Organic fertilizers – types, application, advantages and disadvantages

As long as people cultivate plants to feed themselves or to enjoy their beauty, they make up for nutrient deficiencies with fertilizer. After industrially manufactured preparations were preferred in the 19th and 20th centuries, with all their negative consequences, a return to natural fertilizer methods is now dominant in home gardens. The selection of types is by no means limited to compost alone. Rather, plant and animal waste of various origins provide plenty of material that is processed into valuable humus by industrious microorganisms in the soil. The following lines explain how organic fertilizers are used and what the advantages and disadvantages are.

The species at a glance

  • Compost
  • vegetable manure
  • Guano
  • Hornspäne / Hornmehl
  • stable dung
  • Organic complete fertilizer

Although the organic fertilizers mentioned are all of animal or plant origin, without any addition of industrially manufactured additives, they also harbor the risk of over-fertilization. Consequently, it should be worthwhile for hobby gardeners to take a look at the detailed explanations regarding the composition and application.

Compost

Composition
Even in the smallest home garden, gardeners set up a compost heap in order to feed the plant waste back into nature’s eternal material cycle. To this day, home composting is carried out according to traditional specifications.

  • garden waste
  • green waste
  • Bioabfall
  • Uncooked kitchen leftovers

Properly piled up in the right location, earthworms and other microorganisms set about transforming the waste into nutrient-rich humus over the course of the year. It is primarily a rich soil additive, which secondarily contains nitrogen, phosphorus, potassium, magnesium and other trace elements as an organic fertilizer. On the other hand, if you regard the compost as a biowaste dump and do not rearrange it for good ventilation, you will look in vain for the deep brown, fertile garden soil and the environmentally friendly fertilizer.

Use
Compost produces humus, which plays an important role in hobby gardening. After 6 to 12 months, a classic windrow already provides the desired organic fertilizer, which proves to be extremely useful in many ways. When planting new beds, compost increases the storage capacity for water and nutrients. At the same time, ripe humus releases nitrogen, phosphorus, potassium and minerals.

  • To prepare, sift the desired amount of compost
  • In the spring, work the compost flat into the soil with a rake
  • Depending on the planting, the dosage varies between 2 and 5 l per m²
  • Repeat the process every 2 to 4 weeks during the growing season
  • A thin layer of grass clippings helps prevent dehydration

As an addition to planting holes, knowledgeable hobby gardeners only use 2 to 3 year old, mature compost, the consistency of which is reminiscent of fragrant forest soil. The decomposition process has largely ended there, so that the tender roots of the young plants cannot be damaged. The biological material still provides the desired initial fertilization.

Tip: The coarser components that remain after sieving are the ideal starting material for the next windrow because they are already home to bacteria and fungi.

leaf compost

Composition
The valuable autumn leaves result in composting into a finely crumbly humus, well equipped with potassium, calcium, magnesium and phosphorus. It is composted separately because it is moved more frequently to avoid clumping.

  • Pure leaf compost made from oak leaves fertilizes rhododendrons and other ericaceous plants.
  • Pure compost from beech leaves acts as home-made seed soil.

Alternatively, the fallen leaves remain in the bed as mulch compost in order to act as organic fertilizer and soil additive as part of the decomposition. So that the autumn wind doesn’t blow the leaves away, experienced hobby gardeners sprinkle some stone dust over it and spray it lightly with nettle manure.

vegetable manure

Composition
A particularly mild form of nutrient supply using organic fertilizer is through plant manure. In contrast to broth, tea or extract, production takes up to 14 days. Consequently, the mixture of fresh or dried plant parts and water is extremely rich in nitrogen and potassium. The plants most commonly used by hobby gardeners for liquid manure are:

  • nettle
  • Ackerschachtelhalm
  • Beinwell
  • Knoblauch
  • onions

Application
The plant manure is ready when it no longer foams and turns dark in colour. After straining, it is diluted 1:10. To strengthen the plants, gardeners spray the mixture on the leaves and soil from March/April until late summer. In particular, heavy consumers, such as tomatoes, benefit from this organic fertilizer. Only the root area is fertilized on vegetables that are eaten raw or that are difficult to wash.

Guano

Composition
The droppings of seabirds in South America provide a nitrogen- and phosphorus-containing organic fertilizer called guano. The legacies of European seabirds do not come up with this nutrient content because the frequent rain leaches the bird dung too much.

Use
Before an ecologically responsible hobby gardener holds guano in their hands, the manure is processed into granules, sticks or liquid fertiliser.

  • In spring and summer, fertilize the plants with guano once or twice a month.
  • If possible, do not exceed an average dosage of 2 l per 10 m².
  • Do not fertilize from July, because the nitrogen it contains weakens winter hardiness.
  • Due to the strong smell, guano is less suitable for indoor plants.

So that the soil is not over-fertilized, it is advisable to carry out a soil analysis before using guano as an organic fertilizer, which provides information on the actual need.

Hornspäne / Hornmehl

Composition
Grated or finely ground horns and hooves of slaughter cattle result in a rich organic fertilizer with a nitrogen content of more than 10%. Other trace elements are only contained in small concentrations of less than 1%.

Application
Since horn shavings need quite a long time in the soil before the fertilizing effect sets in, it is advisable to apply this organic fertilizer to the bed in autumn. The finer horn meal releases its nutritious components more quickly into the soil, so that it can be scattered in the spring.

  • Approx. 100 g horn shavings or horn meal are used per square meter of garden soil.
  • Work the organic fertilizer flat into the soil with the rake.
  • Horn shavings, which are added to the planting hole, have an advantageous effect.

Hobby gardeners who use bark mulch under trees and shrubs fertilize these planting sites with horn shavings or horn meal. It has been found that such mulch removes nitrogen from the soil, which in this way is balanced.

stable dung

Composition
Manure from cows, horses and other four-legged farm animals is recognized as a classic organic fertilizer. Applied to the garden soil, plants dig into it like a lavish nutrient buffet. In addition to various minerals, horse manure in particular contains plenty of cellulose, which ornamental and useful plants build into their cell walls.

Application
As stable manure is only effective when it has been properly deposited, it is advisable to purchase pre-composted manure from farmers or horse owners. Alternatively, the fresh manure is stored in the garden itself, although the volume is drastically reduced within 12 to 18 months.

  • Work the composted manure into the bed soil.
  • Alternatively, place approx. 20 cm below the plants.
  • The ideal starting fertilization in spring for vegetable plants.
  • Scatter on the compost heap as a rotting accelerator.

Since stable manure develops a noticeable heat, resourceful hobby gardeners use the material as natural ‘heating’ in their cold frame.

Note: When using organic fertilizers, such as stable manure, guano or plant manure, the neighbors must not be disturbed by odors. In some federal states there are special regulations of the state government on this subject.

Organic complete fertilizer

Composition
Hobby gardeners who do not have their own compost heap are by no means forced to do without organic fertilizers. The specialist trade has a large number of preparations that are also approved for certified organic cultivation. The ingredients are, for example, horn meal, beet pulp and microorganisms.

Application
In view of the wide range of offers, it is advisable to follow the manufacturer’s dosage instructions exactly.

  • Apply from May to September according to dosage instructions.
  • As a rule, 50 g to 150 g per m² bed area are sufficient.
  • Mixed with substrate, 2 to 5 g per liter of soil is sufficient.

The fact that organic complete fertilizers are now also available in liquid form is good for the nutrient supply of potted plants.

Algae juice

Composition
Algae juice is talked about as an excellent organic fertiliser. Cold-pressed from green or brown algae, the result is a juice that consists of 75% organic matter and 25% minerals. In addition to the classic substances such as nitrogen and phosphorus, the remedy comes up with more than 70 different trace elements that the sea has to offer.

application

Since the numerous ingredients in the foliar fertilizer are just as effective as on the roots, it is an advantage that this is a liquid preparation.

  • Diluted application according to the manufacturer’s instructions.
  • After sprouting, algae juice is sprayed on the underside of the leaves.
  • Optionally give with the watering can to the roots.
  • It also serves as an efficient accelerator on the compost.

Good to know that algae juice is ideal for caring for indoor plants. In addition to the rich supply of nutrients and trace elements, the shiny leaves of decorative leaf plants can be wonderfully cleaned with algae juice.

Nach- und Vorteile

Organic fertilizers have a long tradition in home gardens and agriculture. Despite their undeniable benefits for people and nature, there are also some disadvantages to consider.

disadvantage

  • The ingredients are not available in any quantity.
  • There are significant fluctuations in nutrient content.
  • Comparatively very slow bioavailability.
  • In the case of an acute nutrient deficiency, they do not provide rapid improvement.
  • Lower crop yields compared to mineral fertilizers.

Hobby gardeners with little spare time rate the labor-intensive process of producing compost as a disadvantage of organic fertilizers.

benefits

  • Nutrient supply within the natural material cycle.
  • No or only low, environmentally harmful nitrate leaching into the groundwater.
  • Thanks to the long-term effect, there is only a small risk of over-fertilization.
  • Promotion of soil organisms and consequently a healthy soil.
  • Probably the most natural form of environmentally friendly waste management.
  • Thanks to the fertilizer’s own moisture content, the artificial water supply is reduced.

Using organic fertilizers saves money in two ways. Firstly, there is no need to buy expensive mineral fertilizers. Secondly, home composting reduces or completely averts the waste tax for organic waste bins.

Conclusion
The plants in ornamental gardens and kitchen gardens cannot do without an additional supply of nutrients. They have the choice of opting for organic fertilizers when their plants are signaling a lack of nitrogen, phosphorus, potassium or other trace elements. Above all, the compost heap provides free, nutritious fertilizer over time, as well as plant manure or stable manure. Those who do not have access to these organic fertilizers use guano, horn shavings or horn meal and feed their plants with the good conscience of an excellent environmental balance.

Kira Bellingham

I'm a homes writer and editor with more than 20 years' experience in publishing. I have worked across many titles, including Ideal Home and, of course, Homes & Gardens. My day job is as Chief Group Sub Editor across the homes and interiors titles in the group. This has given me broad experience in interiors advice on just about every subject. I'm obsessed with interiors and delighted to be part of the Homes & Gardens team.

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