I didn't look too far into it, but isn't sodium hydrogen carbonate just a synonym for sodium bicarbonate? If so, there shouldn't be a problem adding that to your water...as it's basically the same thing as baking soda. People have used baking soda for ages to raise the pH level of water in fishtanks. It certainly doesn't harm fish, so I see no reason why it would harm your plants.

Hope that helps.:rastasmoke: