[Enviro-lunch] Thursday 5/2: Hanna Ouaknin

[Jing Yan]

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Hello Everyone,
Please join us on May 2nd for this week's Enviro-Lunch talk by Hanna Ouaknin from UC Davis at 12-1pm in room SE2-224.

Irrigation and Nitrogen Management, Monitoring, and Assessment to Improve Almond Production While Minimizing Nitrate Leaching to Groundwater

[WhatsApp Image 2019-04-25 at 11.10.19 AM]

Abstract: Offsite transport of reactive nitrogen (N) in the forms of NH4+, NO3-, NH3, NOx and N2O from agriculture is facing increased regulatory scrutiny due to air quality, climate, and drinking water quality impacts. Thus, one critical challenge facing California almond growers is what causes and what can reduce offsite reactive N loss and improve Nitrogen Use Efficiency (NUE).
While, NUE defined as N assimilated by the tree as a percent of applied N plus mobilized reactive N (N2O and NO3-).

The project provides the first comprehensive assessment of groundwater nitrate impact from a best practice (HFLC) and the first side-by-side comparison of three monitoring approaches to assess nitrate impact to groundwater: (1) Groundwater monitoring is the regulatory gold standard to assess pollution sources, but is expensive. The well impact occurs delayed, 2 to 4 years after discharge. (2) Vadose zone monitoring provides immediate feedback on potential groundwater nitrate discharge but can be labor-intensive. (3) The NUE or nitrogen balance is a tool familiar to growers under the ILRP but its relationship to actual groundwater nitrate discharge is poorly understood.  This project demonstrates the link between WUE and NUE, vadose zone water quality observations, and groundwater nitrate while demonstrating the sustainability benefit of HFLC.
A commercial 150 acre almond orchard west of Modesto, overlying the Central Valley unconfined aquifer system, was equipped for HFLC (10 - 15 fertigation events with nitrogen added during the middle third of the irrigation cycle), and a comprehensive high-resolution nitrogen monitoring system was installed in 2016/2017. The monitoring system consists of three separate elements: monitoring equipment to measure water and nitrogen application rates, ET, and harvest N removal (orchard water and N mass balance); 7 replicate multi-level, multi-instrumental vadose zone monitoring sites (water, nitrate, and ammonium fluxes and storage at 0-10 ft depth); and 20 groundwater monitoring wells (screened at 20 - 40 ft below ground surface, in first encountered groundwater).  This monitoring system allows for detailed assessment and comparison of the three independent methods that are used to estimate nitrate leaching to groundwater.

Bio: Hanna Ouaknin currently is a postdoctoral research associate at the Department of Land, Air and Water Resources at the University of California, Davis. She holds a BSc and PhD in environmental engineering earned from the Technion - Israel Institute of Technology, on the topic "The effect of layered soil on nitrification processes".

When: Thursday 5/2, 12pm - 1pm

Where: SE2-224

Coffee will be provided, please bring your own mugs.

We look forward to seeing you,

Jing & Jennifer

Organizers for Spring 2019: Jing Yan and Jennifer Alvarez
Faculty coordinator: Asmeret Asefaw Berhe

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