Since tomatoes are one of the heavy consumers in the garden, fertilizer is essential when caring for tomatoes. With the right choice of fertilizer, the plants will be stronger and the fruits more aromatic.

Table of Contents

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  1. the essentials in brief
  2. Correct fertilization
  3. Which fertilizer for tomatoes?
  4. Recognize nutrient deficiency and excess
  5. FAQ

    6. the essentials in brief

    • The ideal fertilization varies depending on the location - tub, bed, greenhouse
    • The most important nutrients include nitrogen, potassium, phosphorus, magnesium and sulphur
    • These are added by biological or mineral fertilizers in order to obtain the greatest possible yields
    • Nutrient deficiencies and excesses are easy to spot and fix

    Correct fertilization

    With the right care, tomato plants feel comfortable in the bed, in the greenhouse, but also in the tub and thank the gardener with a rich harvest. In addition to regular watering, squeezing out and, if necessary, a climbing aid, comprehensive care includes, above all, correct fertilization. Because tomatoes are considered heavy consumers and need a lot of nutrients.

    caption: Development phases of a tomato plant

    Depending on the development phase of the plant, the amount of fertilizer must be adjusted

    When and how often to fertilize?

    From the seed to the fruit-bearing plant, the requirements of the tomato are fundamentally different. Between sowing and pricking out, the energy stored in the seed is sufficient for the seedling to develop (1). Additional fertilizers are even counterproductive at this early stage, since the excess of minerals can attack the young roots. As soon as the second pair of leaves has formed, a highly diluted fertilizer application is possible (2).

    When planting out, it is advantageous to use soil that is already well supplied with nutrients, for example from compost or green manure from the previous year. The actual fertilization of the tomatoes begins when they are planted out (2). At the beginning, put the fertilizer in the plant hole at the same time. Since the tomato grows very quickly and the nutrients are in the leaves and flowers, the soil must be regularly reworked with the minerals until the end of the season in September (3).

    How much fertilizer?

    Basically, the tomato in the tub needs just as many nutrients as its siblings in the greenhouse and in the bed. The big difference is mainly in the usable volume of soil. The roots cannot spread far in the pot. Their access to nutrients is therefore limited and the plant has to be fertilized more often.

    • potted plants: Enrich the soil for planting with a slow-release fertilizer. When the first flowers appear, sufficient replenishment should be provided with a liquid fertilizer once a week.
    • Glasshouse: A nutrient-rich soil with a starter fertilizer is sufficient until flowering. After that, you can sparingly fertilize with compost every two weeks.
    • Vegetable patch: Good starting conditions are humus-rich soil and an organic long-term fertilizer. Fertilizer can be applied every two to four weeks during flowering. The basic supply of nutrients in the soil is decisive for the correct rhythm.

    Tomatoes need these nutrients

    Potassium. Potassium is the basis for a balanced water balance and an essential part of photosynthesis. Potassium supports the development and ripening of the fruit.

    Nitrogen. Growth and color This nutrient is crucial for even growth and is particularly important for heavy feeders such as tomatoes. Nitrogen forms the main component in the production of protein and chlorophyll.

    sulfur and magnesium. These two substances are responsible for a regulated metabolic function and at the same time building blocks for the plant pigment chlorophyll.

    Phosphorus. Phosphorus takes care of the metabolic processes and the immune system of the plant. This supports fruit formation, the development of roots and flowers.

    Which fertilizer for tomatoes?

    The inexperienced gardener may feel a bit overwhelmed by the wide range of fertilizers in the specialty store. Liquids, granules, powders in all possible color combinations fill the shelves in the garden center. But what about the attributes "natural", "biological" and "organic"?

    What is the best fertilizer for tomatoes?

    Good yields and nature-friendly are above all the biological, organic fertilizers. These consist of dead plant or animal parts. However, a tomato can only with z. B. compost does not do much, because the important nutrients are still bound in the biomass. Only small garden friends like the earthworm dissolve the minerals and make them available to the plant. Positive side effect: humus-rich and loose soil.

    caption: Overview of fertilizers for tomatoes

    Natural fertilizers are usually more sustainable and cheaper than conventional fertilizers because you can produce them yourself

    mineral fertilizer

    The following fertilizers consist of artificially compounded minerals. Agents marked as tomato fertilizer advantageously already contain the exact mixing ratio of the nutrients. In principle, the manufacturer's instructions regarding dosage and duration for mineral fertilizers should be observed.

    liquid fertilizer. This classic also finds its legitimate application in balcony plants. It consists of nitrogen, phosphate, potassium and magnesium as well as other trace elements. Diluted with the irrigation water, the fertilizer is added to the plant. The addition takes place at the earliest from the 2nd week after planting and then every two to three weeks.

    Fertilizer sticks.(4.48€) The small rods contain microorganisms that are responsible for the important conversion processes of nutrients in the soil. One application provides the plant with all the nutrients it needs for about three months. In order for them to develop their full effect, they need a certain start-up time and should be added to the soil a week or two before planting out.

    blue grain. Blaukorn is a highly dosed industrial fertilizer. It offers a lot of nutrients (especially nitrogen) for a short time. However, the dosage is tricky. It is not uncommon for plants to be over-fertilized with blue grain and even die with bad luck. Therefore, blue grain should only be used once a month and not in combination with other remedies. And keep blue grain away from young plants, children and animals: the granules are poisonous for the latter.

    Biological Fertilizers

    If you not only want to make yourself happy with juicy tomatoes in summer, but also want to give something back to nature, the best thing to do is to use organic fertilizers. They are usually cheaper or completely free, such as the effective nettle manure or simple compost.

    horn shavings. The ground horns and hooves of slaughtered animals are rich in nitrogen. Horn shavings can be worked into the soil before planting. Over time, microorganisms release the nitrogen from the biomass. Since there are no microorganisms in the bucket, the use of horn shavings is more worthwhile in the bed and in the greenhouse.

    vinasse. Vinasse or molasses is a sugar beet extract. This has a lot of nitrogen and little potassium. Due to its high bioavailability, vinasse is almost equivalent to mineral fertilizers. So there is also the danger of over-fertilization with the sugar beet fertilizer. However, vinasse can be used as an ecological alternative to blue grain when there is a severe nitrogen deficiency.

    horse manure. Anyone who lives near a horse farm or keeps horses themselves has access to a very effective fertilizer in the form of horse manure. However, the manure should not be given undiluted and fresh to the plants. On the one hand, enormous decomposition heat develops, which attacks the roots and, on the other hand, the soil can become oversaturated with nutrients.

    lawn clippings. Lawn clippings consist largely of nitrogen, which is good for plant growth. But cutting the lawn alone will not ensure a successful harvest. Therefore, it should always be used in combination. The main benefit turns out to be its function as a mulch: the soil stays moist and small animals are attracted, which in turn decompose biomass.

    nettle manure. A miraculous biological fertilizer is nettle manure. Nitrogen, potassium and many trace elements make the fermented liquid a valuable fertiliser, which in combination with e.g. B. compost of the tomato can provide enough nutrients. As soon as the first flowers appear, diluted nettle manure can be used every two weeks.

    caption: Instructions for stinging nettle manure

    The production of nettle manure takes about two weeks, but is worth it due to the quantity produced

    1 kilogram of stinging nettles is mixed with 10 liters of rainwater in a container and stirred regularly. The fermentation time is about one to two weeks. Once the bubbles have stopped forming, the fertilizer can be diluted with water at a ratio of 1:10. The plant manure can now be used.

    home remedies

    Everyday home remedies can also make an effective and ecological contribution to the supply of nutrients. On the whole, however, adding home remedies is not enough to sufficiently satisfy the heavy tomato eater.

    coffee grounds. Coffee grounds that are left behind usually still contain a large number of nutrients such as potassium and phosphorus. Before use, the coffee grounds should be dried well before being incorporated into the soil.

    Baking powder. Baking soda, the main ingredient in baking soda, is considered a pest control agent. In combination with water, baking soda protects preventively and thus strengthens the immune system of the plant.

    Milk. The tomato plant needs calcium and phosphorus as the main minerals in milk for photosynthesis. The milk (including the vegetable alternatives) is mixed with water in a ratio of 1:5.

    eggshells. Aside from calcium and magnesium, eggshells contain few minerals. In order to release the substances, the egg shells have to be crushed and soaked in water for several days. This fertilizer should only be used as a supplementary fertiliser, as the substances are not sufficient to cover the needs of the tomato plant.

    Urine. Urine contains high levels of nitrogen, phosphorus and potassium, but should not reach the plants undiluted. The tomato can be poured as a diluted solution in a 1:2 ratio.

    green manure after harvest

    When the tomato season is over and the plant remains end up on the compost, a green manure aims to occupy the area that has been freed up with deep roots and legumes. These loosen the soil and transport minerals such as nitrogen from the air into the soil. Towards winter, the plants are cut with a scythe and left on the ground. This creates a soil-friendly mulch layer.

    Recognize nutrient deficiency and excess

    If diseases are excluded and a conscientious supply of fertilizer does not bring the desired success, i.e. the plant appears stunted, then there may be a nutrient deficiency or excess. Because the soil quality is decisive for the nutrient supply: loamy or sandy, acidic or alkaline.

    caption: Tomato diseases triggered by wrong nutrient supply

    Signs of a deficiency or excess of nutrients can be seen in different parts of the plant

    nitrogen deficiency. From the bottom up, the older leaves turn yellow first, then brown, and finally fall off. The plant looks stunted, the overall color is rather pale green. These symptoms can be attributed to a nitrogen deficiency. To remedy this, you can use mineral fertilizers with high nitrogen values or alternatively you can work with nettle manure.

    Potassium deficiency/green collar. The lack of potassium is also noticeable on the leaves: the edges of the leaves turn brown and look dry. This desiccation spreads throughout the leaf down to the veins, which continue to appear green. The fruits do not grow large and remain green at the base of the stem. These signs indicate a potassium deficiency. Possibly not too little potassium was fertilized, but too much nitrogen or magnesium, which have an inhibiting effect on potassium absorption.

    magnesium deficiency. Plants suffering from a magnesium deficiency develop yellow to whitish-brown spots on their leaves. If there is a severe deficiency, the coloring migrates to the middle. Only the large leaf veins remain green until the entire leaf turns yellow and eventually falls off. The plant hardly grows and fruits wither. A magnesium deficiency is caused by too much potassium or sandy, acidic soil. The easiest way to compensate for the deficiency is with inorganic fertilizers.

    Calcium deficiency/blossom end rot. The easiest way to spot calcium deficiency is to look at the tomatoes themselves. The lower part of the fruit does not turn red, dents heavily and turns brown-black. To prevent blossom end rot, care should be taken to ensure that the plant does not grow too quickly. Otherwise it cannot keep up with the calcium supply. In addition, less magnesium and potassium should be fertilized, as these have an inhibiting effect on calcium. Effective lime fertilizers such as algae lime or rock flour (€14.13) can quickly remedy the situation.

    Overfeeding/spoon leaf drought.
    Over-fertilization is reflected in tomato plants growing too rapidly due to too much nitrogen in the soil. Many new shoots and leaves are formed, which curl up softly and limp - the so-called spoon leaf. To solve the problem, you can wait without adding more fertilizer or mulch the soil with straw. The latter method is effective against nitrogen over-fertilization because straw draws nitrogen from the soil.

    phosphorus deficiency.
    A phosphorus deficiency cannot be clearly determined. An indication would be a reddish-purple discoloration of the leaves, starting at the leaf tip. Overall, the leaves of the plant appear smaller and harder. Leaf edges can die off completely. Otherwise the plant grows normally. The reason for this can be that there is too little organic matter in the soil, which is why compost is recommended. However, there may also be too much iron in the soil, which has an inhibiting effect.

    FAQ

    Can I give tomatoes flower fertilizer?

    As a rule, flower fertilizers (€1.95) have a different mixing ratio than real tomato fertilizer. The excess of nitrogen and the lack of phosphorus can, with repeated application, over-fertilize the tomato plant with nitrogen and lead to an undersupply of phosphorus.

    What do I do if my tomatoes are over-fertilized?

    If too much nitrogen fertilizer has been used, a straw mulch can help. Otherwise you should wait and protect the plant or the soil in the meantime. If there is no noticeable improvement, transplant if necessary.

    What is the best fertilizer for tomatoes?

    The best fertilizer for tomatoes is organic fertilizer. A mixture of manure, lawn clippings and, for example, horn shavings is superior to chemical fertilizers due to the sustainability in production and procurement. In addition, costs can be saved when producing your own fertilizer.

    When should tomatoes be fertilized?

    Tomatoes should be fertilized regularly, depending on the fertilizer and the surrounding volume of soil (pot, greenhouse or bed). The fertilizer application should take place outside of midday to avoid burning the plant.

    How often should tomatoes be fertilized?

    Depending on the fertilizer and the surrounding volume of soil, tomatoes should be fertilized every two weeks. If there are signs of deficiency in leaves or fruits, the amount must be adjusted.

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Vegetable garden