Abstract
ABSTRACT The increase in the demand for seedlings of native tree species makes it important to determine their water and light requirements, which are important factors in their production, in terms of costs and time. Water use and productivity in the growth of seedlings of Dalbergia nigra (Vell.) Allemão ex Benth., Apuleia leiocarpa (Vogel) J.F. Macbr and Hymenaea courbaril L. were determined under four light levels (three shading levels and control), using a randomized block design with four replicates. Height, stem diameter, leaf area and biomass, as well as Dickson quality index (DQI) were evaluated. The seedlings were transplanted into 280-cm3 plugs, filled with substrate composed of pure biosolids, and irrigated by a drip system with automatic management. The highest total volumes applied were 3.1 L per D. nigra seedling (in 37 and 58% shading), 2.5 L per A. leiocarpa seedling (in 37% shading) and 3.8 L per H. courbaril seedling (in full sun). Growth indices, confirmed by the DQI, indicate that shading levels of 37 and 58% for D. nigra, 37% for A. leiocarpa, and full sun for H. courbaril are the most recommended. The highest volumes of irrigation promoted the greatest development of the species, in general for intermediate shading, which provided the highest values of DQI and irrigation water productivity.
Highlights
The production of seedlings of native tree species is necessary due to the increased demand for environmental restoration projects (Scalon et al, 2011), mainly in the Atlantic Forest, currently with 12.5% of its original coverage and is considered one of the most threatened biomes in the world (Santos et al, 2019)
There was a small variation in maximum and minimum temperatures between treatments, with the highest average daily temperature (25.5 °C) detected in the S1 treatment (37% attenuation). Such higher temperature compared to the C treatment is possibly a result of the combination between the amount of radiation retained and wind attenuation in the microenvironment formed in the environment covered by the net (Monteiro et al, 2016), which may interfere with the daily temperature amplitude
The seedlings reached 2.5 mm only in the C, S1 and S2 treatments (141 days) (Figure 4D). These results indicate that there were problems with the production of A. leiocarpa and that 58% shading level (S2) is the most indicated for the production of seedlings of this species, due to the lower volume of water when compared to 37% shading (S1) (Table 1)
Summary
The production of seedlings of native tree species is necessary due to the increased demand for environmental restoration projects (Scalon et al, 2011), mainly in the Atlantic Forest, currently with 12.5% of its original coverage and is considered one of the most threatened biomes in the world (Santos et al, 2019). The substrate should provide adequate conditions for germination and initial growth of seedlings, with good physical and chemical characteristics (Dantas et al, 2009) In this context, biosolids, obtained from sewage sludge stabilization, are an alternative for seedling production (Abreu et al, 2017) and its use can minimize the occurrence of environmental problems (Caldeira et al, 2013), due to the need for an appropriate final destination for this waste (Alleoni; Fernandes; Correia, 2012). It is intensively exploited due to its size (height and stem diameter) and the good physical characteristics of its wood (Lacerda; Kanshiro; Sebbenn, 2008), being widely used in civil construction and in furniture industry (Tiago et al, 2018). These species are commonly produced in forest nurseries, usually without management of irrigation systems. Considering the hypothesis that the adequate amount of water and luminosity can contribute to optimizing the growth of forest seedlings, we evaluated the water use and productivity in the growth of seedlings of three tree species of occurrence in the Atlantic Forest, subjected to shading levels and automated irrigation management
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