Determinantes fisiológicos, metabólicos e produtivos na consorciação da rúcula com jambu em função do regime hídrico no semiárido

Abstract

Intercropping can be developed via a combination of numerous species of plants, one of the most used being arugula due to its short cycle and small size. Jambu (Acmella oleracea) is another very promising leafy vegetable, as it has similar vegetative characteristics, albeit differing from those of arugula. Despite being considered a non-traditional vegetable in the northeast of Brazil, the jambu has the potential to develop in the region. In addition to the lack of information regarding the use of arugula and jambu as intercrops, data related to the water requirements and production of the secondary metabolite, spilanthol, in jambu under semi-arid conditions are also scarce. Therefore, this research proposes to evaluate, both agronomically and biologically, monocrops and intercrops of arugula and jambu under different water regimes. The experiment was carried out at the Vale do Curu Experimental Farm of the Federal University of Ceará, in the district of Pentecoste. The experimental design was of randomised blocks in a split-plot design, with 20 treatments (2 + 1 + 1) x 5 and four replications. The plots comprised the irrigation regimes (ID50, ID75, IT100, IE125 and IE150), with the subplots consisting of intercropped and monocropped systems of arugula and jambu: 1) intercropped arugula; 2) intercropped jambu; 3) monocropped arugula and 4) monocropped jambu. To better interpret the research, two crop cycles were carried out, one in 2018 and one in 2019; three trials were conducted in each cycle. In the first trial, agronomic aspects, biological efficiency and water use efficiency were evaluated. In the second trial, physiological behaviour and competitive ability were evaluated. The third trial evaluated the biochemical responses, post-harvest and spilanthol levels of the jambu. The results showed that the morphological characteristics of the intercropped arugula were superior. As for the jambu, the best results for morphological characteristics were obtained when grown as a monocrop. The productivity of both the arugula and jambu were greater for the single crops, however, land use efficiency for the intercrops grown in both years showed mean values of 1.23 and 1.28 in 2018 and 2019, respectively. The best results were achieved with the ID75 irrigation regime for arugula, and IT100 and IE125 for jambu. Water use efficiency was greater in the monocrops; however, similar results were obtained with the intercrops. Intercropped arugula showed better physiological behaviour, whereas for the jambu, the best results for physiological characteristics were obtained as a monocrop. In general, the results showed that intercropping and the ID50 and ID75 irrigation regimes afforded the highest post-harvest crop quality. For the arugula, intercropping and the ID75, IT100 and IE125 water regimes showed lower accumulations of the G-POD, APX, CAT and SOD enzymes, while for jambu, this reduction was seen in the monocrop associated with the IT100, IE125 and IE150 regimes. Intercropping combined with the ID75 irrigation regime afforded an increase of 26.60% in the spilanthol content of the jambu. Based on the above, it is concluded that a combination of arugula and jambu is promising for intercropping under semi-arid conditions..