Use of vegetative filters to recycle soilless culture drainages

We tried two species, the aquatic Eichhornia speciosa Knuth (syn. E. crassipes) and the halophyte Atriplex nummularia Lindl., both with forage value, as vegetative filters to control drainage losses of soilless culture. The leachates from roses cultured in a tuff substrate (pH 4.6 to 5.7, EC 2.6-2.7 dS.m(-1), Na 10.5-11.0 mmol.L-1) were used to grow Eichhornia in small ponds under greenhouse until EC reached 3.7 dS.m(-1) (pH 6.3 to 6.7, Na 18.9 mmol.L-1). Then the remaining solution was used to water Atriplex cultured in pots (open air) using deficit irrigation doses to prevent drainage. The amount of leachates; from 2 roses varied from 0.5 to 1.4 L.m(-2).d(-1) the open system, and was around 0.4 L.m(-2).d(-1) when the nutrient solution was recirculated. The daily average consumption of the vegetative filters ranged from 2.5 L.m(-2) in the colder months to 8.5 L.m(-2) in summer for Eichhornia, and from 1.15 L.m(-2) in winter to 1.7 L.m(-2) in summer for Atriplex. Our results showed that rose drainage could be totally recovered by these vegetative filters, with a required filter surface of 20-30% of the roses area, if the hydroponics rose system is open, and 14-12% if it is recirculated.