too much compost?

In the spirit of continuously questioning all of my habitual garden practices, the thought occurred to me that maybe conventional wisdom needs questioning. Could I be using too much compost?

“Linda Chalker-Scott, a horticulturist at both Washington University and Washington State University, with experience in forests, landscaping, and gardens, devotes several entries in her “Horticultural Myths” column to proving that one can indeed use too much compost…”

Freak out.

“The nutrient content of compost and other organic amendments is much lower than that of most fertilizers. When it is mixed with soil at a ratio of 1:4 or even higher, there’s a huge, but slowly- released nutrient load. Compost increases the nutrients in soil not only by adding those it contains, but also by boosting the activity of microbes that release nutrients already in the soil. The nutrients contributed by compost, therefore, far exceed those actually in it.”

OK.  I ruminate on that.  Mixed with soil at a ratio of 1:4?   I’m horrid at math, but I can come close sometimes.  And there’s no chance, none, that a normal person, with normal compost piles and a normal garden has a compost-to-soil ratio of 1:4.  Maybe someone with a bulldozer and windrows of compost.  Not me.

Still the concept makes sense.

According to the Penn State College of Agricultural Sciences-Coooperative Extension:

“Applying too much compost … can lead to excessive nutrient levels. Excessive levels in the soil can be as detrimental as deficient levels. … Availability of nutrients to your crops will depend on the balance in your soil.”

Balance. I’m good with balance.  It’s a little word with a big meaning, and something I’ve determined to achieve in the autumn of my life.

So as I read Ms. Chalker-Scott’s stuff more carefully (and I’m sorry but I’m a pig, and skeptical of people who hyphenate names), it becomes clear that she knows what she’s talking about.  But what she’s mostly talking about is adding compost to areas of permanent landscape that might suffer from the extra organic matter.

There’s more stuff about chemicals and soil that makes ultimate sense:

“Just about every gardener knows about the three main fertilizers, the primary nutrients, required by plants: nitrogen (N), phosphorus (P) and potassium (K). These three nutrients so dominate many gardeners’ horizons that nothing can be seen beyond them.”

“The development of synthetic fertilizers has encouraged a simplistic approach to agriculture and to gardening: providing the right chemicals solves all our problems. But nutrients alone cannot keep plants healthy if they’re in poor soil. “

Yep, absolutely.  Balance. Moderation.

And in the end I decided that I’m overthinking again.  Generations of gardeners have used mountains of compost for Millenia, and it’s worked so well that compost has become a fundamental principle of modern gardening.  Putting lots of compost into permanent landscapes can probably mess them up.  But I can’t imagine using, let alone making enough compost to screw up my vegetable garden.

Being an old guy, I’ve subscribed to tried and true. I question it, but still trust it. Tried and true says compost is almost always good. A couple of probably reputable sources say too much compost, in some instances, isn’t. Draw your own conclusions.

3 thoughts on “too much compost?

  1. In terms of run-off, there is such a thing as too much compost if your drainage is excessive – the nutrients from the soil in the run-off can cause problems in more delicate ecosystems. But in terms of growing food with steps to avoid erosion (like in most food gardens) – compost is an excellent and nutritious soul ammendment in terms of nutrition and microbial activity. I think it would be very hard for the average farmer/gardener to reach that 1:4 ratio!


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