rinsing water after the cultivation cycle. Replacement of substrate is expensive and not sustainable. Capture of rinsing water and reuse during cultivation after selective removal of sodium can only be feasible at the middle long term if installations for selective removal of sodium are optimized and cheaper. Cascading of rinsing water only decreases the amount of water discharged, not the amount of nitrogen (load). Rinsing during cultivation increases the risks for plant health. Redesign of the cultivation system with a smaller substrate volume and bulb singulation (every bulb in a separate root compartment, pot) can be a solution for the longer term.
|Report / Stichting Wageningen Research, Wageningen Plant Research, Business unit Glastuinbouw