1.keep temps in the 70-80 range, and try to keep them from deviating more than 10 degrees in range.keeping night temperatures and day temperatures the same will greatly increase thc vs a wide variation. 75 day and night is optimal. source: mel franks cannabis grow guide by mel frank & ED ROSENTHAL, High Times' 2006 Seed Guide.
2.keep humidity always above 50% and always below 70%. for veg 55-65% is optimal, for flower, 50-55% is optimal.rh below 48% will cause wilting and excess transpiration of the leaves sources:
3. improved ventilation will help increase co2 getting to the plants.get a fan with a fan speed controller and you can fine tune the temps as well.keep the exhaust fans mounted high as possible with the intake mounted low as possible and on the side opposite the exhaust. this way there is an updraft blowing co2 rich air through the leaves while making it harder for any pests to lay eggs on the undersides of the leaves. i didnt see the need to source
4. dont flush right before harvest. its best to flush 2 weeks before and at least 2 days before cutting so they dry out better. wont exactly help yield but will reduce the chances of mold which actually could help yield.
5. red light during veg is not productive as it causes stretch. however red light improves root growth and a combination of red and blue is very beneficial in the seedling stage but start to switch out the red so that after 1-2 weeks of veg it is mostly if not all blue light.
source:
http://www.plantcell.org/content/14/suppl_1/S207.full
6. it has been noted that talking to your plants is good, this is because of the co2 you breathe out not exactly the sound. although there have been studies of music in the grow room improving yield vs control group. breathing slash talking to your plants whenever you can will yield higher co2 for about a couple seconds. if i breathe on my co2 meter it goes up 600 ppm.
source:
http://www.ertinc.com/c02.php, my co2 meter
7. for the first 2-3 waterings use molasses to boost the microbe population. this will help break down nutrients for your plants to use. after the 3rd watering with molasses dont do it again, normally microbes feed on the sugar from the roots and when you introduce outside sugar they eat that instead. youre just trying to boost their population not help them graze lol. keeping microbe feeding on your roots will help the plant uptake nutes even faster.source:
https://portal.utpa.edu/portal/page.../Benefits of Compost Tea UTPA Nov 16 2011.pdf
8. before flowering give your plants 2 days of absolute darkness. this kicks the flowering hormones into overdrive. likewise before harvest give it 2 days of darkness as well to help leach nutrients out of your bud.source:
Marijuana Grower's Handbook: Your Complete Guide for Medical and Personal Marijuana Cultivation
9. 1-2 tbsp of dolomite lime or similar buffer in your soil as a top dressing would greatly benefit your plants. to ph your water the acceptable range for soil is 5.9-6.5. lemon juice or distilled vinegar is acceptable for lowering, as well as baking soda for raising the ph. these are used in soil only and will complicate hydroponics systems.source:
Marijuana Grower's Handbook: Your Complete Guide for Medical and Personal Marijuana Cultivation
10. aerate your water with an airpump before watering. this will keep it oxygenated and help the plants recover from the watering quicker. likewise adding one capful of hydrogen peroxide to 1 gallon of water will do the same. do both. Source:
http://hos.ufl.edu/sites/default/files/faculty/gdliu/O2Basil.pdf
11. when watering, water completely. you cannot over water at one time this is why flushing works(it is possible to water too much but only if you let it pool in the tray). you want at least 10% runoff in your trays after words but get rid of the run off , the tray should have little to no water in it to prevent root rot. also do not water until the top 2 inches of soil is dry. you basically want to get it completely wet leaving no dry pockets(this removes stale air from the soil) and let it dry 2 inches deep from the top. ,Marijuana Grower's Handbook: Your Complete Guide for Medical and Personal Marijuana Cultivation
12. if you water with nutrients make sure you give it 2-3 waterings with nutes and 1 without and repeat. also balancing your nutrients is important. in organics this isnt much of a problem but if you have been using 7-1-1 or similar nute during veg you want to use a 0-6-7 or similar nute during flower. too much of one nute will lockout the uptake of another.
13. no nutes the last 2 weeks of flower. helps more with bud quality than anything. this applies to inorganic ferts. there has been debate about nutrients getting into bud and it is well none that heavy metals from inorganic phosphate fertilizers are notorious for this mainly lead cadium etc. source:
http://www.academia.edu/2721257/Phosphate_mineral_fertilizers_trace_metals_and_human_health
14. never interrupt the dark cycle with light of any kind except green. source:
http://www.crec.ifas.ufl.edu/academics/faculty/spann/PDF/5.pdf
15. cut a 2 liter in half invert the top into the bottom to make a funnel and fill with vinegar. this will be a trap for almost all pests and they will be more interested in the vinegar than your plants. keep it 10 ft from the grow box. if you are using ph down in the form of vinegar this trap is of the utmost importance. 2 or 3 are cheap and easy to make and will keep your plants away from pests.source: make this put it outside and prove it too yourself.
16. use a negative ion generator. negative ions have been shown to improve plant growth and half another benefit of reducing odors. this is not a co2 generator! you can buy them at walmart. make sure it generates negative ions it shoudl say somethign like 10,000 cubic centimeters per second or something like that.
17. go to radio shack and get the strongest magnifying glass. use this to look at your trichs before harvest. you want mostly cloudy trichs when there are over 10% amber trichs its harvest time
18. use a small amount of clay in your soil. clay has a negative charge and improves nutrient absorbtion. too much though can cause clumpy undesireable soil with much less air. the key is to mix it thoroughly with your regular soil. no more than 1 cup per gallon.
19. add supercoarse perlite(preferred) or fine perlite(still good) too your soil. even soils containing perlite can still benefit from extra perlite added. a study on different soil types concluded that 100% perlite in a hempy bucket is the preferred way to grow. it yielded 1.5 grams more on average than the other soils tested in a series of control groups etc. since this is in the beginner section i would not recommend a hempy setup. or even 100% perlite. the reason being it drains so well and is so airy that the plants will dry out quicker and even though alot of new growers tend to over water, i still feel there should be some dirt in your soil mix. 50% perlite 50% dirt is a good middle ground. also a layer of newspaper on the bottom of your planter with 1-2 inches of perlite will help prevent root rot.
19b. add vermiculite or moisture control crystals to your soil. these will help with over watering and slowly deliver water to your plants. moisture control crystals are not organic they are poly acrylates. use 2 tbsps of crystals per gallon of soil and mix thoroughly.30% vermiculite is a good ratio to have.
20. resist the urge to touch fondle the buds during flower. trichomes can break off and you will reduce the quality.
21. heat the roots.. use an aquarium thermometer to heat the water to 72 degrees farenheit. adding a seedling mat or even an aquarium heater to the soil near the edge of the planter will improve growth as well. keeping the plants roots a stable 72 degrees without fluctuation will help more than you can imagine.