Desempenho agronômico de alface e cebola consorciadas em diferentes níveis de sombreamento sob manejo convencional e orgânico

Abstract

The intercropping system favors the phytotechnical crop management mostly increasing production per area unit and greater profitability for farmer. These benefits to culture can be increased with the use of protected environment, reducing direct sunlight. Face to prospect of sustainable agriculture, there is a need for studies and alternative techniques for vegetable production that minimize the use of mineral fertilizers or agrochemicals. The objective of this study was to evaluate the agronomic performance of onion and lettuce greenery intercropping at different levels of shading under conventional and organic management. Two experiments (conventional and organic) from March to August 2012 were carried out. Each experiment was arranged in a split plot design, and in the parcels a 2 x 2 factorial, and in the split plot five shade levels, arranged in a randomized blocks design with four replications. In the subplots five levels of shading (18, 30, 50%, nonwoven and control) were evaluated, and in the plots two cultivars of onion (Texas Early Grano 502 and Baia Periforme) and two of lettuce (Veneranda and Grand Rapids TBR) were evaluated. The characteristics evaluated for onion were: total fresh weight, percentage of fresh weight loss, fresh weight of bulbs after curing, bulbs height, diameter and commercial and noncommercial weight, dry weight of bulbs, commercial and non-commercial production and total production. The characteristics evaluated for lettuce were: shoot fresh weight, stem, diameter of plants, shoot height, number and weight of commercial and non-commercial leaves per plant, length and stem diameter, shoot dry mass, stem and productivity. The results were submitted to analysis of variance and means were compared by the Scott-Knott test at 5% probability. In both crops the intercropping affected the onion agronomic performance. In the conventional cultivation, Veneranda lettuce was greater than Grand Rapids TBR, and Texas Early Grano 502 onion was greater than Baia Periforme, showing higher commercial productivity in the control environmental (no shading). The combination of Veneranda lettuce with Texas Early Grano 502 onion was presented as the best option among the intercropping. The environment with 30 % shading and nonwoven conditioned better yields for lettuce. However, for onions the best results were observed under no shading and nonwoven. In the organic system, the different cultivars did not influence the results. For lettuce, the best results were obtained with 18% shading. Amongst the onion cultivars, Texas Early Grano 502 was the superior in most traits. The use of shading in organic onion and lettuce cultivation is not feasible.