What’s in that bag? Soil products examined

Any time now, pallets of bagged soil products will be appearing in garden centres. Deciphering the differences and what they are best used for is a challenge.

  • Apr. 17, 2014 8:35 p.m.

Any time now, pallets of bagged soil products will be appearing in garden centres. Deciphering the differences and what they are best used for is a challenge.

Mixing decomposed organic material, compost, manure or peat moss with existing soil improves the soil structure.

When organic matter is mixed with clay soil, it increases that number or air pockets within the soil structure. The larger particles from the organic matter stop the clay particles from compacting and forming a cement-like substance.

The looser soil contains more air, less moisture and it is easier for the roots to expand outwards.

Sandy soils are too loose and do not hold enough moisture. When organic matter is added to this type of soil, it improves the retention of water and nutrients.

Peat moss is harvested from Canadian bogs, where it has decomposed for thousands of years.

The bogs are rarely exposed to weed seeds, therefore the bagged product will rarely contain any weeds. Peat moss is harvested, dried, compressed and baled before being shipped to stores for sale. Peat moss contains little if any nutrients but will absorb fertilizer and release it over a period of time.

Coir is made up of coconut husks that are left over when the coconut meat is harvested. The material is shredded, dried and compacted before being shipped throughout the world. Coir and peat moss have similar attributes.

Compost can be made out of many different products. In Canada, it is regulated under the Fertilizer Act.

The package or shipping bill for bulk materials must contain a product name, weight, address, lot number, guaranteed analysis, directions for use and cautionary statements as required.

Commercial compost is made out of organic materials that are turned on a regular basis to speed decomposition. Once it has the consistency of soil, it is bagged and shipped. If weed seeds were part of the original product, there is a good chance that some will be viable in the compost. That being said, reputable companies will do their best to minimize the number of weed seeds in the finished product.

Sea Soil is relatively new and starting to make an inroad on the compost market. It starts as a half and half mixture of leftover product from fish processing plants and fine forestry byproduct.

The final product is a dark soil-like structure without any fish odor. The material never comes in contact with seeds and is weed free.

Manures start as 60 per cent fresh material (green) and 40 per cent brown (carbon). They are mixed, composted and bagged. Producers do their best to illuminate weeds by keeping the compost hot but some will survive the composting process.

Potting soil is not regulated unless it contains a slow release fertilizer or compost. Then it must comply with the Fertilizer Act.

Different companies put different amounts of information on the potting soil packages, making it hard for the consumer to know what they are purchasing.

Potting soil packages without supplement contain peat moss with some perlite and or vermiculite. Even when ingredients are listed on the bag, it is rare to find percentages.

Unfortunately, most soil packages are opaque, making it impossible to see the texture of the peat moss or the amount of perlite or vermiculite in the mixture.

Soil products are sold by volume as weight changes depending on the moisture content of the soil. To reduce shipping costs, soil is dried before it is bagged.

Before purchasing bagged soil, read the package and, if possible, look at the contents.

Linda Tomlinson is a local horticulturalist who can be reached at www.igardencanada.com or your_garden@hotmail.com.