Fertilizer and the problem of nitrates in fruits and berries
With the use of fertilizers, especially mineral fertilizers, the emergence of environmental and toxicological and hygienic problems has recently been associated. The problem of accumulation of nitrates in crop production became especially acute.
Nitrates are one of the main sources of nitrogen nutrition of plants. Entering it, they undergo a number of complex transformations, including in the composition of proteins, nucleic acids and other compounds. Thus, nitrate nitrogen is a necessary and natural component of the plant organism. Excess accumulation of nitrates indicates that plants do not have time to use them for the biosynthesis of organic compounds. In this case, plants do not suffer from this and can accumulate a large number of them.
However, for a person who consumes such plants or products from them, this is not at all indifferent. Nitrates, getting into the human body with plant food, are restored to nitrites, which lead to the formation of methhemoglobin and disruption of the transport function of the blood, as well as the inhibition of the nervous system and the processes of tissue respiration. Nitrates, in turn, in the human body, interacting with other nitrogen-containing derivatives, form various nitroso compounds that have carcinogenic and mutagenic properties.
Therefore, the problem is not to exclude the receipt of nitrates at all to the plant, but to ensure that their quantity in the products does not exceed the maximum permissible amounts - the MAC limit. It is established that the maximum allowable daily dose of nitrates for humans is 300 mg on average. Approximately 80% of nitrates come with vegetables, the rest - with drinking water, meat, bread and other products.
The intake of nitrates with fruits and berries is very insignificant.these plants are not capable of accumulating them( MPC-50-60 mg / kg).
This is due to the biological characteristics of fruit and berry plants that are not capable of a large accumulation of nitrates. The processing of nitrates in them occurs mainly in the roots and therefore a significant accumulation of them in the aerial organs and, first of all, in fruits and berries, should not take place. If this happens, then we can talk about a violation of the protective functions of root systems and nitrogen metabolism in all organs of the plant.
Excess nitrates in plants and products occur when more soil is absorbed from the soil than is required for the synthesis of protein compounds. Most often, this happens when applying excessively high doses of nitrogen fertilizers, and also because of the imbalance between the content in the environment of nitrogen, phosphorus and potassium. Increasing the accumulation of nitrates is also facilitated by growing plants in darkened conditions and in cloudy weather, when the process of photosynthesis dies down.
And you can not agree with the fact that when growing plants you can not use mineral fertilizers.
We give two illustrative examples.
1. From a natural meadow, samples of grass were taken and analyzed for nitrate content. It turned out that in the samples they are more than the maximum permissible quantities. The question is: where does the fertilizer come from?- No one brought them. However, plant nutrition was unbalanced and this resulted in an excess of nitrates.
2. In the experiment with black currant, various doses of mineral fertilizers were studied - from lack( so-called "zero control") to very high in various ratios. Where were the nitrates found above the permissible amounts? In the control version - without fertilizers. And in the plots with high doses of fertilizers, but in the right proportions, they obtained the greatest harvest of berries without nitrates.
To reduce the risk of accumulation of nitrates in fruits and berries, it is necessary to observe the technology of fertilizer application and create conditions conducive to the processing of nitrates in plants.
Factors contributing to the reduction of nitrate accumulation in products:
1. Exclusion of unilateral and excessive( more than 20 g.v./m2) nitrogen fertilizer. Ensuring a balanced diet by applying phosphorous, potassium and other fertilizers in the recommended doses.
2. Elimination of nitrogen fertilizing during the ripening season.
3. Joint application of mineral and organic fertilizers, improving the conditions for the development of soil microflora, absorbing the excess of nitrogen formed in the soil.
4. Maintaining optimum soil moisture.
5. Good plant lighting.
6. Use of stored and processed products.
Many years of experience show that a balanced diet of garden plants with rational use of organic and mineral fertilizers not only increases their productivity and resistance to adverse environmental factors, but also ensures the production of environmentally safe products.