Potash fertilizers for tomatoes

Potassium, along with nitrogen and phosphorus, is vital for tomatoes. It is part of the cell sap of plants, promotes accelerated growth and rooting of young tomatoes. In the process of growing crops, gardeners repeatedly resort to the use of various potash fertilizers. These can be complex mixtures, purchased ready-made, or obtained by combining various substances. Top dressing containing only potassium can be used to compensate for the lack of this trace element. Potash fertilizers for tomatoes can be used in the form of root and foliar dressings, while the result of the introduction of this microelement will not be long in coming.

Potassium value for tomatoes

Tomatoes have a constant need for potassium. In large quantities, plants consume a trace element during the formation of 3-4 leaves. At this time, seedlings must be fed with potash fertilizers. The second mandatory stage of feeding should allow the plants to better root in the new conditions. In this case, fertilizers are applied a week before the intended planting. Subsequently, potassium is necessary for plants from the moment the ovaries form until the end of fruiting.

Adequate amount of potassium in the soil:

  • allows the leaves and shoots of the plant to develop better;
  • promotes the early rooting of tomatoes after transplantation;
  • increases the proportion of dry matter in fruits;
  • improves the taste of vegetables. Without potassium, tomatoes ripen sour with insufficient sugars;
  • promotes the timely ripening of vegetables;
  • makes tomatoes invulnerable to various fungal and bacterial diseases;
  • allows plants to withstand low temperatures and weather disasters.

Thus, without potassium, it is impossible to grow tomatoes. You can add this mineral to the soil regularly at intervals of 10-15 days. An excess of potassium in tomatoes can be observed very rarely, but every gardener should know the symptoms of a lack of potassium in order, if necessary, to take timely measures to prevent the development of the problem.

Micronutrient deficiency

Potassium deficiency in tomatoes can be diagnosed based on changes in leaves and fruits. The main symptoms of this micronutrient deficiency are:

  • The appearance of a dry border on the leaves. Its color is light at first, but over time it acquires a brown tint. It is worth noting that drying begins from the tip of the leaf plate and gradually spreads along the entire perimeter of the leaf.
  • Tomato ovaries are not enough.
  • Vegetables ripen unevenly.
  • On the fruit, you can see unripe spots at the stalk.

Important! Excessive application of calcium to the soil can cause a lack of potassium. Potassium and calcium are antagonists.

According to such characteristic signs, a caring owner should detect the problem as early as possible and take all the necessary measures to eliminate it, namely, spray or water the plant with potash fertilizers under the root of the plant.

Potash fertilizers

Tomatoes have a negative attitude towards chlorine, therefore, the choice of fertilizers for the crop must be approached with special care. So, for feeding tomatoes with potassium, you can choose one of the following fertilizers:

Potassium monophosphate

This fertilizer is two-component, contains 33% potassium and 50% phosphorus. Such a potassium-phosphorus fertilizer for tomatoes is excellent for feeding after transplanting or at the time of formation, ripening of fruits. The advantage of potassium monophosphate is that the fertilizer for tomatoes is highly soluble in water, so it can be used for root and foliar feeding of tomatoes.

For spraying tomatoes, potassium monophosphate is diluted with water to obtain a concentration of 1-2%. You can water the tomatoes under the root with a solution of the same concentration. Fertilizer consumption assumes the use of 10 liters of solution for 4 plants or 1m2... It is recommended to use top dressing based on potassium monophosphate no more than 2 times during the entire growing season.

Potassium nitrate

Potassium nitrate can be found under a different name - potassium nitrate. The fertilizer contains 3 components at once: nitrogen (14%), potassium (46%) and phosphorus (7%). Such a complex composition allows you to feed tomatoes not only with potassium, but also with nitrogen to activate growth. It is rational to use fertilizer during the period of ovary formation.

The fertilizer is highly soluble in water. It is used for foliar and root feeding of tomatoes. For spraying, prepare a solution with a concentration of 0.5 to 4%. Such a breakdown, permissible by the manufacturer, allows the gardener, depending on the composition of the soil and the condition of the plant, to independently choose the rate of application of minerals. By the way, experienced gardeners recommend adding 10 g of the substance to a bucket of water. This is quite enough to saturate the tomatoes with the necessary substances by spraying.

For watering tomatoes at the root, potassium nitrate in an amount of 10-20 g is added to a bucket of water. This volume of liquid should be enough for watering plants for 1m2 soil.


Kalimagnesia combines potassium and magnesium sulfate. It should be noted that magnesium is also essential for the life of tomatoes. On sandy soils, plants may lack this trace element, which can be compensated for with potassium magnesium.

A symptom of a magnesium deficiency is a discoloration of the leaf. The veins of the leaves retain their green color, but parts of the leaf plates between the veins turn yellow, then acquire a reddish or purple tint. Magnesium deficiency appears starting from the lower leaves.

Thus, it is rational to use potassium magnesium with a lack of potassium or magnesium. Potassium magnesium should not be used regularly as the main top dressing for tomatoes.

All of the listed potash fertilizers can be bought at a specialized agricultural store. Their use must strictly comply with the instructions given so that the increased concentration of substances does not harm the tomatoes. For feeding tomatoes, you should not use the same fertilizer throughout the entire growing period, it is much better to use different feeding depending on the stage of growing tomatoes.

Another potash fertilizer can be found on sale: potassium chloride. It should not be used for feeding tomatoes, since the substance contains harmful chlorine.

Ash as a power source

Wood ash is an affordable, environmentally friendly fertilizer that is always at hand. You can get it by burning solid wood, branches, sawdust, straw. If there is a stove in the house or bathhouse, then there are no problems with the preparation of ash.

Important! Waste incineration products are not fertilizers.

The ash contains a whole complex of trace elements necessary for tomatoes. Their concentration largely depends on what was the source of the raw material:

  • The largest amount of potassium is contained in straw combustion products (30%). Coniferous ash contains no more than 5% of this mineral, valuable birch species make it possible to obtain ash containing 13% potassium.
  • Calcium occupies a large part in the composition of wood ash. For example, when burning pine or birch firewood, the ash contains about 40% calcium;
  • Ash of any origin contains no more than 6% phosphorus.

In addition to essential trace elements, wood ash contains important substances such as magnesium and manganese. The use of ash for feeding tomatoes allows you to saturate the plants with all the necessary minerals, except for nitrogen, therefore, wood ash is used as an independent feeding or in combination with nitrogen fertilizers, organic matter.

Dry ash can be buried in the ground during autumn, spring digging. Also, in a small amount, you can sprinkle it on the near-stem circle of tomato, followed by loosening and watering the soil. On the basis of ash, liquid root and foliar dressings are prepared:

  • For watering under the root, an infusion is prepared from ash. The substance is added to a bucket of water in a volume of 1-2 glasses. After mixing, the resulting mixture is infused for a day and used for watering, 500 ml for each bush;
  • Tomatoes are sprayed with ash broth. To do this, 300 g of wood ash is boiled for 20 minutes. After cooking, the broth is cooled and filtered. Before use, the broth is diluted in 10 liters of water. A little 30-40 ml of liquid soap is added to the resulting mixture. Use a means for spraying leaves in order to feed and protect against late blight, slugs and other diseases, pests.

Thus, ash is a natural, affordable fertilizer with a high content of potassium, calcium, phosphorus. It is quite simple to use ash, while the effect of its use is always positive. You can use ash top dressing on a leaf or under the root regularly 1 time in 3-4 weeks.

You can find out some other details about the use of ash as fertilizer in the video:

Cement dust

Surprisingly, cement dust can also be a good potash fertilizer for tomatoes, since it does not contain chlorine at all, and the concentration of potassium in the substance reaches 30%. On the basis of cement dust, a solution is prepared for watering plants at the root. The substance is readily soluble in water; it is perfectly absorbed by tomatoes.

Important! Cement dust is recommended for use on acidic soils, as it has an alkaline effect.

Complex fertilizers with potassium

For feeding tomatoes with potassium, you can use not only potash fertilizers, but also complex fertilizers, which will contain, in addition to this microelement, additional ones necessary for the growth and development of plants. Such fertilizers can be bought in specialized stores or prepared by yourself.

Ready complexes

Coming to any agricultural store, you can find a lot of fertilizers with completely different price tags. They all contain the same complex of basic substances: nitrogen, potassium, phosphorus, in different concentrations. Among the most affordable, but no less effective complex fertilizers, one should highlight:

Potassium sulfate

Potassium sulfate is a three-component fertilizer with a high content of potassium and sulfur. It is also called potassium sulfate. The concentration of substances in the fertilizer is 50% potassium, 46% sulfur and 4% acidic phosphorus (7% neutral phosphorus). Potassium sulfate is used on alkaline soils. With increased acidity of the soil, it cannot be used.

Potassium sulfate is used for watering plants at the root. In this case, the concentration of the substance should be no more than 0.1% (1 g of the substance per 10 liters of water). This low concentration will slightly increase the acidity without harming the plants.

Important! Continuous use of potassium sulfate fertilizer for tomatoes is not the best option.

It should be used only on alkaline soils, if signs of potassium deficiency appear. Also, potassium sulfate allows you to fight late blight on tomatoes.

Potassium humate

This unique fertilizer contains all the necessary mineral trace elements and a lot of other substances that contribute to the accelerated growth and development of tomatoes. So, at least 80% of the substance is humic acids. They improve the chemical composition and physical properties of the soil, increase the yield of the crop.

You can use potassium humate at various stages of growing tomatoes:

  • To soak the seeds, a solution is prepared by adding 20 ml of the substance to a glass of water. Soaking throughout the day activates the growth of planting material and disinfects the surface of the grains;
  • Watering tomatoes at the root for the entire growing season can be done three times. To do this, dilute 50 ml of the substance in a bucket of water.
  • For foliar feeding, use a solution of the same concentration as for watering under the root.
  • Watering the soil with potassium humate in the process of digging allows you to restore its fertility. For these purposes, the fertilizer is diluted in a ratio of 500 ml per 10 liters of water.

Potassium humate is a natural fertilizer that can be used to feed tomatoes in various ways repeatedly throughout the entire growing period.


This complex, granular fertilizer contains nitrogen, potassium and phosphorus in approximately equal proportions - 15% each.

You can feed tomatoes with this complex, three-component fertilizer at various stages of the growing season. As a rule, ammophoska is used three times: it is added to the holes when planting seedlings, the plants are watered with a solution during the flowering period and during the period of active fruiting. Prepare a solution of ammophoska by dissolving 10 tablespoons of the substance in a bucket of water.


The fertilizer also contains 3 main components, while the amount of nitrogen in the mixture reaches 52%. Potassium and phosphorus in this fertilizer are in equal proportions, about 24% each.

It is recommended to use fertilizer for feeding tomato seedlings, as well as when observing slow plant growth. Granules of the substance are highly soluble in water, therefore, it is recommended to prepare a solution for feeding tomatoes: 1 spoon per 10 liters of water.

In addition to the above, widely known fertilizers, you can find complex substances, which are also mixtures of 3 components, for example, "Universal", "Kemira Lux", "Ava" and others. They must be used strictly in accordance with the instructions.

DIY universal mixes

You can prepare a universal fertilizer for feeding tomatoes containing potassium, nitrogen and phosphorus on your own by mixing several one-component substances. Experienced farmers often use the following recipes:

  • Add superphosphate (40 g) to a bucket of water, as well as urea (15 g) and potassium sulfate (15 g). Superphosphate must be soaked in water a day before using the fertilizer. Add two other components to the solution immediately before use.
  • Add 80 g of ash and 20 g of ammonium nitrate to 8 liters of water. After dissolving the mixture is poured over the tomatoes at the root.

When self-preparation of complex fertilizers for feeding tomatoes, you can use organic substances:

  • Dissolve 200 g of mullein or liquid chicken droppings in a bucket of water. Add one teaspoon of potassium sulfate and superphosphate to the mixture.
  • Add 150 ml of mullein and a spoonful of nitrophoska to a bucket of water.


With regular use of complex fertilizers, tomatoes will not be deficient in minerals, including potassium. However, in some cases, soil depletion, an increased amount of calcium, or some other factor causes symptoms characteristic of potassium starvation. In this case, it is necessary to feed the tomatoes with potash fertilizers, the list and method of using which are given above in the article.

Watch the video: Add Baking Soda To Your Tomato Plants, Just Days Later You Wont Believe What Happens! (October 2021).

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