Root distribution of cactus pear genotypes under different soil water replacement levels¹

Distribuição radicular de genótipos de palma forrageira sob percentagens de reposição de água no solo

HIGHLIGHTS:

Very fine root length density increases as soil water replacement levels rise and decreases at greater distance from the base of the plant.

Fine, small and medium-diameter roots are more concentrated near the plant base at a soil water replacement level of 75% of ET₀.

In general, the Miuda genotype shows better root distribution and Gigante a higher root length density.

ABSTRACT

Knowledge of the cactus pear root distribution system can improve management of the plant by defining the areas of soil best suited to fertilizer application and the installation of soil moisture sensors under irrigation. Thus, the aim of the present study was to assess the root distribution of cactus pear genotypes under different water replacement levels. To that end, a field experiment was conducted in a randomized block design, using genetic material from two cactus pear genotypes (Opuntia fícus-indica Mill. and Nopalea cochenillifera Salm-Dyck) and six water replacement levels based on reference evapotranspiration - ET₀ (T₁, no irrigation; T₂, 15%; T₃, 30%; T₄, 45%; T₅, 60% and T₆, 75% of ET₀), arranged in split-plot, with irrigation treatments allocated to the plots and the genetic material to the sub-plots, and three replicates. The roots of the cultivars were collected for analysis of root length density (RLD) 390 days after planting. The RDL of very fine roots declines as depth and distance from the plant base increases and total, fine, small and medium RDL rise at higher water replacement levels; 75% of ET₀ near the plant base increases RDL; all the root diameter classes are concentrated at a distance of 0-0.20 m from the plant base and depth of 0.10 to 0.25 m; the RDL percentage is higher for the Gigante genotype and Miuda exhibits better root distribution.

Key words:
Opuntia fícus-indica Mill.; Nopalea cochenillifera Salm-Dyck.; roots; water regime