AFRICAN MAHOGANY SUBMITTED TO DRIP IRRIGATION AND FERTILIZATION

ABSTRACT African mahogany (Khaya ivorensis A. Chev.) is a tree species that has been increasing in Brazilian commercial planting. However, the lack of water and nutrition are great obstacles for crop production. The aim of this study was to evaluate the growth of young mahogany plants submitted to drip irrigation and topdressing. The experimental design was of randomized blocks, with three repetitions in subdivided plots. Treatments consisted of drippers: 1, 2 and 3plt-1; flows: 2, 4 and 8L h-1, and a treatment without irrigation. For topdressing, subplots levels were, as follows: 1) 17.5 and 25.2; 2) 35.1 and 50.1; 3) 52.5 and 75.0; 4) 70.0 and 100.2; and 5) 87.5 and 125.1 g plant-1 N and K2O, respectively, divided into five bimonthly applications, which started in the 4th month after planting. Plant height, diameter at root collar and at breast height (DBH), and stem height were evaluated. Results showed statistically significant differences (P>0.05) between irrigated and non-irrigated plants. Mean plant height ranged (from 2 to 20 months in field) from 0.33 to 3.25 and 2.67m for irrigated and non-irrigated plants, respectively. Mean stem height ranged from 0.23m to 0.87 and 0.71m for irrigated and non-irrigated plants, respectively. Thus, irrigation with 1 dripper per tree and flow of 2L h-1 was able to supply mahogany water requirements in the first two years in field. Trees have not responded to N and K topdressing at the beginning of the cycle.

摘要：非洲桃花心木（Khaya ivorensis A. Chev.）是巴西商业种植规模持续扩张的珍贵树种。然而，水分与养分供给不足仍是制约其产业化生产的核心障碍。本研究旨在探究滴灌与追肥处理对幼龄桃花心木植株生长的影响。试验采用裂区随机区组设计，设置3次重复。试验处理包含三部分：滴头数量（每株1、2、3个）、滴头流量（2、4、8 L·h⁻¹），以及无灌溉对照组。追肥处理的裂区梯度共设5组，每组分别对应每株施氮（N）与氧化钾（K₂O）的用量，依次为：1）17.5 g与25.2 g；2）35.1 g与50.1 g；3）52.5 g与75.0 g；4）70.0 g与100.2 g；5）87.5 g与125.1 g。追肥分5次每两个月施用一次，首次施用时间为定植后第4个月。本试验测定指标包括株高、根颈直径、胸径（DBH）以及茎干高度。结果表明，灌溉组与非灌溉组植株间存在统计学显著差异（P>0.05）。在田间种植2至20个月期间，灌溉组与非灌溉组的平均株高分别介于0.33~3.25 m与2.67 m；平均茎干高度则分别介于0.23~0.87 m与0.71 m。综上，每株配置1个滴头、流量为2 L·h⁻¹的滴灌方案，可在田间种植前两年满足非洲桃花心木的水分需求。幼龄桃花心木在生长初期对追施氮与氧化钾无显著响应。