Respostas de Acrocarpus fraxinifolius wight & arn à aplicação de nutrientes

Abstract

To expand the silviculture of Acrocarpusfraxinifolius about mineral fertilization, two experiments were conducted at the Federal University of Lavras. Chapter 1 aimed to evaluate the biometric parameters of Acrocarpusfraxinifolius seedlings associated with the visual symptoms of macro and micronutrient deficiency. The experiment tested twelve treatments in pots with soil under nutrient restriction based on the missing element technique in a completely randomized design with five replications and one plant per pot in a greenhouse. The following treatments were adopted: Control (C1: corrected and fertilized with N, P, K, S, B, Zn), complete 2 (C2: without correction and fertilized with N, P, K, S, Ca, Mg, B, Zn), treatments omitting each one of the nutrients when relevant (C1 - N, C1 -K, C1 -S, C1 -P, C1 - B, C1 - Zn, C1 - lime, C2 -Ca, C2 -Mg) and natural soil. The measurement of height, diameter at soil level, and the number of leaves were 90 days after sowing, then the shoot and root were collected and dried in an oven to quantify dry mass. The data were submitted for analysis of variance and later to Dunnet's test, which compared each treatment with the control. Acrocarpusfraxinifolius proved to be a P-demanding plant in its initial phase yet responded positively to the omission of N up to 90 days after sowing, which was maximized by the application of this nutrient in a single dose. Chapter 2 addresses the application of different NPK doses and phosphate fertilization under field conditions in a complete block design with eight treatments, five replications, and four plants per plot. The treatments consisted of: control (without NPK application and without phosphate fertilization); phosphate fertilization at planting; phosphate fertilization at 65 days after planting; phosphate fertilization in installments at planting and 65 days after planting; nitrogen and potassium fertilization in a single dose at 120 days after planting. Over six months, there was no significant differences between treatments for the seedling's height and diameter at ground level. Factors such as the installation of the experiment in a no-tillage system, lack of liming, and the low content of B and Zn may have contributed to the treatments not expressing potential.