Wednesday, November 7, 2007
307-11

Effect of Amendments on Hydraulic Properties of Soils Irrigated with Saline-Sodic Drainage Water: Methodology and Preliminary Results.

Vijayasatya Chaganti, Dave Goorahoo, Sharon Benes, and Diganta Adhikari. California State University-Fresno, Dept of Plant Science, 2415 E San Ramon Ave, Fresno, CA 93740-8033

Re-use of saline-sodic drainage water (DW) for the irrigation of salt tolerant forages and row crops is an important tool for salinity and drainage management on the Westside San Joaquin Valley of California. The sodic nature of this DW can cause clay dispersion and reduced infiltration of water into soils. Proper irrigation management and on-going soil reclamation are needed to ensure the sustainability of these DW re-use systems now called Integrated On-Farm Drainage Management (IFDM). The objectives of this study are to characterize soil hydraulic properties in three stages of the IFDM operating at Red Rock Ranch and assess the reclamation potential of gypsum, sulfur, and poultry manure. Soils in Stage 1 are freshwater-irrigated while those in Stages 3 and 4 are highly dispersed due to 7 years of irrigation with DW averaging 11.7 and 12.9 dS/m ECw, respectively. A split plot design with soil amendment as the main plot factor and salinity of the infiltrating water (0.5 dS/m, 6 dS/m, and 12 dS/m) as the sub-plot factor was used. The three soil amendment treatments (gypsum and poultry manure at 10 ton/acre and sulfur at 2 ton/acre, applied twice yearly) and a non-amended control were assigned to 1 m2 plots and replicated three times. Infiltration is measured twice a year with Decagon “mini-disk infiltrometers” at three suctions (0.5, 2 and 6 cm) which represent different soil tensions. Initial infiltration data (Nov. 06) and those collected in June 2007 after the first amendment application (Dec. 06) will be presented.