Too Much of a Good Thing? 

Compost is an affordable and sustainable way to add nutrients to the soil in your garden. Applying compost helps maintain good soil fertility because it contains nutrients, builds organic matter, and inoculates the soil with good biology. The key point is that using compost in your garden is only one part of sustainable garden fertility management. Applying compost alone will not provide for the complete nutritional needs of your plants and you may be disappointed in their productivity.

Limits of Compost

Compost is sustainable, especially if you are making and using your own, and it is a great way to add organic matter to your soil, but as a fertilizer it is incomplete. A typical compost has moderate levels of Nitrogen (N) with higher levels of Phosphorus (P) and Potassium (K). If you tried to apply compost to meet the Nitrogen needs of your plants, you would almost certainly be over-applying P and K. In the case of soil, you can have too much of a nutrient. This is best explained by the three underlying principles of organic soil management—moderation, balance, and diversity.

Moderation

Moderation basically means don’t apply too much of any one soil component at any one time. We tend to think that when we add amendments to our soil they are just being used by our plants, but they are also being consumed by the soil life. This is particularly important when adding compost, because the soil life will work to incorporate the over-applied amendment instead of maintaining a relationship with and nourishing your plants.

Balance

Balance means that in order to have healthy soil and healthy plants, macro and micronutrients need to be present in the soil profile in the right ratios. When there is an abundance of one element it can “lock up” or “fix” other nutrients which keeps them from being absorbed by your plant’s root system. Compost needs to be carefully incorporated because of its tendency to be high in Phosphorus which can lead to an unbalanced soil profile.  

Diversity

Diversity is employing a range of growing practices and relying on a variety of sources for nutrients. Using these diverse methods and components promotes a healthy diverse soil life that is able to develop a relationship with your plants and allows them access to more soil nutrition. Adding compost is just one tool for improving your soil, and we have already identified it as in incomplete and imbalanced source of nutrients—so if it is the only tool in your toolbox your plants will not meet their maximum potential. Compost needs to be added in moderation and in conjunction with a balanced organic fertilizer like Super Plant Food 3-2-3 (7 organic ingredients combined in the right proportions) to achieve maximum results.

Too Much Compost?

A final point about the use of compost relates to the amount of organic matter you have in your soil. Organic matter is a desirable component of a healthy soil, and ideally 4-6% of your soil will comprise organic matter. But at higher levels, 7% or more, the breakdown of organic matter will actually rob nutrients from your plants. It is an odd sight to see in a garden with an abundance of carbon rich organic matter: plants that look healthy, but just don’t grow or produce. Or plants showing nutrient deficiencies (especially nitrogen) and yellowing leaves. The problem is too much organic matter, and this is most often associated with applying to much compost – too much of a good thing.

Test Your Soil

For more specifics on establishing healthy soil and maximizing the growth of your plants, order a soil test and receive customized recommendations from Easy Organic. Our testing results include information about the amount of organic matter currently in your soil and recommendations on using compost in conjunction with the right blend of fertilizers to give your plants the right nutrition.