Efeitos do preparo do sulco de plantio nos atributos físico-hídricos do solo, no desenvolvimento radicular de plantas e em parâmetros de produção do citros

Abstract

The dense layer densification present in the Bt horizon of the Argissol (Ultisol) may impair root development of citrus plants promoting damages to the crop yield. The deep tillage for cultivation and the correct choice of rootstock may be the solution to this problem, but this premise needs scientific evidence based on the results of the relationship between root spatial distribution and soil physical-hydric attributes. The present study aimed to evaluate the spatial distribution of the root system of different citric culture rootstocks under Ultisol, where the relationships between the physical-water attributes of this soil, associated with the deep preparation of the area from furrowing, subsoiling, as well as the interrelationships between phenometry and plant yield. The experiment was carried out in a citrus farm in the city of Perdões, physiographic mesoregion Campo das Vertentes, Minas Gerais, in an area of Ultisol. The preparation of the experimental area (EA) consisted of opening planting furrows 0.40 m wide and 0.50 m deep, where the soil was corrected and fertilized, followed by subsoiling at 0.90 m wide and 0.50 m deep and then the pits with dimensions 0.30 m diameter x 0.50 m deep were opened for seedling planting. The rootstocks studied were: 'Cravo Santa Cruz' (CSC); Sunki Tropical (ST) and CitrandarinÍndio (CI). In order to compare EA and an unprepared area, a forest area (FA) was then used. Three years after beginning soil preparation under the three rootstocks, volumetric ring samples (≈ 90 cm3) with undisturbed soil structure were collected in the layers (0-0.05; 0.35-0.40; 0.45-0.50), as well as in pre-established positions away from the center of the plant (Left Furrow: LF; Planting Furrow: PF; Right Furrow: RF). For FA, only samples with undisturbed structure were collected in relation to the evaluated soil layers. The purpose of this sampling was to quantify the soil pore distribution by diameter, water availability potential, and the use of this water from both EA and FA. The root system of the different rootstocks in the EA was evaluated by the cultural profile method in association with 2D digital analysis, with subsequent surface mapping of root variables number (RN) and root diameter (RD) analyzed by kriging. After three years since the deep preparation from furrowing, followed by subsoiling and digging, the Ultisol showed significant changes in its physical-hydric attributes in terms of structural change and greater clay dispersion with a significant contribution to micropore volume. The preparation in the EA was effective in the roots spatial distribution of the different studied rootstocks, with greater emphasis on the CSC, which presented higher RN and RD, as well as greater water use, reflecting on their vegetative growth and on the gain in yield.