Oxygation : aeration of subsurface drip irrigation water and its advantages for crop production

Subsurface drip irrigation (SDI) compares favourably with other irrigation protocols interms of water use efficiency in irrigated agriculture. However, all irrigation forms includingSDI purge the soil of air space (and therefore oxygen), during, and following, irrigation events,thereby upsetting root function and reducing crop performance. This is particularly so for SDIaround the root zone. Replaced by water, which quickly is depleted of its oxygen throughmicrobial and root demands, the temporal lack of soil air ironically constrains water andnutrient uptake. We will present data that shows that when oxygation of the irrigation flow isachieved, it provides a source of air and therefore oxygen in a root environment that suffersfrom temporal hypoxia, and occasionally from anoxia. This is especially so in heavier soils,but we have found benefits on a range of soil types. The oxygen is introduced into theirrigation stream by way of the venturi principle, or with solutions of hydrogen peroxide.Oxygation leads to enhanced yield and water use efficiency under these previouslyunrecognised temporal hypoxic conditions. What is surprising, yet logical, is that oxygationalso improves plant performance and yield at irrigation rates previously considered to beoptimal for crop growth. SDI alone can reduce water losses due to drainage, it can containrising water tables, and it can reduce demand by agriculture for irrigation water, and oxygationimproves on all of these parameters. On top of this, oxygation has been shown by ourselvesto counteract some of the negative effects of salinity and saline irrigation water.Our data suggest that oxygation will allow for the considerable increases in yieldnecessary to keep pace with future food and fibre demands, which, with increased water useefficiency could leave more water for the environment.