Abstract
Pineapple roots need adequate oxygen to function, sustaining growth and yield. The crop is susceptible to soil saturation caused by natural rainfall or irrigation, or even with drip irrigation that creates sustained wetting fronts. Drip and subsurface drip irrigation can develop sustained wetting fronts, particularly in low permeability soils, predisposing plant roots to a low oxygen environment. We evaluated the use of aerated irrigation water “oxygation”, employing Mazzei air injectors which mix air with irrigation (12% air by volume of water) in-line, increasing oxygen concentration in the irrigation water stream. The effect of this treatment was evident in growth, development, and leaf gas exchange parameters. Total fruit yield increased by 44 and 26% whereas industry yield increased by 11 and 6% due to oxygation compared to the control and no irrigation, respectively. High yield was associated with an increase in fruit size and not the number of fruits produced. Phytophthora to the control (4.9%), and without irrigation treatment (10.5%) suggesting that reasonable management of Phytophthora, which is one of the major pathological problems for pineapple production in Australia and elsewhere, can be addressed through aerated water irrigation. Oxygation responses were mediated through root and soil processes involving greater root biomass, root respiration, increased microbial diversity and enhanced soil aeration status.
