check this out 1st 2nd and 3rd grow

got some questions and exct about what to do when im done with my 1st grow i grew them 1 1/2 mo veg and now there 3 weeks into flower the other ones in the cfls are 1 month old 7 of them the other 8 are clones from 2 of the floweing ones and the other 8 are hash plant seeds i got from peakseeds.com ordered 10 and they send 21 seeds i planted 10 and 8 grew 1 dident at all and 1 grew out with no leafs but anyways what do i do with all the dirt when im done ill have 15 gallons of dirt ... what do i do with it can i reuse it or no? i cant just dump 15 gallons of dirt in the trash but maybe slowly? or i dunno what do you do with your leftover dirT? i used alsask fish emulsion and dr shultz plant food for veg and useing alaska moorbloom for flower 12/12 and 18/6 veg it stays 70-78 during the day and 58-65 at night they sleep during the day and are awake at night welp heres some pics any sugesstions id appriciate this is my 1st and 2nd and 3rd grow