6 Best Soil Amendments For Stunning Gardens & Trees

by | Mar 20, 2021 | Pollinator

Choosing The Best Soil Amendments

You might ask yourself what are the best soil amendments when your garden and trees start looking sad. The best soil amendments are different than plant fertilizers because they feed the soil. A healthy soil food web is always the best way to get good garden pest control. Also it will help your plants stay robust, strong and lush for a long time.

1. Kelp Meal

It’s important to do a little research on using soil amendments or you could be wasting them. Some folks test their soils with the help of a soil testing laboratory. But with kelp meal you can use a little, and still get away with not knowing a lot. In fact, kelp meal aids in growing fabulous, dense, green veggies, flowers, even perennials and ornamentals.

Kelp Is One Of The Best Soil Amendments

Miraculously, kelp is full of over 70 plant vitamins and minerals that it naturally sucks out of the ocean. Because y’know, it’s kelp. This includes the most-oft talked about Nitrogen, Potassium and Phosphorus. But there’s 67+ other nutrients that can be just as important as NPK for organic plant health care:

  • Kelp includes iodine, manganese, magnesium, calcium, molybdenum, iron, sulphur, sodium, boron, chromium, zinc, lithium, silver, strontium, bismuth, zirconium, tin.
  • It contains vitamins E, D, C, K, and the B complex as well as proteins, carbohydrate, essential fatty acids. Also kelp has mucopolysaccharides, phenolic compounds, glycosyl ester diglycerides, and polar lipids too.
  • In fact, kelp meal naturally provides the perfect concentrations and bioavailable forms for your plants. Indeed plants and trees need many nutrients to grow vigorously, control plant pests and diseases.

Definitely, choosing one soil amendment to help fertilize my landscape, garden, trees and shrubs, would be kelp. 

Before Spraying Liquid Fertilizers

Quick note about liquid fertilizers. Many fertilizers contain bat guano solutions for boosting nitrogen. Others bird guano and fish fertilizer solutions for phosphorus. Many folks find them pungent and putrid. I feel like I have to take off all clothes and shower and stay indoors after spraying. Also, the health hazard to the workers who enter bat caves can pose an ethical issue to using bat guano.

Kelp and the following amendments can replace smelly liquid fertilizers. Sticking to granules, cakes, or flakes mixed into the soil reduces need for spraying. Just sprinkle on the soil, or soak to extract into a liquid fertilizer tea. 

2. Biochar

My close second recommendation for best soil amendment is biochar. I’ve had some incredible success experimenting with biochar! It’s basically charcoal in that it is organic wood, leaves or other material. Pyrolysis is the process of thermal decomposition at a relatively low heat in an absence of oxygen. Manufacturers of charcoal make large chunks for fuel or art drawing. Biochar makers produce coarse flakes meant for application in organic agriculture.

  • In fact, Japanese, Brazilian and other farmers have used biochar for a long time.
  • Biochar has documented benefits to the long term sustainability of agricultural lands when used.
  • The tiny pores in the biochar surfaces create microhabitat for beneficial microbes like mycorrhizae. There they find refuge from predators and sources of essential carbon and minerals.
  • Also the biochar can absorb some nutrients for slower release into the soil food web.

Biochar For Backyard Gardening

My own backyard gardening experiments anecdotally had stunning results. First one cup of biochar placed into the hole at the time of seedling transplant increased growth by approximately 50%. Then two cups increased growth by approximately 75%. Plants also showed significantly increased signs of general health. Notably a darker green color, resistant to pests like aphids & budworms, and diseases like white powdery mildew. Two cups also substantially increased flower production by approximately 200%.

Biochar Experiment Results

Interestingly, Sprinkling the biochar as a topdress around the drip-line of the plant didn’t produce the same amazing results. Those plants only showed no significant growth increase. So this was good intel. The biochar only seemed to improve the soil microbe habitat when it was placed directly into the rhizosphere.

3. Oyster Shell Powder

Oyster shell powder is an amazing and cost-effective. Undoubtedly it’s one of the best soil amendments. It’s a natural time-release calcium rich plant fertilizer. Some garden supply stores sell oyster shell powder for as low as $15 a fifty pound bag.

Garden Pest & Disease Control

They actually harvest oyster shell powder from underwater deposits of ancient oyster shells. Next they grind those ancient oyster shells into a fine powder to become an organic agricultural amendment. Then we’re ready to start getting pest free gardens and pathogen resistant landscapes in Portland Oregon. Make sure to source it from a local organic agricultural seed & feed wholesaler or retailer like Concentrates, Inc. in Milwaukie Oregon.

Calcium Soil Amendment

Oyster shell powder is mostly calcium carbonate CaCO3 in a form that is generally bioavailable to soil microbes. They begin digesting and circulating calcium through your soil food web into your plants. Your veggies will in turn be full of calcium for you.

  • Mix a generous amount of oyster shell powder into your potted mixes or raised beds.
  • It will naturally encourage a balanced pH in the soil.
  • Your worms, microbes, veggies and herbs will have access to what they need, and they’ll leave the excess.
  • Sprinkle a little extra along the drip-line of peppers and tomatoes throughout the summer to stave off blossom end rot.

The Best Soil Amendments Help With Garden Pest & Disease Control

In summer, blossom end rot and horned tomato worm are garden pests plague our tomatoes. Gardeners know the frustration of noticing brown spots appear on the tips of otherwise healthy peppers & tomatoes. Oyster shell powder is one of the best soil amendments to keep on hand to maintain healthy trees, garden & landscape. Again it is super cheap and available. Moreover you can often find oyster shell powder at local pet stores. 

4. Malted Barley Ground Into Fine Powder

Although this sounds weird. I learned from an old acquaintance that malted barley is actually one of the absolute best soil amendments. Expressly, it blazes a direct trail to healthy pest and disease free garden plants and landscapes.

Indeed, beer brewers make delicious pints of ale with the same malted barley used for organic soil amendments. Since malted barley is full of active enzymes which catalyze certain reactions on a molecular level, gardeners can harness that action.

Best Natural Enzyme Boost For Soil

Underground your soil microbes process small nutrient particles into forms your plant can uptake. Alpha amylase, beta amylase, protease, peptidase, beta glucanase, phytase and other enzymes are found in malted barley.

Barley Malting Process

  • First the dried barley grains are processed into barley malt after harvest.
  • Next the barley is malted through a process of soaking the grains in long shallow containers of warm water overnight.
  • Then this jumpstarts those seeds into germinating.
  • In the middle of the germination process, the water is drained and the grains are carefully heated.
  • Lastly, germination shuts down and the newly malted barley is packaged and shipped off to brewers and gardeners worldwide.

Malted Barley For Soil Amendment

It’s easy to use malted barley as an organic soil amendment. Grind malted barley into a very fine powder to mechanically prepare it. Then mix it into your potted soil or raised beds. Also apply as a topdress around the root zone of the plant. Amylase & the other enzymes will help your microbes digest nutrients into bioavailable forms for your plants to thrive. Consequently this will help bring some the awesome enzyme power of the brewing process into your natural soil ecosystem. 

5. Basalt Rock Dust

Using basalt rock dust for soil remineralization is the coolest new thing in organic agriculture. Gardeners are introducing finely ground rock or stone dust back into the soil. Consequently this provides essential minerals.

  • Naturally, freezing temperatures in conjunction with rain, ice and other geological processes break down rock & stone.
  • Mechanical movements of animals, plant roots and soil microbes begin the process of breaking down minerals.
  • Then microbes digest the minerals and fix them into a form your plants can use.
  • Basalt rock dust can accelerate and create soil fertility from readily bioavailable soil minerals. 

Indeed, lots of successful growers apply rock dust or “stone meal” as one of their best soil amendments.

Bread From Stones

Let’s timewarp to the last part of the 19th century and beginning of the 20th century. A German scientist by the name of Julius Hensel took it upon himself to study the positive effects of remineralization. So he examined the use of rock dust as an organic soil amendment. His book on the subject entitled “Bread from Stones” was published in 1894.

School of Rock

He conducted his own experiments and talked with other growers, farmers and agricultural educators. Resultantly, he was able to show that using rock dust had major positive effects on plant growth.

  • Evidence suggested vigor, survival, resistance to pest & disease, drought and freezing temperatures were all positively affected.
  • He even noted higher, heavier yields of more nutritious fruits.
  • One farmer who used it for five years straight reported that his soil noticeably improved year after year.
  • Others report enhanced shelf life of produce, improved flavors and nutritional value to the consumer.

Sustainable Soil Amendments

In terms of sustainability, rock dust may be one of the best soil amendments. Rock dust sometimes comes from industrial waste sources such as quarry fines and or cement kiln dust. Cheap availability may have potential implications for human rights and food sovereignty in areas without an abundance of food.

Basalt vs. Glacial Rock Dust

Igneous sources such as basalt or granite materials may be more valuable as a remineralizing soil amendment. Beware pre-weathered products like sedimentary sources of glacial rock dust are already subject to nutrient degradation. Cascade Minerals is the best product and it’s widely available throughout the West coast and elsewhere.

Remineralization

Remineralization is actually a really interesting area of study. If you’re hooked I recommend reading the book review of Bread from Stones by Remineralize the Earth. Remineralize the Earth is a non-profit worldwide advocate and newsletter for soil remineralization.

In the article they note how Hensel’s contemporary Justus Von Leibig admired his work. Despite Von Leibig being the author of a somewhat competing theory. Von Liebig’s theory termed “Law of the Minimum” was that plant nutrition was like a barrel full of water. He imagined each board of the barrel represented a different nutrient concentration. Each depicted at a different height, limiting how much water or general nutrition the plant could hold.

Amendments vs. Fertilizers

The barrel theory dominated due to it’s compatibility with the established N-P-K theory. That theory was that nitrogen, phosphorus and potassium were the main limiting factors in plant growth. Many plant fertilizer products were being, and still are, only designed to provide these three nutrients.

Hensel’s rock dust research suggested other minerals like magnesium, calcium, iron, manganese, silica, chlorine, fluorine, sulfuric acid, etc. are key nutrients for healthy, balanced plant growth.

Upon studying Hensel, Leibig was caused to completely rethink his theory of “Law of the Minimum.” Thus he included a broader view of what are considered limiting nutrients and advocated for Hensel’s research. However Hensel’s research was still outshadowed by Von Leibig’s & mostly fell into obscurity. Remineralization was not seriously re-examined until after his death in Berlin around 1903. 

6. Alfalfa Meal

Going over a few plant health tricks & tips, we’ve simultaneously been giving soil health advice too. These soil amendments keep your herbs, veggies and perennial flowers, trees and shrubs looking great and pest free. The best soil amendments also make the soil underneath rich in nutrients. Also they’ll keep your beneficial bacteria, mycorrhizal fungi, protozoans and nematodes functioning happily and healthily. Lastly, you’re even deterring microscopic disease pathogens & garden pest species from causing damage to your priceless landscape.

Alfalfa Meal is one of the Best Soil Amendments

Your soil microbes will appreciate a regular dusting of alfalfa and aforementioned soil amendments directly to your compost. Vermicomposters love to add alfalfa, basalt or glacial rock dust, kelp and other cheap nutrient boosters to feed their worms. Adding alfalfa creates a high quality compost for use in organic agriculture and activated aerated compost teas. 

Best Green Manure

Alfalfa (medicago sativa) is an important crop. Livestock use it as a nutritious food source and gardeners use it as a rich green manure. Indeed, alfalfa’s fast growing cycle and leguminous nature help fix nitrogen into the soil and produce a rich raw compost material. That’s why it’s so popular for feeding cows, horses, pigs and other livestock.

Part Of This Complete Breakfast

Alfalfa includes a well balanced and broad spectrum of essential nutrients including phosphorous, potassium, nitrogen, sulfur, magnesium, iron, copper, zinc, boron, riboflavin, folic acid, biotin, vitamins A, E & B, starches, sugars, and crude protiens. Also alfalfa contains 16 amino acids including tracontanol, a well known fatty-acid plant growth hormone.

Using Alfalfa For Soil Amendments

Mix alfalfa meal into your soil when you’re preparing to put your beds to sleep in the fall or when you start back up in the spring. You can soak alfalfa in water or bubble it around in a compost tea brewer. Use about a cup per 2-3 gallons soaked for about 6-12 hours. Apply it as a foliar spray diluted fifty/fifty to water. Try alfalfa tea as a soil drench to the roots of beloved azaleas, hydrangeas, rhododendrons, jasmine, philodendrons, gardenias, dahlias, hedges and herbs. In fact, alfalfa tea is safe for whatever green thing that photosynthesizes on your premises that you can find. 

Harness The Best Soil Amendments

Using these soil amendments is sure to help boost your landscape plant health, garden pest control & disease resistance. Don’t hesitate to call if you’re interested in boosting soil health or enhancing your Portland pollinator & wildlife habitat.

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