A balanced organic fertilization at the right time is the best guarantee for a rich harvest in the vegetable garden. Here’s how to properly nourish your vegetables.
For vegetables to thrive optimally, the plants need the right fertilizer at the right time. The nutrient requirement depends not only on the type of vegetable, but also on the soil. To find out what the soil is like in your vegetable garden, a soil analysis is recommended first. It provides information about which nutrients are already available in which proportions in the vegetable patch and which you still need to fertilize your plants with.
Fertilizing vegetables: organic or mineral?
The topic of fertilization often leads to a fundamental discussion among vegetable gardeners. Mineral fertilizer fans point out that the nutrient salts are chemically identical anyway – regardless of whether they come from organic or mineral fertilizers. Supporters of organic fertilization refer to the humus-forming properties and the low leaching rate of the organically bound nutrients in horn shavings and other natural fertilizers.
From an ecological point of view, there are good arguments for not using mineral fertilizers in the vegetable garden. However, if chemical nitrate production were to be stopped completely, the world population would no longer be able to be fed and there would be even greater famines. That is why mineral fertilizers are also of vital importance.
The fact is that vegetables can only absorb substances dissolved in water, i.e. mineral salts. Compost, castor meal, horn shavings or cattle manure must therefore first be broken down by the organisms in the soil. The nutrients are slowly released over a longer period of time. This detour is not necessary with mineral fertilizers. They work directly. Mineral fertilizers should be used sparingly and only when the plants suffer from acute nutrient deficiencies, otherwise there is a risk of over-fertilization, especially with young plants.
Organic vegetable fertilizer
The most important ingredients of commercial organic vegetable fertilizers that are of vegetable or animal origin include horn shavings and horn meal, blood meal, bone meal, dried animal droppings, vinasse and soy meal. The garden and vegetable fertilizer from Manna Bio, for example, uses purely herbal ingredients. Plant nutrition in the hobby garden is also possible without animal raw materials. Manna Bio has a wide range of vegetable and fruit fertilizers, which are manufactured using a unique Sphero technology. Thanks to this, the gray rates are the same and contain the same nutrient composition. If the fertilizer grains come into contact with soil moisture, they break down into their smallest individual parts. This allows the plant to optimally absorb the active ingredients it contains.
There are also some natural fertilizers that you can produce yourself or, under certain circumstances, obtain from the local farmer: In addition to compost, these include cow, horse, sheep or chicken manure, nettle manure and nitrogen-collecting green manure plants such as lupins or red clover. As a rule, organic fertilizers – regardless of whether they are produced in-house or purchased – are less concentrated than mineral fertilizers, but they usually work for weeks and months.
Vegan vegetable fertilizers
Veganism is a current trend that also affects fertilization in the vegetable garden. Vegan people generally want to forego animal products – even when fertilizing vegetables they have grown themselves. No slaughterhouse waste such as horn shavings and horn meal obtained from the horns and claws of ungulates, or manure should be used. Instead, purely vegetable fertilizers are used. As long as only vegetable waste is composted, compost is usually vegan. Plant manure or green manure can also do without animal components. But almost all brand manufacturers now also offer vegan vegetable fertilizers in granulated or liquid form. Important to know: Vegan products generally have a lower concentration of nutrients than organic garden fertilizers made from animal components – therefore they usually have to be applied in larger quantities.
Compost as fertilizer in the vegetable garden
Your own compost not only nourishes the vegetable plants, but also provides fodder for the organisms in the soil. If used for several years, dark humus components also improve very sandy, loamy or highly compacted soils and ensure a finely crumbly, easy-to-work soil. Important: You should apply compost when preparing the bed in autumn or spring and work it in on the surface. The amount of compost depends on the main crop: vegetables with high and medium nutrient requirements such as tomatoes, cabbage, celery and leeks receive six to ten liters per square meter. Peas, beans, carrots and radishes are about half satisfied. If you regularly sow nitrogen-collecting green manure plants on the beds as an intermediate crop, you can even dispense with basic fertilization with compost for those who eat poorly.
Horn fertilizer for vegetables
Horn shavings, horn semolina and horn meal are called horn fertilizers. They all have a relatively high nitrogen content for organic fertilizers, but work at different speeds depending on the degree of grinding. They are mainly used for the nitrogen supply of vegetables with medium to high nutrient requirements. With the so-called heavy eaters, you can enrich the compost with horn shavings while preparing the bed. They decompose over the course of the season and thus continuously provide some nitrogen for plant growth. Topping up with finely ground and correspondingly fast-acting horn meal makes sense for most heavy eaters from June onwards. Medium eaters should only be provided with horn meal in summer – in spring they usually get by with the nutrients that the compost provides.
Use vegetable fertilizer correctly
Special vegetable fertilizers made from natural or renewable raw materials are cheaper than compost for basic fertilization when preparing beds and for subsequent fertilization in early summer on soils contaminated with phosphate. They can be used as an alternative to horn fertilizers, as they usually contain even more aroma-enhancing potassium. To be on the safe side, check the nutritional information on the packaging and make sure that the number for “P” (phosphate) is as low as possible. If the ingredients are identified, the proportion of bone meal should be as low as possible – it is the most important source of phosphate in organic fertilizers. To be on the safe side, you should have a soil analysis carried out every three to four years and especially keep an eye on the phosphate content. If this is at a low level, you can also use fertilizers that are higher in phosphate.
In case of doubt, weigh the recommended amount of your vegetable fertilizer on the package beforehand – only experienced gardeners have a feeling for the dose. The right time for fertilization: depending on the crop in the course of bed preparation and in the early summer months during the main growth phase.
Which vegetables need how much fertilizer?
When fertilizing vegetables, a distinction is made between low eaters, medium eaters and heavy eaters. Weak eaters are relatively frugal. Moderate fertilization is also advisable because lettuce and spinach, for example, tend to store nitrate in the leaves. One to three liters of ripe compost per square meter when preparing the bed ensure the basic supply and additional fertilization is usually not necessary. If you keep a consistent crop rotation in the garden and grow low-eaters after medium-eaters, you can even dispense with fertilizing low-consuming vegetables such as lettuce, spinach, peas, beans and radishes entirely.
Medium eaters like kohlrabi have a slightly higher nutritional requirement. You should therefore work three to five liters of ripe compost flat into the soil when preparing the bed. The potassium requirements of carrots and onions can, for example, be covered with a little wood ash. Other medium consumers are beetroot, leek, broccoli, spinach and fennel.
Heavy eaters such as pumpkin, courgette, cucumber, tomatoes, aubergines and cabbage bring the best yields on locations where green manure was sown in the previous year. But not all crops are compatible with all green manure plants. Cabbage plants do not tolerate mustard or rapeseed seeds – they belong to the same family of cruciferous plants and can mutually infect each other with what is known as the club.
In the spring you chop off the green manure and work it into the soil together with six to ten liters of compost. Horn semolina, horn meal or granulated organic vegetable fertilizers from specialist shops serve as a nitrogen source in early summer. A short-term effective natural fertilizer with a relatively high nitrogen content is also nettle manure. It should be used several times during the summer months.
Overview of the nutritional requirements of vegetable plants
- Low eaters (one to three liters of compost per square meter in spring; no fertilization after heavy or medium eaters): parsley, beans, peas, lamb’s lettuce, radishes, cress, herbs
- Medium consumption (three to five liters of compost per square meter when preparing the bed in spring; possibly a top dressing with vegetable or horn fertilizer): black salsify, carrots, potatoes, lettuce, radish, kohlrabi, chives, beets, Swiss chard, fennel, garlic, onions
- Heavy consumers (six to ten liters of compost per square meter when preparing the bed, possibly enriched with horn shavings; top dressing in early summer): Endive, cabbage, celery, tomatoes, cucumber, sweet corn, leek, zucchini, pumpkin
Fertilize balcony vegetables
Liquid fertilizers made from plant substances (mostly from sugar beet vinasse) are ideal for supplying potted vegetables such as tomatoes and peppers with nutrients on the balcony. The organic liquid fertilizers usually work quickly, but not for a particularly long time, so you have to re-fertilize regularly. When using it, the following applies in general: It is better to only add a small amount to the irrigation water and fertilize more often. For a sustainable fertilizing effect, you can also mix some granulated vegetable fertilizer under the soil when potting or repotting the balcony vegetables.