Effect of Irrigation Pattern and Timing on Root Density of Young Citrus Trees Infected with Huanglongbing Disease

Abstract

<jats:p>Citrus (<jats:italic>Citrus</jats:italic> sp.) root length density (RLD) can help in understanding and predicting nutrient and water uptake dynamics. A study was conducted at two sites in Florida to investigate root and water distribution patterns among different irrigation and fertigation systems. The results over the 2 years showed that RLD was highest in the 0- to 15-cm soil depth and decreased with depth for all treatments at both sites. About 64% to 82% of the fibrous roots (&lt;1 mm diameter) were concentrated in the irrigated zones of drip- and microsprinkler-irrigated trees and 18% to 36% were found in the nonirrigated zones at the Spodosol site (SS). At the Entisol site (ES), the RLD (&lt;0.5 mm diameter) in the 0- to 15-cm depth soil for intensive microsprinkler or drip irrigation was 3- to 4-fold (nonirrigated zone) and 4- to 7-fold (irrigated zone) greater at the 0- to 15-cm soil depth than that for conventional irrigation system. The trees at SS were symptomatic for Huanglongbing (HLB; <jats:italic>Candidatus Liberibacter asiaticus</jats:italic>) in the second year, while those at ES were asymptomatic throughout the study. This might have limited the density and extent of root distribution at SS. The water contents remained either close to or slightly above the field capacity. The results showed higher RLD for intensive irrigation and fertigation practices in irrigated zones compared with conventional grower applications suggesting greater water and nutrient uptake potential for the former.</jats:p>

Effect of Essential Nutrients on Roots Growth and Lifespan of Huanglongbing Affected Citrus Trees

“…Ca nutrition for trees budded on Cleo and Ca and Mg combined nutrient treated trees budded on Swc rootstocks significantly improved the FRLD of fine roots d > 1 mm. The variation in FRLD density was associated with the growth flush growth stage [7,17,29], moisture [16,17,30], and fertilization [17,29].…”

“…Studies indicated that 30%-50% of roots of HLB-affected citrus trees are impaired before canopy symptoms appear and 70%-80% of root loss could be prevalent as citrus deprived of intensive cultural management to pacify abiotic and biotic stress [10,15]. The optimum distribution of the root system is mainly restricted by water and nutrients available in soil profiles [16,17]. However, it has been reported that HLB develops an imbalance of nutrient concentrations, which cause nutrient toxicity for some nutrients, including Cu or deficiency for others such as Ca, Mg, Mn, and Zn [18].…”

“…Therefore, split ground and foliar-applied fertilizer improve nutrient use efficiency and reduce both nutrient leaching and application cost [23][24][25]. Moreover, HLB-affected trees are limited in soil nutrient uptake because of the associated decline in FRLD [12,16,26]. The role of adding essential nutrients in improving citrus growth in general and FRLD specifically over the seasons, along with root dynamics, and root lifespan, are not well understood.…”

Ammonium and nitrate transport during saturated and unsaturated water flow through sandy soils

“…The Drip or Microsprinkler Open Hydroponic System practices (DOHS and MOHS) applied water within 15 to 40 cm from the tree. The vertical soil moisture distribution clearly showed differences by irrigation method, depth, and lateral distance from the tree ( Kadyampakeni et al, ; ).…”

“…The detailed experimental design, weather conditions, site description and irrigation systems are described in Kadyampakeni et al (; ). Soil samples were taken at 0 to 15, 15 to 30, 30 to 60, and 60 to 90 cm, 15 June 2010, at Southwest Florida Research and Education Center (SWFREC) and 07 July 2010 at Citrus Research and Education Center (CREC) from the irrigated zones to analyze for ‐N and NO 3 ‐N and describe N movement.…”