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The Balanced Approach to Chemical Fertilizers

September 25, 2014

At the risk of alienating some of my readers I make the following statement, “I do not use any chemical pesticides, fungicides, or herbicides on my garden, but I do use some chemical fertilizers.” I use chemical fertilizers as part of what I like to think of as a balanced approach to soil amendment. Some people will only use organic methods of soil amendment, while other people think that organic growing is a waste of money and is more of a philosophical statement than an actual gardening method. Let me explain my reasoning for a balanced approach to soil amendment and then you can decide if you think it makes sense or not. Here are my reasons for using both natural and chemical soil amendments in my garden.

Reason 1: You can’t raise food without putting nutrients back in the soil.

Everything that grows in your garden represents nutrients that have been taken out of the soil. If you save every non-edible part of the plants that grow in your garden and all of the peels, cobs, rinds, etc from the food that you harvest; and compost all of that and return it to the soil; you will still be removing the nutrients that are contained in the food that you eat. You can rotate your crops so that you plant legumes that add nitrogen back into the soil, but this alone will not be enough to make up for the nutrients that you remove. You can bring in outside organic materials and compost them, as I do; but consider this. My garden is about 3000 square feet. To cover my garden with a three inch layer of compost would require about 750 cubic feet of compost. This would be a 10 foot by 10 foot pile that is 7 ½ feet tall. And since organic material shrinks down by as much as 75% as it decomposes, this means that I would have to start off with as much as 3000 cubic feet of compostable material. Who has the time to do this? So the alternative is that you have to bring in some kind of concentrated soil amendment to add to your garden, which brings us to fertilizer.

Reason 2: Organic fertilizers are not all that organic

So I think I’ve made a reasonable case for having to add some kind of amendments to the soil, but the question is, “What kinds of amendments?” Many people who follow the totally organic method of gardening use natural sources of nitrogen, phosphorus, and potassium. Some people use animal manure for a balanced fertilizer. Blood meal is often used as a good source of nitrogen; bone meal and rock phosphate are used as sources of phosphorus; and hardwood ashes or granite dust can help provide potassium. Let me address these one at a time and tell you my feelings on each of them.


I use manure on my garden, but only the manure that I rake up out of my goat pen. I am about to get back into raising chickens, and I will also use their manure in my compost pile. I don’t buy manure. The bagged manure that you buy at garden centers and big box stores is usually packaged and sold from feedlot operations. The cattle that produce this manure have been injected with steroids and antibiotics. They have been treated with worm medicine and sprayed for ticks and flies. They have also been fed large amounts of salt to increase their weight by water retention. All of this stuff finds its way into the animal’s manure. Doesn’t sound all that healthy or organic to me. If you are going to use manure I would suggest that you use manure from unvaccinated, grass fed animals only. Ditto to everything above as it applies to factory raised chickens also.

If you have a neighbor that ranges cattle you can get some good manure from them but be sure that you compost it in a good hot compost bed to kill the grass seeds. I made the mistake of gathering up a truck load of manure from one of my neighbor’s pastures and throwing it straight onto my garden without composting it. I am still fighting Bermuda grass ten years later.

Blood Meal and Bone Meal

Both blood meal and bone meal are by-products of the slaughter house. The animals that are slaughtered are typically raised in industrial animal operations. This means steroids, growth hormones, antibiotics, etc. All of these unnatural products make their way into the blood and bones of the animals before they are slaughtered. Again, this doesn’t sound healthy or organic to me.

Rock Phosphate

I have no problem with rock phosphate. Rock phosphate is a mined product that contains about 20% phosphorous whereas the phosphorous in chemical fertilizer is also a mined product that has been chemically treated to extract a more concentrated phosphorous from it.

Granite Dust

I have no problem with granite dust as a source of potassium. Well, I do have one problem. If you don’t have access to some kind of free granite dust, it can get pretty pricey. A bag of granite dust costs about $25.00. If applied at the recommended rate, and depending of the condition of your soil, this will treat about 500 sq, ft of garden. For me, that would be about $150 to amend my entire garden. That’s not horribly expensive, but it is a little steep. One advantage of granite dust is that it releases the potassium slowly, so you don’t have to make an application every year.

Hardwood Ashes

Hardwood ash can contain up to 10% potassium, and hardwood ash raises the pH of soil; so it is a good fit for my garden which has very acid soil. I cut hardwoods off my farm to burn in my wood stove, and every time I clean out the stove it is a simple matter to take the ash out and sprinkle it on the garden. Wood ash should be applied at a rate of one to two pounds per 100 sq. ft. depending on your soil. If your soil is already alkaline you may want to stay away from wood ash or be sure to balance out the alkalinity with a lot of compost.

Reason 3: Chemical fertilizers are cheap, convenient, and easy to use; but they won’t solve all of your problems.

Let’s face it, to obtain the same amounts of nitrogen, phosphorus, and potassium found in one bag of chemical fertilizer from natural, organic sources would cost a minor fortune. For example, I looked at a bag of cow manure at one of the big-box stores. It was rated at .5-.5-.5. In other words it would take 26 bags of cow manure to equal the amount N-P-K in one bag of 13-13-13. And here’s the thing, plants absorb nitrogen on a molecular level. They don’t know if the molecules are coming from manure, blood meal, or chemical fertilizer.

Blood meal is rated at 12-0-0, but a 50 lb. bag of blood meal costs around $50.00. Bone meal is rated at 3-15-0; but a 50 lb. bag of bone meal costs nearly $60. Granite dust is rated at about 0-0-5, and a 50 lb. bag costs from $20 to $25. If you add it all up, it would cost about $160 to purchase natural, organic fertilizers that would contain approximately the same amount of N-P-K that is contained in one $20 bag of 13-13-13 chemical fertilizer. Now do you see why the grocery store price of organic produce is so high?

Of course chemical fertilizers are not the be all and end all of good gardening. One of the big arguments against chemical fertilizers is that they only supply the three macro-nutrients (N-P-K) necessary for plant growth, while plants actually require an additional 12 or 14 elements known as micro-nutrients if they are going to have healthy growth and production. I agree with this argument 100%, and I would go on to add that these are only the micro-nutrients that we know about at this time. The scientific study of plant growth is still in its infancy, and I would be willing to bet that, over time, we will find many other things that are necessary for healthy plant growth. So, the bottom line is that you have to do something beyond basic chemical fertilizers to address the need for micro-nutrients.

It is also argued that chemical fertilizers don’t add any bulk to the soil. This is also 100% true. If you have heavy clay soil, adding chemical fertilizers won’t change that. If you have loose sandy soil that loses moisture too quickly, chemical fertilizers won’t change that either. You have to do something else to add bulk to your soil and address proper water retention.

There is much debate over whether chemical fertilizers kill/repel earthworms and soil micro-organisms. It has been my personal experience, using the methods that I use, that I have an abundance of earthworms in my garden. I think that if you use nothing but chemical fertilizers, and if they are applied at a high rate; then this might have an adverse effect on earthworms and micro-organisms, but I don’t know this for a fact. I wonder if the lack of earthworms and micro-organisms in some chemically fertilized soils might be more related to a lack of organic mater in the soil. Again, I don’t know; but I would sure like to see some good scientific data on the subject.

The final argument against using chemical fertilizer, especially from a preparedness perspective, is that it is not sustainable. This is also true. If everything collapses, you will no longer be able to run down to the feed store and buy a bag of 13-13-13 or anything else. But the good news is that chemical fertilizers can be stored indefinitely if they are kept away from moisture. I raise around a hundred ears of corn using a total of about 6 lbs. of chemical fertilizer. I use more fertilizer on corn than on any crop I raise. If I continue raising this amount of corn, two 40 lb. bags of fertilizer would last me for over 13 years. By the way, a 40 lb. bag of fertilizer fits almost perfectly into a 5 gallon plastic bucket with a water-tight lid. After the fertilizer runs out I, and everyone else, will go all organic, but by then I will, hopefully have plenty of time to compost, gather manure, etc. I guess if I need potassium I can always bust up my wife’s granite counter tops, but then survival would probably take on a whole new dimension.

A Brief Summary of How I Amend My Soil

In summary: My soil has a lot of clay in it and it is very acid. I bring in sand to help keep the soil loose, and I turn in home-made compost and uncontaminated manure. I use a pre-plant application of dolomatic limestone, Epsom salts, and borax. I turn in a light broadcast of 13-13-13 fertilizer before planting unless the bed is to be planted in legumes. I rotate my plantings and try to plant all beds in nitrogen fixing legumes every other year. I mulch every year, allow the mulch to decompose, and turn it in. I use targeted side dressings of chemical fertilizers to boost the N-P-K content of the soil. I use 10-20-10 for my root crops like onions, turnips, and sweet potatoes, and I also use 10-20-10 for my cucumbers. I use one application of 13-13-13 around peppers, squash, tomatoes, etc just before they bloom. I side dress my corn with 33-0-0 when it is knee high and again when it tassels. I find that this program works great for me, and I get wonderful yields.

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