Jan 262013

In organic gardening circles compost is sacrosanct. So when somebody with a resume like Steve Solomon says we can use too much compost, as he has in his new book The Intelligent Gardener, organic gardeners recoil in horror.

JI Rodale’s Organic Gardening and Farming Magazine introduced organics to North Americans.
Steve Solomon summarizes Rodale’s approach as follows: “To grow an abundance of highly nutritious vegetables and fruit, make and then dig in compost. Lots of it.”

Rodale encouraged bringing in or importing lots of organic material and putting it in the garden. And then his recommendation was to counteract acidic soil to by adding crushed limestone to bring the pH close to neutral. Roedale said if you’re going to add lime it’s better to use a sort called dolomite because dolomite contains both magnesium and calcium and magnesium is as much a vital plant nutrient as calcium is.

Some compost in the garden is, of course, good. Making composts satisfies our desire to recycle the plant material from our garden waste. Compost increases the organic percentage of the soil and turns to humus which helps the garden hold moisture. And, it does provide some nutrients but, at a point in time, the benefit of compost is lost. And, depending on the materials used to build the compost there might have been much nutritional benefit to start with.

The real problem with using the composting method of organic gardening is that we don’t know the mineral or nutritional makeup of our compost. We are flying blind. We don’t know exactly what our inputs consist of. Thus, if we just keep adding compost we don’t really accomplish very much.

Excessive inputs of compost will usually imbalance the soil’s profile with the result that nutritional outcomes will be degraded. And if, in addition, one adds dolomite as one’s lime source the magnesium in the dolomite will change the behavior of the clay in the soil making it stick to itself and you’ll end up with tight or clumpy soil in your garden beds.

In the Puget Sound region the soil already holds huge supplies potassium but insufficient calcium and magnesium to properly balance that potassium. Plants concentrate potassium into their structural parts. So if we import lots of grass clippings, straw, spoiled hay, tree waste, etc. into our compost we are  adding enormous additional quantities of potassium which will have a devastating effect on the nutritional quality of our food, even though it makes plants seem to grow great.

Here’s the problem with potassium: If potassium gets out of balance, that is top heavy in relation to the other important minerals like calcium and magnesium, plants grow differently. Instead of making proteins they make more carbohydrates. The bottom line is this. Crops on high potassium soils produce about 25% more carbohydrates. At the same time their protein content is lowered by around 25%.

By continually adding compost we end up with the situation where our food looks good, grows well but we’re producing more calories and less proteins. Plus according to Steve Solomon the nature of those proteins changes.

In the Intelligent Gardener he writes, “Proteins are long complex chains chains of about 20 different amino acids. A few amino acids usually are scarce. In plants grown with excess potassium these are even scarcer lowering protein quality and leading to diseases in all the animals eating them including us. Another shift occurs in the food’s mineral content. As soil potassium increases the mineral content of the plant growing on that soil also shifts. Excessive potassium in the soil results much higher levels of potassium in the plant tissues but correspondingly lower levels of calcium and phosphorus and minor nutrients. Our bodies can hardly get enough calcium magnesium phosphorus but
We do not need high quantities of potassium.”

We need some potassium, yes; but not lots.

We don’t have naturally balanced nutrient rich soil in our region. Part of this is because of constant winter rains which leech nutrients particularly calcium from the soil. If we bring in fertility by importing local vegetation we further imbalance our soil.

So this is why the composting method isn’t necessarily the best method and why getting a simple soil test and balancing the nutrients in your garden makes all the sense in the world.

We’ll take up this subject in more detail and learn an easy way to build a customized fertilizer for our particular garden at the Gardener’s Network meeting, Feb. 11, 6:30pm at the Lummi Island Grange.


  7 Responses to “Contrarian Thoughts On Compost”

  1. Given all this new information, am I the only one totally astounding at the (rather simple) fact that humans, not being able to even measure potassium, calcium or anything else until very recently, ever found/grew enough food to grow our population to, what is it, 6 billion? 7 billion?

    Well, I suppose all people really had to do was get to reproduction age …. available nutrional density has clearly been good ‘nuf for that … and still is, from the rate I hear of people having children, grandchildren and great-grandchildren these days.

    I learned from an islander who raises livestock that island soil is shy on boron, so that animals’ diets have to be supplemented with that. So our vegies aren’t probably adequate in that, either. 4-5 Brazil nuts a couple of times a week is enough. I could worry about getting soil tests & buying external amendments to correct this soil ‘deficiency’, but like Brazil nuts better.

  2. Composters, Brazil nutters or Intelligent Gardeners. All are welcome in the Gardeners Network.

  3. Another really useful post to those of us who garden by the seat of our pants. So much good information here.

  4. When applying boron (Borax in water solution) err on the side of too little, but do add it in a very dilute solution. Best to spray it on the garden before planting and till it in with other amendments. It is needed in minute amounts and can be overdone quite easily. I am very interested to know that calcium and magnesium should be applied more liberally than appreciated Compost is dandy, but……

  5. Must be very careful with Boron (Borax). As an example, my soil prescription this year called for 1.6 ounces of Boron for 2300′ of beds. A tiny amount. Twenty Mule Team Borax is approximately 10% Boron. So, would take about a pound of Borax to get the 1.6 ounces onto 2300 sq. ft.

    All of this is covered in some detail in The Intelligent Gardener.

    I think I’ve pointed out earlier that Steve Solomon did my soil analysis this year. He was doing them for free as part of his research for the book.

  6. Ah ha! Full disclosure at last 🙂

    I do appreciate the advice to get soil analysis, even if I probably won’t do it this year. But who knows? My landscaping/gardening to-do list is so long right now that even the thought of adding another possible item (like if the analysis comes back with ‘deficiencies’) is enough to shut down my brain to any more options. At least I have only ~12? 15? trees/shrubs to transplant this year, hopefully in the next week or two. If, that is, the rain stops long enough to dig holes that don’t immediately fill up with mud. Another shoulda done it last fall…

  7. My brain got totally confused: it’s selenium that island soils are reportedly deficient in, not boron! And brazil nuts have lots of selenium, not boron. Don’t know how I got that so totally wrong, except, maybe … I’m not perfect yet?

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