Lots of information in books and on websites recommend a soil test to help you select the right fertilizer numbers. This is very good advice but it has limitations.
Soil Test; Is it a Good Idea?
In the previous post I suggested that buying fertilizer without knowing what nutrients you have in your soil is a poor idea. You need to buy the nutrients that are missing from your soil–not some fertilizer numbers an expert told you to buy.
The only way for you to know what nutrients are missing from your soil is to have it tested. You can’t tell by looking at the soil, or plants, except in some special cases.
If a soil test is such a good idea, why is it that almost no home gardener does them? I am a Master Gardener and we routinely recommend a soil test to our clients. At a recent meeting I asked my fellow Master Gardeners if they have ever had one done. Only 1 person had it done, and that was years ago. It is good advice, but we don’t follow it.
There are two big reasons why people don’t have soil tests done; cost and effort. A good soil test is not cheap and it requires effort to collect samples, deliver them to the lab etc. It is spring and time to fertilizer–we want to get on with things–not wait for test results. These may not be great reasons, but they are realistic excuses. However, there are some more logical reasons for not doing a soil test.
Reasons for NOT Doing a Soil Test
Who Needs Fertilizer?
My garden is doing just fine and I don’t use commercial fertilizers. My 2,500 different perennials are growing and flowering quite well. Most of my 80 different kinds of daffodils bloom like crazy and have never seen bonemeal. If your plants are growing well, there is no reason to fertilize and therefore there is no reason to get a soil test. Don’t try to fix a problem you don’t have!
I don’t use commercial fertilizer, but I do add dead plant material back into the garden. I use a mulching mower so that grass clippings stay put and feed the grass. I mulch with wood chips in perennial and shrub beds; which slowly degrade and fertilize the garden. So I do fertilize–I just don’t buy fertilizer.
Soil Tests don’t Measure Nitrogen
It will probably come as a surprise to most of you, but regular soil tests do not measure nitrogen. But nitrogen is the nutrient that is most likely deficient in your soil. It is certainly the most important nutrient for lawns. You can order a nitrogen test but it is complicated and expensive, so home owners rarely get this done.
If the soil test does not tell you how much nitrogen you have in the soil, is it really that valuable?
Most labs will estimate the amount of nitrogen you need based on your location, and your crop. Another expert telling you which fertilizer to buy without knowing what is in your soil!
Soil Tests Don’t Measure Micro-nutrients
A standard soil test does not measure micro-nutrients. You can upgrade for a more expensive test and get these analyzed, but what do you do with the information? Very few fertilizers actually tell you their concentration of micro-nutrients, so you really can’t figure out how much fertilizer to use based on your test results. For some micro-nutrients, you can get specialized fertilizer that only contains one or two nutrients, for example calcium sulfate for calcium, and you can then add that according to your test result.
The reality is that most soils are not deficient of micro-nutrients. If you suspect that such a deficiency exists–get a soil test done before buying fertilizer.
The Need to Fertilize
Our minds have been conditioned so that they have a ‘need to fertilize’. We just don’t feel like good gardeners if we don’t fertilize. It is time to change that point of view.
You probably don’t need to fertilize if some of the following apply:
- You mulch with an organic material. It breaks down over time and is fertilizing for you.
- You add compost on a yearly basis.
- You return spent plant material back to the garden instead of sending it to landfill. Again you are fertilizing.
- Your plants are mostly growing well. Not all plants do well in all gardens–accept this fact. Adding fertilizer is rarely the answer.
- You have not done a soil test.
If I have not yet convinced you, please consider joining FA (Fertilizers Anonymous). You have a problem and you need help with your need to fertilize.
Next time you are at the garden center and you see someone loading up their cart with bags of fertilizer, shake your head and think to yourself (ie not out loud); poor fellow, he’s wasting his time, his money and his back, to do something that does not need to be done.