Potting Soil

Marijuana Horticulture

by Jorge Cervantes

Potting soil fresh out of the bag often fulfills all the requirements fro a growing medium: good texture that allows good root penetration, water retention, and good drainage, a stable pH between 6 and 7, and a minimum supply of nutrients.

Premium fast-draining soils with good texture that will not break down quickly are the best choice. Potting soils found at nurseries often formulated with a wetting agent and retain water and air evenly, drain well, and allow easy rot penetration. Organic potting soils are very popular. These soils are often fortified with organic nutrients including readily available high-nitrogen worm castings. Potting soils are very heavy, and transportation costs tends to keep them somewhat localized. There are many good brands of high quality potting soil. Ask your nursery person to help in selecting one for fast growing vegetables.

Stay away from discount brands of low-quality potting soil. These soils can be full of weed seed and diseases, hold water unevenly, and drain poorly. Ultimately, saving a few pennies on soil will cost many headaches and a low yield later.

Many potting soils supply seedling transplants and clones with enough food (fertilizer) for the first two to four weeks of growth. After that, supplemental fertilization is necessary to retain rapid, robust growth. Add fine=-grade dolomite lime to buffer and stabilize the pH. Trace elements in fortified soil and soilless mixes can leach out and should be replenished with chelated nutrients, if deficiency signs occur. Organic growers often add their own blends of trace elements in mixes that contain seaweed, guanos, and manures.

Although some growers reuse their potting soil, I do not recommend it. If used for more than one crop, undesirable microorganisms, insects and fungi start growing; nutrients are depleted; water and air retention are poor, causing compaction and poor drainage. Some growers mix their old potting soil with new potting soil to stretch their mix. Cutting corners this way most often costs more in production than is saved in soil.

Potting soil or soilless mix that contains more than 30 percent lightweight pumice or perlite may float and stratify when saturated with water before planting. Mix water-saturated soil thoroughly with your hands until it is evenly mixed before planting and transplanting, if necessary.