Saturday, 15 July 2006

Impact of Air-jection™ on Yield and Quality of Vegetables Grown in California.

Dave Goorahoo1, Diganta Adhikari1, David Zoldoske1, Angelo Mazzei2, and Richard Fannuchi3. (1) California State Univ-Fresno, Center for Irrigation Technology, 5370 N. Chestnut Ave. M/s Of18, Fresno, CA 93740-8021, (2) Mazzei Injector Corporation, 500 Rooster Drive, Bakersfield, CA 93307, (3) Mazzei Injector Corporation,, 500 Rooster Drive, Bakersfield, CA 93307

The concept of aerating the sub surface drip irrigation (SDI) water- referred to as Air-jection™- increases the potential for the air to travel with water movement within the root zone. Physical, chemical, and biological soil characteristics that influence crop growth and yield depend on the relative proportions of the liquid and gas phases within the root zone. The findings of a pilot study conducted in 2000 at the Center for Irrigation Technology (CIT) in California, in which air was injected into the root zone of bell peppers via the Subsurface Drip Irrigation (SDI) system justified follow-up fieldwork on larger plots approaching commercial scale. In this presentation, we review the current research aimed at evaluating the technical and economic feasibility of air injection into a SDI as a best management practice for fresh-market tomato, melon, bell pepper and broccoli production. Through work in other areas, the Mazzei® Corporation has developed high efficiency venturi injectors capable of aerating water with fine air bubbles. The combination of the venturi system with SDI has been patented as Air-jection™. In 2000, a pilot study was conducted at CIT using the Air-jection™ technology on bell peppers. In the study an increase of 33% in bell pepper count, and a 39% increase in bell pepper weight was noted for the aerated plots versus the plots receiving only water. When the roots were examined, there was a significant difference between the root weight to total plant weight ratios for the aerated plants and the non-aerated plants. Since the 2000 small scale study, CIT researchers have been working with commercial vegetable growers in evaluating the feasibility of Air-jection™ in crop production. In Fall 2003, in comparative tests between air injection and water only treated melons (honey dews) on 13acres plots with a drip tape run length of over 400m there was a 14% increase in the number of melons and, a 16% increase in the weight of melons harvested due to air injection. These figures translate into a projected increase of $260 to $350 per acre for the farmer depending on the wholesale price of melons, which can range from $3 to $4 per box. In Summer 2004, for cantaloupes grown on 20-acre plots, there was a 13% increase in the number of melons and, a 18% increase in the weight of melons harvested due to air injection. Data collected for the other crops are still currently being analyzed. Generally, so far we have found that the incorporation of high efficiency venturi injectors in SDI systems increased root zone aeration and can add value to grower investments in SDI. In addition to our research in the San Joaquin Valley (SJV) in California, similar work is being conducted by scientists in Australia, where the concept has been referred to as oxygation, and in Germany. Also, a number of small scale strawberry and cucumber farmers in Japan have being using the Air-jection™ technology in greenhouses. Hence, it is obvious that the issue of aeration of subsurface irrigation water- Air-jection™- is of interest worldwide as growers continue to look for ways to optimize crop production and water use efficiency. Keywords: Air-jection; Oxygation; sub-surface drip irrigation; water use efficiency; root zone aeration.

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