Producing Gourmet-Quality Lettuce
Using Amino Acids
I have very hard well water. In fact, the area I live in was known throughout history for its “magnetic water”, and people used to travel from miles around to bathe in its health-giving springs! But what supposedly was good for people wasn’t so great for my hydroponic garden. The EC out of the tap was 0.7, and it was so buffered with bicarbonates that I had to use 10 times as much acid to reach my target pH than with the city water only 15 miles away. In fact, when I added pH Lower, I could actually see sparkling crystals of calcium phosphate forming and falling out of solution like snowflakes! The lime scale would build up and clog my drip emitters and pumps, and the reservoir would eventually look like a rock garden.
So imagine the challenge of trying to grow commercial lettuce with such hard water. Lettuce is a salt-sensitive crop, with a target EC of 1.0 in the summer and 1.2 in the winter. So with an EC of 0.7 out of the tap, it took only a small amount of fertilizer to reach target. Fortunately, when Sue and I grew our first commercial crop of hydroponic romaine, I had just begun to experiment with amino acid additives, and the results were astounding!
We used Paris Island Cos romaine lettuce in our first trials. We bought the seeds from the hardware store in town, so the genetics were nothing special. Later, I learned that it was an heirloom variety and not recommended for commercial production since it was genetically susceptible to tip burn. We used a re-circulating NFT system outdoors under a variety of temperature and humidity conditions. For a nutrient solution, we used a “hard water” formula, phosphoric acid to lower the pH, and an organic amino acid blend I received from a vitamin manufacturer out East. When I added the amino acids, I noticed an immediate improvement in colour and texture. As the plants grew, the leaves were a dark green, and the rapidly dividing cells at the outer edges were a golden yellow, filling to green. We didn’t lose a single leaf to tip burn, and every store or restaurant that saw or tasted the finished product purchased it at above premium prices. Not one “no”! And brix was off the scale for premium quality.
The biggest surprise was the hardiness of the plants. Markets were storing the lettuce in their coolers, roots on, for up to two weeks. At the end of the season, the plants went through three hard frosts without losing a single leaf, and the only insects I ever saw on a plant were grasshoppers. By the end of the season, even the grasshoppers couldn’t penetrate the plant tissue except at the very edges of the leaf, and I never had to use pesticides.
Lime scale was also completely eliminated. I used a sponge-like pre-filter on the pumps, and over time they became a bit “muddy”, presumably acting as a biological filter for microorganisms. The filters were occasionally squeezed out and rinsed, but no rocky precipitates were observed. To clean the reservoir at the end of the season, all we had to do was wipe off a slight film of algae with a paper towel and give it a quick rinse with a garden hose. Again, there was no lime scale.
So I’d say that the experiment was a huge success! Not only did we harvest crop after crop of gourmet-quality lettuce, but we got a glimpse into the secrets of natural amino acids.