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

Igor N De Castro,Marcelo R Dos Santos,Fernando L Godinho,Silvânio R Dos Santos,Polyanna M De Oliveira,Ignacio Aspiazú

doi:10.1590/1807-1929/agriambi.v25n12p819-825

Abstract

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.

Highlights

The Brazilian semiarid region limits large-scale agricultural production due to the irregular spatiotemporal distribution of rainfall, with average annual rainfall below 800 mm and high evapotranspiration rates, which vary between 5.5 and 7.5 mm per day (Santos et al, 2017a)
Nonparametric analysis of variance indicated that the genotypes did not influence root distribution for the different root classes (Table 3)
There were no interactions between water replacement level (WRL), distance from the base of the plant (DIST) and depth and WRL x PROF for any of the root classes; interactions were observed between DIST x depth for small (2.0-5.0 mm) and medium-diameter roots (5.0-10 mm) and between PR x DIST for fine roots (0.5-2.0 mm)

Summary

Introduction

The Brazilian semiarid region limits large-scale agricultural production due to the irregular spatiotemporal distribution of rainfall, with average annual rainfall below 800 mm and high evapotranspiration rates, which vary between 5.5 and 7.5 mm per day (Santos et al, 2017a) Under these conditions, the cactus pear is a viable option for agricultural production in the region (Pinheiro et al, 2014; Silva et al, 2015). Most of the cactus pears in the region are grown with few formal agricultural practices, preventing them from reaching their production potential (Silva et al, 2012; Donato et al, 2014; Leite et al, 2014) This is due to lack of knowledge and consolidated research on management practices, regarding irrigation conditions in relation to the root system of the plant. Knowledge of the root distribution system is important in sustainable irrigation management, since nutrients and water are not evenly distributed in the soil

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Conclusion