Abstract
ABSTRACT The demand for seedlings of Brazilian native tree species has increased due to the growing number of recovery projects for degraded areas. In order to obtain success in the revegetation, high quality seedlings should be used. Among the factors that affect the quality of seedlings there is nitrogen fertilization, since nitrogen (N) is one of the nutrients required in the largest amount by plants. Thus, this study aimed to evaluate the response of Cassia grandis and Peltophorum dubium seedlings to N sources and doses. The treatments were represented by a factorial of three sources (ammonium nitrate, calcium nitrate and ammonium sulfate) by five N doses (0, 50, 100, 150 and 200 mg dm-3), arranged in randomized complete block design, with four replicates. After 145 days of sowing, were obtained: height (H), collar diameter (CD), shoot dry matter (SDM), root dry matter (RDM), total dry matter (TDM), and calculated the dry matter mass ratio of shoot and root (SDM/RDM) and the Dickson Quality Index (DQI). Nitrogen fertilization resulted in growth gains and improved the seedlings quality of both species. However, the sources and the source × doses interaction were not significant for all variables. For the studied substrate (Red-Yellow Latosol) the recommended dose is 185 mg dm-3 of N for the production of Peltophorum dubium seedlings. For the production of Cassia grandis seedlings was not able to find the optimum dose of N.
Highlights
The demand for Brazilian native tree species seedlings has risen due to the increasing number of recovery projects for degraded areas
Nitrogen fertilization resulted in significant gains in seedling growth of the species studied
For Cassia grandis, a significant effect of N doses was observed for all evaluated characteristics
Summary
The demand for Brazilian native tree species seedlings has risen due to the increasing number of recovery projects for degraded areas. Depending on the degradation level of the site to be recovered, planting of seedlings may result in a higher survival rate and initial growth compared to other recovery methods, such as natural regeneration and no-tillage. According to Parrota (1992), competition with grasses, unfavorable microclimatic conditions for establishment of plants, low availability of soil nutrients and seed bank reduction, are factors that hinder the natural regeneration of tropical forests. In this case, costly, intervention by planting fast growing native species seedlings is more efficient in relation to establishment time, accelerating the recovery process (Suganuma et al, 2008). The quality standard of seedlings can be defined by physiological or morphological parameters, being the morphological ones more used due to a more intuitive understanding by the nurserymen (Gomes et al, 2002)
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