Efeitos da Adubação foliar na produção de frutos e na concentração de ácido ascórbico do camu-camu (Myrciaria dubia (H.B.K.) McVaugh) em condições de terra-firme

Abstract

The camu-camu (Myrciaria dubia (H.B.K.) McVaugh) known as caçari, araçá d água and azedinho can be found in the whole Amazon basin, along the edges rivers and lakes, has a red purple colored fruit when mature. In natural environments annually flooding occurs and the fruits reach maturation when the river is flooding (rainy season). At this time, clear water becomes muddy, full of sediments, and the plants are covered by water, but the stems and leaves absorb these sediments, and influence fruit production and ascorbic acid. The foliar fertilization on uplands is a technology that tries to imitate nature, substituting the natural ecosystem, supplying nutrients to the plants, so that it enhances the ascorbic acid content. The goal of this experiment was to evaluate the effects of foliar fertilization and weekly application on fruit production and vitamin C content. The study was carried out at the Yuricam Farm, Rio Preto da Eva-AM, with an area of 1.5 ha formed by eight year old plants of progenies from Iquitos, Peru. The experimental design was randomized blocks with a 4x4 factorial scheme and a control, with three repetitions. The factors were foliar fertilizer (Ouro Verde; Biocontrol; PT-1; Urea + KCl) and application periodicity (1, 2 ,3 and 4 weeks). The soil analysis showed low levels of nitrogen and phosphate. The leaf analysis was in the adequate range required by plants, except for calcium. There was more production of fruits with Ouro Verde fertilizer (3.6 Kg/ plant), but without effect of application periodicity. The greatest length of fruits (24.2 mm) was with PT-1 fertilizer, the diameter did not show effect of foliar fertilization; the pH varied from 2.61 to 2.76 and Biocontrol caused the highest pH with weekly application; the highest content of soluble solids was with Biocontrol, 6.25º Brix, and the highest value 6.8º Brix was with two weekly applications; the fertilizer application raised pulp yield and percent pulp (Urea + KCl, 1,236 Kg/plant, 74.2%; Ouro verde, 792 Kg/plant, 74%; Biocontrol 795 Kg/plant, 73.8%; PT-1, 906 Kg/plant, 69%, respectively); the fertilizers PT-1 e Urea + KCl harmed vitamin C production, but Biocontrol favored vitamin C yield with two weekly application.