Winter Growing Season

1:59 PM in Aqua, growing, season, winter

The winter growing season was a smash! The lettuce did quite well, and I harvested about eight salads that fed four to six people each from February through April, about two-and-a-half salads per month! The first six of those salads came from the clay pebble bed that had densely planted seeds. The dense planting stimulated quick, vertical growth. It also ensured that plants did not grow woody stems, keeping the growing tip low, just above the surface. I harvested this like mowing a lawn,, cutting at about 2” high straight across. The plants responded well! For the first two months I harvested at a staggered pace, which kept the demand for nutrients relatively constant because some plants were in the high demand regrowth stage as others grew slowly near full size.

Mixed lettuce in clay pebble bed on 2/18/2011 (top) and 3/26/2011 (bottom). 
Gray coloration on bottom is due to grow light being off. Note that the gravel 
grow bed seen in upper right of both pictures has significantly smaller plants.

Meanwhile, the gravel grow bed which had plants spaced about 6” apart, as recommended on the seed packet, grew very slowly, so I did not harvest until late March. The plants did bush out nicely, each producing far more lettuce per plant than the dense plantings of the clay bed. The bushy lettuce led to woody stems and larger leaves, which I found could only get a few harvests per plant before the leaves got too tough or bitter (lots of white sap in them). 

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Gravel grow bed on 4/28/2011 before the last harvest.

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Conclusion: unless I need pretty heads of lettuce, I should plant the seeds dense and harvest often.

And what about the other plants in the system? Well, the chard...

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Winter Growing

6:02 AM in Aqua, growing, winter

After some experimenting with grow bed media in the early winter, I planted my indoor crop of lettuce and rainbow chard in mid-January. After about four weeks the plants look quite healthy. All seeds germinated in the expanded clay bed, and I then transplanted a few into the gravel bed. Ive given the lettuce in the gravel bed plenty of space, and Im curious to see how differently the plants grow in the dense and spaced scenarios.
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Expanded clay bed 2/3/2011

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Expanded clay bed 2/9/2011

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Gravel bed 2/9/11

The conditions in the water are not ideal right now: while there is plenty of nitrate (plant food), the pH is about 8 and the temperature is about 62-65 ^oF.

A pH of 7 or just below is ideal in aquapaonics. Plants absorb the most nutrients in slightly acidic conditions (pH < 7)  while fish prefer it slightly basic(pH > 7). So we compromise and try to make the water pH neutral (pH 7). The nitrificaiton process (turning fish waste into plant food) naturally lowers the pH, so the fact that mine is above 7 means other factors are at work. First, my gravel has lots of limestone in it, and the calcium it contains leaches into the water and raises the pH. Surprisingly, the clay pebbles also raise the pH, even though they are billed as pH neutral. I tested them by letting some clay pebbles sit in fresh tap water (pH 7) for a week, and they raised the pH up to 8 or 9. The plants are growing well now, but Im going to experiment with adding some lemon juice to lower the pH over the next week.

As for the temperature, the nitrifying bacteria prefer water between 72-75 ^oF. At lower temperatures, their growth rate slows down significantly.  I could use water heaters, but they are very energy inefficient, so Im trying my hand under cooler temps. The goldfish and lettuce, however, love the cold water. Currently, there is plenty of nitrate in the tanks, and I will monitor the tank to see if the bacteria are able to maintain sufficient levels as the plants near harvest stage.

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