The tomato is one of the most universal crops in existence and the main source of vegetables almost all over the world. With genetic improvement, tomato production is constantly increasing, but a very important part of achieving this result is crop management and, of course, the use of tomato fertilizers. In this article we will summarize the main questions that may arise in the use of fertilizer for tomatoes. However, we leave you with a summary of the content that we already have on the blog in case it helps you to get more information:
Although the famous NPK 15-15-15 is often talked about, many years ago it ceased to be the most optimal solution for practically all crops, since the needs are not the same for all plants in terms of nitrogen, phosphorus and potassium. In general, the ideal ratio for most plants, including ornamentals, is something like NPK 2-1-3, where the potassium is the main protagonist in quantity and phosphorus, which requires the lowest concentration. However, each of the macroelements and microelements is essential for crops and their absence causes chlorosis and loss of vigor and production.
In the case of the tomato, the ideal nutrient ratio for the entire crop cycle (according to their extractions) is NPK (Ca-Mg) 1-0.18-1.33 (0.74-0.22).
In the case of this crop, with production in intensive crops that can exceed 20 or 30 kg/m2, the use of fertilizer for tomatoes is essential. Locally, for summer production, production will be much lower, but if you want quality and good caliber, you have to provide fertilizer. Whether they are from biological origin (manure, compost, amino acids, etc.) or inorganic origin (calcium nitrate for example), are necessary and irreplaceable.
What kind of fertilizer for tomatoes is recommended?
If we speak in optimal terms, there is no single fertilizer that can be applied to the entire tomato crop. However, if there are no other alternatives, a 2-1-3 NPK ratio would be ideal, also providing calcium, magnesium and micronutrients.
A complete and varied plan of fertilizer use for tomatoes, which covers all the needs of the tomato, would be the following:
Tomato Fertilization Chart
| 1st week after transplant | sprinkling with water |
| 2nd week after transplant | Monoammonium phosphate (0.5 kg/1000 m2) |
| 3rd and 4th week after transplant | Potassium nitrate (0.5 kg/1000 m2). Monoammonium phosphate (1 kg/1000 m2) |
| 4th week to fruit set | Monoammonium phosphate (1 kg/1000 m2) Potassium nitrate (0.5 kg/1000 m2) Calcium nitrate (1 kg/1000 m2) Ammonium nitrate (0.5 kg/1000 m2) |
| From 2nd bunch to fruit set 4th bunch | alternative risks1st wateringMonoammonium phosphate (1 kg/1000 m2) Ammonium nitrate (0.5 kg/1000 m2) Potassium nitrate (1 kg/1000 m2) next wateringCalcium nitrate (1 kg/1000 m2) Potassium nitrate (1 kg/1000 m2). |
| From the 4th bunch to the fruit set 7th bunch | alternative risks1st wateringMonoammonium phosphate (1 kg/1000 m2) Ammonium nitrate (1 kg/1000 m2) Potassium nitrate (2 kg/1000 m2)next wateringCalcium nitrate (1.5 kg/1000 m2) Potassium nitrate (1.5 kg/1000 m2) |
| From the 7th bunch to the end of fruit set | alternative risks1st wateringMonoammonium phosphate (0.5 kg/1000 m2) Ammonium nitrate (2 kg/1000 m2) Potassium nitrate (3 kg/1000 m2) Calcium nitrate (2 kg/1000 m2)next wateringCalcium nitrate (2 kg/1000 m2) Potassium nitrate (3 kg/1000 m2) |
| From the end of fruit set to the end of cultivation | Ammonium nitrate (2 kg/1000 m2) Potassium nitrate (2.5 kg/1000 m2) |
Source: production techniques in protected crops
If you want to use compound fertilizers, such as NPK 15-15-15, to gain comfort (even if it is not the most optimal), it is essential to consider the relationship between nutrients according to the crop stage of the tomato.
| Stage | NPK Balance | Quantity (g/irrigation and plant) |
| Transplant until flowering begins | NPK 13-40-13 | 1-1.5 |
| Flowering and fruit set | NPK 15-15-15 | 1-2 |
| Collection and maturation | NPK 5-15-30 | 23 |
How much tomato fertilizer do you need?
To answer this question, you have to think about extractions. That is, what the tomato needs in terms of nutrients (either absorbed from the soil or supplied by us through the use of fertilizers) to produce 1 ton of harvest.
| nutrient | kg/t of tomato | g/plant |
| No. | 2.7 kg/t of tomato | 27 grams |
| P | 0.5 kg/t of tomato | 5 grams |
| k | 3.6 kg/t of tomato | 36 grams |
| THAT | 2 kg/t of tomato | 20 grams |
| mg | 0.6 kg/t of tomato | 6 grams |
Source: Christou et al (1999). The g/plant calculations are made taking into account a production of 10 kg of tomato per plant.
The g/plant and irrigation data were obtained from the usual planting density. The most common planting density in tomato cultivation is 1-2 plants/m2.
You must consider the nutrients provided by the soil, especially when applying a base of organic matter or manure. Keep in mind that 1 kg of manure can provide the following:
- N: 1.5% (15g/kg)
- P: 0.23% (2.3g/kg)
- K: 2.1% (21.2g/kg)
- Ca: 5.8% (58g/kg)
- Mg: 1.5% (15g/kg)
Organic fertilizer for tomatoes
Taking into account the previous relationship of nutrients that manure or vegetable compost helps to use (although it can vary considerably depending on the origin of the manure), for a production of 10 kg of tomato per plant and taking into account the extraction of nutrients from this crop, we would need to provide 2 kg of manure per plant.
The biggest problem in the use of organic fertilizers is nitrogen, because it is supplied in the form of organic nitrogen, not available to plants initially. It requires it to be transformed into ammoniacal nitrogen and nitrate nitrogen to be taken up by plants.
micronutrients
The optimum way to supply micronutrients is to do so continuously in all or almost all irrigations. The ideal quantity to apply would be the following, per liter of water.
| Iron (Fe) | Manganese (Mn) | Copper (Cu) | Zinc (Zn) | Boron (B) | Molybdenum (Mo) |
| 2mg | 0.7mg | 0.02mg | 0.09mg | 0.5mg | 0.04mg |
Amount of micronutrients per irrigation and liter of water
The most comfortable way is to provide micronutrients based on solid products that have a very similar relationship to the previous case, with an iron concentration between 5-6% in the form of EDTA or iron only in the form of EDDHA, for very calcareous soils.
It is recommended to provide a quantity of 300 grams of micronutrients every 15 days for 1000 m2 of tomato cultivation.
When should tomato be fertilized?
Fertilizer for tomatoes should be applied throughout their life, or at least the soil should constantly provide all the nutrients mentioned above. However, the first weeks of the tomato’s life must be left without water, or at least the first week, depending on how we want to force production.
Increase tomato production
Tomato production is linked to covering all fertilizer needs. However, another essential part is good crop management, starting with maintaining adequate root development, promoting early growth, not losing flowering and reaching fruit size.
Some practical advice:
- Maintain good root development: good soil drainage, avoid excess salts and continually add organic matter to the soil.
- Avoid the loss of flowers: the weather must accompany it, avoiding excess humidity, very low or very high temperatures and constantly supplying micronutrients, where boron is particularly interesting in flowering.
- Aerate the crop: It is recommended to remove the leaves gradually to get good access to light (but not direct sun) for the fruit.
- Pest and disease control: enemy number 1 when it comes to obtaining a good production of tomatoes.
How to stimulate the flowering of tomatoes?
There are several handy tips for stimulating tomato flowering. Some of them are:
- Good lighting: Direct access to large amounts of light, and in some cases direct sunlight, is essential to stimulate flowering in most crops.
- Adequate nutrition: follow the previously mentioned nutrition steps, where phosphorus and the micronutrients boron and molybdenum are essential.
- Use of biostimulants: To improve the quality of flowering, biostimulants are often used as nutritional supplements such as amino acids, algae and humic extracts.
- Optimal temperatures: the temperature difference between day and night is essential so that flower abortion does not occur. The following temperatures must be respected, with a difference between day and night of 8°C on average.
- Temperatures during the day: 23-26 ºC
- Temperatures overnight: 15-18 ºC
When do you add sulfur to tomatoes?
In the following article we answer your question about when to add sulfur to tomatoes and what is its main function, since in addition to being an important nutrient for the cultivation of tomatoes, it also protects the crop from diseases such as powdery mildew and pests such as mites. where to go
Read more: sulfur for tomatoes: when to apply it.