Soil Amendments: The Basics

Just the basics of some of my favorite environmentally friendly, sustainable, and helpful soil amendments. I'll also talk about which plants they are best used with and when.



4/16/20225 min read

Hey there fellow gardeners!
Recently, a friend of mine - who admitted she and her husband truly and thoroughly enjoy gardening but are self-described neophytes - requested I describe and explain some of my gardening practices and why I do them. So, this week I tackle SOIL AMENDMENTS! (Said with a dramatic movie announcer voice, of course).

Compost (purchased or homemade) - Good, rich soil, can't exist without compost, and truly excellent gardening soil is a mixture of topsoil, compost, mulch and just the right amount of sand. Compost is simply: decomposed/broken down organic material like kitchen scraps and yard waste. You can purchase it from any garden store, and many soil/rock/landscaping specialist places. If you want to make your own - don't be intimidated, it's not as hard as it may sound. There are three types: Hot, Cold and Vermicomposting. I personally am a bit lazy with this (2 young kids, 2.5 acres of homestead, a large garden and a fledgling small business made this take a back seat, but who knows maybe I will get a little more 'hands on' in the future) so I went with cold composting (where you just throw all your yard waste and appropriate kitchen scraps in the same receptacle and let it decompose at its own pace). With "hot" composting, you do the same as with cold, but you layer your green (yard) and brown (kitchen) waste, water it, and turn it periodically which produces a quicker return (the entire batch can be done in 3 months during the warm season). And vermicomposting involves the use of worms to break down the organic material. Before I began composting 2 years ago, my favorite brand that I bought was local to my area, from Cedar Grove.

Mulch/Wood Chips - Wood chips and wood mulch can be a good soil amendment if you are looking to plant in ground, have particularly hard dirt or even dirt with a high percentage of clay. In these cases, you'll want to add, not only topsoil and compost, but also wood chips/wood mulch/bark. It's a great way to break up that hard soil and keep it from compacting down again, as well as help retain and conserve moisture. Getting various sized pieces of mulch will improve soil structure and ensure that your plants roots can easily make their way through the soil to grab up necessary nutrients. How much you add, however, will depend on the pre-existing condition of the soil and what you plan to plant there. Keep in mind that wood chips/mulch can elevate the acidity of the soil as it breaks down. It's best to use wood mulch on already established landscaping and not on vegetables. My blueberry patch, however, loves it! Bonus sustainability points if you mulch up that tree that fell down and reuse its pieces in your landscaping!

Coconut Coir - This has been around for a while and if you've ever had a hanging basket with the brown fibrous lining then you already know what it is - but it's gaining new popularity right now as a soil amendment that can help stretch the yardage of your good gardening soil. Made from shredded coconut fiber that has been compressed into compact blocks, you just add warm water, let it expand and you've got a great eco-friendly alternative to peat that adds volume, good drainage, and is 'insect-neutral'. I'm using it this year to build back up the volume of my raised vegetable beds before tilling in some fresh garden soil.

Kelp Meal/Seaweed - This is kelp or seaweed, typically harvested from colder waters, and ideally cold-processed, dried and ground up into a meal that can be added to soil (also available in a liquid that can be added to your plants water). A natural soil supplement that is usually approved for organic gardening and thought of as a great source for micronutrients and growth boosters. It's even been shown to increase a plants tolerance to pests, drought, cold temperatures and other stress. My personal favorite (and the one I use) is "Liquid Seaweed" from Blue Planet Nutrients. This can be used with ALL varieties of plants, throughout the season.

Bone Meal - Bone meal is exactly what it sounds like - dried and ground up animal bones (usually cows, but you can get Fish Bone Meal specifically which is a slightly different ratio of nitrogen to phosphorus, but still generally the same). Phosphorous is the second number in the guaranteed analysis on fertilizers and soil amendments and it's the nutrient responsible for helping a plant bloom and produce bigger and healthier blooms. For really happy pumpkins and squash feed phosphorous once a week while flowering until flowers turn into fruit. Also excellent for bulbs. Something of note: if your soil pH is already high (test kits are available online and should be in your local garden store) bone meal will be wasted. Adjust your pH first, then add your bone meal to gain the benefits. My favorite one to use is from Espoma Organic.

Blood Meal - There's no real way to sugar coat this one - it's dried animal blood. Yep, an EXCELLENT source of slow feed nitrogen, but an animal product (usually cow's again) so won't work for vegan gardeners. Nitrogen helps plants grow lusher and greener, and also adds acidity to your soil - which is great for plants that love a soil with a lower pH. This includes carrots, cucumbers, celery, squash, pumpkins, sweet peppers, garlic and tomatoes. For really happy pumpkins and squash feed nitrogen once a week to adult vines until they flower. My favorite one to use is from Down to Earth All Natural Fertilizers.

Alfalfa Meal - Made from fermented and then dried alfalfa seeds. Alfalfa meal can be used to super boost your garden and a quality product will be weed free. It's also typically alkaline so shouldn't be used with plants that like acidic soil. Instead use it with ALL blooming perennials and shrubs (including roses) in your landscaping in the spring before first bloom (and again mid-season before second bloom for plants that repeat bloom). Down to Earth All Natural Fertilizers makes a good one.

Worm Castings - Gardener's Gold, vermicast, worm waste...or the most nutrient dense version of organic compost soil amendment out there. Yes, earthworm poop is the best there is for easily absorbable, all-natural nutrition for plants that also happens to be a natural 'pesticide' to many pests that aim to misbehave - including aphids and spider mites. What else can it do, you ask? Well, it's also great for aerating the soil, helping with drainage, retaining moisture and is the ONLY form of fertilizer than can be put directly on and around your plant buddies without risk of burning them or their roots. You can purchase worm castings, or you can opt to venture into the art of vermicomposting and make your own. You can always spot a seasoned gardener: they are the ones bending over, picking up the wiggly worm that got caught out on the sidewalk in the rain and carrying it to a far more suitable soil home, making it a little hole and covering it up. Reverence for these little critters is one part understanding of the food chain, and two parts respect for what those hard-working little poopers do for the soil. Eating up compost, pooping out excellence...literally.

I was not paid to mention any of these products, I've just used them, and would use them again.