Use of soil and foliar fertilizers in beetroot

Beetroot stands out as a vegetable of great economic and agricultural importance for Brazil. Brazil is close to planting 20 thousand hectares (ha) of this vegetable, produced on more than 100 thousand properties.

The beetroot (Beta vulgaris L.) is a tuberous root, native to Europe, belonging to the Chenopodiaceae family. Like chard and spinach, it has a dark red coloration, due to betalain, a natural pigment that can be used as a dye, which also occurs in the veins and petiole of the leaves, it is globular-flattened and has a markedly sweet flavor.

Beetroot has specific characteristics among vegetables that place it among the main foods, as it has a nutritional composition above other plants, especially in B vitamins. Its consumption occurs both in the leaves and in the root, which is eaten raw or cooked. Its root is considered tuberous and consists of the swelling of the hypocotyl-root axis and a limited upper portion of the taproot, being its main organ for storing reserves and for its growth.

In Brazil, its cultivation is predominant in the Southeast Region, which represents around 250 thousand tons per year, generating income for more than 500 thousand people per year, with a turnover of approximately R$ 256,5 million per year in retail. The value of the production chain of this vegetable reached around R$ 841,2 million in the last 10 years. In the country, its cultivation is designated exclusively for the table, unlike European countries, which use the crop as a source of sugar.

However, beetroot is a very demanding crop in nutritional terms, requiring a balanced fertilization program capable of replacing the nutrients extracted by the crop, thus avoiding soil depletion.

Therefore, soil management regarding its structure and fertility must be judicious in terms of fertilization, leading to high productivity. However, to achieve this, producers must satisfy the nutritional needs of the crop by adopting techniques that provide greater efficiency in the use of fertilizers, with the rational application of mineral and organic fertilizers.

Agriculture, in general, has sought forms of cultivation that present lower implementation costs, that cause the least possible damage to the environment, especially to the soil, aiming at conservationist management and that the use of inputs, such as fertilizers and pesticides, is as low as possible.

Two types of fertilizers stand out. Mineral fertilizers, which have high concentrations of nitrogen, phosphorus and potassium, as well as other macro and micronutrients. And organic fertilizers, which are fertilizers that contain high levels of organic matter in their structure.

The cultivation of vegetables with organic fertilizers has increased in recent years, due to the high costs of mineral fertilizers and the beneficial effect of organic matter on intensively cultivated soils. The staggering productivity obtained by the intensive use of inorganic fertilizers and pesticides. In addition to the high cost, questions have also been raised not only about economic and environmental conflicts, but also the neglect of important quality aspects of agricultural production. Several studies have shown the beneficial effects of the use of organic fertilizers in agriculture, especially in combination with mineral fertilizers, and when used in the system, it can reduce or even eliminate the need for mineral fertilizers.

However, in some specific regions of Brazil, the use of organic fertilizer may be unfeasible or even unnecessary due to the lack of nutrients in the soil. The vast majority of Brazilian soils have acidic reactions and low fertility, with a high phosphorus retention capacity, which leads to the need to apply high doses of this nutrient and a reduction in the non-renewable natural resources that produce these inputs.

Phosphorus is of significant importance for plant growth and is related to protein synthesis, as it constitutes nucleoproteins necessary for cell division, acting in the process of ionic absorption, favoring the development of the root system of vegetables, increasing the absorption of water, nutrients, quality and yield of harvested products.

In addition to phosphorus, nitrogen (N) is an important macronutrient, as its internal chemical reactions can be decisive in achieving high beet yields. Proper fertilization management tends to emphasize and enhance the use of organic and mineral fertilization methods. However, excessive fertilization containing N can affect root quality, causing the accumulation of glutamine, in addition to the plants becoming visually unattractive.

In specific doses of correction in the soil and for the plant, nitrogen contributes to the increase in crop productivity by promoting leaf expansion and the accumulation of green mass. In addition to being a constituent of several organic molecules, such as proteins, nucleic acids and chlorophylls, it also has a great effect on plant growth and the quality of plant products.

It is important for the reader and the producer to always follow the research that is involved in their commercial exploitation crops, as many researchers from the North to the South of Brazil are studying various and various factors, methods and methodologies that meet the management of fertility issues.

In a study conducted by Damasceno and other researchers in 2011 in Minas Gerais, doses of 0, 100, 200 and 300 kg per hectare (kg/ha) of nitrogen were tested on beetroot. A linear increase was observed as the doses increased, and the maximum productivity of fresh matter of the aerial part and root, and root diameter, was obtained with the dose of 300 kg/ha of N. Similar results were obtained by Oliveira and other researchers in 2003 in the coriander crop, in which doses of 0, 20, 40, 60, and 80 kg/ha of N were analyzed, meaning that the use of nitrogen in beetroot crops is of utmost importance, but in specific doses, always observing the analysis of soil and leaves.

By applying phosphorus (P) to beetroot, some researchers observed that there was an increase in growth, in the foliar phosphorus P content and in the fresh mass of the tuberous root.

Observing the accumulation of nutrients in beets, Grangeiro and other researchers in 2007 determined that this vegetable has a greater demand for calcium between 40 and 50 days after sowing, which accumulates preferentially in the leaves. Its low concentration in the roots is associated with low mobility in the plant. And, according to the authors, after being absorbed by the roots, the nutrient is translocated to the leaves and is not redistributed. On the other hand, magnesium is required in greater quantities from 40 to 60 days of the beet cycle, also accumulating in greater quantities in the leaves because it is part of the chlorophyll molecule.

When it comes to organic fertilizers, the increase in doses both in association with mineral fertilizers and in exclusive use, allowed linear increases in the fresh and dry mass of tubers. Thus, the highest productivity values ​​were observed in studies with the association of poultry litter and mineral fertilizer, presenting a productivity of 41,12 t/ha of fresh mass of tubers, 18,8% higher compared to cattle manure associated with mineral fertilizer. An increase of 0,456 t/ha and 0,246 t/ha was observed in the productivity of beet for each ton of poultry litter and cattle manure applied, respectively. When exclusively organic fertilization was used, the plants with poultry litter reached a productivity of 28,39 t/ha of fresh mass of tubers, 47,06% higher compared to fertilization with cattle manure.

It can be observed that at a dose of approximately 30 t/ha of poultry litter, there was a yield of 29 t/ha of fresh mass of tubers, values ​​higher than exclusively mineral fertilization, with 27,44 t/ha. Thus, the use of poultry litter has a characteristic appropriate for beetroot.

When talking about organomineral fertilization, increases of 30% are observed for each ton of bedding and 20% with the use of cattle manure in partnership with mineral fertilizers.

Therefore, it is known that the fresh and dry mass of tubers has a better response to the use of fertilizers when an organomineral (mineral + organic) is applied in relation to the pure organic and only the mineral, as in this fertilizer model it has high doses of minerals and organics.

Observing similar results, some researchers analyzed the dry mass of leaves in an application of an organomineral fertilizer, obtaining an increase of 80% in results when the fertilizer dose was 20% higher. On the other hand, even increasing the dosage of the mineral fertilizer, the increase in results was less than 10%.

In general, treatments under organomineral fertilization interaction present the highest values ​​of yield and product quality components, except when evaluating the total soluble solids content.

With the use of exclusively organic fertilization, treatments that receive poultry litter present higher average values ​​than those obtained with cattle manure, for variables: fresh and dry mass of tubers and fresh mass of leaves.

By Emmanuel Zullo Godinho (USP), Amanda Alves Arruda (UNESP/FCA), Meirieli Nunes Beladeli (UFPR)

Article published in issue 138 of Revista Cultivar Hortaliças e Frutas