Manure is an organic matter that is used as organic fertilizer in agriculture. Most manure comprises of animal feces; other sources include compost and green manure. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are used by bacteria, fungi, and other organisms in the soil. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web.
The solid, semisolid, and liquid by-products produced by animals grown to produce meat, milk, eggs, and other agricultural products for human use and consumption are called animal manure. They are mixtures of animal feces, urine, bedding materials (e.g., straw, sawdust, rice hulls, wood chips), and other materials linked with animal production, such as waste feed, soil, wash waters, and any chemical or physical amendments used during manure handling and storage.
Manures continue to be regarded as valuable agricultural resources today because they are important sources of plant nutrients and are well known to improve soil physical and biological properties through the addition of organic matter. However, the changing nature of animal production in some countries, the move away from small farms that have sufficient land bases to recycle manure nutrients through crop production, and the move toward geographically concentrated confined animal feeding operations (CAFOs) have raised concerns about the environmental and human health impacts of modern animal production and manure utilization practices.
Adding nutrients to the landscape is an important part of land stewardship. Manure is one soil amendment that can help return those nutrients and juice up the soil, making it an effective growing medium for the next season’s crops. There are advantages and disadvantages of using manure as an amendment. The different types of animal manure have different levels of macro-nutrients and, therefore, must be sufficiently composted for effective use and used at different rates to prevent destroying plants with too much of one nutrient or another.
Types Of Manure
Manures have been used as beneficial soil adjustments since the dawn of civilization and were the primary soil amendment used in agriculture until the advent of chemical fertilizers in the 1940s. The types of manure used are:
#1. Animal manure
Traditional domestic livestock manures also contain varying amounts of nutrients and should be used at different times and in different ways. The most common types of manure used in gardening are Chicken, Cow, Horse, Sheep, Goat, and Pig. Since manures contain different levels of nutrients, they need to be carefully applied to those plants that need the higher nutrient available.
It is known that most animal manure consists of feces. Common forms of animal manure include farmyard manure (FYM) or farm slurry (liquid manure). FYM also contains plant material (often straw), which is used as bedding for animals that absorb feces and urine. Agricultural manure in liquid form, known as slurry, is produced by more intensive livestock rearing systems where concrete or slates are used, instead of straw bedding. Manure from different animals have different qualities and requires different application rates when used as fertilizer.
For example horses, cattle, pigs, sheep, chickens, turkeys, rabbits, and guano from seabirds and bats all have different properties. For instance, sheep manure is high in nitrogen and potash, while pig manure is relatively low in both. Horses mainly eat grass and a few weeds so horse manure can contain grass and weed seeds, as horses do not digest seeds the way that cattle do. Cattle manure is a good source of nitrogen as well as organic carbon. Chicken litter, coming from a bird, is very concentrated in nitrogen and phosphate and is prized for both properties.
#2. Green manure
Green manures are crops grown for the sole purpose of plowing them in, thus increasing fertility through the incorporation of nutrients and organic matter into the soil. Leguminous plants such as clover are often used for this, as they fix nitrogen using Rhizobia bacteria in specialized nodes in the root structure.
Other types of plant matter used as manure include the contents of the rumens of slaughtered ruminants, spent grain (leftover from brewing beer), and seaweed.
Compost is the decomposed remnants of organic materials. It is usually of plant origin but often includes some animal dung or bedding.
Best Manure for fertilizers
Ideally, the best manure for gardens is probably chicken, since it has a very high content of nitrogen, a need all plants require, but it must be composted well and aged to prevent burning plants. Chicken manure is a rich source of nutrients and is best applied in fall or spring after it has had a chance to compost.
Similarly, cow manure, which has a 0.5-0.2-0.4 ratio, is composted beforehand for better results. Sheep manure has a high nitrogen content but a lower ratio in the other macro-nutrients; however, its pellet size makes it a quick waste to compost. Horse manure takes longer and has similar content to cow manure but its larger size and the weed seeds the animal digests means it takes much longer to age and compost.
Fish manure, along with other fish byproducts such as fish meal and fish emulsion, is another excellent fertilizer derived from animal waste. Unlike livestock animal manure, which has to take months to break down and make nutrients available for growing plants, fish manure is a fertilizer that acts fast and provides a quick nutrient boost to the soil. Fish manure is rich in nitrogen, but also provides lower levels of the macronutrients; phosphorus and potassium. Fish fertilizer products can be applied and mixed into vegetable garden soil or used as a foliar spray directly onto ornamental plants such as roses.
Worm fertilizer production, also known as vermicomposting, is ideally suited for home gardeners because worm compost bins require little space. The manure product left behind by worms is called worm castings, and it makes an excellent garden fertilizer. Worm manure provides a balanced source of nitrogen, phosphorus, and potassium, as well as micronutrients; unlike fish manure, which can have an unpleasant aroma, worm castings are odorless. Also, worm manure will not burn plants or their roots, which can be a problem with livestock manures because of their high urea content. Another benefit observed with the use of worm castings has been fewer problems with plant disease and insect pests.
For home gardeners who live near zoos, fairs, or wildlife parks, exotic animal manure also makes a great garden fertilizer. Manure from animals as varied as alpaca, elephants, rhinos, zebra, ostrich, and wildcats is rich in soil nutrients and an excellent source of organic matter that improves overall soil composition and structure. Bat, seabird, and pigeon manures also make some of the best garden fertilizers, although the nutrient levels may vary. For example, some bat guano has high nitrogen content, but depending on its harvesting site, other bat manures may have more phosphorus. Bat and bird manure should be composted or cured for several months before application.
Methods of Manure Application
Broadcasting manure on the surface of a soil is the oldest method of spreading; it is easy, cheap, and can be done during almost any season. But, there are also some significant disadvantages. From a nutrient standpoint, a substantial amount of nitrogen can be lost within a few days of application. This happens when ammonium (inorganic, plant-available nitrogen) converts to ammonia gas, a process called volatilization. The organic nitrogen is not lost, however, and some of it may become available later in the growing season. Other concerns are odors and the possibility of nutrient or pathogen runoff in large rain or snowmelt events.
Broadcasting with incorporation means mixing, or incorporating, the manure into the soil immediately or within a few days after broadcasting. This method greatly reduces ammonia gas losses, especially if the manure is incorporated quickly. Because the manure is thoroughly mixed into the soil, it also promotes the conversion of organic nitrogen into inorganic nitrogen, a process called mineralization. That means you can expect more nitrogen to be available for plant growth than when manure is left on the soil surface. One drawback is that this requires tillage, which disrupts the soil surface and may not fit in all agricultural systems.
The following methods are types of manure injection used for liquid manure. The injection is when the manure is placed below the surface of the soil. It was developed to reduce odors and issues with ammonia gas losses. It is more expensive because it takes longer and requires more tractor horsepower and fuel.
Knife injection is when vertical shanks, similar to knives, pull through the soil. This in turn creates a vertical slot approximately six to eight inches deep for the manure to pass through. Using this method reduces ammonia volatilization loss, but concentrates the manure and nutrients into small strips in the soil, which may not be optimal for plant growth.
Sweep injection systems were developed to reduce the concentrated zones of manure beneath the soil surface. Rather than creating a vertical band of manure where a knife shank runs through the soil, this method creates a broad, horizontal band. Sweep injection is more effective at reducing ammonia volatilization losses and does a better job of incorporating manure and soil. It does require more tractor horsepower than other types of injection.
Disk or Coulter injection systems use a rolling disk or a wavy disk called a colter to open a vertical slot in the soil for the manure to pass through. Some people use closing disks to close the slot and reduce ammonia volatilization losses. This method requires less horsepower than knives or sweep injection, but manure applied at high rates may still end up on the soil surface if it overflows.