By Matt Gibson and Erin Marissa Russell
To figure out what organic fertilizers you need, you need to find out what type of nutrients your plants need. This will depend on the soil conditions in your area, what fertilizers you have used previously, and what type of plants you want to grow.
In order to find out what your soil is lacking, you need to run a soil test. One option is to purchase a home test kit, which are somewhat inaccurate and can be fairly expensive. You could also try contacting your local extension office and sending off a few soil samples to have them professionally tested. This can cost anywhere between $10 and $50 per test.
The results of your soil tests will let you know what nutrient levels in your soil have been depleted and what your pH level is. Professional tests results will include recommended soil amendments so that you know exactly what to do to get your soil in optimal shape for growing the plants that you want to grow in the upcoming season.
Soil tests will give you a list of what nutrients are present in your soils at recommended amounts and what nutrients need to get a boost from natural soil additives. Certain companies also offer soil tests at reasonable prices which you can send off by mail to be analyzed by experts who will recommend specific courses of action for preparing your garden soil for cultivation, and may even recommend the types of plants that will grow well in your area.
When looking for an organic fertilizer to treat your soil with once your test results come back, beware of fertilizers with high NPK numbers. The NPK ratio is on every fertilizer label to indicate what percentage of nitrogen, phosphorus, and potassium (K) are in the feed. Usually, organic fertilizers have NPK numbers that add up to around 20 or less. Higher NPK ratio numbers are usually a sign that the fertilizer is not purely organic.
Lower NPK numbers do not mean that the product is weak in nutrients. With organic feeds, the low numbers are generally indicative of the immediate availability of the nutrients, as is the case with slow release fertilizers that release nutrients into your soil slowly and keep releasing more and more over time.
Most organic fertilizers are slow-release, so the NPK ratio should always be pretty low, adding up to no more than 20. Also keep an eye on the ingredient list and avoid products with ingredients such as super phosphate, muriate, urea, nitrate, phosphoric, or ammonium. These ingredients are regular additives in inorganic feeds, and mean that the product is not truly organic.
Always follow the instructions on the label of the fertilizer you purchase. Read them over carefully before use. The label should tell you exactly how much to apply, when to apply it, and what method is best for adding it to the soil. You can usually pre-treat your beds in the springtime as soon as the ground softens up and becomes workable, followed by regular monthly applications to keep.
Slow release fertilizers can be added any time before planting. Fast-release fertilizers should never be added prior to planting, however, as the nutrients can be washed away before your plants get a chance to get any benefit from them. If you follow the directions carefully and make sure your plants get plenty to eat, you will have a much better chance of growing healthy, prolific producers.
Why Choose Organic?
Many gardeners prefer organic fertilizers over inorganic options for many reasons. Organic fertilizers are just products that are not over-processed or altered, meaning you are giving your plants the nutrients that they need to thrive in their natural form. Inorganic fertilizers are extracted, refined and processed forms of the same nutrients, or synthetic replicas. Organic feeds are typically made of animal waste, decomposed plant matter, and powdered minerals. Commonly used fertilizer ingredients include manure, compost, and ground bone and cotton seeds.
Organic fertilizers release nutrients into the soil, improving the water retention and soil structure as they break down and give sustenance, and strength to your plants to help them develop. Organic fertilizers take time to break down naturally, which means it is slowly releasing its nutrients into the soil. Going organic is good for the environment as well, as there is no risk of toxicity, or salt buildup, and no waste or issues involving runoff. Another plus is that you can make your own organic fertilizer by composting in your backyard, saving you money, all while improving your soil and supplying nutrients to your garden. Organic options are typically cheaper than chemical fertilizers as well.
Is Fertilizing Really Necessary?
If you are actively growing your own food, keeping your soil rich with nutrients is a must. But there are other ways to do it than by adding plant fertilizers directly to your soil. Some gardeners simply side dress their plants with compost or manure regularly and amend their soils every year with lots of organic materials. This keeps the soil in a state of constant improvement, which keeps most plants happy enough. But there are also certain crops that will need additional nutrients.
Whether you are a gardener who is focused on the beautification of their landscape, a gardener determined to create a sustainable lifestyle by growing their own organic food, or a gardener/chef who loves having fresh herbs available for their dishes, you need to know what fertilizers to use for the type of plants that you grow. Organic fertilizers are the best choice for both your plants and the soil in your garden. Here are the best organic fertilizer choices for growing each major plant type.
Organic Fertilizers for Fruits and Vegetables.
For fruits and vegetables, there are several excellent organic choices available. Jobe’s Organics Vegetable & Tomato Fertilizer Spikes are spikes that you bury in the ground in your vegetable garden that break down in the rain. You don’t have to mix it into your soil and they are easy to transport and store. This blend is a 2-7-4 NPK combo that also includes calcium, magnesium, and sulfur. Just drive the pikes into the ground as close to the root system of the plant you need to fertilize and it will begin to receive nutrients after the first watering. If you have dogs that like to dig up the yard, put up a barrier so they can’t dig up your spikes.
Organic Fertilizers for Shrubs and Trees
Humboldts Secret Golden Tree Fertilizer is a great option for trees, and a bunch of other plants that works by activating enzymes in the roots in order to strengthen the plant and encourage quick growth and extensive production. It improves your plants ability to benefit from photosynthesis. Aside from trees, Humboldt’s formula is excellent for veggies, flowers, and roses. However, when using this fertilize, it is good to run a small test with small amounts of fertilizer first to see how your plants will react to it. There have been some issues with gardeners experiencing fertilizer burn when using Humboldts Secret Golden Tree Fertilizer, as it is highly concentrated.
For shrubs and trees that prefer an acidic environment, which is quite a few of them, SEA-90 is a good fertilizer choice, but it will definitely raise the acidity of your soil pH. SEA-90 is an all purpose feed that can be used for hydroponics, as well as for in-ground planting. It is made from the mineral deposits found on the ocean floor. SEA-90 is water soluble, so it words well in a sprayer. It is free of odors, which is important when using ocean-extracted products, as they can be pretty putrid. If you have an especially alkaline soil or you have plenty of plants that prefer acidity, give SEA-90 a try for shrubs and trees, as well as flowers.
Organic Fertilizers for Lawns
When you’re choosing an organic fertilizer to use on your lawn, experts recommend thinking about your purchase as a product to feed the soil, not something you’ll be feeding your grass. When you really think about it, your fertilizer doesn’t start nourishing your lawn instantly. The microscopic organisms that live in your soil are the first to consume the fertilizer you choose. As the fertilizer passes through their bodies, these fungi and bacteria convert the nutrition into a form your plants are able to take in. After leaving the microorganism’s bodies, the nutrients are carried by rainwater or water you provide to the root system of your lawn. In combination with photosynthesis, this is how plants feed themselves and get energy to build new cells.
Add nutrients to improve your soil by applying an organic fertilizer, or to address issues with soil structure, you can amend the soil where your lawn grows with all kinds of organic materials. Compost is another option, as it’s really a mixture of different soil amendments that have already been decomposed by microorganisms. We’ve listed some popular soil amendments below, along with their purposes. You can use these amendment on their own or choose fertilizer products that contain them as ingredients to get their benefits.
Although its nutrition becomes available at a slow to moderate speed, alfalfa hay is well rounded and offers all three of the major nutrients. It contains 2-3 percent nitrogen, .5-1 percent phosphorus, and 1-2 percent potassium.
Offers nitrogen, phosphorus, and potassium in a slow release, with an N-P-K ratio of 2.5-1,-1.5.. Consists of ground alfalfa, the plant often used to feed farm animals. Use a tiller to incorporate alfalfa meal into the soil in the spring, long before you will be planting in an area.
A moderate to intermediate source of nutrients, containing 8 percent nitrogen, 6 percent potassium, and 1 percent phosphorus. Bat guano can be taken in and used by plants rather quickly, so it can be used before you plant a crop in the spring or in between crops during crop rotation.
Blood meal increases the nitrogen available in your soil. It won’t burn your plants like an overdose of nitrogen will because the blood meal provides a slow release of the nitrogen. However, it is a very rich source of nitrogen, normally added directly over the root systems of plants and covered in mulch. It contains 12 percent nitrogen, 1.5 percent phosphorus, and .5 percent potassium.
Amend your soil with bone meal, and you’re mixing in calcium and phosphorus for your plants as well. This is a good additive when your soil already contains plenty of nitrogen or when your plants have been showing signs of being burned by nitrogen. Bone meal contains 4 percent nitrogen, 20 percent phosphorus, and 0 percent potassium.
If you could only choose one organic fertilizer for your soil, we’d recommend choosing compost no matter what kind of soil you have. Mixing a few inches of compost into your soil will help sandy soil retain moisture longer. Amending your soil with compost will also loosen heavy clay soils. It also boosts the population of the beneficial microorganisms in your soil. Best of all, you can make your own.
Good compost should include a mix of all required nutrients, because good compost contains a mix of ingredients. Be careful not to include too much of any one ingredient or type of ingredient in your compost. Adding compost tends to increase soil alkalinity along with soil nutrition. The exact nutritional makeup of compost varies, but a sample N-P-K value would be 1-3 percent nitrogen, 1-2 percent phosphorus, and 1-2 percent potassium.
Cottonseed meal will fortify your soil with nitrogen, phosphorus, and potash. It adds all three of these nutrients in a slow release. Cottonseed meal contains 6 percent nitrogen, 3 percent phosphorus, and 1 percent potassium.
Contains nitrogen as well as potassium and phosphorus, but only a small amount of each, with an N-P-K ratio of .5-.5-1. Commonly used in winter to stabilize the soil.
Soil Amendment: Dried Leaves
Collected fallen leaves can be incorporated into your soil to increase its moisture retention. They’ll also provide your plants with potassium and phosphorus. Dried leaves contain these nutrients, but they are moderate and not a rich source of them. Dried leaves that have already started to decay should be applied in the fall so they will have time to break down before spring. You can also use dried leaves as you would mulch to get the same benefits.
This amendment contains 12 percent nitrogen (but no phosphorus or potassium). It’s most often used to fortify the soil in spring before plants are placed in the garden.
Fish emulsions are high in nitrogen, containing about 9 percent nitrogen with no potassium or phosphorus. Better yet, the nitrogen is immediately available to plants growing where you add fish emulsion. It is slightly acidic, which some plants are sensitive to.
Fish meal works well because plants are able to take it in quickly, and it’s well balanced between the big three nutrients. Fish meal contains 6-12 percent nitrogen, 3-7 percent phosphorus, and 2-5 percent potassium.
Soil Amendment: Grass Clippings
Grass clippings can be used as an organic soil amendment both fresh (high in nitrogen) and when they have been drying for some time (high in carbon). Incorporating grass clippings into your soil will add a moderate amount of potassium and phosphorus. Amending your soil with grass clippings will also increase your soil’s moisture retention;.fresh clippings are rich in nitrogen, while dried clippings are rich in carbon. A sample N-P-K reading for grass clippings might include 1-2 percent nitrogen, 0-.5 percent phosphorus, and 1-2 percent potassium.
Soil Amendment: Greensand
The exact amounts of the nutrients in greensand are variable depending on where the greensand comes from. It is a shallow marine sediment made of ground-up limestone, so it has some of the same benefits as seaweed or fish emulsions.
Soil Amendment: Hoof/Horn Meal
This amendment will increase the alkalinity of your soil, and it’s quite high in nitrogen. A sample N-P-K reading for hoof/horn meal could include 12-14 percent nitrogen, 1.5-2 percent phosphorus, and 0 percent potassium.
Soil Amendment: Humus
No, we don’t mean hummus, the Middle Eastern chickpea-tahini dip. Humus is made of decaying leaves and parts of other plants. It changes the texture of your soil, making it easier for it to retain moisture and increasing the air circulation. Humus also helps make your soil more fertile due to the nutrients in the organic materials it contains.
Kelp is a moderate source of all three of the major nutrients and is especially high in potassium. It also boosts the soil’s level of iron and zinc. Kelp includes 1 to 1.5 percent nitrogen, .5 to 1 percent phosphorus, and 5 to 10 percent potassium.
There are many different kinds of manure you can use, such as cow manure, sheep manure, or chicken manure. Whichever you choose, it’s important for you to use well rotted manure. If you must use fresh manure, wait to spread it in your garden and mix it into the top layer of soil until the beginning of winter, when plants have faded and the garden is going dormant. Then it will have time to decompose more before the spring.
Fresh manure can burn your plants if you apply it when they are in the garden because they contain so much nitrogen. Another reason to make sure manure you add to your garden is well rotted is that it’s possible for many types of manure to contain weed seed, which may still be viable. Poultry and sheep manure contain the highest nutrient levels.
Soil Amendment: Paper. Cardboard, or Newspaper
Some gardeners save used paper, cardboard, or newspaper from their personal waste supply, or they may use paper mill waste. All three of these materials are high in carbon. Use only a limited amount at a time to avoid reducing the soil’s nitrogen content.
Soil Amendment: Pine Needles
This amendment offers a slow release of nutrients and also will increase the acidity of your soil. Pine needles contain .5 percent nitrogen, 0 percent phosphorus, and 1 percent potassium.
Soil Amendment: Sawdust
Sawdust is a high-carbon soil amendment. Make sure to only use the recommended amount. Adding too much sawdust to your soil can both leach nitrogen from the surrounding area and give your soil an overdose of carbon that is too much for plants to handle. Sawdust contains 0-1 percent nitrogen, 0-.5 percent phosphorus, and 0-1 percent potassium.
Seaweed extract makes all three of the major nutrients, along with zinc and iron, speedily available for your plants. Seaweed extract holds around 1 percent nitrogen, 2 percent phosphorus, and 5 percent calcium.
Soybean meal is a good amendment for providing well-rounded nutrition for long-lasting results. It contains 3 percent nitrogen, .5 percent phosphorus, and 2.5 percent potassium.
Soil Amendment: Sphagnum Peat
When you mix sphagnum peat into your soil, you’re changing the pH balance, boosting the soil acidity. Sphagnum Peat will also increase the water your soil is able to retain, helping to keep moisture accessible to your plants for longer. You’ll notice that dry soils stay more moist, and you won’t have to water your plants as frequently.
Soil Amendment: Straw
Some gardeners use straw to make the soil looser and increase its ability to drain out excess water. However, be advised that straw will also add lots of carbon to your soil. Those who use straw as a soil amendment normally time things so that they’re amending the soil a month or two before planting in the spring. A sample N-P-K reading for straw includes 0-.5 percent nitrogen, 0-.5 percent phosphorus, and 1 percent potassium. You can also amend your soil with corn stalks, which have a very similar N-P-K value and amendment process.
Soil Amendment: Wood Ash
Amending your soil with wood ash increases the phosphorus and potassium it contains. It also changes the pH level, making your soil more alkaline. You only need a little bit of wood ash. Wood ash usually contains 0 percent nitrogen, 1-2 percent phosphorus, and 3-7 percent potassium.
Soil Amendment: Wood Chips
Choose wood chips that have been decomposing for a while already or mulch products made with wood chips. This amendment will boost the amount of carbon in your soil.
Choosing organic fertilizers lowers the demand for chemical fertilizers and is the environmentally responsible way to garden the green way. Using organic fertilizers also encourages others to follow in your footsteps and help reduce the damage done to our ecosystems by inorganic methods. Choosing organic fertilizers and promoting their use to others will not reverse the damage we have done to our environment from centuries of harmful plant feeding methods overnight, but every time we choose environmentally friendly organic methods over their chemical counterparts, we are taking a step in the right direction.
Learn More About Organic Fertilizers and Soil Amendments
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