Effects of nitrogen fertilization on the growth and on photochemical efficiency in plants of Handroanthus heptaphyllus

Abstract

Handroanthus heptaphyllus is a tree species with wood of high economic value, used in the manufacture of furniture and civil construction. When grown in soils with low availability of natural nitrogen (N), it demonstrates low growth potential. Thus, the study aimed to define the growth and physiological responses in H. heptaphyllus plants subjeted to N fertilization after planting. Five rates of N (0, 45, 90, 180 and 270 kg N ha−1) were tested at three vegetative phases of the plants (6, 12 and 18 months after planting). At each age, the height, stem diameter, concentration of N and photosynthetic pigments in leaves, chlorophyll a fluorescence and total N content in soil and tissue were determined. The addition of N increased total N content in the soil and the leaves, the concentration of photosynthetic pigments, the use of light energy and the maximum quantum yield of photosystem II, resulting in greater plant growth. In the period between the 6th and the 18th month after planting, the plants showed an increase of 135 cm in height. The concentrations of N and photosynthetic pigments in the leaves decreased over time, because of the effect of dilution and remobilization of N. The use of 260.0 kg N ha−1 kg divided in 35% of the dose added in small holes in the soil at planting; 32.5% three months after the first application; and the remainder in the sixth month after planting increased growth in height and stem diameter at 18 months after planting.