I vividly remember as a toddler watching my father boil down a can of saline water to show all the salt that was left behind. I think of that when week after week I water a potted plant during a long dry season or in a greenhouse where it never receives rain. As the water evaporates or is taken up by the plants, more and more salt builds up. Sometimes you can even see a white crust appear on top.
David Silber writes in the June 1992 issue of The Fruit Gardener that one way to correct this problem is to “semi-annually leach the soil with tap water (rainwater is better) that has been acidified to a pH of 4.0. I use a commercial grower’s acid blend containing nitric and phosphoric acid. But you can also use vinegar as an acidifier: 2 tablespoons per gallon of water will yield the desired pH. The solution should be flushed through the growing container three times. In my experience the leaching water went in at a pH of 4 and came out at 6.5. This effectively removes lime and bicarbonates as well as sodium. I’ve used this on miracle fruit, coffee, pitomba, jaboticaba and lychee. The plants responded within two weeks with a new flush of normal leaves.”
ECHO used this technique in the greenhouse where we grow rainforest plants. Plants were not thriving and leaf margins were turning brown on some species. They seemed generally healthier after the treatment.