Monday, November 13, 2006

Lysimeter and Surface Renewal Estimates of Forage ET under Saline Irrigation.

Sharon E. Benes1, Stephen Grattan2, Diganta Adhikari3, and Richard Snyder2. (1) California State Univ, Dept of Plant Science, M/S AS72, 2415 E San Ramon Ave, Fresno, CA 93740-8033, (2) Univ of California, LAWR Dept, Co-Op Ext, Davis, CA 95616, (3) Center for Irrigation Technology, California State University, 5370 N Chestnut Ave, M/S OF18, Fresno, CA 93740

Water use (ET) of three salt tolerant forages, tall wheatgrass (TWG, Thinopyrum ponticum var. ‘Jose’), creeping wildrye (CWR, Leymus triticoides var. ‘Rio’), and Paspalum (PASP, Paspalum vaginatum var. ‘SeaIsle 1’) was measured under irrigation with saline-sodic drainage water from the westside San Joaquin Valley of California. These forages are top candidates for drainage water re-use systems being developed for salinity and drainage management in this area.  The forages were grown in sand-filled, drainage lysimeters consisting of lined, sunken basins (1.3 m square) and irrigated with saline-sodic drainage water (ECw= 13.1dS/m, SAR= 23 and B= 20.0 mg/L). Cumulative ET (Jan. to Dec., 2005; 343 days) was 1470, 1376, and 1275 mm for TWG, CWR, and PASP, respectively.  Reference ET (CIMIS105) for the same period was 1500 mm resulting in Kc’s of 0.98, 0.92, and 0.85 for these forages, respectively.  Average daily ET in the summer was 7.95, 8.24, and 7.36 mm/day for TWG, CWR, and PASP, respectively which was equal to, or higher, than the reference ET of 7.37 mm/day for the same period.  Surface renewal (SR) ET stations were also used to verify the ET estimates for TWG.  Kc’s from the SR estimates will be presented for this forage.  The high ET maintained by these forages under saline irrigation indicates a high degree of salt tolerance and the ability to consume saline drainage water which is desirable for drainage water re-use systems.