After a long and hot summer, my indoor grow room is just about empty, so I have lots of room to start up a large batch of new plants. For a while, I have been wanting to do an experiment to determine whether aerating the fluid in the buckets would be beneficial for plant growth. My general approach with Bucket Hydroponics has been to ‘Keep It Simple’, but I am curious about whether aeration would provide a significant benefit.
In this experiment, I will be growing El Dorado Swiss Chard. Half of the plants will receive aeration, and the plants will be grown in 5 gallon buckets. I will sow enough seeds for 15 plants, and I will pick out the best plants for the experiment.
For aeration, I will be using the General Hydroponics Dual Diaphragm air pump, model GH2716. I bought this pump used from my local hydroponics store for $40, so my investment is not large. This pump is a bit noisy for using inside my house, so I will have to see some real benefits to justify its use.
Sep 25 = Day 0. 15 plants started from seed (Park Seed). Seeds sowed in 1.5 inch rockwool cube in 2 inch net-pot. Moistened with Seedling Blend, a dilute blend of fertilizers. N-P-K (in ppm): 22-29-16.
Sep 27 = Day 2. 4 of 15 plants have germinated. Placed seedlings directly under a fluorescent light (2 ft. T8 bulb, 17W, 6500k) for 16 hours per day.
Sep 28 = Day 3. 8 of 15 plants have now germinated.
Sep 30 = Day 5. 12 of 15 plants have now germinated, but 4 of the plants are growing too leggy and are falling over, or have a bit of mold on the stems. These 4 plants were discarded. The remaining plants were put into a sunny window with a small fan blowing on them for 3 hours per day, in an attempt to toughen up these plants. The rest of the day, the plants are under the fluorescent lights.
Oct 5 = Day 10. Plants are still getting too leggy, so they were moved directly under an LED grow light for 11 hours per day, with a fan blowing on them.
Oct 8 = Day 13. Installed the plants into 5 gallon buckets using the Masterblend-based Regular-Strength Blend. N-P-K (in ppm): 103-95-202. Plants continue to receive 11 hours of light per day from the LED grow light. Additionally, 3 of the buckets are getting aeration from small air stones connected to the GH2716 air pump. The other 2 buckets are non-aerated. In some of the buckets, more than one plant is growing in the rockwool cube; I am planning to thin down to 1 plant per bucket eventually.
Oct 19 = Day 24. The plants are growing, but they tend to flop over and have difficulty standing upright. The grow room is still too hot at this time of the year, fluctuating daily between 75-80 °F. Checking the quality of the solutions, the aerated fluid is crystal clear, while the non-aerated fluid seems cloudy and turbid.
Nov 6 = Day 43. Thinned down to 1 plant per bucket.
Nov 13 = Day 50. The plants are getting larger, and they were starting to flop over, so I installed rigid collars to keep the plants upright. The best collars are shown on the left, consisting of 4 inch ABS couplings. The ABS collars are heavy and stable. Other collars were made of cardboard, but these did not work quite as well as the ABS couplings. I placed the ABS collars on the 2 largest plants, the ones in the non-aerated buckets.
Nov 18 = Day 55. The plants without aeration are clearly bigger than the plants in the aerated buckets. The experiment was concluded at this time. The result of this study is surprising, I had expected that aeration would provide some benefits to the plant growth, but it did not. Perhaps the aeration resulted in turbulence to the roots in the bucket, which was inhibitory to growth. On a positive note, the fluid in the aerated buckets was very clear and clean. In contrast, the fluid in the non-aerated buckets is slightly cloudy, and the stagnant fluid has a ‘skin’ on the top with lots of precipitates at the bottom of the bucket. Movement of the fluid within the bucket is helpful for keeping the fluid fresh and clean, but is not necessary for healthy plants.
The 3 plants in the aerated buckets were harvested. The pH of the fluid in the buckets was measured: 4.5, 5.0, 6.5. I’m not sure why these buckets had different pH values.
The 2 plants in the non-aerated buckets were allowed to continue growing. These plants were placed in front of a window receiving about 3 hours of sunlight per day. The use of the LED grow light was discontinued. The pH of the fluid in the buckets was measured: both buckets read 4.5. Since this is a bit on the low side for optimal plant growth, the pH was raised up to 6.0 by the addition of 5 mL of pH Up diluted in 1 cup of tap water.
Dec 30 = Day 97. Started harvesting lower leaves.
Feb 3 = Day 132. I have had 3-4 big harvests of leaves. The plants are still going strong. Checked the pH of the fluid in the two buckets. Both were 6.0.
Mar 13 = Day 170. Both buckets were getting a bit light, so I added 1.25 gallons of Regular-Strength Blend to each bucket.
Mar 31 = Day 188. Added 1 gallon of Regular-Strength Blend to the bucket on the left.
Apr 14 = Day 202. Added 1 gallon of Regular-Strength Blend to the each bucket.
May 5 = Day 223. Added 1 gallon of Regular-Strength Blend to the bucket on the left, 0.5 gallons to the bucket on the right.
May 25 = Day 243. Added 1 gallon of Regular-Strength Blend to the each bucket.
Jun 19 = Day 268. Added 1.5 gallons of Regular-Strength Blend to the bucket on the left, 0.75 gallons to the bucket on the right.
Jul 6 = Day 285. Added 1 gallon of Regular-Strength Blend to the each bucket.
Jul 17 = Day 296. Added 1.5 gallons of Regular-Strength Blend to the each bucket.
Aug 3 = Day 313. Added 0.75 gallons of Regular-Strength Blend to the bucket on the left, 0.25 gallons to the bucket on the right.
Aug 15 = Day 325. Added 1.5 gallons of Regular-Strength Blend to the bucket on the left, 1 gallon to the bucket on the right.
Aug 22 = Day 332. Added 1 gallon of Regular-Strength Blend to the each bucket.
Sep 4 = Day 345. After almost a year of growing, I am finally going to harvest the remaining leaves. I find that the stalks are a bit fibrous and inedible, but the leaves are still OK for steaming. Each bucket has about 0.5 gallon of fluid remaining.
Total fluid consumed: 17 gallons (left plant), 13.75 gallons (right plant).