Tuesday, November 6, 2007
194-11

Assessing Nitrogen Rates for Organic Bell Pepper Production Subjected to AirjectionŽ Irrigation.

Namratha Reddy1, Dave Goorahoo1, and Diganta Adhikari2. (1) Department of Plant Science, California State University-Fresno, 2415 E San Ramon Ave, M/S AS 72, Fresno, CA 93740-8033, (2) Center for Irrigation Technology, California State University-Fresno, 5370 N Chestnut Avenue, Fresno, CA 93740

Evaluating the impact of air via subsurface drip irrigation (SDI) system through the incorporation of high efficiency venturi injectors, referred to as AirJection® Irrigation, has been the focus of our research over the past five years. Our major objective has been to assess the technical and economic feasibility of AirJection® Irrigation as a best management practice for various crops in the San Joaquin Valley (SJV). For conventional cropping systems, we have found that AirJection® Irrigation can increase root zone aeration and add value to grower investments in SDI.  In this phase of the research, we are assessing the impact of four nitrogen (N) rates on the yield and quality of organic Bell Peppers subjected to AirJection® irrigation.  This study is being conducted in an organic plot at CSU-Fresno Agricultural Laboratory (UAL) on beds that are 5ft wide and 50ft long. The experiment is a split plot design comprising of 8beds representing 4 replications of air-injected and no-air treatments (control) as the main treatment, and N rates as subplot treatment.  Four rates of nitrogen ranging from 30, 60, 90 and 120 lbs/acre were applied as commercially available organic fertilizer (12-0-0) derived from feather meal.  Currently, the crop has been established and a number of soil and plant characteristics are being monitored. For example at 59 days after transplanting (DAT), both AirJection® Irrigation and N rate had a significant effect (P<0.05) on transpiration rate and water use efficiency (WUE). Nitrogen rate had a significant effect (P<0.05) on photosynthesis rate and stomatal conductance. Additional photosynthesis, transpiration rates, WUE, and in-situ soil respiration measurements will be determined at approximately 66, 72, and 80 DAT. Soil samples taken before and after the cropping season will be used to assess the impact of AirJection® Irrigation on soil fertility. Yield data, tissue analysis, and plant biomass data will also be presented.

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