How nutritional balance can promote good results in onion cultivation

The importance of nutritional balance for the productivity and quality of onion bulbs.

Onion cultivation, in recent years, has expanded in different regions of Brazil, either due to increased consumption and its importance in national production, as well as due to the evolution of genetic materials and planting technology for this crop. In this context, in the production system, the aim is to increasingly increase the technological level of crops in a sustainable manner, with the aim of maintaining the highest levels of production and final quality of bulbs, to meet a growing and demanding consumer market.

In order to increase production potential, it is necessary to meet the requirements of each genetic material, whether in temperature, light, water and nutrients, in quantities and proportions related to each stage of development, from germination to harvest. For each growing region in Brazil, practices are used that provide the best conditions for plant development. Among these practices, adequate irrigation, population density of onion plants, phytosanitary and weed control, as well as the physical preparation of the soil and its adequate fertility correction and, finally, the supply of quantities and balances stand out. specific nutrients according to each phenological phase of the crop and the productive potential of the chosen cultivar.

For plant nutrition, the mineral elements considered essential are those that participate in some structural or physiological function of the plant, and without these elements, the plant's development and productivity are compromised. For macronutrients, nitrogen, for example, provides more vigorous growth, with adequate vegetative development and boosts productivity; phosphorus, in turn, provides root development and plant longevity; Potassium, magnesium and sulfur intensify photosynthesis and the transport of photoassimilates, favoring better filling and maturation of onion bulbs. Calcium and the micronutrient boron directly participate in the formation and growth of plant tissue structures, such as the cell wall. Boron also contributes to the firmness of the bulb skin and contributes to the transport of carbohydrates. Other micronutrients such as copper, manganese, zinc and iron participate in various metabolic processes, whether primary, such as photosynthesis and respiration, as well as secondary metabolism, which is related to plants' natural defense mechanisms against environmental stressors. And, thinking about the action of the nitrate reductase enzyme, which works in the amino acid production process, molybdenum is essential.

Therefore, it is essential to maintain adequate nutritional levels for the normal development of the crop, since in conditions of deficiency or imbalance of these, in the respective stages of development of the onion plants, both the productivity and the final quality of the bulbs may be compromised.

Therefore, it is necessary to pay attention to factors such as correcting soil acidity by increasing base saturation so that it reaches around 80%, as well as the use of planting and covering fertilizers, which are efficient in releasing and supplying nutrients appropriately for each phase of cultivation. Furthermore, it is necessary to use nutrients via the leaves to assist in the adequate formation of new vegetative tissues and in the important maintenance of the plants' physiological activities, such as photosynthesis and respiration.

To provide greater efficiency in foliar absorption and offer nutrients in specific and balanced quantities in each phenological phase of cultivation, currently in agriculture there are solutions based on amino acids and plant extracts, which, combined with the nutritional elements mentioned above, provide an increase in in the efficiency of nutrient absorption, better meeting the cultivation requirements and achieving higher levels of quality and productivity of onion plants. Furthermore, these amino acids and plant extracts influence the reduction of the negative effect of physiological stresses on plants and promote better plant sap flow, also providing more balanced development, whether of the roots, leaves or onion bulbs.

Regardless of the onion cultivar, the type of soil and climatic conditions, it is always necessary to be efficient in the nutritional management of the plants, so that they can complete their production cycle within the appropriate time, for a greater accumulation of assimilates, thus allowing a better expression of its bulb production potential and greater final profitability.

Marcos Revoredo, Alltech Crop Science, Unesp Jaboticabal