Cow Manure Can Give Your Garden a Huge Boost, But It May Also Contain Harmful Pathogens – Here's How to Use It Safely

Cow manure has been used as a fertilizer by farmers in many countries for centuries. Frugal and sustainable gardening was once the norm rather than today’s methods of utilizing synthetic products to provide nutrients to your soil.

This type of manure is not as rich in nitrogen as many other types. However, the high ammonia levels can burn plants when the fresh manure is directly applied. Composted cow manure, on the other hand, can provide numerous benefits to the garden.

The traditional practice of using composted cow manure is seeing a resurgence in small farm production and home gardens. Cow manure compost is now a common product in big box stores and nurseries.

But is using cow dung as manure good for gardens? And how do you use it the right way to benefit plants? I’ll walk you through everything you need to know to get the most out of this unexpected organic fertilizer for your garden.

What Is Cow Manure Made Of?

Cow manure isn’t just cow poop. It is a combination of bedding and other items collected when cow manure is harvested. Often, hay or straw are part of its composition. These items lend texture to the manure, add tilth, and improve your soil.

Cellulose and lignin are also present in cow manure, but the main nutrients released from cow manure compost are nitrogen, phosphorus, potassium, calcium, and magnesium. There are also trace elements present, such as zinc, iron, manganese, and copper. Cow dung is high in organic materials and rich in nutrients.

In addition, cow manure also contains high levels of ammonia and potentially dangerous pathogens. For this reason, it's usually recommended that it be aged or composted prior to its use as a fertilizer.

Is Cow Manure Good for Gardens?

In spite of the nutrient content in cow manure, much of the nitrogen is not available for plants to use initially since it releases very slowly. But cow manure has other benefits besides enriching the soil. It can also enhance soil texture and structure.

Cow manure changes soil texture by creating spaces in the soil. In sandy soil, this will increase the soil’s ability to absorb moisture. This allows you to water less frequently, as the roots of plants can use the additional water and nutrients when needed.

Additionally, it will improve aeration, helping to break up compacted soils. In heavy soils, cow manure will make spaces in the soil that will help increase percolation.

Composted cow manure, which you can order from Walmart for only a few dollars, also contains beneficial bacteria, which convert nutrients into easily accessible forms so they can be slowly released without burning tender plant roots.

Make Sure Cow Manure Is Safe to Use

In order to be safe to use, cow dung needs to be properly aged or decomposed first. This process will kill most pathogens, making the product safe to use around our food plants, and is called composting cow manure.

Manure needs to be composted at temperatures between 140-160°F (60-71°C) before applying it to your garden. Use a compost thermometer, like this one from Amazon, to make sure compost is getting hot enough to kill off harmful pathogens.

But even with proper aging, cow manure can still harbor some pathogens. For this reason, you should apply it no later than 60 days prior to harvesting foods that do not contact the soil and 120 days before harvesting those grown in the ground, such as carrots.

Cow manure should be aged before using on crops, not only to reduce pathogens, but also because it is too “hot” when it is fresh. If applied when fresh, the manure can burn plants.

The general rule of thumb is to apply 2-3 inches (5-7.6 cm) of composted manure to the soil and till it well. By using this organic soil amendment, nutrients are slowly released and enrich the soil all season.

Drawbacks of Cow Manure

Even when composted manure has been treated to high heat and the proper length of time, it may still contain diseases that can affect our food and, in turn, us. E. coli, Giardia, Salmonella, Campylobacter, and other potential health hazards may be harbored in cow manure and can spread to our food sources.

In addition to the potential presence of certain diseases and parasites, cow dung has another drawback. Manure may also harbor weed seeds if it was not composted long enough or at a high enough temperature.

Overusing manure can lead to high amounts of phosphorus in the soil as well. This isn’t bad for the soil, but over time it will leach out and end up in the waterways. The phosphorus is especially damaging to aquatic life by causing algae blooms.

Another potential problem is herbicide residue in cow manure. This happened to me when a broadleaf herbicide was still in my manure. It affected my nightshade plants in particular and caused stunting and failure to fruit.

The problem persisted in my soil for three years. So it's worth taking into consideration before using manure, especially if you are using free manure with an uncertain origin.

How to Compost Cow Manure at Home

Composted cow manure makes an excellent growing medium for garden plants. When turned into compost and fed to plants and vegetables, cow manure becomes a nutrient-rich fertilizer. It can be mixed into the soil or used as topdressing.

Like any compost, you need the right mixture of nitrogen and carbon to result in a balanced product and to create the right conditions for material breakdown. You will need 1 part nitrogen for 3 parts carbon. This means adding plenty of straw, sawdust, or other carbon sources to the manure.

Heavy manures – like cow manure – should be mixed with lighter materials, such as straw or hay, in addition to the usual organic substances from vegetable matter, and garden debris. Small amounts of lime or ash may also be added.

An important consideration when composting cow manure is the size of your compost pile. If it's too small, it won't provide enough heat, which is essential for the composting process. Too big, however, and the pile may not get enough air. Therefore, frequently turning the pile is necessary.

Layer the manure with carbon in a pile at least 3 feet (0.9 m) high and wide. Turn the pile frequently and keep it moist. You also need to monitor this type of manual composting for two to three months to fully age the manure and make sure it is safe for garden use.

How to Use Cow Manure in the Garden

The best way to use manure is as an amendment to soil. Whether you compost your own cow manure at home or buy a bag of composted cow manure, like this one from Home Depot, you use it the same way in the garden.

Work manure into the soil several months before planting for the best effect. One way to make sure the manure is fully incorporated into the soil is to amend soil in fall and let manure break down over winter. Then your beds are fertilized and ready for planting in spring

You may also sidedress with well-rotted manure. Only use it during the vegetative growth stage, not when the plant is actively flowering and fruiting. You may also steep cow manure in water for several days, strain it, and then dilute to create a manure tea you can use as an organic liquid fertilizer.

Cow manure adds significant amounts of organic material to the soil and can greatly benefit your garden, when used properly. With the addition of cow manure fertilizer, you can improve the overall health of your soil and produce healthy, vigorous plants.