Location: Water Quality and Ecology Research
Project Number: 6060-13660-009-029-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Mar 1, 2024
End Date: Dec 31, 2024
Objective:
1. Sample irrigation water throughout the growing season and at farms across the Delta utilizing both surface and groundwater to capture the spatial and temporal variability of irrigation events. Samples will be measured for micro and macro nutrients in water, as well as pH, conductivity, dissolved oxygen (DO), and temperature to determine water quality at the time of irrigation application in soybean fields.
2. Evaluate the variability in water quality and identify potential components or concentration levels that may be detrimental to soybean growth based on the literature.
3. Conduct saturated paste tests of soils at each farm with irrigation water at the beginning and end of the growing season to determine changes in dissolved nutrients, metals, and salts. Evaluate soil physical, chemical and biological properties in irrigated and non-irrigated soils at study sites.
4. Collect yield data from participating farms to evaluate relationships between source water type and yield.
Approach:
Irrigation water will be sampled at working farms throughout the growing season. Farms utilize groundwater for some of their farmland, have tailwater recovery systems, and some sites also draw from surface water for irrigation. A minimum of 3 irrigation events per sampling site will be sampled – one at the beginning of the growing season, one in the middle, and one near the end. Proposed locations overlap with USDA-ARS study sites where auxiliary data has been previously collected and analyzed. Samples will be collected, placed on wet ice, and immediately transported to the USDA-ARS National Sedimentation Laboratory for analysis. Samples will be analyzed for total, dissolved, and suspended solids (TS, DS, SS, respectively), total dissolved organic carbon (TDOC), nitrate (NO3), nitrite (NO2), ammonium (NH4), orthophosphate (PO4; also known as soluble reactive phosphorus), total nitrogen (TKN), and total phosphorus (TP) according to standard methodology using a FIALab flow injection analyzer. A Perkin Elmer Optima 8000 Inductively Coupled Plasma (ICP) Mass Spectrometer using both universal extractants Mehlich III and calcium chloride (CaCl2) will be utilized to determine potassium (K), magnesium (Mg), manganese (Mn), iron (Fe), aluminum (Al), copper (Cu), zinc (Zn), and P concentrations. Dissolved oxygen, pH, temperature, and conductivity will be measured in-situ at each site collection. Fields will be identified that rely on a solitary source of irrigation water (e.g. groundwater vs. surface water). Soil samples will be collected from the top 0-6 inches within a 2m2 area to create triplicate composite samples.
To relate the water and soil quality results to yield, we will compile yield data from the sampled fields and create a database to link irrigation water quality, water source, soil characteristics, and yield. We will focus on fields that are irrigated with one source only. While there are many factors that affect yield, this database will allow for exploration of factors related to soybean yield and can be expanded over time to improve understanding of the link between irrigation water quality and soybean yield.
