Benefits of intercropping lettuce and onion

Lettuce cultivation is a good alternative for intercropping with onions, as it is small in size, has a short cycle, has good regional adaptation and is well accepted by consumers. Furthermore, there is little information on the best time to establish this consortium, which justifies the present work, which aimed to determine the agronomically recommended time(s) for transplanting lettuce seedlings in beds sown with onions.

The study was carried out in a teaching, research and extension garden at the State University of Montes Claros, Janaúba campus. This region is located in the Brazilian semi-arid region, located at 15°47'18'' south latitude and 43°18'18'' west longitude at an altitude of 515 meters, with an average annual rainfall of 740mm. The predominant soil in the experimental area was classified as fluvic neosol. Fertilization was carried out according to soil analysis. The onion cultivar used was the short-day Texas Early Grano, with a cycle of 100 days to 120 days, being classified as a super early cultivar. For lettuce, the Grand Rapids curly type cultivar was used, which was previously planted in trays, being transplanted to the beds when they had three definitive leaves. For lettuce and onion, the recommended cultivation populations were 250 thousand plants/ha (0,20m x 0,20m spacing) and one million plants/ha (0,20m x 0,05m), respectively. The onion was planted directly in the beds in a consortium with lettuce and in single cultivation, with the lettuce planting carried out at 0, 20, 40 and 60 days after the direct planting of the onion. Phytosanitary treatments were carried out in accordance with recommendations for onion and lettuce crops, under conventional management. After harvest, agronomic and quality characteristics were evaluated in the onion bulbs. The agronomic variables were: total and commercial productivity (t/ha), bulb height and diameter (mm), number of bulbs, average total and commercial weight of bulbs (kg), dry matter (%). The quality characteristics were: water loss (%), total soluble solids (ºBrix), total titratable acidity (eq.mg.pyruvic acid 100ml-1) and SST/ATT ratio. After harvesting the lettuce, the following agronomic variables were evaluated: fresh and average weight; commercial and medium fresh pasta; number of heads; diameter of the plant head (measuring the distance between the opposite margins of the head, at the time of harvest, expressed in cm); total number of sheets, commercial and non-commercial; productivity (fresh shoot matter in t/ha) of lettuce.

Regarding onion, the results reveal that, for all agronomic characteristics, there was no difference between the intercropping in relation to the onion monoculture. However, lettuce grown alone showed higher yield compared to intercropped cultivation. Considering the intercropped cultivation of onion and lettuce, in relation to the time of transplanting lettuce in beds sown with onion, it was found that planting lettuce at the same time (season zero) or 60 days after planting the onion, can be a good intercropping alternative for onions (as quality analyzes showed that seasons zero and 60 days were the ones that best conditioned bulb quality). In periods zero and 60 days, onions had less competition with lettuce due to the fact that the period in which the translocation of photoassimilates to the bulbs begins to occur is between 60 days and 75 days. During this period, lettuces from the first season were already harvested and in the last season, onions were already well developed, competing more than lettuce for natural ecological resources.

On the other hand, in relation to lettuce, it was found that the average diameter of the head reduced as the lettuce transplanting seasons progressed in beds cultivated with onions. Lettuce transplanting in conjunction with onion planting (season zero) presents less effect of onion competition on lettuce intercropping, with greater agronomic yield. The little shading caused by the onion leaves on the lettuce plants favored the increase in the photosynthetic rate and, consequently, influenced the development of the lettuce plant. With the delay in transplanting the lettuce, the onion plants were more developed, which favored greater intraspecific competition for water, nutrients and especially light.

Therefore, intercropping between onion and lettuce is considered viable, as long as onion is the main crop, as it obtained the same yield in both systems: intercropped and single. Unlike lettuce, where the average productivity in the intercropped system (although lower than that in the single system) conditions its management as a secondary crop in the intercropped system, representing an additional source of income for the system and the producer. In this way, the change in the planting time of one of the crops (lettuce in the present study and, therefore, in the establishment of the consortium) changed the period of complementarity and competition of the intercropped crops, with an impact on productivity, conditioning the transplantation of the lettuce in conjunction with onion planting as the one that provides better results, both for the agronomic and qualitative aspects of both crops.

  Onion and lettuce

Onions and lettuce are widespread vegetables with great economic importance throughout the world. In Brazil, these species are among the most important vegetables, in terms of production, marketing and nutritional value. Therefore, consumption is high in natural form, in salads or in the preparation of seasonings. Therefore, onions are the third most popular vegetable in the country, and lettuce is the most consumed leafy vegetable. These vegetables have great socioeconomic importance, as they require a large amount of labor, generating employment, and by making small rural properties viable through income generation, taking into account that the production of onions and lettuce is practiced mainly by small producers. According to the latest census by the Brazilian Institute of Geography and Statistics (IBGE), in Brazil around 84,4% of rural properties are part of family farming, which are generally farmers with a low level of education, holding small areas for their cultivation and need to diversify the products grown to dilute costs and increase their income. Furthermore, according to the World Health Organization (WHO), the consumption of vegetables, such as lettuce and onions, is low in Brazil. Therefore, it is necessary to adopt cultivation techniques that can provide this to small producers, without damaging the environment. Among the techniques, intercropped cultivation of vegetables is suggested.

  What is

Intercropped cultivation is an agronomic practice characterized by the intensive use of renewable and non-renewable resources, in addition to presenting economic and agronomic advantages that may arise from the use of this technology for small producers. In recent decades, horticulture has sought to develop technologies to increase productivity, crop quality and produce with less impact on the environment. A consortium is nothing more than an association of two or more crops, with different cycles and vegetative architectures, explored simultaneously in the same area. However, crops are not necessarily sown or planted at the same time, therefore, they are also harvested at different times, but during an appreciable part of their vegetative periods (there is simultaneity, forcing interaction between them). Diversified production systems are more stable because they make it difficult for a certain pest or disease to multiply excessively, increase productivity per unit area, diversify food production, increase vegetative protection of the soil against erosion, control of invaders and allow for a better balance in the production system, through the multiplication of natural enemies and other beneficial organisms. The success of the intercropping system lies in the ability to determine the crops to be used and, mainly, the management of the consortium. The architecture of cultivated plants is an important point in intercropping. The greater the difference in the architecture of the plants involved, the better the use of environmental factors.