Let me start by saying there is no such thing as the perfect soil. Of all the factors in growing plants the most complex is the soil. It has its own ecology, which can be modified. You can modify the soil to enrich or to destroy, which can determine the crop success or failure.
Each variety can grow within a wide range of soil conditions. Your goal is to garden the soil within the range for the healthiest growth possible. Marijuana grows poorly, if at all, in soils, which are extremely compacted, have poor drainage, low in fertility, or have an extreme pH level. Soil type, texture, pH, and nutrient content are important soil factors for the grower to know. Some types of soil are sandy, silts, mucks, clay, loams, humus, and composts.
Soil texture refers to density, particle size, and stickiness. All of which affect the soil’s drainage and water-holding characteristics. The most important for marijuana is that it drains well. You don’t want the water to stand in pools after rain and you want to make sure the soil is not constantly wet. Medium-texture soils are the best for marijuana, the soils that drain the best help good root development. You always want to test when the soil is moist, but not wet to make sure the consistency and drainage qualities are good for your soil. Good healthy topsoil will contain abundant of worms, bugs, and other little animals interlacing with the roots. You want to be able to penetrate the top layer with ease, otherwise you will definitely have a soil problem that you don’t want.
To test for drainage just fill the hole with water. Wait about half an hour to let the moisture penetrate. After the surrounding soil has soaked that up fill the hole again with water. If it doesn’t drain completely in 24 hours your soil has poor drainage.