The Soil is Alive – Updates from University of Kentucky Integrated Plant and Soil Science

KCl Extractions Lab.png

The Soil Is Alive!

Did you know that a teaspoon of productive soil contains between 100 million and 1 billion bacteria? That adds up to equal the weight of two cows per acre! When you look down, you don’t see them, so they are easy to forget about. However, when you look down and see plants growing you have billions of microorganisms to thank! These microbes are vital in nutrient cycling and many other important processes taking place in the soil.

what's in a handful of soil

How Microbes Are Running My Master’s Degree

As I discussed in my earlier blog post, I am currently a graduate student at the University of Kentucky studying nutrient management in soil science. For my research I am conducting a laboratory incubation study comparing different types of poultry litter and the factors influencing the nutrient content of these manures. During my time at the University of Kentucky I took an in-depth soil microbiology class with a lab that opened my eyes to the importance of these organisms in agriculture. Soil microbiology is also a big part of my research.  I am in the middle of the first study and am currently processing samples as they finish incubating. The reason an incubation process is used is to facilitate microbial activity in the sample cups. These microbes are the ones doing the work to break down the poultry manure and transform the nitrogen into a usable form for plants to use. To create optimal conditions for microbial growth, the sample cups I prepare are kept at about 77°F and the soil is kept at about 50% of field capacity (that is a scientific term that pretty much means the soil is moist but will still crumble in your hand). This is important because it gives the microbes enough water but also allows for air to get to them. They are living organisms, so they need oxygen and water just like us. Over time I take out samples and analyze them for inorganic nitrogen content. I am specifically interested in ammonium (NH4+) and nitrate (NO3) in the soil that the microbes are releasing. This is done by extracting the nutrients from the soil with potassium chloride (KCl), filtering the samples, and then analyzing with flow injection analysis. Once two months of samples are collected, I will have a record of how much nitrogen was released and when it was released.

assembling sample cups with manure and soil            sample cups in the incubator

Goals of the First Study

This first study focuses on two main factors; the rate of manure (poultry, specifically broiler litter) applied and the method the manure is applied. Half of the cups received manure at a rate of 100 lbs of plant available nitrogen while the other half received 400 lbs of plant available nitrogen. This comparison will shed light on differences in the rate of nitrogen release as you increase the amount of manure applied. This study is also comparing a tilled and no-till manure application. For this comparison I mixed the manure into one cup and in an identical cup, I sprinkled the manure on top of the soil. This study is a chance for me to perfect my procedures and techniques before I begin the bigger study that will compare eight types of poultry litter from all around the country.

The end goal of my project is to collect data that will help crop producers improve their decision-making when considering using poultry manure. I am excited to see the results and will be sure to have an update post once I have the results of this first study!

If you want to learn more about the living soil and the microorganisms beneath your feet, check out these websites!

USDA NRCS Soil Health

USDA SARE The Living Soil

Lydia Fitzgerald: Student, writer, flower & vegetable farmer!





About Lydia

Lydia grew up on a farm in Nelson County, Va and helped raise wholesale pumpkins, apples, corn, and soybeans. She did work in food safety and certifications and started a retail sector with pumpkins, gourds, sunflowers, Indian corn, and sweet corn for a pick-your-own operation. Lydia has been involved in home vegetable gardening and loves to learn about different management and marketing strategies for small and large scale production systems. She is currently a student at Virginia Tech studying Crop and Soil Science planning to attend graduate school in the fall.


Life Beneath the Soil

Life beneath the soil

For the market farmer, soil health is critically important. The soil is a generic term for the upper layer of the Earth’s crust. In fact, there are six soil layers that impact market farming and even big Ag via the life within the soil, the overall soil health, and the relationship therein. Inside we discuss the life beneath the soil and how those organisms affect soil health.

Soil Biota

Biota is the life – animal or plant – that exist in a specific habitat or environment. All the fish, plants, algae and other organisms in the Pacific Ocean would be the biota of the Pacific Ocean. Soil Biota is the organisms that live in the soil of a specific area or environment, such as your garden or market farm. For most plots of land, we are talking about organisms such as bacteria, Fungi, spiders, worms, arthropods – insects, spiders, crustaceans, etc., small rodents and mammals, etc. In short, there is a lot of life in the soil – Some of it good and some a little challenging for farmers and gardeners – all of it seems to be essential for growing food.

The Layers of the Soil from top to bottom

  1. Humus — In healthy soil, there is a thick layer of humus which is the off-cast parts of plants — leaves, bark, stems, fallen fruit, etc. It is in the humus where new soil is created and nutrients within top soil replenished. That process is in thanks to the soil biota and the hydrologic cycle — rain and water.
  2. Topsoil — a nutrient-rich layer — usually — where most plant roots are found. Larger trees and shrubs may have roots that extend as deep as the subsoil layer.
  3. The Eluviation layer — Often a sink for soil nutrients as they are carried down through the humus and topsoil layers by water. This is generally a small grained layer of soil particles.
  4. Subsoil — The subsoil layer is made up of tiny grains of rock, soil, and clay. There is not much organic residue in the subsoil layer, but it can be an excellent place for the natural storage of excess water – especially in areas with a lot of clay. This can also be a place where hardpan forms.
  5. Regolith — Upper Bedrock – a broken layer of bedrock – this is where bedrock begins to decompose thanks to physical and chemical weathering.
  6. Bedrock — The bottom layer of the soil is bedrock on which the upper layers of soil rest. Bedrock is exposed due to erosion. We see that naturally on the upper reaches of the mountains. We also see it farming in extreme cases where air or water erosion is uncontrolled.

Little Creatures with a Big Impact

Bacteria and fungi are microscopic, but both do a fantastic job converting organic compounds into nutrients. Nitrogen-fixing bacteria are literally the driving force behind life on earth through a process called the nitrogen cycle. The air we breathe is nearly 78% nitrogen, yet plants cannot use nitrogen in its gaseous form. There are a few ways that nitrogen becomes usable to plants and nitrogen-fixing bacteria are one of the most efficient means.

However, it is not just nitrogen that makes soil healthy. It is also aeration thanks in part to critters like earthworms, moles, voles, shrews, and even insect larva that help to “fluff” up the topsoil and humus layers so that air is available for all organisms to use. It is also about the ratio of organic matter in the soil to the amount of moisture that the ground holds. The humus layer helps the topsoil layer to retain water and by decreasing the amount of evaporation that occurs. In the humus layer are all kinds of organisms that help to reduce plant matter so that the bacteria and fungi can do their jobs. That is a natural, organic cycle. The plants grow, shed their fruit and leaves, which become the humus layer where the organism’s consume the debris and turn it into usable nutrients.

Supplements for Soil Health

In commercial farming, the humus layer is burned off or removed. Over time, the topsoil layer becomes compacted due to the reduction of organic material and the farmer must then supplement their lands with inputs — nitrogen-based fertilizers — because there is not enough life in the soil to regenerate the nutrients. Market farming does not have to follow this path. Many small farms are using other methods such as no-till to improve the condition of their soil. There are other tricks too, such as cover crops that utilize nitrogen-fixing plants. Nitrogen fixing plants are a symbiotic relationship between specialized bacteria and the plant. Together they help to absorb nitrogen or nitrogen components and then convert it into a usable material that the plant can use to grow.

Soil health is a relationship between many small organisms, the plants that grow in the soil and the amount of water available. The small farm can take advantage of these relationships to produce more food or flowers and use fewer resources.

David Stillwell organic gardener

About: David Stillwell is an organic gardener, entomologist, writer and student. David specializes in hymenoptera – bees, wasps, and ants, and the study of cecidology – Plant galls. He has a fondness for recognizing natural circles and energy webs that exist in nature — those interconnected natural systems such as food webs. He is a native of California and an advocate for conservation, locally grown, and farmer’s markets.