Importance of Soil Health
Soil health is a well-known topic in the irrigation world, with new research bringing to light the importance of irrigation on soil health. This research has shown that the importance of creating a hospitable environment for the many microbes that enable the growth of the plant, is key.
The research showed that aerating irrigation water promotes a shift toward bacteria that convert's ammonia into plant-available nitrate.
The Science Behind it All
Dr Goorahoo and his colleagues studied clay soils from a vegetable field in California, in the state’s highly fertile Central Valley. Treated soils had been irrigated for five years with subsurface drip tape that was aerated with Venturi injectors. The injectors use the flow of irrigation water to draw in air and mix it with the flow to form what Dr Goorahoo describes as “an air/water slurry.” Untreated soils on the same farm were irrigated through subsurface drip tape without the injectors.
Using sophisticated DNA analysis techniques, the research team measured the balance of nine genes in the soil samples, each associated with a specific type of bacterium or Archaea fungus. The soil irrigated with aerated water had a higher proportion of bacteria known to fix nitrogen in the soil into a form usable by crops, while the un-aerated plots had a higher ratio of nitrate-reducing bacteria that convert nitrite into nitrous oxide (N2O)–a potent greenhouse gas–and NOx compounds.
The presence of more plant-available nitrate in the root zone as well as healthier roots to channel it into the plant is likely to improve nutrient use efficiency (NUE) and reduce nitrate leaching, Goorahoo added.
Proof is in the Yield
In 2013, Dr Goorahoo addressed an Irrigation Association conference with results from eight years of field trials on a large produce farm with 1,500 acres of AirJection-equipped buried drip systems. A 2008 paper Dr Goorahoo presented to the association highlighted yield increases in California coastal strawberries of 18.3 percent #1-grade fruit and 6.9 percent of #2-grade fruit in aerated plots, in addition to larger root systems in aerated peppers and increases in the size and weight of aerated cantaloupes. In another California study, tomato yields rose 21 percent with aerated irrigation water in normal soils and 38 percent in saline soil.
Dr. Srikanth Pathapati, from Mazzei Injector Company, who design and manucaturfe the Venturi injectors had this to say:
We design, model and precisely construct our injectors to optimize not only how much air the injector can pull in, but how effectively it can shear the bubbles. That shearing action thoroughly mixes the gas and liquid so the irrigation system can deliver water with high levels of dissolved oxygen rather than just entrained bubbles. Design, materials and quality control are extremely important to getting a high-quality injector.
Dr Goorahoo stated aerated irrigation water’s impacts on soil microbial activity, crop performance in saline soils, rooting characteristics of various crops, pest resistance, nutrient use efficiency and water use efficiency are all areas ripe for exploration.
In the meantime, he noted, “Venturi injectors can increase root zone aeration and add value to growers’ investment in SDI (sub-surface drip irrigation)”–important news for irrigation suppliers and farmers facing the current challenging agricultural economy.
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