Distribuição de raizes de porta-enxertos, produtividade e qualidade de frutos de tangerineira ponkan em cultivos irrigado e sequeiro

Abstract

Tangerine trees are among the most prominent citrus crops, with 'Ponkan' being the most cultivated in Brazil. Crops that are totally dependent on rainfall may have their production unfeasible or reduced due to the lack of water available in the soil, and in most producing regions there is some water deficit during the crop cycle. In addition, there is a restricted number of rootstocks used in the crops, for many of which there are no studies on the behavior of the 'Ponkan' mandarin scion on them. Thus, the objective was to evaluate the distribution of roots on rootstocks, productivity and fruit quality of 'Ponkan' mandarin (Citrus reticulata Blanco) in irrigated and rainfed cultivations. The experiment was conducted in the field during the years 2017 and 2022, at latitude 12o 36' S, longitude. 39° 01' W and altitude of 216 meters, in the state of Bahia, Brazil. In the orchard, the plants were spaced 5 m x 2.5 m. The experimental design adopted was randomized blocks (DBC), in a 6 x 2 factorial, with three blocks and each plot consisting of three plants. The treatments were: six rootstocks - TSKFL x CTTR-017; LCRSTC; TSKC x TRBK- 006; TSKC x TRFD-003; LCR-003; LCR-004 and two water conditions (irrigated and rainfed). The analyzes were carried out in the first, second and third year of production, related to productivity; accumulated production; productive efficiency of the canopy; water productivity; rainwater productivity; irrigation water productivity; transverse and longitudinal diameter and fruit shape index; juice yield; pH, soluble solids; Titratable Acidity and Ratio. The two- dimensional evaluation of root distribution was carried out in combinations of 'Ponkan' mandarin with LCRSTC and TSKFL x CTTR-017 rootstocks under irrigated and rainfed conditions. Trenches were opened to collect soil monoliths measuring 0.20 m x 0.10 m x 0.10 m (volume of 0.002 m3) parallel and perpendicular to the planting line from a distance of 0.2 m to 1.2 m from the stem and depth up to 1 m, configuring a two-dimensional distribution of roots. The monoliths underwent a washing process to separate the roots. The roots obtained were scanned and processed to create two-dimensional maps. Irrigation provides greater productivity and cumulative fruit production for all scion x rootstock combinations. The highest water productivity is verified in the combinations with the rootstocks LCR-003, LCR-004 and TSKC-TRFD-003 from the second year of production. Among the rootstocks used, it is verified that the effective irrigation in the increase of the productive efficiency of the canopy on the rootstocks TSKFL x CTTR-017 and LCR-003 in comparison to the rainfed culture. The combination with the rootstock LCR-003 provides greater production to 'Ponkan' mandarin both under irrigated and rainfed conditions. All evaluated rootstocks provide desirable physicochemical characteristics to the fruits, both under irrigated and rainfed conditions. In the irrigated condition, roots with up to 1 mm in diameter are concentrated up to 0.20 meters deep. In the two growing conditions, irrigated and rainfed, the combination of 'Ponkan' canopy with the LCRSTC rootstock (Rangpur lemon tree Santa Cruz) presents a greater amplitude of root distribution when compared with the tangerine rootstock 'Sunki da Florida' x 'Troyer' citrang (TSKFL x CTTR-017), which indicates greater hardiness. The management of water in plants under irrigation and of nutrients for both crops must be carried out up to a depth of 0.40 m for the scion x rootstock combinations studied. The horizontal distance from the stem for irrigation and nutrient management should be 0.8 m and 0.6 m for 'Ponkan' mandarin x LCRSTC rootstock and 'Ponkan' mandarin x TSKFL x CTTR-017 rootstock, respectively.