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Soil nutrients play essential roles in plant growth and better crops. Farmers apply fertilizers to add extra nutrients and offer long-term soil fertility. There are three different types of fertilizers: plant, mineral, and animal-based. You can use them depending on the nutrients that you need. Moreover, they can either be organic or inorganic. This article will compare worm castings vs. Milorganite, two popular organic fertilizers.

Are Worm Castings Better Than Fertilizer?

Organic fertilizers consist of natural materials from plants and animal byproducts. You can use them to add nutrients to the soil and crops. Plant-based organic fertilizers consist of soybean meal, alfalfa meal, and cottonseed. Animal-based organic fertilizers from animal byproducts are rich in nitrogen. These byproducts include fish emulsion, chicken manure, and blood meal.

Synthetic fertilizers come from chemicals and inorganic minerals. They are composed of nitrogen, phosphorus, and potassium (NPK). Moreover, these minerals are good for a healthy soil ecosystem.

Worm castings and Milorganite are examples of organic fertilizers. Milorganite contains about 85% organic matter. That is why people classify it as an organic fertilizer. It is, however, not a certified organic fertilizer.

Worm Castings vs. Milorganite: Which Is Better?

Both fertilizers provide the soil with all the nutrients a plant requires for growth. The tie-breaker comes from how well they perform on various soil and to what extent.

Nutrients Each Organic Fertilizer Contains

The waste from earthworms produces worm castings. As the worms feed through compost, they release waste that makes an excellent soil enricher. Worm castings contain an active composition of microbes, enzymes, and plant waste debris. Moreover, you can use it with animal manure and vermicompost pods. The N-P-K ratio in worm castings is around 3.2:1. Worm castings contain essential minerals and have non-burning qualities.

Milorganite is a biosolids fertilizer. Manufacturers get it from processed sewage sludge in Milwaukee Metropolitan Sewerage District. However, it is a bit lacking on the nutrient side. It has an N-P-K ratio of 6:4:0, implying a potassium nutrient deficiency. Also, it contains iron that makes it an ideal lawn fertilizer. Iron contributes to giving lawns the green most lawn growers desire. Contrary to what most people think, Milorganite does not contain excessive heavy metals.

Rate of Nutrient Release

The earthworm's alimentary tract processes the organic material. It forms a thin layer of oil on the castings as it passes. Over two months, this layer erodes. As the worm casting breaks down over time, the nutrients become accessible to the soil.

Milorganite has a slow-release rate. Yet, it releases its nutrients a bit quicker than worm castings.

Where Do They Come From?

You get worm castings when worms and microbes consume and decompose organic waste. That results in a mulch rich in organic materials, microorganisms, and biosolids. Most people refer to this process as vermicomposting.

All the organic material the worm consumes produces bacteria-rich cast in the form of a capsule. The mucus that covers the worm excrement is thick with microbes. It is effortless to make worm castings, and you can do it anywhere in your home. You also do not need much space to harvest your worms for the worm castings. All you need is a worm bin, food scraps, and some worms.

Milorganite requires more effort to make. The Milwaukee Metropolitan Sewerage District collects wastewater. They then use natural microbes to break down nutrients in the water. The end product of this industrial process is Milorganite. You need to have knowledge and skill to do it, not to mention the proper facilities and materials. To get Milorganite, you will have to buy it.


Compost made from worm castings is cost-effective. So, what is the best way to go about it? You will need a supply of worms, a composter, bedding materials, and healthy produce to get started. These materials are inexpensive. You can even recycle your old bins. You have to provide proper care and maintenance for these worms to survive. Furthermore, you will be on your way to breed worms without stress and get worm castings for free.

Milorganite costs a bit more than worm castings. Much of the expenses go to the production of Milorganite in facilities.

What Are the Disadvantages of Worm Castings?

Worm castings have no disadvantage in nourishing your plants and garden. Moreover, they cannot burn the roots of plants and provide enough nitrogen for soil aeration.

Are Worm Castings Good for Lawns?

Yes, they are suitable for lawns and gardens. Plant growth hormones are abundant in worm castings. It can impact plant development, root growth, and productivity. Also, worm castings contain water-soluble plant nutrients, beneficial microbes, enzymes, and organic matter. Moreover, you can also mix it with days-old poultry manure, among other things. Worm compost also maintains soil structure and increases plant health. That happens by introducing more beneficial microbes into the soil's system. The compost also aids in the purification of the soil. Also, it helps remove excess microorganisms and soil-borne pathogens. It is perfect for use on your lawn, gardens, and even golf courses.

Do Worms Like Milorganite?

Worms like Milorganite because it has a similar composition to organic fertilizers. Milorganite also offers a lot of benefits to soil and plants. It is rich in organic materials, feeding soil microbes and nourishing the plant. The soil's capacity to grow grass and other plants improves as a result. Milorganite is an excellent organic matter for the soil surface and does not leach. As a result, the water-soluble nutrients do not get washed away.


We have seen a clear comparison of worm castings vs. Milorganite. Both organic fertilizers have excellent features that yield fruitful results when used in gardening. Compared to synthetic fertilizers, these two stand out.

Milorganite has proven to be an excellent nitrogen-based organic fertilizer for gardening. You can mix it with grass clippings and manure to serve as the best compost for your lawn, garden, and turf.

However, nature provides the best solution to every need. That is true with worm castings. Also, it is rich in nitrogen, phosphorus, and organic matter. Furthermore, the slow release of nutrients allows the crops to make the most out of it. You can rest assured the growing season in your turf will turn out great when you use worm castings.

Grow Bigger Plants with Simple Grow

Do you wish your plants would grow bigger? Was your garden less than it should've been last year?

If you're tired of growing puny vegetables and fruits, it's time for an upgrade...Simple Grow Worm Castings!

What are worm castings? Another term for worm manure. Why would you want to use it in your garden, raised beds, and house plants? Because it makes them grow bigger, faster and healthier...with no chemicals!

How do worm castings do this? It's like giving your plants a powerful multivitamin with everything they need to grow. Trace minerals, nutrients, and most importantly...worm castings are chock full of beneficial microbes. Why does that make a difference?

In recent years, we've learned the importance of gut bacteria for humans and know that it impacts so many different parts of our health. The same thing applies with worms. Gut bacteria from the worm's digestive tract gets into the soil from the worm castings and promotes plant health. Plants have a symbiotic relationship with the microbes from the worm's digestive tract. Plants respond to it and grow really big...really fast!

If you've never tried worm castings before, you owe it to yourself to give them a try. Instead of using traditional chemical fertilizers from the big box store, why not try fresh, certified organic worm castings this year? You'll be able to grow bigger, healthier plants that you actually can feel good about eating. 

Take advantage of our special bundle sale on 25lb bags today!


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