Root distribution of cultivated macauba trees

Abstract

Macauba (Acrocomia aculeata Mart.) is a palm tree native to tropical regions in the Americas. This species has been the subject of several studies in the last decade because of its high yields and potential as a new global source of vegetable oil. However, the root system of this plant species has not yet been described. An evaluation of the root distribution in the soil is essential to improving crop productivity. Moreover, the root distribution pattern directly affects the cultivation practices of future plantations because it is strongly associated with crop nutrition, water use, and plant anchorage in the soil. Thus, the objective of this study was to promote the first evaluation of the horizontal and vertical distribution of the root system of macauba trees of different ages. The effective (>80% of the roots) depth and distance from the stem of the root system of macauba trees grown for 1.6, 4.8, and 9.0 years were evaluated using the excavation method and the monolith technique, with the collection of soil and root samples in the crown projected area. The root distribution of macauba seedlings cultivated for 3 and 8 months in nurseries was also evaluated. The total root mass of all evaluated plants was measured. The results indicated that the root mass increased with as the age of the plant increased, and varied from 0.0006 kg in seedlings (3 months) to 80.73 kg in adult plants (9 years). The effective depth of the root system also increased with as the age of the plant increase, reaching 0.4 m (1.6 years), 0.6 m (4.8 years), and 1.0 m (9.0 years). The effective distance of the roots from the plant stem coincided with the crown projection area. An important and unprecedented identified characteristic of young macauba plants was that their root system is concentrated in the direction of the tuberous region of a saxophone stem. The effective depth of macauba roots increases with as the age of the plant increase and the effective distance of the macauba roots coincides with the crown projection area. These features are relevant to crop production, as they can be used for fertilization and irrigation purposes.