"Animal manure has long been used as a fertilizer in gardens and on farm fields, creating nutrient-rich, moisture-retaining soil for your plants. See the best type of manure for your garden and the best time to apply—as well as a few things to consider first.
All manure is not created equal. Depending on the kind of animal, its age and health, its food, what kind of bedding is incorporated into the manure, and how the manure is collected and stored, the nutrients the manure contains can vary widely. Also whether the manure is fresh, composted, aged, or dried has a great impact on its nutrient values. To really know exactly what it contains, you would need to get the manure tested."
https://www.almanac.com/what-best-manure-compost-gardens
"Using manure as fertilizer is centuries old. With organic gardening and organic lawn care on the rise, the question of using manure as a top dressing or as a garden fertilizer may have crossed your mind. With manures in general, you have two basic choices: Composted manure or raw manure.
Horse manure and cow manure may be the the most common, but goat, poultry, rabbit, and others can be used. Using horse manure seems to be less offensive than using cow manure, at least for some people."
https://www.lawn-care-academy.com/manure-as-fertilizer.html
"Composted manure is animal manure left to decompose. It can then be used as a nutrient-rich soil amendment for gardens. It no longer smells or contains dangerous pathogens. It may be made solely from manure, but most often it contains other composted materials like straw or sawdust.
“Either way, manure is high in organic matter and nutrients that are essential to plant growth,” says Barbara Shea, a master gardener with Tertill."
https://www.familyhandyman.com/article/what-is-composted-manure/
"Manure is one of the best additions for your garden. It improves soil and fertilizes your plants by helping them to absorb water, oxygen and other nutrients, which are essential for their health. Other benefits of manure are that it's inexpensive, readily available and easy to mix into your garden soil.
Fertilizer and amendment
Manure is both a fertilizer and a soil amendment (material added to improve soil). Manure slowly releases nutrients into the soil that plants can easily absorb. Manure contains nitrogen, phosphorus, potassium and micronutrients, which are important for plant health."
https://www.tractorsupply.com/tsc/cms/life-out-here/garden-home-land/gardening/fertilize-with-manure-without-damaging-plants
"Nutrients such as nitrogen, phosphorus, potassium and sulfur, to name a few, are present in manure and available at various rates for plant growth. Besides the bump in fertility, there are other benefits to using manure in your cropping system. Manure has been shown to increase water holding capacity and bulk density along with improving biological properties of the soil.
Manure has many positive attributes, but it also has some drawbacks. One of the drawbacks is lack of uniformity and another is the issue of weed seed management"
https://www.ndsu.edu/agriculture/ag-hub/impact-stories/manure-fertilizer
"One of the best ways to use manure as plant fertilizer is by mixing it in with compost. Composting manure eliminates the possibility of burning the plants."
https://www.gardeningknowhow.com/composting/manures/the-benefits-of-manure-in-your-garden.htm
"Farmers, gardeners, landscapers, and others commonly use livestock manure as a fertilizer to provide nutrients needed for crop production. Manure nutrients have real value as fertilizer. Manure’s fertilizer value will increase as the price of commercial fertilizers increase.
Like commercial fertilizer, manure must be managed properly to avoid environmental impacts. Manure has fertilizer value in its raw form; however, processing manure through digestion, composting, or other means can yield materials that are more portable and whose nutrients are more available to plants, more balanced to crop needs, or less prone to environmental losses."
https://www.epa.gov/npdes/animal-feeding-operations-uses-manure
"Agricultural producers can return manure and crop residues to the soil as fertilizers or soil conditioners on their own property unless prohibited by other State or local laws."
https://www.epa.gov/agriculture/agriculture-nutrient-management-and-fertilizer
"The value of manure as a fertilizer depends on where it is located, how expensive it is to transport and apply, and its crop nutrient composition."
https://www.ers.usda.gov/amber-waves/2023/april/despite-challenges-research-shows-opportunity-to-increase-use-of-manure-as-fertilizer/