It is all about the dirt

September 25, 2022

I guess to start out with I should go with the disclaimers. I am not a soil scientist, I am not an agronomist, and I am not even a life long farmer. I am a farmer that came to agriculture with an open mind and experience in observation and engineering. It is my intention to try to explain the basics of soil fertility so you can be a better manager of the "dirt" in your life whether that is a flower bed, food plot, pasture or just your front yard.

There are several variables in soil fertility management that I will discuss over the next few weeks but like any former engineer I live by the credo - "If you can't measure it, you can't manage it". So we need to start our soil fertility management journey with being able to answer our first question.

Like any journey this one has 2 things in common with all journeys a beginning and an end. The beginning of the journey is where you are today. To know where you are at, or better said where your soil is at you will need to evaluate it. You will need to have it tested. You will need to learn about it. Soil has many attributes and you will need to know a little about each of these major attributes. The first is what type of soil you have. The second will be what nutrients are present in your soil and third and maybe most importantly to the health of your soil is how much organic matter and how healthy is the soil food web in you dirt? We will discuss each of these independently even though they are completely interrelated.

I said there were two things this journey has in common. I mentioned the first, but the second is a destination. Like the old adage, If you don't know where you are going, any road will get you there. Therefore it is important to know what you are attempting to grow. What do you intend to grow in your soil and what type of soil does that vegetation like to grow in. Because as we test our soil there will be recommendations (course corrections) to what should you do to improve your soil. That will depend on the plants or types of plants you intend to grow. So let's start this journey with our first step.

How do I know what kind of soil I have?

Soil can come in many different types, from sandy to clay or loam, or a combination of these (for example, sandy loam).

It’s easy to find out what kind of soil you have by performing a simple “jar test”. You can find instructions in this easy-to-follow how-to article from Horticulture magazine.

How do I test the soil?

Soil Sampling Tools – You can collect soil samples using a shovel or spade, a soil sampling tube, or a soil auger. Tubes and augers should be stainless steel or chrome plated. A wooden rod will be helpful for removing soil from a sampling tube. If using a shovel or spade, make sure it’s clean and rust-free.

Amount of Soil Needed – You’ll need to collect enough soil for the lab to run the necessary tests – usually about 1 to 1 ½ cups. Many labs will send you a special bag in which to place your soil sample; just fill the bag to the marked line.

How to Collect Soil Samples – Each soil sample consists of small amounts of soil collected from a specified area. For example, if you’re testing the lawn, you’ll take small samples of soil from 10 to 20 random spots across the lawn. If you’re using a sampling tube or auger, simply withdraw as many core samples as you need. With a spade or shovel, dig a V-shaped hole to sampling depth and then remove a thin slice from one side. In all cases, remove vegetative matter from the surface before you sample.

You will be able to affect only about the top 6 inches of soil by adding amendments. For that reason, it’s best to take your soil samples from the top 6″ only.

As you remove the soil samples, mix them together in a clean container. Because soil will vary in color, texture, and consistency throughout the garden, soil testing is usually done on a ‘composite’ sample. If you’re using a pail to collect the soil, it should be plastic to avoid contamination from any trace metals. For example, soil will pick up zinc from a galvanized pail.

Remove 1 to 1 ½ cups of mixed soil from the container and place it in the sampling bag.

And that’s it – soil sample collected!

Where do I get my soil tested?

There’s no excuse not to test your soil – it’s easy and affordable. There are many soil testing companies found in the Yellow Pages or online. However, for most homeowners, the local Cooperative Extension offices provide all of the analyses needed, and at a very reasonable cost.

Cooperative Extension Offices – The Cooperative Extension offices of most state universities provide an excellent and affordable soil testing service. Most provide both testing and recommendations for adding fertilizer or amendments. Here is the link to the soil testing services for Ohio State University.

Commercial Labs – You may prefer to get your soil tested at an independent lab. Prices are often comparable to those offered through the Cooperative Extension offices and these labs may also offer additional tests, such as for pesticide or herbicide residue, nematode analysis, and plant tissue analysis. Bear in mind that many of these labs are focused on agricultural soil testing so be sure to use the right form when submitting your samples (i.e., a form for home gardeners). The lab I use is Spectrum Analytic.

How do I submit a soil sample?

Complete instructions are found on the websites of the various Cooperative Extension offices or commercial labs. Generally, the lab will provide a bag in which you will submit the sample. Some labs will even provide the shipping labels and boxes. Be sure to complete the order form with all the correct information. The lab will need to know what you’re growing in the area being tested (e.g., flowers, lawn, specific crops) so that they can provide accurate fertilizer and amendment recommendations.

How much does soil testing cost?

A basic soil test (e.g., Standard Nutrient Analysis) performed through a Cooperative Extension office generally costs around $10.00. Commercial labs are comparable for a basic soil analysis. Additional tests will add to the cost. Commercial soil food web analyses are in the $50 to $75 range.

How soon will I receive my soil testing results?

The typical turn-around-time for soil testing results is 3 to 4 business days from time of sample receipt except during April and May when it may take 1 to 2 weeks due to heavy sample load. Check with your local provider before sending in your soil sample, as times may vary.

Interpreting Results

There are 5 things to be looking at with the results of your soil test. We will discuss each of these in greater detail in the coming weeks but here they are: Type of soil, pH, Organic matter, Macro nutrients NPK, and micro nutrients. Most tests, when you submit your sample, tell the lab what you will be doing with the soil and they will make pH, macro and micro nutrient recommendations.

Summary

I know that this is as lot more detailed than I wanted to go on testing but I really need to stress if you are having any problems at all with production of whatever you are growing you need to know where you are at. That is what a soil test will get you. Next week we will discuss more in the management discussions.

Mike Jones

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