EFFECT OF INJECTING HYDROGEN PEROXIDE INTO HEAVY CLAY LOAM SOIL ON PLANT WATER STATUS,
NET CO₂ ASSIMILATION, BIOMASS, AND VASCULAR ANATOMY OF AVOCADO TREES

ABSTRACT

In Chile, avocado (Persea americana Mill.) orchards are often located in poorly drained, low-oxygen soils, situation which limits fruit production and quality. The objective of this study was to evaluate the effect of injecting soil with hydrogen peroxide (H₂O₂) as a source of molecular oxygen, on plant water status, net CO₂ assimilation, biomass and anatomy of avocado trees set in clay loam soil with water content maintained at field capacity. Three-year-old ‘Hass’ avocado trees were planted outdoors in containers filled with heavy loam clay soil with moisture content sustained at field capacity. Plants were divided into two treatments, (a) H₂O₂ injected into the soil through subsurface drip irrigation and (b) soil with no H₂O₂ added (control). Stem and root vascular anatomical characteristics were determined for plants in each treatment in addition to physical soil characteristics, net CO₂ assimilation (A), transpiration (T), stomatal conductance (gs), stem water potential (SWP), shoot and root biomass, water use efficiency (plant biomass per water applied [WUEb]). Injecting H₂O₂ into the soil significantly increased the biomass of the aerial portions of the plant and WUEb, but had no significant effect on measured A, T, gs, or SWP. Xylem vessel diameter and xylem/phloem ratio tended to be greater for trees in soil injected with H₂O₂ than for controls. The increased biomass of the aerial portions of plants in treated soil indicates that injecting H₂O₂ into heavy loam clay soils may be a useful management tool in poorly aerated soil.

Key words: stomatal closure, net photosynthesis, root histology, oxygen injection, root hypoxia, subsurface drip irrigation.