I have been looking all over for someone, anyone, who has grown a successful marijuana crop with a DIY autopot system. It has been challenging, to be mild. I have set up my own because I don't want to buy a pre-made version at a retail price. Also, there is the bother with timers and pumps, which most systems rely on. If there is a power outage, you better have a generator on hand.. Or you could water manually, daily, which is fine if you don't get out much.
Don't be fooled by assumptions; I have done my homework and researched the costs & benefits of many systems. My eventual choice was based on a blend of advantages including cost-saving, eco-friendly, ease-of-use, proven results, and dummy-proof. I found after several failed attempts and generations growing in soil, that I am not a green-thumb. The clearest benefit of the autopot system is The Plant Waters Itself. The device is designed and patented in Australia, for dry climates far from electricity. A reservoir feeds the device via the mystical powers of Gravity, and a valve shuts off until the plants drink that supply of water. If you start with sterile conditions and provide your plants all the nutrition they require, this system can produce bountiful harvests with far less energy consumption. The system works fine in soil and hydroponic setups.
Here is a breakdown of my current grow. I will keep updating as the weeks progress.
THE SETUP
Room Preparation
I used an extra room in the basement, with a window to outside. The room was already white, conveniently. I used heavy duty clear poly to completely sheet the inside of the room, and a double layer on the floor that seamlessly seals the bottom of the room and goes ~18' up the wall like a bathtub (except for the doorway). A piece of plywood, also painted white, covers the window for several reasons: a) provides a place to mount my ventilation fans. b) discourages any possible spy or snoopy neighbour activity. c) control the amount of airflow, temperature, and humidity in the room. d) discourages mold damage to the house.
I have split the room into 2 separate sections; a permanent grow/flowering side and a nursery/germination area. The main grow area dimensions are approx. 7' x 5' x 8' (l,w,h). The nursery area is approx. 7' x 2' x 7'. There is a single light switch with a single light fixture built in. There is a baseboard heater with its own thermostat control (currently unused). There is only one power outlet in the room.
Lighting
Currently I am using a Lumatek electronic digital ballast with a Hilux GRO bulb as the main grow light. I have been setting it to 300 watts at early veg and sexing stages (18/6 cycle), 400w during mid-veg, and then up the dose to 600w during flowering phase (12/12). Inside the nursery is a single fluorescent fixture holding two 48', 40w ecolux grow bulbs, permanently on an 18/6 cycle. [SUP]NOTE:[/SUP] I intend to modify the lighting in the nursery; it is too weak to be a permanent vegging area. Final solution not fixed, therefore no direction taken at this point.
Water
I have been using regular domestic water, but for the latest grow have installed Culligan on-tap filters to help cut some of the hardness from our water supply. Several previous generations suffered from magnesium deficiency because there was a buildup of calcuim which can cause a nutrient lock-up. I have been letting water stand for at least 24 hours, and then treating with vinegar to lower the pH to 5.5 - 6.5. For this grow I have added a 3-part nutrient formula from Advanced Nutrients, the pH-perfect Grow/Bloom/Micro series. I also added some Piranha beneficial fungi. The nutrient reservoir is a 20-gal dark-colored garbage bin, raised up on a few milk crates for a good gravity-feed. Standard gardening irrigation tubing is used throughout (1/4' dia.).
Ventilation
I used two 4' computer muffin fans to vent warmer air to the outside. There is enough of a gap at the bottom of the door to bring in fresh, cooler air. So far the ambient humidity has not been a problem, around 50%. The daily temperature ranges from 15 - 25 [SUP]o[/SUP]C, and I have found the HID light is enough to heat the room (hence, the unused baseboard heater).
Germination
I started with some seeds from Vancouver Island Seed Company, and used rockwool cubes to germinate inside a humidity dome. No, that's not completely true. I started where everyone starts; with a few bag seeds that I wanted to actually try to grow. Some sprouted between two sheets of damp paper towel on a plate. Most sprouted between two sheets of damp paper towel in a ziplock baggie. Most sprouted in damp rockwool cubes. I think germination success all depends on the quality of your seeds and the care the young plants receive in the first few days.
THE GROW
Week 1
Germination and early seedlings. The young plants need high humidity to survive until their root systems fully develop. Rockwool does not provide adequate structure for the plants as they grow, so I have placed each small cube into a 3' net pot filled with hydroton. Every day I spray the shoots and all the rocks with a plain water mister, and give the dome some fresh air. I spray only with plain water because nutrients can hurt the sensitive baby and there is enough energy in the seed capsule to grow the first few inches. There are some additonal clay rocks in the tray to maintain high humidity.
Week 2
Still under the Dome. When the seedlings are big enough (2 pairs of leaves) they can be removed from the humidity chamber. I placed them into a flood tray and surrounded each net pot with more hydroton. Also, (this is key) I added an autopot smartvalve in its own container and surrounded it with rocks too. I have loosely placed a dome over the seedlings to gradually transition them to the ambient humidity of the grow room, while continuing to mist several times a day with plain water.
Week 3
Seedlings are still only 4' tall, have 3-4 pairs of leaves. The autopot watering system delivers 1' depth of water to the tray at once. I found it is too much at once for the tiny plants, even surrounded by clay rocks. I drained off some of the water and have slowed down the watering regime (manually) until the plants are big enough to drink more. It is worth noting that the plant vigor and growth have increased since treated with the innoculated (piranha) nutrient water.