EC (electrical conductivity) values for Cattleyas?

[fswechsler]

Hello all, greetings from Brazil. I started an orchid collection about a year ago, and am planning to expand it (currently some 15 Cattleyas and 1 Phalaenopsis).

My Cattleyas are grown in home-made plastic slatted boxes. I am using a substrate containig ca. 80% wood chips (from either Tabebuya spp. or Mimosa caesalpiniifolia) and 20% terracota pieces (from broken tiles or bricks), on a volume/volume basis. The medium is thus well aerated and will not stay moist very long.

These plants are watered every day, with either tap water (EC=ca. 0.2 mS/dm) or nutrient solution. Nutrients are furnished 2-3 times a week via nutrient solution, which I make up myself based on the MSU formula. The EC values of the solution for N=130ppm stay around 1.3 mS/dm. Thus, for fertigation purposes, I dilute this solution to reach about 0.4 mS/dm, which is the only recommendation for Cattleyas I have been able to find in the available literature.

I wonder whether there is a more up-to-date recommendation for Cattleyas, since the above mentioned value is described as "tentative".

Thanks in advance for your help!

Francisco S. Wechsler