Get the Scoop on Using Your Poop

Phewy! Smell that? From an early age, we are often told the old phrase “That’s the smell of money!” Although this phrase is often used to indicate cattle profits, the manure in those pens also holds a wealth of resources that can help enrich and strengthen your soil. Once used routinely in integrated farming systems, manure plays a critical role in returning nutrients to the soil. With the shift from integrated livestock and row crop farms to separated specialized operations, the natural cycle of many nutrients has been disrupted. This separation of practices has led to an overabundance of manure in some areas and a lack of nutrients in others, causing a shift to synthetic fertilizer use. So, what does manure do to our soil?

Manure is an important source of raw or partly decomposed organic matter. The nutrients in manure can vary depending on the animal type, health, age, feed ration, bedding and water content. In addition, the various management practices associated with handling manure, manure storage, duration of storage, application amount, application technique and weather can all dramatically alter the nutrient content in manure and thus the amount of nutrients available in the soil and for future crop use. Understanding and applying the correct amount of manure to your fields can be accomplished by testing your manure prior to application. You would be surprised how much it can vary! The table below highlights the difference in nutrient levels found in beef cattle manure that we have processed at the lab in the past five years. Want to see how swine, poultry, dairy cattle, or compost fared? You can check it out here.

Beef Manure

 

First, let’s set the stage. Before manure ever touches the soil, soil fauna (e.g. ants, earthworms, arthropods etc.) and microbial populations (e.g. bacteria, fungi, viruses) naturally exist in your soil. These populations, or communities, are incredibly diverse and have varying community structures that reflect your soil quality, or “soil health”. The majority of the microbial populations exist within the top few inches of your soil, clustered around the root structures of plants, known as the rhizosphere. Soil microbial activity is responsible for the main decomposition of all litter inputs into the soil. Larger fauna in the soil are important for the preliminary break down of residue into small pieces, creating greater surface area for microbial activity. They also move fragments of litter throughout the soil structure, exposing the litter to larger microbial communities, which provides a natural incorporation without resorting to mechanical methods. When food is scarce (e.g. winter months when no living plant is present), microbes have the natural ability to enter a low energy requiring comatose-like state to preserve their nutrient supply until food is readily available again.

Initial introduction of manure is a feeding frenzy for soil microbes. Manure not only contains a large amount of macro and micro soil nutrients but also inoculates the soil with microorganisms excreted by livestock. The nutrients in manure, although processed by the host, require a suite of soil microbe activity to alter the chemical structure of nutrients to make them available for microbe and plant use. Much like hungry teenagers at a buffet, microbes attack the most easily accessible forms of food first: sugars, starches and other soluble nutrients. This initial process is often rapid. Once these resources have been used, the breakdown of more complex soil compounds begins and is a slower process like preparing a box of mac and cheese. It takes time and a little bit of effort. This process includes the breakdown of cellulose and hemicellulose, both found in plant tissues. Lastly, complex compounds, such as tannins and lignins (found predominantly in woody plant species) are broken down. This process occurs over a long period of time and with a lot of help. It’s almost like preparing a Thanksgiving feast. This process requires the specific activity of select microbes (e.g. White Rot) to breakdown these compounds.

Microbes are very similar to people in the way they act. Although the main end product of aerobic (or oxygen loving) microbial activity is to release carbon dioxide (CO2) and water, microbes require nutrients to support growth, maintenance and reproduction. Thus, microbes make a living by harvesting carbon and other nutrients from the soil organic matter. Microbes are responsible for converting many minerals from organic to inorganic forms (often referred to as “mineralization”) that are easy to take up for both the microbe and plants. For instance, microbes need N to meet many microbial needs (e.g. protein building). If there is an abundance of N in the organic matter, extra microbial processed N, in the form of ammonium-N (NH4+-N), is released into the soil environment. Due to the close proximity of microbial communities and plant roots, the released, easily available N is taken up by the plant. Increases in nutrient sources, such as the addition of manure, stimulates microbial growth and reproduction, resulting in a larger, more active microbial community. Larger populations lead to greater microbial turnover, in which the death of the microbe releases nutrients gathered during its lifetime and can now be utilized by plants.

In addition to the minerals microbes liberate for plant use, manure and microbes can also help build your soil structure. Increased presence of organic inputs promotes microbial activity and decomposition. During this process, polysaccharides are produced as a by-product and help bind macroaggregates together in the soil. Polysaccharides  are sticky, glue-like substances that form bridge-like structures between aggregates and are resistant to degradation in the soil. The accumulation of this activity creates a snowball effect in the soil. Stabilized aggregates create tunnels that increase soil porosity, soil water holding capacity, nutrient cycling and nutrient availability to microbial communities. In turn, these characteristics support an improved soil drainage system, a decrease in bulk density and compaction, and a decrease in soil crusting and erosion.

The rate at which decomposition occurs in the soil is dependent on the quality and composition of the manure, the microbial community structure, weather and time. This rate causes manure to act like a slow release fertilizer, ensuring all the nutrients are not lost during initial application or shortly after. A manure analysis report often provides a “First Year Availability” value to help you understand and apply the correct quantity of nutrients needed for your crop. These manure mineralization approximated values are calculated based on similar mineralization rates found in research for each manure type. If you like to apply manure in the fall but are concerned about potentially losing nutrients due to soil moisture and microbial activity, consider incorporating cover crops into your rotation to help cycle nutrients in the soil. As they breakdown in the winter and spring, they will release the nutrients consumed from your manure application while supporting a healthy, thriving soil microbial community.

Applying manure to your soil can be an efficient way of stimulating an active, healthy microbial community while providing nutrients to your crop. Manure quality is dependent on various factors that contribute to the dominate microbe community and nutrient forms. Be sure to properly analyze your manure before you apply to ensure you are getting the most out of your valuable resource. Understanding and properly applying manure could help save fertilizer costs in the future while boosting your soil microbial community resiliency and soil health. So go ahead and take a deep breath. That’s the smell of money.

Cattle and Crops: Completing the Nutrient Cycle

How many of us producers have a shovel in our pickup? When was the last time we used that shovel to thoroughly examine our soil?  Are we able to determine what a truly healthy soil looks like? Grab a shovel and take a look at your soil. Check out your soil profile. Does the shovel easily enter the ground? Is there a cottage cheese like structure? Is there a nice, deep rich brown color to your soil? Is the soil easily crumbled in your hand? All of these characteristics indicate a healthy soil. If you answered no to any of these questions, a look into your soil’s health may be just what you need.

Soil health has become a buzzword in agriculture. It is used as a way of understanding the impacts we have on the living soil ecosystem. The five principles of soil health are: cover the soil, minimize soil disturbance, create a diverse plant population, maintain continuous living roots and integrate livestock to complete the nutrient cycle and promote a healthy soil ecosystem. Highly disturbed soils with low organic matter, high weed pressure, poor soil structure and poor soil drainage are only a few symptoms of a “sick” soil. Continued interest in influences that impact soil biology, an important link to the physical and chemical characteristics of soils, have led to the reduction of tillage, fertilizer and pesticide use, thus reducing producers’ input costs.

Soil health also relates to the crops we choose to grow. When a plant is growing, it harvests energy from the sun and converts it into simple sugars for plant growth. As the nutrients begin to deplete around the root zone, the plant roots begin growing towards nutrients in the soil. The roots cannot grow quickly enough to harvest adequate nutrients for continued growth. They release simple sugar based compounds called root exudates that gather a microbial community that will help harvest nutrients from the soil. As microbial communities grow and expand, they release “super glues” in the soil that promote soil aggregation. Aggregation not only acts as a home for microbes but also creates channels that promote water infiltration and increases the soils’ ability to retain water.

Furthermore, root growth density, structure and depth are plant dependent, so care should be taken when deciding what to plant. Cover crops can be excellent nitrogen scavengers, soil builders, erosion preventers, weed suppressors and forage sources. As interest in cover crops continues, it is important to realize that although there are numerous benefits to keeping a living plant on your ground, each plant species can have harmful characteristics. Certain species may be better at suppressing undesirable weeds than others. Some species may become hosts to harmful pests. For example, cereal rye is a popular, fast growing cover that has the ability to reduce soil-borne diseases, nematodes and weeds, but it does not control weedy grasses and can increase cut worms and wire worms. Thus, rye would not be the most suitable cover to plant prior to grass crops such as corn, sweet corn, sorghum or wheat. Multispecies cover crops not only provide a variety of benefits, but helps fill gaps or mitigate the weaknesses of monoculture cover crops. Multispecies cover crops mimic nature, which uses a wide variety of plant species to maintain an effective system. Selecting the correct mix of cover crops for your production will take time, research and trial and error. A cover crop that is ideal for one producer may not be the best for another, so it is important to select cover crops that grow well in your area and meet you own soil health goals.

Producer oriented conferences, such as the Western Canada Soil Health and Grazing Conference we recently attended, can aid producers in forming a plan of action for their soils as well as start a conversation with local producers as to what management practices have worked well for them. While at the conference, producers and researchers alike shared principle ideas about incorporating cattle and cover crops into a cropping system. This approach has created healthier soils and a more cost-effective feed source for livestock. So, what happens to the soil when cattle graze?

Cover crops can provide a mixed culture forage for cattle to gain key macronutrients such as proteins, carbohydrates and fats. In exchange for the plant’s nutrients, manure and urine left behind provide a source of new microbes and new organic matter for plants and existing microbes. Addition of new microbes often signals to prevailing microbes that a new source of nutrients is available for consumption and use. This process feeds the continued growth of plants and completes the nutrient cycle.

But it doesn’t end there. An animal feeding on the plant also impacts its root growth. When cattle feed on plants, they trigger a survival response in plants that requires the plant to decide which roots best support the continued survival of the plant. The other roots are abandoned, but still serve as a home and food source for the microbial community. As the abandoned roots degrade, the tunnels left by the roots increases the soil’s water infiltration rate and improves the soil for macrofauna such as earthworms and arthropods. As the plant recovers, roots will resume growing normally and further improve soil structure.

The use of cattle and cover crops in agriculture operations provide the link to completing the nutrient cycle in the soil. The strong root systems of multispecies cover crop mixes provide numerous benefits to soil microbial communities and positively influence soil structure. These mixes can provide nutrients to cattle who in turn return nutrients to the soil. Successful implementation of management practices by well-known regenerative farmers such as Gabe Brown and David Brandt are excellent examples of soil health practices but should not be viewed as the silver bullet to healthier soils. Instead, their principles and view of soil management in a holistic manner can provide helpful guidelines to producers interested in improving their soil. Soils, like people, differ greatly and will require different strategies to strengthen them. So, grab your shovel. Get down. Get dirty. And get to know your soil.