How To Test And Amend Your Garden Soil

Have you ever started a garden and struggled with it? Like no matter how much babying you do, you just can’t get your veggies to grow properly? It’s probably because you have poor soil. Having poor soil can cause stunted plant growth, issues with plant disease, and poor harvests. This is why you should test and amend your garden soil every year.

Wait, TESTING the soil? Is that even a thing? You bet it is! You should regularly test your soil to check what nutrients it is lacking in, the pH levels, and to check the organic matter in the soil. If you want to grow nutritious food, your soil has to be nutritious. So yes, we test!

How to test your garden soil

First, you need to gather some soil from your garden. You should try to get a little from each corner of the garden, as well as some from the middle section. You don’t need a lot, usually just a small scoop from each location. Try to dig down just a bit when getting your scoops, so you can get an idea of more than just the top layer. I like to scoop down about 4 inches.

Put all your scoops in a bucket, and give it a shake to mix it all up. This way, you’ll be taking an average of your garden soil.

There are soil test kits that you can buy at the store, you can send off a sample, or you can go the homemade route. Last year, I bought a DIY test kit for $15 at the feed store. It can be used several times. Most store-bought kits test for pH, Nitrogen, Phosphorous, and Potash.

You can also send off a sample. They do usually charge a fee, but you will probably get the most accurate results. You can find a list of places to send a soil sample to here. Sending off a sample will give you a very detailed write-up of your soil nutrients.

DIY garden soil tests

Probably the least expensive (and likely the least accurate) is a homemade soil test. With a DIY soil test, you are also very limited to what nutrients you can test. Here are a few DIY soil tests if you want to go that route.

The easiest, most accurate soil test you can do at home is a soil composition test.

1. 1. Fill a straight-sided mason jar about halfway with your garden soil.
   2. Fill the jar with water, leaving 1/2 inch headspace.
   3. Shake vigorously to get all of the air pockets out of the soil and break up the clumps.
   4. Let this mixture sit somewhere without disturbing it for 5 minutes.
   5. The sand will have settled to the bottom. Use a permanent marker to mark the level of the sand.
   6. Wait for 2 hours. The silt will have settled on top of the sand. Use a permanent marker to mark the level of the silt.
   7. Wait for 24 hours without disturbing the jar. The clay will have settled on top of the silt. Mark that level as well. You will also notice a some murky water with some “floaties”. These “floaties” are the organic matter that is in your soil.

With this simple test, you can see a “snapshot” of your garden soil so you know how to amend it.

Amending garden soil from test results

So, you did a soil test, now what? Well, here’s the fun, experimental, sciency part!

Soil pH

The ideal soil pH for vegetable gardens is 6.5. Some plants, like blueberries and azaleas, prefer more acidic soil. But for most vegetable gardens, anything between 6.0 and 7.0 is good.

• • Low pH (less than 6.0) – means your soil is acidic and your plants will likely suffer. To raise your pH to more acceptable levels, you can add dolomite, lime, or fireplace ashes to amend garden soil.
  • High pH (more than 7.0) – means your soil is alkaline, and your plants still won’t be happy. To lower the pH, you can add sulfur, sphagnum peat moss, aluminum sulfate, compost, or even rotten manure.

Soil composition

Vegetable gardens thrive in loamy soil. Loamy soil has nearly equal amounts of clay, sand, and silt. This type of soil resists compaction, allows water absorption, and holds nutrients in.

• • Sandy soil – both water and nutrients will drain away quickly. Sandy soil needs lots of organic matter, like rotted manure and compost. The more the better! You can also add vermiculite or peat moss. Mulch should be used to retain moisture and keep the ground cooler. Cover crops are very beneficial for sandy soil.
  • Clay soil – holds nutrients better but is prone to compaction and water bogging. It also tends to get difficult to dig in when dry, and is typically more alkaline. Clay garden soil needs organic matter added, such as grass clippings, compost, or shredded leaves. Gypsum is a wonderful amendment for clay soil. Greensand is also very beneficial. You can even add sand to help counteract some of the less desirable qualities of clay soil. Just make sure you’ve added lots of organic matter first, or you may make some concrete!
  •  Silty soil – the best of the three types, silty soil holds nutrients well and allows adequate drainage. Again, adding organic matter is key in improving this type of soil. Perlite is another good addition, as it helps aid in aeration.

Nitrogen (N)

Nitrogen is a vital nutrient for plant growth. It is a major component of chlorophyll and amino acids. Plants need an adequate supply of nitrogen for photosynthesis, as well as proper growth and yield. If you buy fertilizer, nitrogen is the first number listed (ex: 5-10-10 fertilizer has 5% nitrogen).

• • Low nitrogen – You can buy fertilizers at the store, but if you’re looking for a more organic approach, I have 3 words for you – compost, compost, compost! Also, try banana peels, coffee grounds, blood meal, fireplace ashes, egg shells, fresh grass clippings, seaweed, kelp, and urine (yes – urine!). Any of these are fabulous additions to your compost pile.
  • High nitrogen – If your soil has a very high nitrogen content, your plants will be very green and lush but will not yield much fruit or vegetables. Removing excess nitrogen is not a quick or easy process. First, you will need to mulch heavily with wood chips. Using wood chips in the garden helps to use up some of the nitrogen in order to break the wood down. Then you will want to plant nitrogen-loving crops, such as corn, squash, cabbage, and broccoli. You may not be able to grow plants that require less nitrogen this year if you have too much nitrogen.

Phosphorus (P)

Phosphorus helps provide energy to the plant. It helps plants capture the sun’s energy and converting it into a form the plant can use. Phosphorus encourages plant bloom and healthy root growth. Phosphorus is the second number on store-bought fertilizers (ex: 10-6-4 fertilizer has 6% phosphorus).

• • Low phosphorus – The most efficient, yet slowest acting way of increasing the phosphorus in your garden soil is using rock phosphate. Bone meal is another valuable addition, as it provides both phosphorus and potassium, which are often low together in garden soil.
  • High phosphorus – Too much phosphorus in the soil can cause your plants to have stunted growth. Excess phosphorus is usually caused by adding too much fertilizer or manure to the soil. This problem is very, very difficult to solve. Excessive phosphorus can stay in the soil for years. The best thing you can do is to plant nitrogen-fixing plants like beans and peas, or clover as a cover crop in the off-season.

Potassium (K)

Potassium, also known as potash, is essential to photosynthesis. It helps plants regulate uptake of CO2, and facilitates protein and starch synthesis. It helps strengthen plants against cold, heat, disease, and pests. If your soil is potassium deficient, your plants will likely be yellow and stunted. Potassium is the third number on commercial fertilizers (ex: 10-6-4 fertilizer has 4% potassium).

• • Low potassium – To increase potassium levels in garden soil, you have a few options. Banana peels are high in potassium, an excellent compost addition, and you can make a banana peel fertilizer very easily at home. You can also add fireplace ashes (but watch the pH levels – ashes can make the soil more alkaline). Other amendments are kelp meal, greensand, or granite dust.
  • High potassium – Excessive potassium usually doesn’t cause too many problems in vegetable gardens, unless it’s a very high amount. High potassium levels can, however, interfere with the uptake of other nutrients, especially calcium. To counteract excess potassium, try to create a good balance of all 3 macronutrients. Regular watering will help literally flush out the extra potassium. Working the soil deeply is good practice too, as it spreads the potassium out more evenly throughout the soil.

Garden soil needs balance

Vegetable garden soil needs to have a balance. All of the macronutrients, all the micronutrients, and the organic matter all work together in perfect harmony in healthy soil. Earthworms help aerate the soil and deposit valuable fertilizer. Microbes like bacteria, fungi, and protozoa further help benefit the plants in healthy soil.

The nutrition in the vegetables we grow are a direct reflection of the nutrition in the soil. Doesn’t it make sense to pay special attention to the soil in order to get the most delicious, nutritious food we can?

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