SEEDLING GROWTH OF TREE SPECIES UNDER DOSES OF HYDROGEL AND TWO LEVELS OF LUMINOSITY

ABSTRACT Hydrogels (polyacrylamide compounds) are recommended in agriculture and forestry as soil conditioners because they are able to absorb water and increase its stocks in the soil. The aim of this study was to determine the most suitable dose of hydrogel to establish seedlings of Enterolobium contortisilliquum (Vell.) Morong under two levels of luminosity. Seedlings of Enterolobium contortisilliquum (Vell.) Morong were planted in pots, following a design of subdivided plots, consisting of two levels of luminosity in the plots: full sun and 50% luminosity, and 10 doses of hydrogel in the sub-plots: 0.0, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5 and 6.0 g L-1. Seventy-two days after the seedlings were transplanted to the pots, plant height and diameter were determined, together with the height to diameter ratio, root length and diameter, shoot and root dry weight, and the shoot to root ratio. The lowest ratios between height and stem diameter (8.50 and 8.68) occurred in the seedlings in full sun at the doses of 0 and 2 g hydrogel L-1 respectively. For shaded seedlings the lowest ratio (8.14) occurred at the dose of 3.0 g L-1, but with a lower coefficient of determination (R2 = 0.68). Shoot dry weight increased with the dose of 2 g L-1 in full sun, and 3.5 g L-1 under shaded conditions. The doses of hydrogel giving the best initial development in seedlings under evaluation were 2 g L-1 in full sun and 3.5 g L-1 in the shaded environment. Although a response by the species to the doses of hydrogel was found, the benefits of the polymer were not evident under the conditions of the present study.

摘要：水凝胶（hydrogels，聚丙烯酰胺类化合物）作为土壤调理剂被推荐应用于农林业领域，因其可吸收水分并提升土壤储水量。本研究旨在确定最适宜的水凝胶施用剂量，以在两种光照水平下培育雨树（Enterolobium contortisilliquum (Vell.) Morong）的实生幼苗。试验采用裂区设计，将雨树实生幼苗栽植于盆钵中，主区设置两种光照水平：全光照与50%遮光度，副区设置10种水凝胶施用剂量：0.0、2.0、2.5、3.0、3.5、4.0、4.5、5.0、5.5及6.0 g·L⁻¹。在幼苗移栽至盆钵72天后，测定植株株高、茎粗、株高与茎粗比值、根长与根粗、地上部干重、地下部干重及地上部与地下部干重比。试验结果表明：全光照组中，当水凝胶施用剂量为0与2 g·L⁻¹时，幼苗的株高与茎粗比值最低，分别为8.50与8.68；遮阴组中，水凝胶施用剂量为3.0 g·L⁻¹时株高与茎粗比值最低（8.14），但该指标的决定系数较低（R²=0.68）。全光照组的地上部干重在施用2 g·L⁻¹时达到峰值，遮阴组则在施用3.5 g·L⁻¹时达到峰值。本试验中，供试雨树幼苗的最佳初始生长施用剂量为：全光照组2 g·L⁻¹，遮阴环境组3.5 g·L⁻¹。尽管本研究观测到该物种对水凝胶施用剂量存在响应，但在本次试验条件下，该聚合物的增效效果并不显著。