Spring is a busy time for gardeners. We spend hours cleaning out beds, cutting back perennials, pruning fruit trees, trimming shrubs, weeding and mulching. The list seems endless, but one of the most important spring chores gardeners undertake is improving the soil by adding organic matter to improve soil structure and increase water-holding capacity. It also adds both macro- and trace nutrients and improves overall soil health by feeding the beneficial microorganisms living there. Whether you choose to use it as a top-dressing or till it into the soil, just a few inches of organic matter added once or twice a year supplies all the nutrients plants need for optimum growth.
Organic matter comes in many forms, but they’re not all created equal. Here’s some information to help you determine which type(s) of organic matter is best suited to your garden.
1. Compost
Either homemade or commercially produced
Average pH:
7
Nutritional Content:
Compost is typically well-balanced and contains a great blend of all nutrients.
Notes for Use:
Good-quality compost should smell earthy and be a rich, dark brown. Check with any commercial source to ensure that bio-solids (sludge) were not used. If the product smells like urine, it’s likely the nitrogen content is too high. It’s always best to make your own compost to ensure it is balanced and well-rotted, though you can find quality commercial composts.
2. Mushroom Soil/Compost
Average pH:
8
Nutritional Content:
Although fairly high in organic matter, mushroom soil or mushroom compost has low nutrient levels; however, the nutrients are slowly released over time so they’re constantly available.
Notes for Use:
A byproduct of mushroom production, this compost contains ingredients like horse manure and shredded corn cobs. It can be fairly high in soluble salts but also contains a substantial amount of organic matter. Because of its high pH, I don’t recommend adding it every year.
3. Sphagnum Peat Moss
Average pH:
4
Nutritional Content:
Very low in all nutrients.
Notes for Use:
Peat moss helps loosen compacted soils, but can alter the pH. It’s weed free but adds very few nutrients to the soil. It’s a great amendment for acid-loving evergreens.
4. Leaf Mold/Humus
Average pH:
7.5
Nutritional Content:
Leaf mold and humus have moderate but balanced nutrient levels, and also contain many minor nutrients.
Notes for Use:
Primarily composed of municipally collected leaves, these products are high in many trace nutrients, as well. They’ve also got great water holding capacity.
5. Manures
Average pH:
depends on type
Nutritional Content:
The nutrient content of manure is variable but generally very high in all nutrients. The type of bedding used with the animal can also affect the nutrient content.
Notes for Use:
All manures are not created equal. Horse and cow manures are more mild, while chicken and sheep are highly concentrated. Manures contain many weed seeds and should be composted for at least 90 days before use.
