This nutrient element, which occurs naturally in the soil, has different states. While a large part is in a bound form, i.e. bound to clay minerals, in the soil, only a small part is directly available for plants. Because plants can only absorb these nutrients in dissolved form. As a result, potash must be supplied through appropriate potassium fertilizers. Wood ash and comfrey broth, for example, contain a particularly large amount of this nutrient, which is valuable for the plants. In order not to over-fertilize the soil but also to prevent a deficiency, a previous soil analysis is fundamentally useful.
Table of Contents
Need for potassium fertilizer
Potassium fertilizers can regulate the potassium levels in plants. This is important for plant health and can improve resistance to environmental influences, diseases and pests. Regardless of whether it is fruit trees, berry bushes, vegetables such as tomatoes or cucumbers, ornamental plants or lawns. Potassium occurs naturally in plants, the younger they are, the higher the percentage. This means that deficiency symptoms can quickly arise in the course of growth, which can be counteracted by adding potassium fertilizer.
This plant nutrient controls the water balance of the plants, builds up the plant tissue and strengthens it. It increases the aroma of various types of fruit and vegetables and at the same time improves their shelf life. This important nutrient element causes plants to store more sugar in their cells, which lowers the freezing point of the cell fluid and thus improves frost protection.
Recognize deficiency or excess
The potassium content of the soil usually depends on the type of soil. Young and freshly planted specimens in particular have a large supply that provides them with sufficient nutrients in the first few weeks. At some point this nutrient is naturally used up in the plant. If it is then not supplied in the form of potassium fertilizer, symptoms of deficiency can quickly arise. These occur particularly frequently in sandy and calcareous soils, so that additional fertilizers are usually required here.
If a plant suffers from a deficiency, the potassium migrates from the older leaves to the young ones, so that it is first noticeable in the older leaves. The leaf tips and the edges of the leaves are particularly affected. Further signs are a reduced resistance to diseases, for example on tomatoes or other vegetables, as well as a lower stability. A lack of potassium also increases the evaporation of water from the above-ground parts of the plant. As a result, fruit, vegetables and other harvested products are more susceptible to frost and drought, and taste and shelf life deteriorate.
Since plants absorb potash very quickly, they usually recover within a few days after appropriate fertilization. Of course, there can also be an excess of potassium. Too high a concentration of water-soluble potassium can lead to growth disorders, root damage (burning) and over-acidification of the root area. In addition, it can hinder the uptake of nutrients by the plants and manifest itself in a crumbly soil structure.
Previous soil analysis makes sense
While vegetable growing areas are often oversupplied with different nutrients, lawns are undersupplied. Both are problematic for plants. To counteract this, a previous soil analysis is recommended. Ideally, it should be repeated every 3 – 4 years between autumn and spring. This determines which nutrients are sufficiently available in the soil and which are lacking. As a rule, humic soils can store nutrients very well. In contrast, acidic substances can promote and increase a potassium deficiency. Corresponding soil analyzes are all the more important.
- Always have several parameters determined
- Many soil nutrients influence each other depending on their availability
- Magnesium excess inhibits the availability of potassium
- Take soil samples for a soil analysis before the first fertilization
- Extraction in vegetable patches at an excavation depth of 25 cm
- For lawns excavation depth of 10 cm
- Take between 10 and 15 individual samples at different locations
- Mix samples and send in about 400 g
- Send to a suitable laboratory or soil analysis center
Tip: You must also indicate whether fruit trees, vegetables, flowers, ornamental plants, lawns or bog plants are to be grown on the area in question. Depending on the provider, a soil analysis can cost between 10 and 50 euros.
Areas of application
Especially with fruit and berries, this main nutrient can have a positive effect on the quality of the fruit in terms of taste, aroma and shelf life. For example, tomatoes, potatoes, sugar beets, cucumbers, pumpkins, Brussels sprouts, carrots, leeks and celery have a particularly high need for potassium. Fruit trees, raspberries, gooseberries and grapes as well as roses, geraniums and fuchsias often suffer from a potassium deficiency.
Potassium fertilizer for lawns is at least as important. If the lawn is covered in snow and ice for a long time in winter, it ensures that the grass can survive the cold season. A lack of potassium makes the lawn more susceptible to disease, which is reflected in yellow discoloration in spring. That is why this element is a main component of the mandatory autumn fertilization of the lawn.
Commercial potassium fertilizers
Various potash fertilizers are available on the market as mineral as well as organic and humus fertilizers. The latter, such as wood ash, liquid manure or comfrey manure, contain a particularly large amount of this nutrient. So-called combination fertilizers are usually offered as mineral fertilizers, which also contain other plant nutrients in different concentrations, because a potassium deficiency rarely occurs in isolation. Mineral potash fertilizers are also available in the form of potassium sulfate and potassium chloride, although most garden plants are sensitive to potassium chloride. It occurs in a chloride-containing form in liquid manure, among other things.
In the home garden, it is advisable to give preference to a sulphate-based potassium fertilizer. Consumers can clearly see from the type designation whether a single potash fertilizer contains sulphate or chloride potash. Your residual chloride content must be below 3%. If it is above 3 percent, it is automatically assigned to the potassium chloride type. In case of doubt, the respective packaging contains a label stating whether it is a low-chloride fertilizer or not. Common sulphate-based potassium fertilizers are, for example:
Kalimanesia also known as Patentkali
- Chloride content below 3%
- In addition to 25-30 percent potash, it contains around 10% magnesium
- For bed preparation in spring and for nitrogen-free autumn fertilization
- For crops sensitive to chlorine such as fruit, vegetables, potatoes, vines, sunflowers
Potassium sulphate granulated
- High-percentage potash fertilizer or two-nutrient fertilizer on a sulphate basis
- Contains 50% potash and 45% sulfur
- Direct plant availability
- For fruits, vegetables, berries, leeks, cabbage, sunflowers
- Approved for organic cultivation
application
Commercial potassium fertilizers
Potash fertilizers from specialist retailers should always be used in accordance with the manufacturer’s instructions. The amount of fertilizer that should be applied depends on the nature of the soil and the composition of the fertilizer. In spring the potash stores of the plants are almost exhausted due to the exhausting winter. As a result, it makes sense to use potash fertilizer to prepare beds in spring, so that the soil is optimally nourished to give the plants the best possible start. It can be worked into the soil as a solid fertilizer, used for green or top fertilization. When new fruit trees and berry bushes are planted, the fertilizer is mixed with potting soil.
Wood ash
When using wood ash, less is more. If it is applied in too large quantities, it would be tantamount to liming the garden soil, which not all plants can tolerate. We recommend a maximum of 100 g of wood ash per square meter per year. This can be distributed and incorporated directly on the ground or applied with the irrigation water, which is particularly useful in dry and windy weather. In addition, wood ash can benefit the plants via the compost. To do this, they are distributed in thin layers between other compostable materials.
Tip: Since wood ash occurs almost exclusively in the winter months and rotten plant material is then hardly available, it is advisable to collect it in a separate storage container.
Herbal manure
Plant manure are very effective fertilizers containing potash and nitrogen and at the same time an effective means of strengthening plants. They are particularly suitable for feeding heavy consumers such as cabbage and tomatoes. After fermentation, the solid plant components are sieved out and the liquid manure is diluted with water in a ratio of at least 1:10. The more sensitive the plants to be fertilized, the more water should be added. In addition, when fertilizing with plant manure, make sure that it is only poured onto the ground and not over the leaves. Otherwise the plants can be burned and in the worst case lost.
Coffee grounds
If you want to use coffee grounds for fertilization, there are two options. On the one hand, the dried compound can be administered via the irrigation water or distributed directly around the plants and worked into the soil. If coffee grounds are applied moist, they usually start to go moldy very quickly.
Tip: Basically, a soil analysis should be carried out before the first fertilization. This is the only way to ensure that the plants are optimally supplied with all the important nutrients and trace elements.
Instructions for making
Wood ash fertilizer
Hobby gardeners can produce organic potash fertilizers from wood ash, for example. Wood ash is a natural fertilizer that is rich in potassium and also contains lime and trace elements. Basically, the ash should come exclusively from untreated wood, ideally from alder, birch or poplar. With other types of wood there is a risk that they are particularly heavily contaminated with heavy metals. The wood should not be varnished, glazed or chemically treated. The paper for lighting should also be untreated.
Wood ash fertilizer does not have to be produced separately, the ash is generated automatically when wood is burned in the fireplace or wood stove. You spread them directly on the garden soil and work them in or compost the ashes and then bring them out with the compost. Wood ash fertilizer is suitable for large areas of new sowing, ornamental plants, lawns, potatoes, raspberries, gooseberries, carrots, leeks, Brussels sprouts, tomatoes, leeks, celery, wine as well as flowering perennials, roses, fuchsias, mallows and geraniums. Wood ash is unsuitable for bog plants or plants that prefer acidic soil. These include camellias, rhododendrons, peonies, azaleas, busy lizards and orchids.
Potassium fertilizer from plant manure
Potash and nitrogen-containing fertilizers in the form of herbal manure can be made from comfrey or nettles. In order to prevent burns on the plants, such manure should only be administered diluted. For a nettle manure you use all the green parts of the plant before flowering. In contrast, comfrey only uses the leaves.
To prepare a liquid manure, put about 2 kg of fresh herb and 2 handfuls of stone flour in a large wooden, plastic or earthenware container and pour 10 liters of water over it. The subsequent fermentation causes the liquid manure to foam up, so that the vessel should not be filled to just below the edge. The whole thing is covered with an air-permeable cover such as a lattice, left to ferment for 10-14 days and stirred every now and then. The cover can then be removed.
Coffee grounds fertilizer
Potash, phosphorus and nitrogen are also found in significant amounts in coffee grounds. In order to be able to use it as fertilizer, it is spread over a large area on a plate or something similar and allowed to dry. The dried coffee grounds can then be stored in an unlocked container until they are used in the garden.
