Estresse hídrico na produção de mudas de Mimosa caesalpiniifolia Benth e Erythrina velutina Willd.

Abstract

The Caatinga, a unique and exclusively Brazilian biome, has suffered constant degradation in recent years due to disordered and predatory use. Thus, several strategies have been sought to conserve forest resources and to produce native seedlings with desirable characteristics and tolerance to adverse conditions. The quality of the seedlings depends on several factors, such as irrigation management and substrate type. In this context, this study aimed to determine the effect of water stress on the development of Sabiá (Mimosa caesalpiniifolia Benth) and Mulungu (Erythrina velutina Willd) seedlings, in the forest nursery of the Rural Health and Technology Center/CSTR, Patos/PB campus. The design was completely randomized (CRD), in factorial scheme 3 x 2, with 3 levels of water stress (WS), WS1 (100% of water requirement, WR) without stress, WS2 (70% WR), WS3 (40% WR) and two forest species (Sabiá and Mulungu), with 5 repetitions. Germination, growth, phytomass production, seedling quality, water consumption and water use efficiency were evaluated up to 150 days after sowing (DAS). The results indicate that irrigation with 100%, 70% and 40% of WR did not influence the germination phase of forest species, with a germination percentage of 45% for Mulungu and about 25% for Sabiá. In irrigation with 100% of WR the Mulungu presented higher average values of growth, fresh and dry weight (shoot and root) and Dickson Quality Index (DQI). At the end of the experiment, it was found in the treatment without water stress the DQI of 0.55 for Sabiá and 9.48 for Mulungu. It was observed that the water deficit increase affected the growth variables of Mulungu seedlings, while the species Sabiá had no significant influence. At 150 DAS, the Mulungu obtained water use efficiency (WUE) higher than the Sabiá with the application of 70% and 100% of the WR of this species, with water consumption (WC) of 3.25 L and 4.65 L, respectively. In this context, when evaluating all variables, it is suggested the application of 40% of the WR depth for Sabiá and Mulungu in the germination phase, providing a 60% reduction in the use of irrigation water of these species. It is recommended to use the irrigation of 40% of the WR for the Sabiá and 100% of the WR for the Mulungu during the growth phase of the seedlings, aiming to obtain seedlings with greater vigor in a shorter period, resulting in greater efficiency of water use.