Soil Fertility: How you can Improve it

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soil fertility

Did you just take a soil test and now they are back that indicates low soil fertility?

Or they might be indicating that potassium or phosphorus is low on some fields, here, and there, and there is also zinc deficiency.

However, you are organic and do not use synthetic fertilizers.

Adjusting soil fertility is certainly an important part of good management, however, you won’t see any return from the adjustments.

Unless, you will need to take steps like crop rotation, choice of adapted varieties, legume cover crops, like rotation, tillage, weed control, and other factors.

But if there are still some deficiencies and imbalances, there are some ways you can add to the soil to improve soil fertility.

Keep on reading to learn more about it in detail.

Manure for Soil Fertility

Animal manure provides a different amount of nutrients that often depends on the animal species, feed, bedding, and manure storage practices.

Moreover, the amount of nutrients that are available to the plants also depends on the time of the year your apply manure and how quickly it works.

It is important to note that existing soil conditions also affect how quickly the nutrients in manure dissolve.

natural sources

On average, cow manure contains 10 to 15 pounds of N, 5 to 10 pounds of phosphorus, and 10 to 12 pounds of potassium per ton.

On the other hand, poultry manure has a higher percentage of these three elements.

The most preferred type of manure is composted manure, however, if you apply raw manure, then the timing of application is critical.

An important thing to note is that when you are applying raw manure on crops for human consumption, you should apply it within 120 days of harvest.

Make sure to apply them where the edible portion touches the soil or 90 days of harvest where the edible portion does not touch the soil.

Compost for Soil Fertility

For a product to technically quality as compost under NOP, it must start with a carbon to nitrogen ratio between 25:1 and 40:1.

Moreover, you will need to maintain it between the temperature range of 131°F and 170°F for 15 days.

During this time, you will turn the material at least 5 times, and thus, you can apply it to your plants, if you make compost in this way.

soil fertility 1

On the other hand, if you are using composted manure or compost that is made from manure and want to apply it less than 90 days before harvesting on food-grade crops.

However, if the compost contains manure or other animal products, then you should make sure to apply it according to the timing restrictions of raw manure.

While, if the compost only contains plant material, then it carries no timing restrictions.

Plant and Seaweed Products for Soil Fertility

Some plant and seaweed products you can use are as follows:

Alfalfa Meal or Pellets

These contain about 3% nitrogen and are commonly used as animal feed. Moreover, it is an excellent fertilizer material in high-value horticultural crops.

However, you might find it a little too expensive.

Additionally, many researchers are of the view that alfalfa meal contains certain growth factors that makes its mineral content more effective as plant nutrients.

Leaf and Plant-waste Compost

This one is increasingly available or you can also make it yourself.

In many cases, compost is a good product, however, it can sometimes contain impurities like car waste, pesticides, and garbage.

soil fertility 2

Soybean Meal

Soybean meal is about 6-1.4-4 NPK and can be very useful.

However, it is extremely expensive. It is important to note that as an organic farmer you should be careful about not using conventional GMO soybean mean though it is not strictly prohibited.

Kelp Meal

Most seaweed fertilizers come from kelp that comes from harvesting, drying ground.

You can apply kelp meal directly to the soil or in starter fertilizer.

It flows well and you can easily apply it with most fertilizer applicators. You can also apply it with other dry fertilizers and amendments.

The application rate for kelp meals ranges from 150 to 250 pounds per acre for pastures, forges, and small grains.

About 200 to 400 pounds per acre for corn, horticultural crops, and gardens.

Dried Raw Seaweed

It contains about 1% nitrogen, a trace of phosphorus, and 2% of potash, along with magnesium, sulfur, and numerous trace elements.

Animal Byproducts

Some of the animal by-products are:

Blood Meal

A blood meal is dried slaughterhouse waste and contains about 12 to 13% of nitrogen.

However, make sure to use it carefully, as it can even burn your plants.

Moreover, it can also lose much of its nitrogen through volatilization, and even encourage fungal growth.

soil fertility 3

Feather Meal

A by-product of poultry slaughterhouse, it contains about 7 to 10% nitrogen and releases more slowly nitrogen than other products.

Bone Meal and Fish Emulsion

Just like animal by-products are rich in nitrogen, so are the bones.

Moreover, fishmeal contains about 10% nitrogen with 6% phosphate.

The fish emulsion may also be fortified with chemical fertilizers or synthetic preservatives.

Thus, make sure to use it with care.

The above examples are nitrogen sources for increasing soil fertility. Now let’s discuss the phosphate sources.

Phosphate Sources for Soil Fertility

The 3 main types of mineral phosphate are:

  • Colloidal phosphate from clay
  • Soft rock phosphate mostly from ancient sea deposits, and
  • Hard rock phosphate from volcanic deposits

Clay-based phosphate is more readily available than rock phosphates, and soft rock phosphate is more available than hard rock phosphate.

The bone meal typically contains about 27% of total phosphate and nearly all of it is readily available.

Rock phosphate is made up not only of phosphorus, but also of calcium, carbon, and different trace elements. Most of these are valuable plant foods.


However, some sources that come from mining can also be high in heavy metals.

Organic phosphate materials are most effective when you apply them to a growing cover crop a year or more before the crops will need the nutrients.

This gives the soil microbes an opportunity to convert insoluble phosphate into more readily available and stable forms.

Another way to use rock phosphate is to add it directly to livestock manure in the barn where the manure acids will dissolve it.

Moreover, the phosphate stabilizes the nitrogen in manure.

Potassium Sources for Soil Fertility

Potassium sulfate and potassium magnesium sulfate can provide potash to your plants readily.

Moreover, potassium sulfate is a good choice for high Mg soils, however, it is fairly reactive and you should use it carefully.

Granite dust slowly provides potash to your crops. It typically contains 1 to 5% potash depending on the overall mineral composition.


However, granite is mostly feldspar, a highly insoluble mineral.

Another source is the clay-type mineral glauconite or greensand.

Total potash content is around 7% in greensand, all of which is deeply locked into the mineral and only slowly available.

However, its uses are limited to high-value horticultural applications or too small amounts of banded starter fertilizer.

Calcium Sources

Lime and gypsum are important products to moderate soil pH and deliver essential calcium.

If the soil has high Mg content, then the tendency of the soil to become hard, compacted, and crusty is high.

These soil conditions favor tough species of weed.

Moreover, gypsum is also a valuable source of sulfur that is critical for healthy plants.

However, make sure that you are using lime and gypsum are naturally mined, not industrial waste products.

Secondary and Minor Nutrients from Rock Powders

You can supply micronutrients in small quantities in a variety of rock dust. Moreover, certain types of synthetic micronutrients may also allow tiny quantities in a mixed organic fertilizer.

As with most rock powders, transportation costs are a major factor in determining cost-effectiveness.

Most of the rich volcanic soils come from basalt.

Even when in applications, it can be beneficial if you mix it with manure in the composting process and then apply it to your plants.

Final Thoughts

Soil fertility and sustainable agriculture practitioners know that most soils need their health and vitality to be rebuilt. Moreover, in bast, nature was solely responsible for healthy soils and there is value in coping nature in rebuilding soil health.

However, today you do not have millions of years to rebuild the health of your soil. With interventions like cultivation, grazing, composting, soil conservation, green manuring, soil testing, soil remineralization, fertilization priorities, fossil humates, and visual soil assessment all play a role in establishing self-regenerative, self-sufficient, fertile soils.

The biological activities at the basis of self-regenerative soil fertility occur at the surface where minerlas come in contact with water, air, and warmth. It is at these surfaces where biological activities provide nitrogen fixation and silicon release.

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