Fertile Ground: Soil Health Basics for Growers

by Deanna Williams

Alright – this is going to be a long one as we deep dive into soil health, so I am going to list some shortcuts below to help you jump to specific sections if needed:

My first year farming flowers I didn’t know anything. I had no experience or knowledge about flowers, growing plants, or soil health and it was very overwhelming. Hours were spent on the internet looking for some guidance on sampling soil but I felt like I didn’t really know enough for the information I could find to sink in.

I knew I needed a soil sample and I knew I needed a lab to run tests on it but that’s it. I blindly took samples, followed the instructions from the extension office, sent them in,  and hoped for the best. I was excited when I got the results back because that meant that what I sent in was at least something that could be sampled and that gave me a sliver of confidence – but then I had no idea what the results meant or what I had to do with them.

Before we get into the nitty-gritty, I do want to say that a big part of growing is failing and learning and gaining intuition. My mom has grown a beautiful garden for years and years without ever taking a soil sample. She’s learned what her soil needs by observing her plants and a lot of trial and error. There’s never a one-size-fits-all when it comes to growing at any scale so figure out what works best for you and run with it.

The Basic-Basics

Sticking to the very basics of soil health, let’s look at some easy ways to assess and get to know your land:

  • COLOR: My rule is that if your soil is a rich, dark color and looks like chocolate cake you’re in a great spot! If it’s looking a little pale (light brown) or reddish that’s a sign that you’re going to want to add in more organic matter (compost).

  • TEXTURE: Give it the squeeze test. Grab a handful of soil and squeeze it in your palm. The hope is that the soil molds together. If it isn’t sticking and crumbles apart or if water is squeezing out of it and it’s completely saturated, you’re going to want to add in more organic matter.

  • SMELL: Soil should have a distinct fresh, earthy scent to it. If it smells sour or metallic, this is a sign that your pH is out of whack and you’re going to want to really make sure to test it. Below are a couple options for at home tests if you want to try those before using a lab.

N-P-K is going to be something you want to get familiar with. These are the macronutrients (Nitrogen, Phosphorus and Potassium) in your soil and they play a major role in determining how your plants will grow.

  • NITROGEN is number one. It’s essential to overall plant growth. The goal with your soil is to make sure that there is enough nitrogen to support the plants you’re growing.

  • PHOSPHORUS is the key player when it comes to healthy roots and the development of flower, seed and fruit development.

  • POTASSIUM is what helps your plants fight off disease, manage water needs and enhances the plants hardiness – it’s what will make your plants tough! 

Without detailed tests to know what levels of nitrogen, phosphorus and potassium are available in your soil it can get tricky when trying to determine what your soil needs. If you’re just getting started, there’s always the option to only add to the soil what your plants will use throughout the growing season. Down to Earth Fertilizers has some of my favorite, organic mixes and plenty of options specific to different plants you might be growing. 

I would start by looking at their blended mixes if you’re planning on growing flowers, fruits and/or vegetables. This will help get you started and give your plants what they’ll need.

Keep in mind that more isn’t always better. Too much nitrogen can cause excessive growth in plants which leads to succulent leaves and could cause outbreaks of mites or sucking insects. Too much potassium could cause nitrogen and calcium deficiency. And too much phosphorus could prevent your plants from taking in important micronutrients and make them sick. So if you’re going to use a fertilizer, be sure to read the instructions on how much to use.

Remember, most fertilizers (especially synthetic ones) can be good for your plants in your garden, but they leave a lot to be desired for your soil.

Soil Health Indicators

There are many things that contribute to healthy soil, but let’s focus on the top five:

Soil Cover

Soil cover prevents erosion from wind and water and I believe it to be the most important factor when determining soil health. If your soil is bare and exposed then the facts of the matter are that you do not have a working ecosystem in your land.

Keeping things simple, assessing your soil cover is easy. Walk out in your field and look straight down. Covered soil is a great place to start, bare soil is also a great place to start but with a lot more steps.

What you’ll want to see when looking at the plants covering your soil is a diverse mix of green and/or dormant plants. You might also see dead plants, plant residue, or manure if you graze. During the season, as your soil gets healthier, you’ll see green cover.

TEXTURE and STructure

Your soil texture is determined by the portions of your soil that are clay, silt and sand. An ideal ratio. would be 20% clay, 40% silt and 40% sand. A ratio like this would indicate that you have a good amount of organic matter and drainage for your plants. 

The structure of your soil is mostly focusing on your soils ability to hold its particles together, this is known as aggregate stability and it increases as the organic matter in your soil increases. 

Rooting Resistance

Rooting resistance is going to tell you if you have compaction issues in your land. You’ll be looking for shovel samples of plants where their roots grow downward and then curve into a ‘J’ shape. This shows you that where that root begins to curve, there is a compact layer (commonly caused by previous tilling or previous, repetitive compaction from the ground surface).

This is a problem for growers because it limits root penetration and creates a barrier where you could have waterlogged soil. It’s a problem for your soil because it limits healthy soil to just above that compaction layer. Compacted soil can be fixed with aeration and (you guessed it) adding organic matter.

Biological Activity

Your soil is an entire system and cycle of its own. You’re looking for evidence of worms, beetles, fungus, spiders – you’re looking for signs of life. Earthworms are incredible in the soil. They are machines that breakdown organics and as they move they create porous soil and tunnels for water movement. Their castings offer significant amounts of nitrogen, potassium and phosphorus in the soil for your plants and they create channels for plant roots. They are workhorses!

Color

You want your soil to look like chocolate cake. The darker it is, the more organic matter you’re working with. A dark, rich brown is an indication that your soil is balanced.

  • Black soil is an indication of high concentrations of organic matter. If your soil is black or extremely dark, it could be an indication that organic matter is accumulating and not decomposing the way you would want for healthy soil and plant growth.
  • Red and yellow soil is usually an indication of high amounts of clay and iron oxide minerals.
  • Gray soil is often found in wetlands and have usually been submerged in water for extended periods.
Two dahlia plants from the same tuber, one grown in managed soil with added organic matter, the other grown in soil with low organic matter and no inputs.
Bare soil that is exposed to erosion.

Signs of Poor Soil Health

The list of things that contribute to poor soil health is a long one. If you’re starting from scratch with land that hasn’t been managed for gardening or crop production, then odds are that you’re going to have some decent ground to work with.

If you’re digging into land that has been previously managed and you don’t have records to tell you how, then you could have some potential hurdles to get over. Some agriculture practices that used heavy applications of synthetic fertilizers, irresponsible tilling, or farmed monoculture crops could leave you with reduced soil fertility and low organic matter.

If your soil is struggling, that’s ok. There are ways to fix it and get it back on track. And don’t borrow trouble by worrying about it before you’ve had a chance to look at it and run some tests. Below are the key indicators that you could be dealing with poor soil health:

  • LACK OF MOISTURE: Water is crucial for productive plant growth and healthy soil. If your soil is dry and dusty that indicates that you have low organic matter.

  • POOR CROP/PLANT GROWTH: This one might seem like a no-brainer, but if you’ve already tried growing and your plants are just not producing the way they should be, that doesn’t mean you’re missing a green thumb – it means your soil is missing the nutrients and organic matter it needs.

  • WEAK PLANT GROWTH/DISEASED PLANTS: Maybe your plants produced alright but you noticed you had issues with pests and bugs or had some diseased plants. That’s another clue that something in the soil isn’t where it should be.

  • HEAVY WEED PRESSURE: If you are spending hours on end dealing with weeds, you have a problem. Your issue could be exposed soil, low nutrients, or even compaction where your soil doesn’t have enough air in it.

  • LOW ANIMAL LIFE: Worms and other bugs in the soil tell you that you have a healthy cycle happening below ground. An easy way is by doing the Earthworm Test where, once your soil has warmed dup to around 50ºF, you dig up one cubic foot of soil and then break it apart and count the worms. If you have 10, you’re in great shape – any less then that and you’re low on organic matter.

I’m sure you’re seeing the trend of adding organic matter to your soil and creating biodiversity. That’s the great news. It’s not the end all, cure all, but it’s huge when it comes to building healthy soil. Below is a framework showing the different pieces that makeup a healthy, biodiverse soil.

SoilBON Essential Biodiversity Variables framework
SoilBON Essential Biodiversity Variables framework

At North Star, with the size of my growing space composting at home just wouldn’t be enough to keep up with it. My first few years growing, I brought in 20 to 40 yards of compost each year. My soil was compacted, waterlogged, full of clay and had very little animal life. It was a huge investment those first few years but it was worth every penny.

Now, I leave a lot of my annual crops in the ground to breakdown over winter that add organic matter. It looks like a mess until things warm up, but it’s been incredibly beneficial. 
I also make sure to move my crops around each year so that I’m not growing the same crop in the same row year over year – this helps add more biodiversity to the soil by growing different plants each season.

If you’re looking for a deep-dive into biodiversity, SoilBON is a great place to start!

How to Take A Soil Sample

Whether you’re taking a sample to run some tests at home or to send out to a lab, getting a good specimen that represents your soil is going to be the key to successful results. Using a soil auger is the most efficient way to collect a sample, but you’ll be just fine with a shovel or a soil knife – just use what you have and you’ll be good to go.

1. When to Collect

The best time to collect soil samples is in the late summer or early fall. The second best time to collect soil samples is now. Take a sample at the beginning of the season is going to do you more good than not taking one at all and waiting a whole season to start seeing what your soil needs.

2. Taking Samples

For best results, plan to take a handful of samples in your growing space, combine them in a bucket, and use that for testing. If I have a 1,000 sq foot growing area, I’ll usually take 3-5 samples.

Taking the samples themselves is easy. In most cases, you’ll want your sample depth to be 0-8 inches deep. Meaning that if you dig a hole that’s 8 inches deep, you’ll take your shovel or knife and get a couple scrapings of soil that include matter from the surface down to the bottom of the hole. This way, you’re getting samples from different depths.

If you have multiple areas that you’re growing, grab a separate bucket for each specific area and get a couple samples from each. Doing so will give you the variable information you need to manage each growing space the best you can.

At North Star, I have three separate areas that are all a little different so each year I send in three bags of soil to be tested. Each bag consists of a mixture of 5-7 different soils from each area.

3. Letting your Soil Air Dry

The last step is to let your samples air dry. You can do the right thing and spread the soil out to let them evenly dry but I usually forget about them for a week or two and the buckets sit in the mud room – once I finally remember to get back to them, they’re dry. What I’m saying is that you can’t go wrong with his step, but letting your soil dry is especially important if you’re sending your samples into a lab.

At Home Soil Tests

You don’t need a lab to get to know your soil. While sending our soil in for testing will give you the most accurate and detailed results, there are a couple things you can do at home that will help you make improvements to your soil and see better growth in your garden.

Rapid Ph + NPK Test

These are affordable and I was honestly surprised at how accurate they were. I tested the same soil I sent into a lab and saw the same results for pH and N-P-K. You can usually find them at any hardware or gardening store – I found this one at Ace Hardware and it has enough capsules to run each test 10 times. 

The pH test can be done right away with some of your air dried sample and the other tests can take a few hours or up to a day depending on your soil type. As long as you read through and follow the instructions, you’ll be good to go!

pH Pantry Test

You can test your soil pH with just a couple ingredients that you already have in your kitchen: vinegar and baking soda.

To test for alkaline soil, simply take 2 tablespoons of soil and add 1/2 cup of vinegar. If you get a reaction and your soil fizzes, this indicates that your soil is alkaline. Typically, alkaline soil is managed by adding ground sulfur.

To test for acidic soil, take 2 tablespoons of soil and saturate it with water until you have a muddy liquid (2-3 tablespoons). Add 1/2 cup of baking soda and if you get a reaction, this indicates that your soil is acidic and can be corrected by adding limestone.

If you don’t get a reaction from either test you have a neutral pH.

This is a quick, easy way to get an idea of your soil’s pH at home, but it won’t give you an exact measurement. For growing flowers and vegetables you will aim for a pH of 6.5 (slightly acidic) to 7.0 (neutral). Soil pH is important because when your pH is too acidic or alkaline it will affect how plant roots uptake nutrients. A neutral pH indicates that there is healthy microbial activity and plants will have the best access to everything your soil has to offer.

Here’s a great tutorial video on the pH Pantry Test: DIY Soil pH Test – Garden Quickie Episode 114 from The Ripe Tomato Farms

jar test soil texture

Jar Test

The jar test is going to tell you what you need to know about the texture of your soil. If you’re struggling to get plants to grow but you feel like your soil is healthy, it could be that the plants your choosing aren’t compatible with your soil’s texture. 

For example, if you have sandy soil, it’s going to drain really well and  you’re going to have really great luck with yarrow, black-eyed susans and lavender. Look for plants that are drought tolerant. If your soil is silty or has a lot of clay, it can be hard to get it wet, but once it’s wet it holds a lot of water so you’ll want to find plants that like “wet feet” like calla lilies, bleeding hearts and Rose of Sharon.

To test for texture, find a jar and fill it with one part soil and five parts water. put a lid on it and shake it for 3 minutes to separate all of the soil and mix it into the water. Set the jar down and then take measurements with a ruler at the following times:

  • One Minute: This measurement will tell you how much sand is in your soil.
  • Five Minutes: The accumulation will be the amount of silt you’re dealing with.
  • 24 Hours: Now you will see how much clay is in your soil

Calculate the percentage of each measurement by dividing each section’s measurement by the total. A good, loamy soil will have a mixture of 20% clay, 40% silt and 40% sand. Below are the measurements I found form doing the jar test with my samples.

Sand = 7/16″     Clay = 3/16″     Silt = 1/4″     Total = 14/16″

Convert to decimals:

Sand = 0.44     Clay = 0.19     Silt = 0.25     Total = 0.88

Divide each texture by the total:

Sand = 0.44 ÷ 0.88 = 50%

Clay = 0.19 ÷ 0.88 = 22%

Silt = 0.25 ÷ 0.88 = 28%

Once you have your percentages, you can use the soil texture triangle to determine what kind of soil you have.

To use it, start with your sand percentage and follow the diagonal line to the left to meet your clay measurement. From there, you can match it with the diagonal line to silt.

For my soil, I am loam, but just barely and leaning towards a sandy clay loam.

This tells me that while my soil texture is in a pretty good place, it could be improved by incorporating more organic matter.

Soil Labs

I have used a couple different labs for testing soil over the years and my favorite is the Soil Health Assessment through Ward Labs. What I love about this specific assessment is that is offers more than a routine analysis. Below are some of the results that I find most useful:

  • SOIL RESPIRATION: This is the amount of carbon dioxide released from your soil. It helps measure the amount of microbial activity and reflects the condition of the physical and chemical environment of a soil.

  • SOIL HEALTH CALCULATION: Determined by the overall results from your sample, having an idea of where you fall for soil health will be huge in helping you make progress. With this test, the result typically falls between 0-30. You’ll want to see your results come in above 7.

  • COVER CROP SUGGESTION: I love getting recommendations for traditional inputs, but having a recommendation for a cover crop is awesome! 

Your assessment will have much more information than the list above, but those measurements are the ones that I feel really set Ward Labs apart from other labs I have used. It gives me a snapshot of what’s really going on in my soil.

Below are my fall ’23 results so you can see everything that is included in the assessment.

Soil Amendments

If there is only one thing you add to your soil, it should be organic matter like compost or aged manure. For any problems you have with biological activity, texture and soil nutrition, organic matter is going to be what supports the organisms that are already in your soil.

Amending for Biomass

When it comes to caring for the microbial aspects of your soil, avoiding certain practices and applications is just as important as your inputs. Be sure to avoid synthetic fertilizers, pesticides and fungicides, and over-tilling. Really – avoiding tilling in general is the way to go because tilling can lead to soil erosion if the land isn’t properly cared for afterwards and it also releases a lot of carbon from the soil that is important for mineralization and the soil’s microbial activity.

To increase biological activity the best amendments you can implement are, of course, adding organic matter as well as getting your soil to a healthy pH by adding limestone to acidic soil or increasing the amount of organic matter/compost for alkaline soil.

It is also worth looking into compost tea. There is a bit of back and forth on whether or not compost tea is effective, but I use it here at North Star regularly throughout the growing season and believe that it has been a tremendous help to building healthy soil. I use Growing Solutions catalyst – they are a great resource for researching the benefits of compost tea and soil fertility.

Amending for Texture

  • SANDY SOIL can be amended by adding organic matter such as aged manure or bringing in heavy, clay-rich topsoil. Some growers will also add peat moss but keep in mind that peat moss will make your soil a little more acidic so be sure to check your pH after making amendments.
  • SILTY SOIL is going to need more drainage so adding coarse sand and compost or well-rotted manure is going to be your saving grace.
  • CLAY SOIL is a lot like silty soil and will benefit from coarse sand and compost as well.

Amending for Nutrients

Fertilizer can be a hot topic when it comes to farming and gardening. Some would argue that if you’re focusing on sustainable and regenerative practices there’s no room for fertilizer in your operation. 

My opinion is this: There are fertilizers that are “natural” and meant to feed the soil, not pinpoint crop growth, and if your soil needs those amendments you should use them. Would growing cover crops and integrating livestock grazing be better? Absolutely. But that’s not an option for every operation and you can’t spend your whole life rotating cover or grazing crops waiting for your soil to be perfect for growing. You still need to grow and make a living.

  • NATURAL FERTILIZERS (often referred to as organic fertilizer) are typically mixed directly in to your soil and have a slower release rate than synthetic fertilizers. They slowly feed your soil, and in-turn, eventually feed your crops. They are typically made up of mined minerals or animal materials such as manure, powdered blood, and finely pulverized fish. They usually stink, but it seems that the worse something smells, the more plants love it.
  • SYNTHETIC FERTILIZERSare derived from chemicals. They are a quick pick-me-up for your crops but they wreak havoc on your soil and soil health. 

There are many organic blend and single-ingredient fertilizers that will help you meet the needs of your soil. For example if you’re only needing nitrogen you can add blood meal which is typically 12 parts nitrogen and zero parts phosphorus and potassium. If you’re equally deficient in nitrogen and phosphorus but good on potassium, shrimp meal is a great go-to. It will take a little bit of research and intuition finding the right things your soil needs, but usually a quick google search can get you on the right track. 

For flowers, I usually look for a 4-8-4 blend. Down to Earth’s mix is made up of fish bone meal, blood meal, langbeinite, alfalfa meal, seabird guano, rock phosphate, and kelp meal. 

For vegetables, going for something with equal parts all across the board, like a 4-4-4, is a good place to start.

48 yards of compost

Calculating Amendments

There is a lot of math involved with agriculture and if math isn’t your strong suit don’t let that deter you. I’ll go over the formulas below and share a link to a calculator that will do the math for you.

My first season growing I had sent in a soil sample for testing and received results stating that I needed 2-3 (we’ll go with 2.5 for the formulas below) lbs of nitrogen, 1.5 lbs of phosphorus, and 0.75 lbs of lime per 1,000 square feet. My potassium was good. 

When you’re looking at fertilizers, the N-P-K values are going to be the percentage of each specific element in your bag. So if you have a 25 pound bag of fish bone meal that has measurements of 4-12-0, you have 4% nitrogen, 12% phosphors and 0% potassium. Let’s say that we also have 25 pounds of blood meal that is 12-0-0.

The quickest way to solve this problem is to ignore the weight and start with the fertilizer that has both nitrogen and phosphorus. We know that we have an amendment (the blood meal) with only nitrogen, so our first problem to solve is how much fish bone meal we need to get our phosphorus level where we need it.

Divide the phosphorus desired (1.5 lb per 1,000 sq ft) by the percentage of phosphorus in the bag (12%, or 0.12). 

(1.5 lb per 1,000 sq ft) ÷ 0.12 = 12.5 lb of 4-12-0 per 1,000 sq ft.

If we add 12.5 lbs of 4-12-0 per 1,000 square feet, we know that we are hitting our need for phosphorus, but how much nitrogen is this, and then how much more nitrogen is needed for optimal results?

(??? lb per 1,000 sq ft) ÷ 0.04 = 12.5 lb   >>>   multiply both sides by 0.04

??? = 0.5 lb of nitrogen per 1,000 sq ft will be added to the soil with 12.5 lb of 4-12-0

This means we still need to add 2 lb of nitrogen per 1,000 sq ft using the blood meal that is 12-0-0

(2 lb per 1,000 sq ft) ÷ .12 = 16.7 lb of 12-0-0 per 1,000 sq ft

To get this soil to optimum N-P-K levels we could do so by applying 12.5 lb of fish bone meal and 16.7 lb of blood meal per every 1,000 square feet.

The math is simple enough, but personally I don’t like doing it. I use this online fertilizer calculator and have it bookmarked on my computer and phone.

Conclusion

This isn’t the cleanest or most accurate how-to when it comes to learning about soil, but it’s what I’ve learned over the past few years and I know it doesn’t scratch the surface. Thanks for letting me share my findings and I hope my resources help you through your journey to better soil.

Over the next few years my plan is to dive more into cover and grazing crops and livestock impact. Plant diversity and animals are natural parts of our soil’s system and finding ways to integrate them into our farms and gardens will give us the best results. We just have a little bit of unlearning and planning to do.

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