Once your soil quality is where it needs to be, you probably won’t need organic garden fertilizers other than the continual reapplication of compost. In the meantime, this page will help you keep your plants happy and fruitful…
Nitrogen (N), phosphorous (P) (also called potash) and potassium (K), along with the nutrients listed to the right, are all needed in relatively large quantities in order for plants to grow. Micronutrients, as the word implies, are required in lower amounts. Trace elements are required by plants in even smaller (but equally essential) amounts.
The reason N, P and K are singled out so frequently is their lack of abundance in most soils. Whereas your garden plants can always get plenty of carbon, hydrogen and oxygen from the air, their growth quickly depletes N, P and K (along with some of the other nutrients) from the soil. Enter fertilizer.
Plants require a specific balance of macronutrients, micronutrients and trace elements in order to thrive, so when amending your soil with any fertilizer, it is extremely important to NOT overdo it. Only apply the amounts designated on the label. When in doubt, add less, wait then add more if necessary.
Most commercial fertilizers are sold with an NPK percentage rating such as 10 – 20 – 10. A fertilizer with these NPK percentages would have 10% nitrogen, 20% phosphorous and 10% potassium.
The easiest way to determine which nutrients your garden soil has and which it lacks is through at-home soil testing kits. You can also contact your local Cooperative Extension for a more detailed test.
In the meantime, here’s a quick reference for identifying and fixing N, P and K deficiencies…
Leaves – turn purplish/bluish color. Usually starts with lower leaves (leaves usually will NOT turn yellow with phosphorous deficiency).
But we’ve gotten ahead of ourselves.
What about all of the synthetic (chemical) fertilizer options? Shouldn’t you consider them as a valid option, especially since scientists are able to “allocate” much more specific plant-required nutrient percentages into them?
Chemical fertilizers appear miraculous, giving you the most beautiful and fruitful plants imaginable. Unfortunately, “if it seems too good to be true, it usually is” is a very fitting cliché.
There’s more going on with chemical fertilizers than simply giving the plants exactly what they need. If that were the case, we could just stick some seeds in a container of fertilizer, water it and call it a day! Even with the highest-tech synthetic fertilizer, plants still require good old fashioned soil in order to grow.
Why is soil so important for plant growth in the presence of nature-conquering chemical fertilizers? Here are a few key reasons:
All of this is entirely made possible by the living soil organisms that break down the organic matter (food for the soil organisms) and turn it into soil in which plants can be grown. Without the soil organisms and their broken down organic matter, the dead soil would lose its texture and not be able to retain water or nutrients that plants need to grow. In other words, chemical fertilizer applied to dead soil would flow right through (or sit on the soil’s surface) and render it useless to plants.
Where organic garden fertilizers replenish the soil with organism-feeding organic matter with each application (organic fertilizer comes directly from living things), chemical fertilizers contain only the nutrients that the plants require to grow. With nothing left behind for the soil organism to feed on, soil that is exclusively fertilized with chemicals will eventually die.
So why don’t we take a “best of both worlds” approach? Hit ‘em with chemical fertilizer for neighbor-impressing tomatoes while keeping our garden soil healthy through composting and other organic techniques?
That would certainly be better than a chemical-fertilizer-only route, but unfortunately you’d just be slowing down the inevitable conclusion...
...let’s forget for a moment the damage caused to the planet as a whole by the drilling, refining, transport and burning of fossil fuels required to create, produce and sell chemical fertilizer and just focus on the impact it has on your garden.
Let’s also not weigh in on the effects chemical fertilizer run-off may have on your local water supplies or on wildlife and plant life that are downstream from a chemically fertilized garden.
Let’s also dismiss the peak oil facts and the impact peak oil will have on the cost of all oil-dependent goods (including chemical gardening and farming) and therefore the economy.
At the end of the day, the only way to make the “best of both words” approach work (at least in terms of creating a sustainable garden) is to keep your soil relatively healthy through the rigorous application of organic techniques. And those techniques would get your soil healthy to the point that fertilizers of any sort – chemical or organic - wouldn’t be needed.
To cap off the discussion… considering the effects that chemical fertilizers and their production and delivery have on the environment and your soil, would you ever consider using chemical fertilizers if there were organic fertilizers that were equally fast-acting and effective?
We’ve got good news… liquid organic garden fertilizers such as fish and seaweed emulsion are that good, while dry organic fertilizers provide a longer-term and more sustainable impact…
There are two types of organic garden fertilizers: liquid and dry (we'll get into the specific types of each in the next section).
Siphon mixers attach directly to your spigot and, after your garden hose is attached, allow you to easily mix your liquid fertilizer with the water in the hose.
This siphon mixer will mix your liquid fertilizer at a precise 1 to 16 fertilizer to water ratio. It also has built-in features that prevent clogging.
Liquid organic garden fertilizers are usually sprayed (on “fine” or “mist” sprayer setting) once or twice per month. Apply at the base of the plant above its roots along with both sides of its leaves (called “organic foliar feeding”) until the leaves are covered. Outside of the once or twice per month guidelines, consider applying organic garden fertilizers…
To side-dress means to apply a dry fertilizer on the ground outside of the plant’s leaf line.
When using this technique, be sure to apply the dry fertilizer well outside the plant’s leaf line, slightly turn fertilizer into the soil after applying (about an inch/2.5 cm or so) and closely follow the label’s instructions and recommended amounts.
Dry organic garden fertilizers should be used much less frequently than liquid organic fertilizers. Apply them once or twice throughout the growing season to strengthen your crops or give them an extra boost. After applying, gently rake them into the top few inches (8 cm) of soil and water the area lightly.
If you apply dry fertilizer more than once throughout the season, try to space out the timing. Following are times when you may want to consider adding dry organic fertilizer…
As mentioned in the introduction, if your soil is healthy you probably don't need to fertilize. Healthy soil comes from...
If your soil is less than ideal, liquid and/or dry organic garden fertilizers will provide a nice helping hand. Even with perfect soil, fertilizing can go a long way towards getting the hungry feeder crops the nutrient levels they prefer.
When should you use liquid fertilizer versus dry fertilizer? Liquid organic fertilizers should be thought of as fast-acting immediate fixes while dry fertilizers work more slowly and consistently by amending the soil.
Following are common types of each (Nitrogen(N), phosphorous (P) and potassium (K) percentages are indicated next to each fertilizer)...
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