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

ABSTRACT Root architecture affects plant growth and agricultural productions. Although it is related to genetic factors, soil physical limitations can affect the root system and volume of explored soil, compromising plant growth and fruit production. Considering the need to mitigate these restrictions, the objective of the present study was to evaluate two planting types (planting of protected seedlings and planting of seeds in definitive place) and two scion-rootstock combinations (‘Pera’ sweet orange, CNPMF D-6 selection, combined with ‘Santa Cruz Rangpur’ lime and ‘Sunki Tropical’ mandarin rootstocks). The experiment was conducted at the Lagoa do Coco Farm, Rio Real, BA, Brazil, in a Oxisol under rainfed conditions. Biometric, physiological, and soil water content evaluations were made during the experiment. Soil mechanical resistance to root penetration and root system characteristics were also evaluated. Roots were concentrated on the soil surface layers (0-0.40 m), extending horizontally up to 1.50 m from the plant, regardless of the management practices used. The total root length in each root diameter classes studied, root length density, and total root mean diameter were higher for planting of protected seedling, resulting in greater root development. Plants from ‘Pera’ sweet orange scion grafted on ‘Santa Cruz Rangpur’ lime rootstock had earlier production and were more vigorous. Soil structure affects root growth, and the root distribution up to 0.40 m depth is correlated with plant vigor, yield, and water status under rainfed conditions. RESUMO A arquitetura radicular afeta o crescimento da planta e a sua produção agrícola. Embora esteja relacionada a fatores genéticos, limitações hídricas e físicas do solo podem reduzir o volume do sistema radicular e do solo explorado, comprometendo, assim, o desenvolvimento vegetal e produtivo. Para mitigar essas restrições foram adotados dois tipos de plantio (plantio de mudas protegidas e plantio de sementes no local definitivo) e duas combinações copa/porta-enxerto: laranjeira ‘Pera’, seleção CNPMF-D6, enxertada em limoeiro ‘Cravo Santa Cruz’ e em tangerineira ‘Sunki Tropical’. O experimento foi conduzido na Fazenda Lagoa do Coco, Rio Real, BA, em um Oxisol e condição de sequeiro. Foram realizadas medidas biométricas, fisiológicas e umidade do solo ao longo do experimento. Também foram avaliadas a resistência do solo à penetração mecânica e várias características do sistema radicular. Independente das prá