Fertigation management to increase banana productivity

Brazil occupies the fifth position in the ranking of banana producing countries, with 7,3 million tons, in 2013. São Paulo is the second largest producer with 1,2 Milhwill tons, surpassed only by Bahia (1,4 Milhwill tons).

In São Paulo, the Vale do Ribeira region is considered a major banana producing hub. However, in recent years, banana farming in São Paulo has advanced to the Planalto Paulista, requiring a specific technological package, since the soil and climate conditions of these regions are different.

The water deficiency present in the autumn/winter months in the Planalto Paulista makes practical irrigation essential in banana plantations. Despite This technique provides the water demand of plants during periods of drought, it is necessary to combine a other cultural practices, such as nutritional and phytosanitary management of banana trees.

It should be noted that the banana tree is a species that is highly demanding on water; studies show that its productivity is linked to plant transpiration, which, in turn, is dependent on offer of water in the soil profile.

In addition to water, the nutritional aspect is fundamental for the expression of the plant's productive potential. Nutrients are, in part, supplied by the natural fertility of the soil, but need to be replaced through chemical and organic fertilizers. The cultural remains left in the banana plantation itself (leaves, pseudostems and others) contribute to this replenishment, but the decomposition of these materials, with consequent offer of nutrients, occurs slowly, not being enough, since the banana tree is a fast-growing species.

The application of fertilizers through irrigation water is called fertigation. This technique provides the offer of water and nutrients to plants in a rational way, increasing the efficiency of fertilizer use, improving the cost/benefit ratio of fertilizers, in addition to significantly reducing the negative environmental impact caused by the loss, mainly through leaching, of nutrients allocated to the banana plantation .

Other positive points related to the fertigation technique are the reduction in the need for labor and the possibility of dividing fertilization throughout the vegetative/reproductive cycle, which specifically meets the nutritional and water requirements of each phenological phase of these plants.

What is the water requirement of banana plants?

Studies show that about 80% of the banana tree is composto by water. The larger the leaf area, the greater the fruit production and, consequently, the greater the water consumption. On average, it is estimated that a banana tree needs 18 a 20 liters of water per day, but this value is extremely flexible, since the plants' water demand depends on the climate (for example: the greater the insolation incident on the plants, the greater the water consumption), the age of the plant, the genetic component of the variety, the productive potential of the plant, the volume of the root system and others.

Therefore, it is to be expected that irrigation manifests itself in different ways, depending on the interaction of all these variables. Each location will need a level of irrigation, for example, banana plantations installed in higher locations tend to require greater water depths when compared to plantations at lower altitudes. The same can be inferred in the case of plantings carried out in sandy soils, when compared to more clayey soils. The fact is that the management of the irrigation depth (volume and frequencyuence) will depend on the soil and climate conditions of the region, in addition to the characteristics of the varieties (leaf area, plant height, pseudostem circumference, productive potential, etc.), in addition to other variables, as spacing adopted in planting, crop management and the method used to irrigate the plants.

Regarding the irrigation method, it can be said that practically all of them are used in banana farming. The advantages and disadvantages of each method depend on the cost of the system, type of soil, topography of the land, offer and water quality on site, in addition to labor available to manage the system. More efficient methods of using water are priorities.

Other factors must be considered when choosing the methodology and. Irrigation systems that promote wetness of banana trees (conventional sprinklers, for example) tend to contribute to the emergence of diseases, especially diseases. Sigatokas black e Yellow, making banana plantation management difficult and costly.

In general, studies indicate that localized irrigation systems (drip and microsprinkler) are the most recommended for banana plantations in Planalto Paulista, due to greater efficiency, ease of management, water and energy savings., in addition to the uniformity of water distribution in the soil profile. The assembly of the systems (number of drippers or micro sprinklers, number and position of lines) must be defined in each situation. The use of micro sprinklers in lines alternating with um micro sprinkler for groups of four plants have shown excellent results. ; Neste In this case, crop residues are placed on streets where there are no irrigation lines, optimizing water absorption by plants.

Figure 1 -. Bananal irrigated by microsprinkler, with crop residue management in alternating rows. Palmital, SP. (Photo: Adriana N. Martins)

Correct management of the irrigation system, whatever it may be, is fundamental to the efficiency of the technique. The volume of water to be applied (irrigation depth), e a frequencyuence of irrigation, will be determined in each case, taking into account all the variables already listed. The place where the water will be applied, especially in the case of localized systems, is also important, and knowledge of the plant's root system is necessary.

Another fundamental point is the quality of the water used in irrigation, and contaminated and/or saline water should not be used in the process.

To determine when and how much to irrigate, Producers can use several methods, with the installation of tensiometers in the field being considered the most practical and accessible method for monitoring the system, as long as they are installed correctly and measured with frequencyuence. Analyzing the root system of banana trees, It is observed that the zone of greatest water absorption is around 30 cm deep, with a depth of 50 cm being considered as a safety margin; therefore, tensiometers installed at a depth of 40 cm provide reliable parameters for monitoring irrigation.

Figure 2 -. Irrigation monitoring using tensiometers (20cm, 40cm and 60 cm deep, in the experimental area). Palmital, SP. (Photo: Adriana N. Martins)

What is the nutritional requirement?onal of the banana tree?

The banana tree is also a very demanding plant in nutritional terms, as it develops quickly, exporting significant amounts of nutrients when the fruits are harvested. Studies show that this requirement may vary according to the genetic material (variety), but is considered high in all cases. There is no point in fertilizing the banana plantation if there is no water available; on the other hand, you're welcome solves irrigating the plants and not supplying them nutritionally. Hence the importance of fertigation.

All nutrients are important for the banana cycle, however, nitrogen (N) and potassium (K) are the main ones. In terms of micronutrients, boron (B) stands out, o copper (Cu) and o zinc (Zn).

Currently, all nutrients can be applied via fertigation, as there are several soluble formulations on the market; even organic fertilizers are capable of being used, as is the case with humic acids.

The dosage of each nutrient to be applied to the banana plantation must be defined based on soil and plant (leaf) analyzes, visualizing an expectation of productivity, paying attention to the age and phenological phase of the crop.

Studies conducted in banana plantations, in Planalto Paulista, showed that nitrogen must be applied in a fractional manner, during the vegetative development period of plants; fertigation favors this fractionation, significantly reducing leaching losses.

Potassium must also be applied fractionally throughout the banana cycle. Research results showed that applications of higher doses of potassium, through fertigation, two months before the onset of winter promotesm a reduction in damage caused by cold winds, typical of this period in the Planalto Paulista, both on leaves and fruits. Another important characteristic of pre-flowering applications of this nutrient concerns the quality of the fruit in powder form.- harvest, with better filling and resistance, providing an increase in the market price in natura, especially in the case of Cavendish varieties (Nanica type banana).

Figure 3 -. Banana bunches ccultivate. Willians, harvested from plants managed with potassium application in pre-flowering. Palmital, SP. (Photo: Arlindo Pinheiro da Silveira)

Other nutrients, such as sulfur (S), magnesium (Mg), calcium (Ca) and phosphorus (P), in addition to micronutrients, can also be applied using the same technique, respecting the plants' development phase.

For fertigation to return favorable results, it is important that water quality analysis is carried out regularly, as in cases where the water source comes with a very high organic load, flocculation of certain formulations may occur, causing damage to the irrigation system. and reducing fertilization efficiency. Another very important point concerns the quality of the fertilizers used,; which must come from suitable sources, with guaranteed solubility and dosages, otherwise clogging and corrosion problems may occur in the irrigation system, compromising the performance of the technique.

Irrigation is a fundamental technology for the viability of banana farming in Planalto Paulista and in other places where there is water deficiency. However, this technique alone does not work miracles. Intensive production requires the interaction of several sectors such as irrigation, nutritional management, phytosanitary management, choice of variety, use of healthy seedlings of proven origin. It is this set of techniques that, when combined, guarantee the banana farmer the success of his enterprise.

This article was published in issue 88 of Cultivar Hortaliças e Frutas magazine. Click here to read the edition.