Climate Friendly Gardening & Food Production
Homemade Garden Fertilizers: An excerpt from our Spring 2024 Newsletter
In our previous e-Newsletters we provided information and tips on how to create less food waste, start seeds indoors, do container gardening and many other topics. All of our past e-Newsletters are now available to browse at IMPACT Bulletin - Sault Climate Hub e-Newsletter Archive.
Gardening season is fast approaching and connecting with the land and growing your own food can save money, taste great and help the climate too. Plants require 16 essential elements to survive and grow. Carbon, hydrogen and oxygen come from air and water but the other 13 nutrients come from the soil. Nitrogen, phosphorous, potassium, calcium, magnesium and sulphur are considered macronutrients since plants need lots of them, while iron, manganese, zinc, copper, boron, molybdenum and chlorine are known as micronutrients with plants needing less. The pH of the soil, its acidity or alkalinity, is also an important property. While plant nutrients are more optimally available at a slightly acidic pH of 6.5, some plants prefer more acid or alkaline conditions as shown in this Reference Guide to Soil pH Levels.
Composting kitchen and yard scraps and applying to soil is one way to recycle nutrients and fertilize your soil but there are even simpler methods to make homemade fertilizers from common household waste products that anyone can do.
Coffee grounds are high in nitrogen, potassium and magnesium and have an acidic pH. If you dry them out on a cookie sheet they are easier to spread in the garden.
Egg shells are high in calcium and similar to agricultural lime they can increase the alkalinity of the soil. Rinse the shells out with water after cracking the eggs, let them dry thoroughly, crush the shells up finely by hand and then apply them to the soil.
Wood ash from a wood stove, fireplace or campfire is high in calcium, potassium and magnesium. Ash will also increase the alkalinity of your soil, increasing nutrient availability to your plants.
Using these homemade fertilizers decreases the need to produce and purchase synthetic industrial fertilizers, saving you money and decreasing greenhouse gas emissions. You can spread them across your garden or around your plants and work them into the soil with a rake or small hand cultivator. It is important to note that even though plants need all of these nutrients, too much of any particular one can be toxic and decrease growth and even cause the plant to die. So the best approach is to apply them lightly and spread any type of fertilizer evenly across an area.
A good practice is to do a soil test of your garden to determine if your soil is actually lacking any nutrients and if it is, what you need to add. The Ontario Ministry of Agriculture, Food and Rural Affairs provides a list of Accredited Soil Testing Laboratories. Samples that you collect will need to be sent to a laboratory in southern Ontario for analysis. A basic soil test can cost less than $30 and the report includes the condition of your soil and recommendations for nutrients required to improve fertility.