There are a lot of different types of organic soil amendments. I’ve decided to go ahead and breakdown some of the more common and less common ones, what they are used for and where they come from (some are not exactly environmentally friendly). While researching all the different amendments I was rather surprised at how many were unsustainable, nonrenewable and involved open pit mining to obtain.
Alfalfa Meal – Balanced fertilizer that contains moderate amounts of nitrogen, phosphorus and potassium but also includes trace minerals. Is good for adding organic matter to the soil. As the name entails, it’s made from alfalfa. May be of concern now that GM alfalfa has been approved. Could introduce glysophate into your soil.
Azomite – Slow release fertilizer of trace minerals. It’s open-pit mined from ancient deposits of aluminum silicate and marine minerals in Utah. It is a nonrenewable product.
Bat Guano – Fast acting fertilizer with high amounts of nitrogen and phosphorus and a smaller amount of potassium. It’s the accumulated manure of bats which is then mined.
Blood Meal – High nitrogen fertilizer made from the blood of animals, which is a waste product of the meat industry. Water soluble so it can be used a foliar feeding. We don’t use it primarily because I can’t keep my dog out of it.
Bone Meal – Slow release, high Phosphorus fertilizer with some nitrogen made from the bones of animals, which is a waste product of the meat industry. It is also a good source of calcium.
Compost – Plant material that’s been broken down by microbes. It can have a variety of nutrient profiles depending on what plant materials were put in it to create it. Currently homemade compost is the safest to use as persistent herbicides and pesticides are being found in commercial compost.
Cottonseed Meal – Slow release fertilizer containing mostly nitrogen, moderate amounts of phosphorus and small amounts of potassium. It is acidic so it works well for acid loving plants. May be of concern considering a lot of cotton is GM. Could introduce glysophate into your soil.
Dolomite – High magnesium and calcium amendment that is used for raising the pH of acidic soils. It is calcium magnesium carbonate and should only be used on acidic soils that are deficient in magnesium. It is open pit mined and non-renewable.
Feather Meal – Slow release high nitrogen fertilizer made from feathers, which is a by-product of the poultry industry.
Fish Emulsion – Moderate nitrogen with some phosphorus and potassium. Is good for foliar feeding. It’s a by-product of the fish oil and fish meal industries. It’s really stinky and another fertilizer I can’t keep the dog out of.
Green Manure – A cover crop that is turned into the soil before it goes to seed. It adds organic matter to the soil and can be used for weed suppression. Unless it’s a nitrogen fixing legume or very deep rooted it will not add additional nutrients to to soil.
Greensand – Slow release high potassium fertilizer which also contains trace minerals. It is open pit mined from 70-80 million year old marine deposits and is nonrenewable.
Gypsum – Fast release calcium and sulfur. It also acts as soil conditioner improving compacted and heavy soils. Open pit mined and nonrenewable.
Humic Acid/Humates – Not a fertilizer but helps aids plants in the absorption of minerals and nutrients. Open pit mined and nonrenewable.
Kelp Meal – Good potassium and micronutrient source that also aids in increasing microbial activity. Obtained from kelp.
Manure – Various animal manures contain different profiles depending on the animal they came from. They contain trace minerals and nutrients along with NPK. By-product of the livestock industry.
Oyster Shell Lime – Amendment made from oyster shells that helps condition soil, provides calcium and trace minerals and increases the pH of acidic soils.
Peat/Sphagnum Moss – Soil amendment that aerates soil, helps with water retention and helps lower pH for alkaline soils. Unfortunately it is mined from very fragile ecosystems that can take thousands of years to reestablish themselves.
Rock Dust – Mined minerals that provide trace minerals to soil.
Seabird Guano – Fast acting fertilizer with high amounts of nitrogen and phosphorus and a smaller amount of potassium. It’s the accumulated manure of seabirds which is then mined.
Sulfate of Potash – Very high fast release source of potassium. Also includes sulfur. Open pit mined product.
SulPoMag – Also known as langbeinite. Good source of sulfur, potassium and magnesium. Mined underground and is nonrenewable.
Worm Castings – Water soluble fertilizer with lots of nutrients, trace minerals, microbes, and enzymes. Produced from the droppings of worms.