The Living Soil

our most precious resource and what makes all this possible

The soil offers us security and farm viability -- making or breaking our overall success.  From an attra.org site "Individuals who study and pay close attention to there soils structure and content will see far better results in cultivation and yield and will better be able to address negative issues encountered while growing on, and managing farmland."

Our motto for soil management is "give back more than you take away."  This generally helps us to maintain good soils teeming with microscopic activity.

There's much much more to this practice that includes soil amending, soil tillage, water management, organic matter, dealing with weeds, pests, and nutrient/mineral management.  Each one of these things is related to the other and we continually strive to find these connections and further understand this complex organism.

While soil management is very important for how we run our business and farm, soil science is equally as valuable.  So, I hope to over the next few paragraphs cover what we all probably learned at one time and perhaps forgot over the years.  

Soil Basics -- Q+A

Where did soil come from?

Soils are formed from 'parent' rock materials.  The creation of soil is influenced by climate, organisms, topography, parent material, and time.

Since soil is transported by wind and water, soils vary greatly along different topographies (ridge vs. valleys).  Glaciers played a role in our soil fertility across the country.  During the last period of glaciation, the moving glaciers would grind up rocks and create rich and nutritious topsoils.  The glaciers would mix many types of parent materials making for balanced soil.

What is soil made of?

Approximately 50 % of a soil particle is made of mineral content and organic matter.  Usually the organic matter in this area ranges from .5-5% depending on soil quality.

Organic matter is the 'living or recently dead' portion of your soil.  This includes fresh residues (grass clippings), living organisms (earthworms), or decomposed residues (the dead things in the soil).

The mineral content is the portion of soil created from the parent rock. Mostly around here, our parent rock material is granite.  In parts of our farm, the granite bedrock is exposed and in many places just 3-4' below our soils!  It's a wonder we can grow anything.

The mineral content can be made up of one or all three of these soil particles: sand (mostly quartz, large particle visible to naked eye), silt (smaller particles), or clay (the smallest particle).  The quartz is made of silica and silicon is the most bountiful element other than oxygen in our planet.  Clay is an oddball becuase it's made from a chemical change of the rock particle.  Because it's so small it binds tightly with other clay particles and has the ability to hold onto nutrients and prevention of leaching of nutrients (good ole chemistry -- ions with positive and negative charges).

The last 50% of the soil particle is made up of water and air.  This is known as pore space...it can be fully filled with water, or (almost) fully filled with air depending on the moisture of the soil.  Porosity is very important to plant growth -- so the plants can access water and have space for roots to grow.  Air is also vital so that plants can have adequate gas exchange.

Tell me more about the soil texture.

Sandy soils have low water and nutrient holding capacity and can be considered droughty because of quick drying.  Clay soils have a high water and nutrient holding capacity, but low permeability and poor tilth.

What's best?  A loamy soil.  This is a combo of all three types of soil.  It can hold nutrients and water (but not to a fault) and also offers good soil structure.

Soil texture doesn't change with time or amendments.  Soil texture can be changed by importing soil or removing soil.  And that would be a big job on a large scale.

What is soil structure?

The arrangement of soil particles into aggregates or 'peds' - the actual clumps that you see in your soil.  In these, there are small pores and larger pores (for air and water movement) and are vital to a good structural soil.

While soil texture cannot easily be changed, soil structure is a result of soil organisms, plants, and our management.

Adding organic matter, keeping healthy soil organisms, reduced and proper tillage, freezing and thawing, and erosion control can all aid in better soil structure.

So what is meant by "The Living Soil"?

Soil biology!  There are many more individual life forms within the soil than live on the surface of the earth.  This includes each individual plant, animal and insect living on the surface.  There can be 1 to 4 billion single-celled bacteria per teaspoon of soil, and up to 1 million fungi.  Soil algae may run as high as 100,000 per teaspoon under favorable conditions.

 The things that you'll find in that teaspoon of soil include all sorts of fun microscopic life: bacteria, protozoa, fungi, algae.  And in a slightly larger piece of soil you may find animal life-nematodes, arthropods, rodents, earthworms, ants, snails, spiders, mites, worms.  There are tons more small guys in the soil so those are the ones that make the biggest difference -- and we can't even see them!

Well, what do all those things do?

Earthworms - air & water penetration, high-nutrient castings, secretion of plant growth stimulant, natural soil tiller
Arthropods (sow bugs, centipedes, slugs, snails, springtails) - primary decomposers
Bacteria - make plant growth hormones, make nutrients and minerals available to plants, fix atmospheric nitrogen, fight root diseases, detoxify soils
Fungi - break down organic matter (OM) and release nutrients available to plants, produce plant hormones and antibiotics; mycorrhizal associations
Actinomycetes - (threadlike bacteria that look like fungi) decompose OM, produce root disease-fighting antibiotics, produce sweet, earthy" smell
Algae - upper ½ inch, fix nitrogen and enhance soil structure by producing biologic glues
Protozoa - free-living organisms that swim in soil water, eating bacteria and speeding up the nutrient cycle
Nematodes - eat decaying plant litter, bacteria, algae, protozoa, and other nematodes (most nematodes are good, just a couple are bad)
(more info on www.attra.org)

To sum up, overall life in your soil does the following:
1.    Builds soil structure (increasing drainage, holds soil conglomerates together)
2.    Supresses diseases
3.    Improves nitrogen and nutrient retention
4.    Increases crop quality and nutrition
5.    Offers plant growth hormones

What about soil nutrients?

As you know our soils here don't offer a very well balanced soil nutrient spectrum.  When I arrived here at Serenbe almost six years ago, our soil was a different beast than it is now.  We've added thousands of dollars of inputs to help our soils become valuable for growing vegetables.

There are major nutrients required for plant growth as well as micro nutrients and trace elements.  Every element is needed for good plant growth...some in a much higher quantity.

The major nutrients are nitrogen-N, phosphorus-P, and potassium-K.
Secondary nutrients include: Sulfur-S, Calcium-Ca, and Magnesium-Mg.  

The micronutrients are boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn).

Since all plants use and are made up of these things, compost is a good source of all nutrients.

Soil particles (especially those with lots of clay) can hold onto the positively charged nutrients (cations).  These that are bound to soil particles include Calcium, Magnesium, and Potassium.  This is important to realize becuase these nutrients in a properly managed soil will not move within your soil profile like the negatively charged soil nutrients (Nitrogen + Sulfur mobility and leaching).  The soil's measure of ability to hold onto cations is known as your Cation Exchange Capacity (CEC).
(Interested?  Check out the Albrecht system of balancing these cations.)

Good organic sources for:
Nitrogen: alfalfa meal, compost, feather meal
Phosphorus: bone meal, rock phosphates
Potassium: greensand, granite dust, potassium sulfate
Calcium: calcitic lime, bone meal, gypsum
Magnesium: dolomitic lime, epsom salt (usually our soils have plenty of magnesium)
Sulfur: elemental sulfur, potassium sulfate

And what about pH?

PH is the measure of soil acidity.  Application of lime is important in acidic soils (most of our soil).  This will help to get your soil in balance (balancing the soil cations (Ca, Mg, K, Na) and acidity (H) makes way for a healthy soil with good texture).

So after all this information, how can I use it to make my soil better?

-Build soil organic matter.  Use cover crops, field rotations, compost.  Use wise and conservative (or no) tillage.  Consider the cycling of nutrients and carbon.
-Test your soil to see what's going on with it.  Soil tests are to be taken lightly because each lab can create different results.  These are better to establish patterns and ability to learn by observation and trial and error.
Most soil tests include: major, secondary, and minor nutrients, pH, and CEC.
My favorite lab is A and L Laboratories in Richmond, VA because they are consistent and quick to return results.  Always test your soil at the same time of year.
-Consider managing the air (by cultivation, not allowing crusting, reducing compaction from walking, tools, or tractors) and the water (irrigation, compaction).

Any other tips?

-If possible keep soil covered with mulch (to prevent organic matter burnup, crusting, erosion).
-Know your soil structure and how to improve it.
-Create a tillage plan and know when it's too wet or dry to till.
-Always fertilize with organic nutrients (utilizes and encourages soil biology, doesn't create salt buildups that kill organisms, and most don't affect soil pH unless containing calcium or magnesium).
-Know your soil profile (do texture test by feel...see feel method, also check the NRCS website to see your soil type and agricultural viability...note that we're growing on an unsuitable location...so don't take this too seriously)