Ability of Citrus Root System to Overcome a Strong Wax Layer

Abstract

The present work aimed to investigate the effects of mechanical impedance of wax layer (wax discs were installed 0.1 m deep) on root system deepening of citrus seedlings growing in columns with sand and nutrient solution. Two planting systems were evaluated: direct seeding (DS) and planting of seedlings (PS) (plants obtained from seed germination in tubes). Two experiments were carried out in a sequence: first to investigate the wax layer resistance levels (0.14 to 2.7 MPa) on root system penetration and two planting systems (DS and PS). The second evaluated the root and plant development of the two planting systems and two resistance of wax layer to root penetration: control (0.14 MPa) and a strong wax layer (1.06 MPa). The experimental design was randomized blocks, the first experiment in a 2 × 4 factorial scheme with 4 replications and the second a 2 × 2 factorial scheme with 6 replications. Resistance level ≥ 1.52 MPa (60% hard wax and 40% soft wax) completely limited root penetration in the artificial strong layer. The presence of strong wax disc reduced the citrus root system in both planting systems. PS was associated with greater root and shoot vigor, indicating that, in soils with good physical structure and porosity or allowing root deepening beyond the cohesive layer, this planting system is fully adequate, despite the possible benefit of not cutting the pivoting root in direct sowing.

Subsoiling and Planting Method on the Initial Growth of ‘Pera’ Sweet Orange (Citrus sinensis (L.) Osbeck)

“…Total root length and root length for the diameter classes tended to decrease in subsurface, and PNT was superior to PS along the profile (Figure 2). The results corroborate the fact that the presence of physical impediments to root growth close to soil surface (Table 1) increases root diameter, because it is an adaptive response to this abiotic stress (Gregory et al, 2009), as observed by Oliveira et al (2018) for citrus. L. D. Souza, Ribeiro, L. S. Souza, Ledo, and Cunha Sobrinho (2006) also observed, in 'Valencia' orange grafted on 'Volkamer' lemon (C. volkameriana Ten.…”

“…When the data were analyzed along with those of plant shoots, it was observed that the higher activity of the root system of plants grown from PNT, compared to PS, led to higher vegetative vigor in PNT, since it favored the increase in the canopy volume (CV) and vegetative vigor index (VVI) of young 'Pera' orange plants, in comparison to PS (Figures 1 and 2, Tables 3 and 4). In protected environment, Oliveira et al (2018) also verified that conventional planting (PNT) was associated with greater root and shoot vigor, indicating that, in soils with good physical structure and porosity or allowing root deepening beyond the cohesive layer, this planting system is completely adequate, despite the possible benefit of not cutting the pivoting root in direct sowing (PS). Davoglio Junior, Bordin, and Neves (2006) demonstrated the existence of correlation between the shoots and root system of 4-year-old citrus trees, due to the higher seedling vigor at planting and to the horizontal exploration of the soil by the roots.…”

“…Carvalho (2001) discussed that root pruning procedures performed in the conventional process of seedling production (PNT) force the growth of secondary roots, promoting higher root development. Oliveira et al (2018), in a simulation of cohesive layer in protected environment, showed that the planting of seedlings, simulating the PNT, led to greater root development with physical impedance < 1.52 MPa, explained by the fact that this planting system already had structures of secondary roots favoring the increase of absorption roots. Additionally, 'Rangpur Cravo Santa Cruz' lime has a very vigorous root system, easily breaking the physical impedance, increasing root length density and root capacity to absorb water and nutrients, because of length increase of thin roots compared to plants originated from direct sowing (PS).…”

Rootstocks and planting types on root architecture and vegetative vigor of ‘Pera’ sweet orange trees

“…The PSD practice for citrus supposes to result in a higher root deepening because the original architecture of the root system remains intact (Rezende, 2013;Rezende et al, 2015). However, there was no difference in root deepening system between planting types as also found in field conditions by Oliveira et al (2018) in a greenhouse study, in which the PPS of SCRL was correlated to higher root and shoot vigor, despite possible benefits of not cutting the pivoting root in the direct sowing.…”