We apply fertilizer to make our plants grow better. But when do we apply fertilizer? And how do we apply fertilizer to the garden? In one page, we’ll cover the basics of using fertilizer in your garden.
- What Is Fertilizer?
- Always Take a Soil Test
- How to Read Fertilizer Labels
- Processed vs. Organic Fertilizers
- When to Fertilize Your Garden
- How to Apply Granular Fertilizers
- How to Apply Liquid Fertilizers
- Learn More About Fertilizing Your Garden
- 1. Feed it an Organic Diet
- 2. Till With Worms
- 3. Grow Your Own Soil
- 4. Test for Success
- Go no further than your pantry, backyard or the beach for materials to make your own organic fertilizer:
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- Applying fertilizers
What Is Fertilizer?
Think of fertilizers as nutritional supplements. Plants need a variety of life-sustaining nutrients—such as nitrogen and phosphorus—which they take up from the soil. Many soils contain adequate nutrients for the plants to absorb, but some soils do not, which is where fertilizers come in.
Fertilizers are plant nutrients that are added to the soil. The plants absorb these essential nutrients from the soil to improve health, growth, and productivity. Soil nutrient deficiencies reduce and modify plant growth. You can also tell which nutrients your soil is lacking by the deficiency symptoms they display, which can range from yellow leaves (lack of nitrogen) to reduced flowering (lack of phosphorus) to weak stems (lack of potassium) to blossom-end rot (lack of calcium).
Not all soil needs fertilizer. Think about a natural setting where fallen leaves and plants decompose in place. Nutrients are naturally recycled into the soil and made available to growing plants. If your soil is rich in nutrients and the microbial life that aids in the plants’ uptake of these nutrients, then adding more can upset that healthy ecosystem. In fact, more fertilizer is not better! Plants use only the nutrients that they need. To absorb more than are unnecessary can result in abnormal growth.
However, many garden soils do need fertilizer, especially if the soil has been cultivated previously. If you’ve grown and harvested plants in your garden in the past, they have taken up nutrients from the soil, and those nutrients need to be replaced before more plants are grown there. This is where fertilizer (organic or processed) plays a role. Fertilizer replaces lost nutrients, which ensures that soil nutrient levels are at an acceptable level for healthy growth.
Always Take a Soil Test
The only way to truly determine the level of nutrients in your soil is to test it. Soil tests are usually available for free or low-cost from your local cooperative extension. A soil test is easy to do and the results guide your fertilizer applications. You may even find that if your garden has been fertilized for years, you have high levels of nutrients. You do not want to add nutrients to your soil if it’s already available in high amounts; this may inhibit your plants’ growth. Read more about how to take a soil test.
How to Read Fertilizer Labels
Ever seen those confusing labels on fertilizer bags? The numbers can seem daunting at first, but once you know what they mean, they tell you exactly what you need to know about a fertilizer.
A fertilizer label on a package will have three numbers, such as 5-10-10. These numbers refer to the percentage of Nitrogen (N), Phosphorus (P), and Potassium (K), the three nutrients that plants need the most. If you add up the numbers, they are the percentage of the bag’s total weight (the rest is simply filler to make it easy to handle). There may also be other nutrients, including calcium, magnesium, iron, and manganese.
You can find these nutrients in many strengths; they can be processed or organic, and may come in liquid of granular formulations.
“Complete” fertilizers contain all three nutrients (example, 10-10-10). Sometimes, the nutrient ratios are important. For example, if you’ve ever experienced lush green growth without flower blooms, you may have too much nitrogen. You might choose a fertilizer label with 3-20-20 (low in nitrogen). Alternatively, vegetables planted in cold soil may need extra phosphorus for root growth; you might choose a fertilizer labeled 10-50-10.
Read more in our article on fertilizer basics and the NPK ratio.
Processed vs. Organic Fertilizers
- Processed fertilizers (also called “synthetic” or “chemical” fertilizers) are manufactured from natural ingredients such as phosphate rock (P) and sodium chloride (NaCl) and potassium chloride (KCl) salts, but these are refined to be made more concentrated. Most (but not all) processed fertilizers are quick-release in a water-soluble form to deliver nutrients quickly to the plant, which can be useful in some situations. (There are some processed fertilizers that are coated to slow down the release.)
- Organic fertilizers are materials derived from plants that slowly release nutrients as the micro-organisms in the soil break down. Often applied in granular form (spread over the soil), most organic nutrients are slow-release, adding organic material to the soil so that you don’t need to apply it nearly as often. (Plus, they don’t leach into and pollute waterways, as do many of the synthetic, water-soluble fertilizers, which plants can’t fully absorb.) While most organic fertilizers are slow-release products, some release a portion of their nutrients quickly (examples are animal manure, biosolids, and fish emulsion).
Chemically, the nutrients for processed and organic fertilizers are the same. Ideally, slow is the way to go. Slow-release granular fertilizers meter out nutrients in a controlled, “digestible,” and safe manner, as opposed to fast-acting, synthetic, water-soluble fertilizers, which are, in essence, an overdose.
In terms of cost: While organic fertilizers can be more expensive upfront than processed fertilizers, they are often still economical for small gardens. Plus, you don’t need to apply as often. When you add the long-term benefits to your soil, organic outweighs processed.
When to Fertilize Your Garden
If you are correcting a soil nutrient deficiency based on a soil test, it’s best to fertilize well before you plant so that you can work the fertilizer deep into the soil.
Otherwise, fertilize in the spring before planting annual flowers and vegetables and as growth begins for perennials. Many gardeners use a general-purpose fertilizer at this time (either an evenly balanced fertilizer or one that’s slightly higher in nitrogen). Incorporate fertilize into the soil several inches deep for annuals and vegetables. For perennials, work fertilizer lightly into the soil around the plants.
Plants need the most nutrients when they are growing most rapidly. This occurs earlier for spring plantings of lettuce and other greens. Rapid growth occurs midsummer for corn and squash. Tomatoes and potatoes also will need extra fertilizer (N) mid-season as the plants takes us nutrients.
For a long-season crop such as corn, many gardeners apply a small amount of fertilizer as a starter at the time of seeding, and then add a larger amount in early summer, just before the period of rapid growth. When using organic fertilizers for long-season crops, a single application is usually adequate because these fertilizers release their nutrients throughout the season.
For perennial plants, the timing depends on the plant’s growth cycle. Blueberries, for example, benefit when fertilizer is applied early in the season at bud break, while June-bearing strawberries benefit most when fertilized after harvest.
Ornamental trees, shrubs, and perennials are often fertilized at the beginning of their growing season as dormancy breaks.
How to Apply Granular Fertilizers
For the first fertilizer application of the season, apply granular fertilizers by broadcasting them either by hand or with a spreader over a large area. Or, side-dress the fertilizer alongside your rows or plants or seeds. All dry fertilizers should be worked or watered into the top 4 to 6 inches of soil with hoe or spade work after being applied to help the fertilizer leach down toward the plants’ root zones. If your plants are already growing, cultivate gently so that you do not damage any roots.
During the growing season, lighter supplemental applications can be made to the top inch of soil in crop rows and perennial beds and around the drip lines of trees or shrubs. (Read the label to find out how often applications should be made.)
In general, applying granular fertilizers just before a good rain can be beneficial, as it aids in working the fertilizer down into the soil where roots can access it.
How to Apply Liquid Fertilizers
All water-soluble fertilizers are applied by dissolving the product in irrigation water and then applying it to the leaves of the plant and the soil around the plant.
Don’t apply liquid fertilizer at the exact same time that you plant. No matter how carefully you remove plants from their containers and place them in the ground, some root hairs will break. The fertilizer will reach the roots immediately and enter them at the broken points, “burning” them and causing further die-back.
Many gardeners wait 2 to 3 weeks after planting before fertilizing with liquid solutions; by then, the newly set-out plants should have recovered from any root damage.
It is important to water plants thoroughly with plain water before applying the liquid fertilizer to avoid burning the roots if the soil is dry. Also, take care that the fertilizer is indeed diluted based on instructions, or you could burn the leaves. If you have a watering system, you can use an injector device to run the fertilizer through the system.
In the case of liquid sprays, it is best to apply them on dry days in either the early morning or the early evening, when the leaves will have time to absorb the material. Avoid extremely hot days when foliage is subject to burning.
Learn More About Fertilizing Your Garden
If you have more questions about fertilizers, please ask below, or we encourage gardeners to call their country’s free cooperative extension office for local advice.
We hope you’ve learned a lot about fertilizers! When is your soil ready to plant in the spring? See our minimum temperature for seeds to germinate.
I’m a soil scientist and a former faculty instructor for Oregon State University’s Extension program, where I’ve taught and consulted with farmers and gardeners. My own half-acre garden in southern Oregon is my laboratory where I experiment to find new ways to improve the soil.
After spending years learning how to make garden soils light, fluffy, and easy to work, I wrote Building Soil: A Down-to-Earth Approach, a guide to everything you need to know to improve soil. Here are 10 of my top tips to improve soil:
1. Feed it an Organic Diet
Above: Florist Clare Day raises her own organic flowers on her 12-acre farm in British Columbia. See more at Organic Flowers at Red Damsel Farm.
Spring brings a flurry of underground activity that we can’t see. Billions of soil organisms stretch and yawn, exploding into existence. It’s this living soil below ground that helps gardens thrive above ground by recycling nutrients, capturing water, improving soil tilth, and fighting pests and disease.
We build soil health all year-round by feeding and caring for it. How? Living soil has the same four basic requirements we do: food, water, shelter, and air.
Autumn is the best season to start. Organic materials, the key ingredients for healthy soils, abound. You can add fallen leaves, garden debris, kitchen scraps, and even apples raked from beneath fruit trees to soil.
Chop organic material directly into the top 2 inches of soil with a heavy bladed hoe and cover with mulch. Ideally, add concentrated manures, mineral phosphorous and potassium fertilizers, and lime at the same time. Adding these materials in the fall gives them time to break down for use when plants need them in the spring.
2. Till With Worms
Above: Photograph by Jim Powell for Gardenista. For more, see DIY Composting: A Man Obsessed.
Instead of breaking out the rototiller, or breaking my back double digging, I like to let the worms do my tilling for me by using sheet mulching techniques.
Sheet mulching is the process of building compost right on the soil surface. For new gardens, I’ll add a smothering bottom layer of cardboard to kill existing vegetation, then alternate 2- to 4-inch-inch thick green and brown compost layers. This invites worms to burrow through the soil as they transport food. In the process, they dramatically improve soil structure, while depositing power-packed worm manure castings.
Sheet mulching takes advance planning. Ideally, start sheet mulches for new gardens the year before you plan to plant (and for existing gardens a few months before planting). Sheet mulching will build new garden soil literally from the ground up. It maximizes nutrients, smothers weeds, and keeps soil life intact and undisturbed.
3. Grow Your Own Soil
Above: Photograph by Justine Hand.
Green manures and cover crops—such as buckwheat and phacelia in the summertime and vetch, daikon, and clovers in the fall—are my favorite way to improve soils. Whenever I have a window before planting, I grow a cover crop to add organic matter, lighten and loosen soil structure, and enrich garden nutrients. Cover crops also act as a living mulch to shelter soils and control weeds in the off-season.
Chop over-wintered cover crops directly into spring soils a few weeks before planting. During the growing season, sow a quick-growing cover crop, such as buckwheat, to fill the gap between spring and fall crops. When it’s time to plant, pull the buckwheat cover and use it as a mulch for fall garden beds.
4. Test for Success
Above: A Soil Test Kit in a sturdy plastic case is $20.95 from Home Science Tools.
Soil tests are an indispensable garden tool. I always recommend taking one when starting a new garden, or when garden health declines. If an essential nutrient is missing, garden and soil health will suffer. For best results, take nutrient tests in the late summer or early fall. Submit a soil test to a certified lab to add the right balance fertilizers and lime materials to new gardens. For a list of certified labs visit NAPT.
Plants grow using energy from the sun combined with nutrients taken from the soil. Because the organic matter in soil holds nutrients like a sponge until they are needed by plants, soil that is fertile, well-drained, and regularly enriched with compost often holds a reasonable supply of plant nutrients. Unimproved, though, newly cultivated soil is usually low in organic matter, so it is also low in nutrients.
All edible plants remove some nutrients from the soil, and some have such huge appetites that they will quickly exhaust the soil (and then produce a poor crop) without the help of fertilizer. Fertilizing is especially helpful early on, when plants are making fast new growth. You can mix a continuous-release fertilizer, such as Miracle-Gro® Shake ‘n Feed® Tomato, Fruit & Vegetable Plant Food, into individual planting holes, work it into furrows, or use a turning fork to mix it into beds. Or, you can apply a liquid fertilizer, such as Miracle-Gro® LiquaFeed® Tomato, Fruits & Vegetables Plant Food, at the same time you water your plants. Whichever type of plant food you choose, be sure to read the label for directions.
Always follow the rates given on the fertilizer label when deciding how much to use. Too much fertilizer can be worse than too little! Overfed plants often grow huge, yet bear a light crop late in the season.
In addition to feeding your plants, it’s important to give them a high quality soil environment—fertilizer and soil work together to provide your garden with what it needs to grow big and produce a great harvest. When planting in-ground, improve your existing soil by mixing in a layer of Miracle-Gro® Garden Soil for Vegetables and Herbs. If you grow in containers, fill them with lighter, fluffier Miracle-Gro® Potting Mix.
Healthy soil is the basis of healthy plants and a healthy environment. When garden soil is in good shape there is less need for fertilizers or pesticides. As author and respected gardener Frank Tozer writes, “When building soil you not only improve your plants health, but you can also improve your own.”
Organic soil is rich in humus, the end result of decaying materials such as leaves, grass clippings and compost. It holds moisture, but drains well. Good organic garden soil is loose and fluffy — filled with air that plant roots need — and it has plenty of minerals essential for vigorous plant growth. It is alive with living organisms — from earthworms to fungi and bacteria — that help maintain the quality of the soil. Proper pH is also an essential characteristic of healthy soil.
So, how do you know if your soil is healthy? And what do you do if it isn’t?
Get your gardens off to a great start and keep them productive with premium quality soil amendments. Need advice? Our Soils Blog provides the ideas, information and practical experience you need to get the job done right.
Determining Soil Health
Of the 17 or so elements thought to be essential for plant growth, nitrogen, phosphorus and potassium are the most important (see What’s in a Number?). They are known as primary or macronutrients because plants take them from the soil in the largest amounts. Fertilizers that contain all three of these nutrients are labeled complete fertilizers, but they are hardly complete in an absolute sense. Calcium, magnesium and sulfur, known as secondary nutrients, are also important to many plants. Lesser or micronutrients include boron, copper, iron manganese and zinc. Some plant micronutrients have specific functions such as cobalt, which isn’t used by most plants but helps legumes fix nitrogen. Another critical component of your soil is its acid-alkaline balance or pH reading. All these essentials — and the proper texture — makes for healthy soil.
One way to determine what minerals are lacking or abundant in your soil is to get it tested. Local Cooperative Extension Services often offer low cost soil tests. These tests usually measure levels of soil pH, magnesium, phosphorus, calcium, potassium, and sometimes nitrogen. They may also report the soil’s micronutrient content, but this isn’t essential to the gardener who adds plenty of organic matter to her soil. For a less intensive test, pick up a do-it-yourself version such as the Rapitest Soil Test Kit and do your own simple, rewarding chemistry.
#1 SOIL TESTER
The Rapitest® Soil Test Kit features a “color comparator” and capsule system that’s designed for simplicity of use with accurate results. Give it a try! It’s a fast and fun way to achieve better results from your gardening efforts!
pH levels can be critical to your plant’s ability to absorb nutrients. Most minerals and nutrients are best available to plants in soils with a pH of between 6.5-6.8. If your soil is acidic (low pH, at or below 6.0) or alkaline (high pH, above 7.0) it doesn’t matter how rich it is in nutrients, the plants won’t be able to absorb them. pH is usually included in a soil test, or you can buy a pH Meter and determine the acid-alkaline balance of your soil on your own.
The best time to get the soil tested is in the spring or fall when it is most stable. This is also the best time to add any soil amendments or organic fertilizer should your soil fall short of minerals or nutrients.
Soil Texture and Type
In addition to uncovering your soil’s pH, macronutrient content and mineral levels you’ll want to examine its texture.
Soil texture depends on the amounts of sand, silt and clay it holds. A handy description of the three main soil components and an easy test to determine your soil type can be found at NASA’s Soil Science Education Page. Sand constitutes the biggest pieces of soil particles and feels gritty to the touch. Next in size are the silt particles which are slippery when wet and powdery when dry. The smallest pieces are clay. They are flat and tend to stack together like plates or sheets of paper. You don’t need an expert to determine soil texture. Just pick up a little and rub it between your fingers. If the soil feels gritty, it is considered sandy. If the soil feels smooth like talcum powder, it is silty. If the soil feels harsh when dry and slippery and sticky when wet, the soil is heavy clay. Most soils will fall somewhere in between.
Sandy soils tend to be nutrient-poor since water and nutrients rapidly drain through the large spaces between the particles of sand. These soils also tend to be low in beneficial microbes and organic matter that plants thrive on.
Silty soils are dense and do not drain well. They are more fertile than either sandy or clay soils.
Heavy clay soils are quite dense, do not drain well and tend to be hard and crack when dry. Because there isn’t much space between the clay particles, there usually isn’t much organic matter or microbial life in the soil. Plant roots have a hard time growing in the hard material.
Improving Garden Soil
Adding organic matter in the form of compost and aged manure, or using mulch or growing cover crops (green manures), is the best way to prepare soil for planting. Adding chemical fertilizers will replenish only certain nutrients and do nothing for maintaining good, friable soil. Organic matter will help supply everything your plants need.
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Just like humans, plants need air, both above ground for photosynthesis and in the soil as well. Air in the soil holds atmospheric nitrogen that can be converted into a usable form for plants. Soil oxygen is also crucial to the survival of soil organisms that benefit plants.
Good soil provides just the right space between its particles to hold air that plants will use. Silty and heavy clay soils have small particles that are close together. These dense soils have little air. Sandy soils have the opposite problem; their particles are too big and spaced out. The excessive amount of air in sandy soil leads to rapid decomposition of organic matter.
Adding organic matter, especially compost, will help balance the air supply (the perfect soil is about 25% air). Also, try not to step in the beds or use heavy equipment that can compact the soil. Avoid working the soil if it is very wet.
All forms of life, including plants and soil organisms, need water, but not too much or too little. Healthy soil should be about 25% water.
In soils with too much pore space (sandy soils), water quickly drains through and cannot be used by plants. In dense, silt or clay soils, the soil gets waterlogged as all the pore space is filled with water. This will suffocate plant roots and soil organisms.
The best soils have both small and large pore spaces. Adding organic matter (see below) is the best way to improve the structure of your soil through the formation of aggregates. Additionally, organic matter holds water so that plants can use it when they need it.
A healthy organism population is essential to healthy soil. These little critters make nutrients available to plants and bind soil particles into aggregates that make the soil loose and fluffy. Soil organisms include earthworms, nematodes, springtails, bacteria, fungi, protozoa, mites and many others.
Some of these organisms can be purchased and added to the soil, but unless the environment is suitable for them, they will languish. Better to create an ideal habitat by providing the food (organic matter), air and water they need and let them thrive on their own.
If you’re looking for a fast, convenient way to compost your kitchen throw-outs, grass clippings and organic yard waste, our compact unit is just right for you! The ComposTumbler quickly recycles it into nutrient-rich compost.
Adding compost will improve almost any soil. The texture of silty and clay soils, not to mention their nutrient levels, are radically improved from initially having the compost mixed in. All soils get better with annual applications on top. Organic compost can be purchased by the bag or by the yard, or you can make it yourself at home.
Compost and other organic materials hold soil particles together in aggregates and help to retain moisture. They also absorb and store nutrients that are then available to plants, and compost is a food source for beneficial microorganisms.
Making your own compost can be as easy as piling brown layers (straw, leaves), and green layers (grass clippings, livestock manure, food waste) on top of one another. Keep the pile moist and turn it often.
If a pile is too messy, or you are concerned about rodents and other animals getting into your pile, there are all kinds of composters and bins available for purchase to contain your vegetable scraps and make turning a cinch.
Organic (straw, hay, grass clippings, shredded bark) cover the soil and insulate it from extreme heat and cold. Mulches reduce water loss through evaporation and deter the growth of weeds. They break down slowly, enriching the soil with organic matter. Visit the Clemson University Cooperative Extension Service for an in-depth discussion of mulch and mulching techniques.
Inorganic mulches (pebbles, gravel, black plastic, landscape fabrics) will prevent rapid evaporation and keep weeds down just as an organic mulch does. Unlike organic mulches, they do not need to be replaced every year and will not attract insects and rodents. However, inorganic mulches do not benefit the soil by breaking down and adding organic matter which improves soil structure and nutrient content. If you’re looking to improve your soil structure, use a clean, seed-free, high-quality garden mulch.
Dry or liquid fertilizer can add nutrients to the soil that might not get there any other way. Organic garden fertilizers work a little slower than their synthetic counterparts, but they release their nutrients over a longer time frame. Additionally synthetic fertilizers are bad for the environment and can make the soil worse in the long run as beneficial microorganisms are killed off.
Organic dry fertilizers are mixed into the soil according to the directions on the label and then watered. They work more slowly than liquid fertilizers, but last longer. Fertilizer blends contain different amounts of nitrogen, phosphorus and potassium. The ratio is listed on the label (for example 5-10-5). Other fertilizers may contain bat guano, rock phosphate, molasses or other ingredients. There are dozens of recipes for making your own organic fertilizer. Most are variations on nitrogen-phosphorus-potassium theme with added nutrients that come from seed meals, ash, lime, greensand or other mineral dusts and additional organic materials, often kelp, leaf mold or cured manures. You can find good basic recipes here and here.
High performance and easy to apply! Nutri-Rich Fertilizer Pellets offer the most natural source of slow-release nutrients to promote healthy plant growth, bountiful yields and brilliant flowering. Each 50 lb bag covers 1,000 sq ft.
Liquid fertilizers are sprayed directly on the plant foliage or onto the soil. Popular organic liquid fertilizers include fish emulsion and seaweed blends. Compost teas are another liquid fertilizer that is easy to make and takes advantage of the compost you have piling up in the yard.
If you are using a foliar spray, be sure to wet the underside of the leaves. This is where the stomata, the microscopic openings that take in gases, are located. As they open to let in carbon dioxide and release moisture, they will quickly absorb the fertilizer. Read the labels of the liquid fertilizer you choose as some could burn crops and should be applied only to soil.
Cover crops are a temporary planting, usually sown in the fall, that help protect the soil from wind and erosion and add valuable organic material. They also establish a dense root structure that can have a positive effect on soil texture. Cover crops also suppress weeds, deter insects and disease and help fix nitrogen. When the crops are turned into the soil, they become green manure (see Overview of Cover Crops and Green Manures). Rye and alfalfa are common cover crops.
Cover crops are planted at the end of the growing season (winter cover crops) or during part of the growing season itself (summer cover crops). Legumes such as cowpeas, soybeans, annual sweetclover or velvet beans may be grown as summer green manure crops to add nitrogen along with organic matter. Non-legumes such as sorghum-sudangrass, millet, forage sorghum, or buckwheat are grown to provide biomass, smother weeds, and improve soil tilth.
Winter cover crops are planted in late summer or fall to provide soil cover during the off season. Choose a legume crop for the added benefit of nitrogen fixation. Growers in northern states should select cover crops, such as hairy vetch and rye, with enough cold tolerance to survive hard winters. Many more winter cover crops are adapted to the southern U.S. Cool-season legumes include clovers, vetches, medics, and field peas. They are sometimes planted in a mix with winter cereal grains such as oats, rye, or wheat.
After you have harvested your summer crops, add compost and any other amendments (such as lime) that you have determined your soil needs. Disperse the cover crop seeds and rake lightly. If you grow vegetables into the fall, plant cover crops seeds in between the rows a month or less before you expect to harvest.
Don’t let your cover crops go to seed or they may prove invasive. When spring comes around, till the crop into the soil 2-3 weeks before planting. A rototiller is an easy way to incorporate cover crops into the soil.
Don’t plan on changing the pH of your soil with one dose of a wonder material. As explained at Savvy Gardener.com it should take a season or two to moderate the pH and then a little effort every year to maintain it. Whether the soil is acidic or alkaline, adding lots of organic material every year will help balance it out.
Finely ground Oyster Shell Lime is a byproduct of the seafood industry. Contains up to 39% calcium plus a natural balance of other nutrients and micronutrients. Raises pH in acidic soils and corrects calcium deficiencies, too! Each 50 lb bag covers 1,000 sq ft.
Acidic soil can be buffered with powdered limestone added to the soil in the fall. (Autumn is the prime time to do this because it takes several months to work). Be aware that plants like azaleas and blueberries grow better in acidic soil, but most plants don’t.
To raise the pH of sandy soil by about a point, add 3-4 pounds of ground limestone per 100 square feet. For loamy soil, 7-8 pounds of limestone per 100 feet should help, and 8-10 pounds per 100 feet is appropriate for heavy clay soil. Limestone should be applied at least two to three months ahead of planting to give it time to work.
Wood ash can also raise the pH of soil, but care must be taken in its use. Applying too much wood ash may result in high pH readings and take nutrients from your soil. Spread only light amounts on top of your soil in the fall and make sure to thoroughly turn the soil in the spring. Seeds that come in contact with ash may not germinate. If using wood ash every year, keep a close eye on your soil’s ph and stop using it when the proper reading is achieved.
Alkaline soil on the other hand, needs to be made more acidic. This can be done with the addition of sulfur, sawdust, conifer needles, sawdust or oak leaves. In sandy soil you can lower pH by approximately one point by adding 1 pound of ground sulfur per 100 feet to sandy soil, 1.5-2 pounds per 100 feet in loamy soil and 2 pounds per 100 feet to heavy clay soils.
To make sandy soil less sandy, mix 3-4 inches of organic matter (like compost) into the soil. Use wood chips, leaves, hay, straw or bark to mulch around plants and add at least 2 inches of organic material each year. If possible, grow cover crops and turn them into the soil in the spring (see cover crops discussion above).
If silty soil is a problem, you can improve it by adding an inch of organic material each year. Try to avoid compacting the soil — don’t walk on it or till it unless absolutely necessary. Raised beds are a great way to use silty soil without having to intensively work it.
Heavy clay soil will be improved with the addition of 2-3 inches of organic matter worked into it. Then add another inch or more to the top each year. Raised beds will improve the drainage and keep you from walking on it, which can compact the soil. Try not to till unless necessary.
Lowers pH in alkaline soils! Yellowstone Brand® Elemental Sulfur contains 90% sulfur with 10% bentonite as a binder. Also useful as a soil amendment around acid loving plants such as blueberries, azaleas and rhododendrons. Broadcast 10 lbs. per 1,000 sq ft.
Typically, bone meal is recommended to boost phosphorous levels in the soil while blood meal is suggested for raising nitrogen levels. However, both of these are products of slaughterhouses. Fortunately, there are some alternatives.
In lieu of blood meal or fish emulsion, try alfalfa meal or alfalfa pellets (sold for rabbit food). Or grow alfalfa as a cover crop to make nitrogen available to plants. Alfalfa also adds a bit of phosphorous and potassium and works well as a compost accelerator.
Like alfalfa pellets, cottonseed meal can be purchased at your local feed store and provides nitrogen to the soil. It is pretty acidic, however, so use it in combination with lime unless you want to lower the soil pH.
As a substitute for bone meal, add soft-rock phosphate to increase phosphorous levels.
As a side note, unless you can find organic alfalfa or cottonseed meal, adding them to the soil isn’t strictly “organic.” Non-organically grown alfalfa and cotton seed may contain pesticide and herbicide residues. Organic fertilizers will add nutrients without danger from chemicals.
Go no further than your pantry, backyard or the beach for materials to make your own organic fertilizer:
- BANANA PEELS – Eating a banana helps replenish lost potassium. Roses love potassium too. Simply throw one or two peels in the hole before planting or bury peels under mulch so they can compost naturally. Get bigger and more blooms. I also use banana peels on my vegetables. See more pictures and get many more recipes and tips in this eBook.
- COFFEE GROUNDS – Acid-loving plants such as tomatoes, blueberries, roses and azaleas may get a jolt out of coffee grounds mixed into the soil. But more likely it’s the nitrogen that helps. Sprinkled on top of the ground before watering or pour a liquid version on top of the soil. If using as a soil drench, soak 6 cups of coffee grounds in a 5 gallon bucket of water. Let it sit for 2-3 days and then saturate the soil around your plants.
- EGG SHELLS – Wash them first, then crush. Work the shell pieces into the soil near tomatoes and peppers. The calcium helps fend off blossom end rot. Eggshells are 93% calcium carbonate, the same ingredient as lime, a tried and true soil amendment! I use eggshells in my homemade potting mix. This gives me healthy, beautiful fruits fit for seed saving. Get the 7 Secrets to Saving Tomato Seed in the Home Garden.
- SEAWEED – Fresh seaweed does not need to be washed before use to remove salt. Learn much about using seaweed and kelp. See examples. Asian markets sell dried seaweed. Both fresh and dried versions are considered excellent soil amendments. Seaweed contains trace elements and actually serves as a food source for soil microbes. Chop up a small bucket of seaweed and add it to 5 gallons of water. Let it sit for 2-3 weeks loosely covered. Use it to drench the soil and foliage. 2 cups work well for a small plant, 4 cups for a medium plants and 6 cups for a large plant. Experiment with amounts. Combine seaweed with other tea fertilizers.
- WEEDS – You’ve got your own fertilizer growing under your feet! Nettles, comfrey, yellow dock, burdock, horsetail and chickweed make wonderful homemade fertilizer. There are several ways you can use them to make your own brew or to speed up your compost pile. If your weeds have not gone to flower you can dry them in the sun and chop them up to use as a mulch. They are high in nitrogen and won’t rob your plants of nutrients. Borage (starflower) is an herb but for some people it’s a weed. It has many of the same nutritional properties as comfrey. I dry the entire plant, root and all, and put it in my compost tumbler. It helps break everything down and gives the pile and extra dose of heat. Some folks let the weeds soak for many days. For an extended brew, get out the bucket and your bandana! The bandana you’ll need for your nose because this technique gets stinky! I’m not a fan of fermented fertilizers but if you want to take the “putrid plunge” place a bunch of weed leaves and roots in a 5 gallon bucket. Weigh down the leaves with a brick to ensure the plant matter is covered and add water to cover. Stir weekly and wait 3-5 weeks for the contents to get thick an gooey. Then use that goo, diluted 1:10 or more as a soil drench fertilizer. To make it even more convenient, you can use two buckets and make a hole in the bottom of the bucket that contains the plants. The goo will seep through to the lower bucket. It’s always best to apply the liquid fertilizer diluted – it should look like weak tea.
- MOLASSES – Using molasses in compost tea supposedly increases microbes and the beneficial bacteria that microbes feed on. If you want to start out with a simple recipe for molasses fertilizer, mix 1-3 tablespoons of molasses into a gallon of water. Water your plants with this concoction and watch them grow bigger and healthier.
- HUMAN URINE – Sounds disgusting, but urine is considered sterile if the body it’s coming from is healthy and free of viruses and infection. High in nitrogen, urea contains more phosphorous and potassium than many of the fertilizers we buy at the store! If serving tomatoes that have been fertilized with pee gives you the “willies”, try it in the compost pile. A good ratio of urine to water would be 1:8. You can collect a cup of urine and pour it into 8 cups of water in a plastic bucket used outside for fertilizing plants. Pour 2 cups around the perimeter of each SMALL plant. For MEDIUM plants add 4 cups and LARGE plants deserve a good 6 cups of your personal home brew.
- GRASS CLIPPINGS – Rich in nitrogen, grass breaks down over time and enhances the soil. Fill a 5 gallon bucket full of grass clippings. You can even add weeds! Weeds soak up nutrients from the soil just as much as grass. Add water to the top of the bucket and let sit for a day or two. Dilute your grass tea by mixing 1 cup of liquid grass into 10 cups of water. Apply to the base of plants using the same amounts as listed above in the urine recipe.
- MANURE – With a little effort, you’ll find folks that are giving away composted chicken, horse or cow manure for free. Composted and aged manure is bestAdd the composted manure to a small permeable bag made from recycled cloth, e.g., a t-shirt or old towel. Let it steep in the shade for a few days and apply it to your soil to condition it before planting. Bury or discard the used bag. Some people use manure tea to soak bare root roses!
- CAT AND DOG FOOD – Depending on the dog food you recycle, this soil amendment may not be organic. However, even the cheap stuff contains protein and micro-nutrients that benefit the soil. To prepare a garden plot for planting, sprinkle dry pet food on the bed, turn the soil and water. Let it decay naturally. To discourage wildlife from visiting for a snack, cover with cardboard until the food decomposes. The cardboard will also trap moisture and discourage weeds. Make sure the cardboard get wet all the way through and cover with mulch. Water thoroughly every week for four weeks. Soybean meal and alfalfa pellets from the grain store work great too. Sometimes grain stores will sell for cheap or give away spoiled grains. Check the feed for salt content and try not to add pet or animal food considered high in sodium. The AAFCO (Association of American Feed Control Officials) recommends dry dog food contain a minimum of 3% sodium to support normal growth and development.
- MY FAVORITE – WORM CASTINGS – Make your own worm tea -it’s easy. Start with a handful of red wiggler worms and set them up with some tasty cardboard and kitchen scraps. Learn how. I started about 8 years ago and haven’t stopped since. Check out our video on composting with worms to see how easy it is to make this amazing fertilizer!
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“I throw so much stuff away everyday, now I can use a lot of it to make my soil better & fertilize my veggies! I like how the book is organized with lots of great information up front & then for each recipe it explains why it works, which plants will benefit from it, what to combine with it& how to make it several ways. It’s go a lot to work with. Any ideas for houseplants? Please write a book on homemade fertilizers for houseplants!”
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“These are some really “down to earth” ways to fertilize! I got some great ideas and since I don’t consider myself having a green thumb, this gave me a little boost in confidence that I can do this too! I would recommend this to any beginner or advanced gardener!”
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Five Ways to Keep Pests at Bay
How to Grow Garlic from the Grocery Store
Difference Between Straw and Hay
When to fertilize
To get your plants off to a good start, fertilize when the spring growing season begins. Many gardeners use a general-purpose fertilizer at this time (either an evenly balanced formulation or one slightly higher in nitrogen); others add only nitrogen. How often you fertilize later in the year depends on the plant. Nutritional needs differ, so it’s important to check the particular requirements of the plants you buy; for general guidelines on bulbs, lawns, annuals, and many other kinds of plants, go to our Plant guide..
Some plants are heavy feeders and benefit from regular applications of general-purpose fertilizers and extra nitrogen throughout the growing season. Others ― often those that evolved in nutrient-poor environments ― may need only one annual feeding with a general-purpose fertilizer (or they may flourish with no feeding at all).
Tip: Don’t apply liquid fertilizer at the same time you plant. No matter how carefully you remove plants from their containers and place them in the ground, some root hairs will break. The fertilizer will reach the roots immediately and enter them at the broken points, “burning” them and causing further dieback. Wait 2 to 3 weeks after planting before you fertilize; by then, the newly set-out plants should have recovered from any root damage.
Use a spading fork to work a dry granular fertilizer into a new garden bed. This technique puts phosphorus and potassium at the level where they can best be absorbed by plant roots. Water thoroughly after incorporating the fertilizer.
Using a cultivator, gently scratch the soil beneath plants with roots growing close to the surface. Apply a dry granular fertilizer and water thoroughly. Because roots may extend several feet beyond the drip line, be sure to spread fertilizer out wide enough to reach all the roots.
Liquid fertilizers can be applied with a watering can. You can also use an injector device to run the fertilizer through your watering system. A simple siphon attachment (above) draws a measured amount of fertilizer into a hose from concentrate in a pail.