What Are the Best Organic Fertilizers?

What are the Best Organic/Natural Fertilizers?

The best organic fertilizers are ones that naturally occur in nature such as compost, worm castings, manures and mulches. They are not chemically produced in a lab or chemical plant.

Let’s discuss some of the more common organic or naturally occurring in nature, fertilizers.

Garden Compost Fertilizer

Organic Compost

Organic compost is the most common organic fertilizer used today and for good reason. Compost is natural and is found throughout the world’s forests and grasslands. When trees looses their leaves, the leaves pile up on the ground and become compost. It decomposes and fertilizes the soil. Is it the best? Probably, just look at the rain forests. They are fertilized by compost.

Organic compost is comprised of chopped up organic plant material like leaves, wood chips, grass clippings, tree clippings and other plant waste. It is composted before used so that it is partly broken down chemically. This makes the nutrients more available for plant absorption.

You can make your own compost or buy it bagged at any nursery or home improvement store like Lowes and Home Depot. You can make your own compost by mixing Green and Brown materials together in a specific ratio outside in the yard. You have to keep it moist and aerate it by turning the pile over regularly. It takes a few months for the compost to be ready for use. It’s fun to make your own compost but it’s not speedy.

I buy compost at Lowes. I like Kellogg’s N-Rich Soil Amendment and GardenTime Composted Mulch Soil Conditioner and some of the Steer manures. I always read the ingredients to make sure it’s all organic.

Compost is always a safe bet when fertilizing. You don’t have to read the instructions or worry about using too much. Compost will never harm plants no matter how much you use. However, compost is a slow release type fertilizer. It will take a few weeks to months for it to make a significant difference in your plants. Don’t expect overnight changes.

I like to apply compost on top of the soil and mixed in with the top 12 inches of soil. Mixing compost in with the soil will help with moisture retention, reduce soil compaction, fertilize and aerate the soil. It also allows water to penetrate deeper into the ground, allowing roots to get more water. After mixing the soil 50/50 with compost, I add 2-3 inches of compost on top of the root line. This top layer will drastically reduce water evaporation and provide essential nutrients. Moist soil will stay soft which is good for plant roots.

Compost is a great fertilizer however it is low in Nitrogen and will not supply enough for rapid plant growth by itself. Tomatoes, peppers and watermelon will need additional Nitrogen when fruiting. Try Urea [46-0-0 NPK] and Ammonium Sulfate [21-0-0 NPK] for high Nitrogen fertilizers.

Worm Castings

Now we’re talking “complete fertilizers”. Worm castings really can’t be beat. Worm castings are better known as “worm poop or manure”. It is totally organic and safe to use in any amounts. Worm castings have a NPK [Nitrogen, Phosphorus, Potash] of 5-5-3 which is a really good “All Purpose” fertilizer for gardens, lawns, trees and shrubs.

Worm castings provide much more than Nitrogen, Phosphorus and Potassium/Potash. It is an amazing compound of nutrients, microbes, enzymes and bacteria that provide the “Perfect” food for all plants. The nutrients are broken down into the most absorb-able form that nothing else comes close. It’s like Baby Food for infants.

Try worm castings on one of your shrubs or trees that look a little “needy”. You will be surprised in a few weeks time.

You can buy worm castings in a bag or create your own with a small worm farm. I wrote an interesting article on worm castings and how to start a worm farm. You can buy worm castings locally in most states or you can shop online. Worm castings sell for about $20/bag. It goes a long way so you can use it very sparingly. Just sprinkle some around your plants or mix it in with the soil. You can use 1 or 2 tablespoons around a medium sized plant.

Composted Manure

Composted manure is animal waste products but only from specific animals like Steer, Cow, Horse or Chicken.You can’t use just any animal poop. Mainly animals that are herbivores or eat plants will have organic and useful manure. Their waste or poop is broken down organic matter. The most common is Steer and Cow composted manure.

Animal manure has to be composted before it can be used as a fertilizer. Composting kills pathogens and seeds because of the high temperatures of composting. The composting process also breaks down the organic matter so that it is easier for plants to absorb.

Composted manure is rich in Nitrogen and will encourage plants to grow and produce more fruit.

Composted Chicken Manure

Composted chicken manure is the absolute best manure for plant growth and productivity because it has the most amount of Nitrogen compared to other manures. Chicken manure is especially beneficial for vegetable gardens where productivity is the goal. It’s NPK ratios are 3-2.5-6.

Composted Steer or Cow Manure

Composted Steer or Cow manure is a great all purpose fertilizer for gardens, trees, shrubs and grass. It’s especially great for mulching on top of grass seed. It keeps the soil and seeds moist which helps with germination. The NPK ratio is 3-2-1.


Mulch is an amazing fertilizer but does much more. It is also a weed killer, weed barrier, water retainer and attracts beneficial insects like worms, ladybugs and nematodes.

Mulch can be anything organic like compost, leaves, grass clippings, straw, shrub clippings, wood chips, wood mulch, etc. There are lots of things that make good mulch. You can also use non-organic materials like rubber and plastic. These 2 will only kill/reduce weeds and retain water, they will not fertilize the soil.

Organic mulch will slowly decompose and fertilize the soil beneath. This will provide nutrients for plants over a long period of time, like 5-6 months. Mulch will slow down water evaporation significantly too. When I started mulching my garden with grass clippings, I noticed the soil stayed moist for days whereas it used to dry out in 1 day. This is really useful when planting seeds. If the soil dries out around the seeds, they will not germinate. Mulch will guarantee germination. I swear by mulch for starting plants from seed.

Mulch also enhances soil that is sandy or mostly clay. It modifies the texture so that water and air can penetrate it. Mixing mulch with clay type soils will stop it from drying out and compacting into rock-like structure. Roots have a hard time developing in hard and compacted soils. Along with softening and moisturizing soil, mulch will attract earth worms which are miracle workers in a garden. My garden never had worms until I started mulching. Now every where I dig there are lots of worms.

Blood Meal

Blood meal is dried and powdered blood from cattle. It is very high in Nitrogen and is good to use when starting a garden. Apply blood meal before planting. It will provide lots of Nitrogen for rapid growth. Only use blood meal as directed which is sparingly. Too much can burn plants and kill them

Bone Meal

Bone meal is powdered bone from cattle. It is high in calcium and phosphate which help plant roots develop and promotes flowering. It is ideal for flower beds and fruit trees.

Bat Guano

Bat Guano is another great fertilizer and contains high amounts of soluble Nitrogen, Phosphorus and trace elements. It is recommended for flower gardens and fruit trees.