There are many growers that prefer to know the mixture of their soil, and one of the mixtures that works best for healthy marijuana plants is:

• For each four gallons of soil, there should be two parts of moss added, one part sand and one part either perlite or sponge rock added to the soil. This is a winning combination for growing cannabis, to keep the soil moist, to hold in the nutrients, and the mixture should be tested for the proper pH level after being mixed.

Using yard dirt is something that is not recommended and for the person that does use yard soil it will need to be sterilized and that is something that will take work and make the house smell, the odor might cause leaving the house until it is aired out. This is because soil from the yard contains parasites and will need to be baked in the oven to kill these at 250 degrees for approximately an hour. The parasites must be killed, or it can mean risking the entire crop to disease.
 After the soil has been baked and cooled, then it is important to add fertilizer like Rapid-Gro and mix it in thoroughly. Depending on the amount of soil it might take about a teaspoon per oven load and if the pH level is low a half pound of lime added to one cubic foot of soil will raise it one point.  The soil can be tested with litmus paper that can be found in soil testing kits that are stocked at most plant stores.