Tips for farmers: How to grow low-nitrate vegetables in greenhouses?
The Ministry of Agriculture and Food of the Republic of Tatarstan informs that specialists of the branch of the Russian Agricultural Center for the Republic of Tatarstan have prepared recommendations for growing vegetable crops on school plots and in private subsidiary farms.
Such products must meet sanitary requirements and standards. Every year, the excess of nitrates is detected in vegetable products grown on school grounds.
Nitrates are salts of nitric acid that accumulate in food and water when there is an excessive content of nitrogen fertilizers. For example, in agricultural plants, most nitrates are found in lettuce (especially greenhouse), radish, parsley, beets, cabbage, carrots, and dill. In beets and carrots, there are more nitrates in the upper part of the root crop, and in carrots also in the core of it, in cabbage – in the stalk, in the thick petioles of the leaves and in the upper leaves. All vegetables and fruits have the most nitrates in their skins.
According to the ability to accumulate nitrates, vegetables and fruits are divided into three groups:
- with a high content of nitrates (up to 5000 mg / kg of raw weight): lettuce, spinach, beetroot, dill, kale, radish, green onion, melons, watermelons;
- with an average content of nitrates (300-600 mg): cauliflower, zucchini, pumpkin, turnip, radish, white cabbage, horseradish, carrots, cucumbers;
- low in nitrates (10-80 mg): brussels sprouts, peas, sorrel, beans, potatoes, tomatoes, onions, fruits and berries.
The high content of nitrates in plants is usually due to the excess amount of mineral fertilizers.
The accumulation of nitrates in plants depends on many reasons:
- from the biological characteristics of plants and their varieties;
- from the age of plants ( there are more nitrates in the early vegetables than in late ones);
- from the regime of mineral nutrition of plants,
- frоm environmental factors (temperature, humidity, duration of light illumination). For example, the longer the daylight hours, the less nitrates there are in plants. Normal illumination of plants reduces the content of nitrates. It is important to choose the optimal lighting for a greenhouse in order to reduce the content of nitrates.
To normalize the content of nitrates in vegetables, it is necessary to observe the agrotechnical rules for growing crops. Special attention should be paid to the uncontrolled use of fresh manure.
The Ministry of Agriculture and Food of the Republic of Tatarstan recalls that a large number of nitrogenous compounds are found in pig manure and bird droppings. Therefore, these types of manure can not be consumed fresh. Even semi-decomposed material must be used in small doses and diluted with water. In the process of decomposition of manure, most of the nitrogen is volatilized, so the use of humus is considered safer for both plants and consumers of fresh vegetables.