Soil Calculator: How Much Soil or Amendment Do I Need for My Garden Project? — Seattle's Favorite Garden Store Since 1924 - Swansons Nursery (2024)

FAQs

How much soil amendment do I need? ›

To figure out how much of an amendment you need by weight, multiply the square footage by the application rate on the package. For example, if the application rate is 2 pounds per 100 square feet, and the bed is 350 square feet: (2 pounds / 100 square feet) x 350 square feet = 7.0 pounds.

Soil amendments are meant to improve your soil, but unnecessary amendments can backfire and cause more problems than they solve. Lowering soil pH too much can create toxic conditions. Raising soil pH too high sets off a chain of nutrient imbalance. Even organic matter can cause problems if used too much.

Length in feet x Width in feet x Depth in feet (inches divided by 12). Take the total and divide by 27 (the amount of cubic feet in a yard).

Compost is the most commonly used organic amendment, but other products are available. Over time, organic matter improves soil aeration, water infiltration, and both water- and nutrient-holding capacity. Many organic amendments contain plant nutrients and act as organic slow release fertilizers.

It's really very simple, but a lot of homeowners don't get it: Topsoil is just that--dirt scooped from the ground. Soil amendments are organic or chemical products that improve dirt--make it softer or help it hold water. There is no difference price-wise if you are buying good topsoil or amendments.

Remember, amending the soil takes time and patience. It could take a couple of years to get unhealthy soil back into shape.

Excess application of amendments onto land can lead to negative impacts on soil quality and crop production caused by salt effects alone. Salt levels are gauged by a manure's or soil's electrical conductivity.

Coffee grounds are best at improving soil. As the coffee grounds feed the soil microbes, microbial glues are released that promote good soil structure and improve drainage. When using coffee grounds as a soil amendment, Brewer recommends working in a half inch to a depth of 4 inches.

Mostly, perennial roots do not reside in the planting hole for long, so the time that amendments would be effective is very short. Since amending can also harm some plants if done incorrectly, University of California does not recommend the practice, neither did Harris for trees, shrubs and vines.

Bulk Soil. Bulk soil is measured in yards. 1 yard equals 27 cubic feet. Think about it as a cube that is 3′ X 3′ X 3′.

What is a good garden soil ratio? ›

Gardening magazine's trial of the best soil mixture for raised beds found that a blend of 50% topsoil, 25% coarse sand and 25% compost was best.

For a 4x8–foot raised bed with a 10” height, about 1 cubic yard of soil is needed. For a 4x8-foot raised bed with a 6” height, using Mel's Mix: about 5 cubic feet each of compost, peat moss, and vermiculite is needed.

To amend existing soil with compost or soil-building conditioner. A ratio of 20% soil amendment to 80% existing soil is recommended.

PerFect Amendment is a soil additive with a high concentration of patented beneficial Streptomyces on an iron and humic acid carrier that when added to the soil produces healthier plants that more effectively resist stress, and reduces the need for excessive watering.

Effective mulches include shredded hardwood bark, pine needles, coarse compost, and shredded native tree trimmings. Mulching helps hold moisture in the soil, controls weeds and buffers soil temperature. It also protects and stimulates microbes and enriches the soil with nutrients as it decomposes.

Amending Soil around Existing Plants

Till in to about 2 inches if close to a plant, and a little deeper if further away. Simply try not to disturb the roots too much and always water when you're done to settle any roots that may have been disturbed.

Measure your yard and/or garden to figure out how much soil conditioner you will need. The recommended application rate is usually specified on the soil conditioner package, and it is important to follow the manufacturer's guidelines to avoid over-applying and potentially causing harm to the plants.

If you're adding amendments like compost or other nutrients (preferably based on recommendations after a soil test), do so and then pass over the soil with the tiller a third time. If you haven't had a soil test done, you can add 3 inches of compost on a poor sandy soil or heavy clay soil.

Mostly, perennial roots do not reside in the planting hole for long, so the time that amendments would be effective is very short. Since amending can also harm some plants if done incorrectly, University of California does not recommend the practice, neither did Harris for trees, shrubs and vines.