Production of baby leaf vegetables

Baby leaf vegetables constitute a growing market in Brazilian and global horticulture. At the same time, research and the search for production alternatives have grown for the sector, which is characterized by the supply of leaves that are not yet completely expanded and harvested early.

The baby leaf concept integrates vegetables such as lettuce, watercress, beetroot and arugula, among other species, with leaves that have not yet fully expanded and are harvested early in relation to the time in which they are traditionally harvested for consumption.

Baby leaves are soft, tasty and can have different colors and shapes, depending on the species used and for these reasons they have already won over consumers in European countries, the United States and Japan.

In Brazil, this niche market has aroused the interest of producers, consumers, and restaurant chefs, who are always looking for something new.

The introduction of baby leaves in the Brazilian market arouses the curiosity of consumers and can also help to stimulate the consumption of vegetables among the population, including children, who are fond of smaller-sized products and different colors. According to the latest official figures, vegetable consumption in Brazil is still small, an average of 73,9 g per inhabitant per day, compared to countries in Europe and North America which have an average consumption of 411,2 g per inhabitant / day.

In the Brazilian market, baby leaf can be found in individual form, with just one species or in a mixture of several species with leaves of different shapes, colors, textures and flavors. The mixture of leaves gives the product better nutritional value, as well as a pleasant visual appearance.

Another advantage of the baby leaf is its practicality. There is a version of the product where the leaves are sold sanitized and packaged, that is, ready for consumption. In this case, just open the packaging and start preparing the fresh salad, or cover the pizza with lettuce or arugula without having to go through the trouble of cutting the leaves.

In addition to loose baby leaf leaves, whole young plants are also being sold, produced in a hydroponic system, packaged with the root system. In this case, the consumer is responsible for separating the baby leaves from the rest of the plant and cleaning them for consumption.

Regarding marketing channels, the product is already found in supermarkets, mainly larger ones. However, restaurants, hotels and buffets, which seek to offer increasingly creative products and dishes on their menus, with a visual appearance that is more attractive to the eyes and palate, are now offering baby leaf to their customers.

Regarding the size of baby leaves, there is no official classification for marketing. The length of the leaves depends on the species and how they are used. Leaf sizes ranging from 5,0cm to 15,0cm in length are suggested to be considered baby leaves.

For use as a component of dishes and canapés, the size of the leaves baby 5,0 cm may be an option. In restaurants like self-service e buffets, where there is a need for leaves for consumption in natura to fit inside the containers in which they are served, leaves measuring 10,0cm to 15,0cm would be more interesting than large, chopped leaves, which end up having a less pleasant visual appearance.

Regarding its production, it can be carried out in the soil, inside or outside a protected environment, in hydroponic systems and in trays used to produce seedlings.

Abroad, in regions with a semi-arid climate in Europe and the United States, cultivation is carried out on the ground, in an open field, with mechanization in planting and harvesting due to the large number of seeds used per hectare, which can vary from 2 to 6 million. In this type of cultivation, the cost of mechanization is high (not yet used in Brazil).

Cultivation can also be carried out in an NFT-type hydroponic system (Nutrient Film Technique), due to the speed of production and quality of the product obtained. However, the cost of installing and maintaining the system is high. This system is being used by some producers in the State of São Paulo to produce baby leaf for the sale of whole plants with the root system.

The tray production system is also a production alternative for baby leaf. In this production system, growing plants is simpler to carry out than in the hydroponic system and also presents a lower cost, but it still requires the development of machinery to carry out the harvest, if the objective is scale production.

The Campinas Agronomic Institute (IAC) has been developing research into the production of baby leaf. In the system using trays, IAC studies have already evaluated the production of watercress, lettuce, beetroot and arugula in seven different cell volumes (15,0 cm³; 24,0 cm³; 27,0 cm³; 31,0 cm³; 55,0 cm³; 70,0 cm³ and 100,0 cm³) of trays used for the production of vegetable seedlings and found that the best option for producers are trays with a cell volume of 24,0 cm³, 27,0 cm³ and 31,0cm³, depending on the species cultivated.

Studies with baby leaf, theme of master's theses, were developed by students Alex Humberto Calori and Lívia Aguiar Sumam de Moraes, from the Postgraduate Program in Tropical and Subtropical Agriculture, at the Agronomic Institute, coordinated by researcher Luís Felipe Villani Purquerio.

One of the studies was developed at the Regional Center for Technological Development of Agribusinesses in the Northeast of São Paulo (Mococa, SP). This study evaluated the productivity of four species of vegetables (watercress, lettuce, beetroot and arugula) in an NFT hydroponic system, varying the electrical conductivity of the nutrient solution (0,4 mS cm^-1; 0,8; mS cm^-1 1,2 mS cm^-1 and 1,6 mS cm^-1) and the spacing between plants (2,5 cm; 5,0 cm and 10,0 cm). In Figure 1, you can see an overview of the crops grown with watercress, lettuce, beetroot and arugula.

As a result of the research, it was verified the possibility of producing baby leaf, of the different species studied, in nutrient solution concentrations lower than that recommended by Furlani and collaborators, of 2,0 mS/cm for adult leafy vegetables and higher than the recommendation of approximately 1,0 mS/cm for seedlings of the same species. For watercress, beetroot and arugula, the electrical conductivity of the nutrient solution that enabled the highest productivity was 1,6 mS/cm and for lettuce, 1,4 mS/cm.

The spacing between plants also resulted in a difference in the productivity of the species studied. The spacing that allowed the highest productivity was 2,5 cm. It was found 5,9 kg m^-2; 4,9 kg m^-2; 4,2 kg m^-2  and 4,0 kg m^-2 for watercress, lettuce, beetroot and arugula, respectively.

The second study, developed at the Technological Park of the Horticulture Center, at IAC, aimed to verify the effect of reusing coconut fiber substrate for one, two and three times, on the production of baby leaf of lettuce, cv. Elisa, in the tray production system, in a protected environment.

In this production system, the substrate used, as well as the root system of the plants that had their leaves harvested, remains in the trays, becoming waste. This residue can be reused in new cultivation, reducing the production cost, as well as the environmental impact, due to the reduction of substrate discarded in the environment.

At the same time, care was taken with the health of the reused substrate. With successive reuses, there is the possibility of the appearance of the agents causing lettuce tipping over (Pythium aphanidermatum e Rhizoctonia solani) and consequently there may be losses due to the onset of the disease.

Therefore, the solarization technique was used to clean the reused substrates. This method is efficient in controlling pathogens, pests and weeds and basically uses solar energy, having a low cost. The equipment used to carry out solarization in the research carried out was the Solar Collector, developed by IAC and Embrapa Meio Ambiente. In this equipment, the substrate was left for 24 hours, on a clear day with high sunlight, so that the pathogens that caused damping-off were eliminated.

As a result of the research, it was possible to produce lettuce baby leaves in reused coconut fiber substrate, up to three times. The productivity, 39 days after sowing, verified in the third reuse substrate was approximately 38% higher than that obtained in the substrate without reuse. There was an average of 7,4 kg/ m-2 in the third reuse substrate, 5,9 kg/ m-2 in the second reuse, 5,6 kg/ m-2 in the first reuse and 4,6 kg/ m-2 on the substrate without reuse. The chemical and physical characteristics of the coconut fiber substrate, regardless of the number of reuses, made it possible to grow lettuce, with emphasis on the pH, which was close to 6,7 and the EC, which varied from 0,28 dS/m to 0,35. XNUMX dS/m depending on the number of substrate reuses. Regarding the health of the substrate, the solarization process used was efficient in eliminating the pathogens that cause damping-off in lettuce.

It is not yet possible to predict whether the baby leaf market will reach a larger number of consumers in the future. However, it is a potential market, a very interesting niche that emblematically demonstrates how the vegetable agribusiness is dynamic and is always looking for innovation.

Luis Felipe Villani Purquerio, Alex Humberto Calori and Lívia Aguiar S. de Moraes, IAC

Article published in issue 80 of Cultivar Hortaliças e Frutas