some people prefere not to use chemicals some others go crazy with em. Depending on your medium you can avoid or totally require them. Hydroponics rely on the premise of someone adjusting the nute mix almost on a dayli basis. This will help the plant develop to full potential cause (youre supose to make it right) it wont be deprived of any nute. Hydroponics require you to use ferts of some kind to give the plant absolutely everythng it needs. If you grow in soil and it is a very good soil (rich of nutrients, sandy, preferably mixed with humus or worm castings) then you might get away with some pretty looking plants. Another thing is the size of your pot. If you have an virtually un.exhaustable nute resources in the soil then no nutes needed, but that hardly adjust to the reality. The fact is that the plant will suck up a lot of nutes during veg and a lot more during flowering. Lets say your soil is not good enough, or simply not enough; your plant may veg ok, but grow shity bud. An intermediate approach is using the best soil you can get and watering the plants with a light nute mix. This way it wont mess around much with your soil pH, burn the root or the leaves and the nutes will be there as a backup in case the soil runs out of food. Thats why you must never reuse your soil, the nutes have been sucked out. Then you smoked them. If your bag says 20-20-20 chancesare that there arent really 20% weight available of P and K. This is because the chemical form used isnot readily available for the plant. So, take the P, K amounts with a grain of salt. Better to undernute a few days and then up bit by bit,than burning the plant and then going crazy about flushing that might end up in root rot if you become obsesed. Go slowly and find out what your plants like. No plant reacts exactly the same, not even clones.
'a bag'' sounds like your talking about granulated time released ferts,,,,not a good idea,,it being time released it may be fine till one day it rleases too much and you burn them up,,,i shun away from time release ferts. unless its a outside grow and they are 3 months into the grow,,,, your best bet would be get a water soluble fertilizer,,, scotts .schultz,miracle grow,, a all around plant food would do,, a higher nitrogen count would be better,,,only use 1/4 of what the directions call for,,if you know someone with a fish tank,,that water will do you wonders,,or you can buy fish emulsion which has a 5-1-1- ratio,,,,excellent for young plants,,,,its a lot safer to go with organic ferts. the chemical ones if used wrong,,,spell disaster good luck
I got a bag of 20-20-20 it is water soluable blue powery crystals. I use 1/3 teaspoon per 1.5 litres of water. (Not much at all)
That should be fine for vegging. What brand is it -- Peter's? Ideally it should also include micronutrients. Start about 3 weeks after it sprouts, use 1/4 the formula recommend on the box. Over time you can increase that to 1/2 strength. Better too little than too much.