Tuesday, November 14, 2006

Vadose Zone Monitoring of Fields Irrigated with Winery Stillage.

Diganta Adhikari, Dave Goorahoo, and Florence Cassel S. Center for Irrigation Technology, Fresno, CA 93740

Irrigation of fields with recycled water allows for the beneficial reuse of nutrients and water, while utilizing the soil profile to treat the recycled water and prevent degradation of groundwater. However, some constituents present in the recycled water may pass through the soil profile and detrimentally impact groundwater. The objective of our current work with the City of Fresno's Public Utilities was to collect soil water (vadose zone) samples at 60cm and 120cm depths at the disposal areas and evaluate the concentrations of chemical constituents in those samples. Analysis of soil solution samples collected from fields indicated that Total dissolved (TDS) and suspended (TSS) solids, nitrate-N (NO3-N) and ammonium-N (NH4-N) loadings were very high and variable among beds. NH4-N concentrations were relatively low in most samples. NO3-N levels were less than 1 mg L-1 in many beds. The 2nd phase of the research currently in progress, involves the monitoring of solution and soil within the top four feet of fields planted with two forages- Sudan grass and Elephant grass in an effort to evaluating the scavenging ability of these grasses. Results to date indicate that both grasses helped in salt removal. Generally, the Elephant grass showed better capability with salt, removal throughout the 120cm profile, while the Sudan grass decreased salinity mostly in top 30cm of the profile.