Over the past few decades, California farmers have steadily improved their water use efficiency (or “crop per drop”). However, the current drought and future climate change provide an imperative for even greater efficiency. Russell Ranch, UC Davis’ sustainable agriculture research facility, helps inform this effort via long-term irrigation field trials. Here are some highlights from this year’s Russell Ranch Field Day (June 8, 2016), themed “Farm Water Management in Times of Scarcity.”
Several Russell Ranch trials focus on subsurface drip irrigation. Surface drip irrigation has taken off in California since 1980, but subsurface drip irrigation (SDI) remains relatively uncommon due to its greater upfront expense and more complicated operation. However, SDI has promise for reducing evaporation and minimizing soil disturbance in crops such as tomatoes, a high-value commodity grown in water-limited areas.
Amelie Gaudin showcased her lab’s Russell Ranch experiment on organic tomato systems, examining effects of SDI on soil health. Her preliminary results show that SDI (compared to furrow irrigation) has so far maintained high tomato yields while reducing weed pressure, but it also seems to reduce soil aggregate size, which may pose a concern for long-term C storage.
Dan Putnam and others described their long-term study of SDI in alfalfa at Russell Ranch. Currently, SDI is used in less than 2% of alfalfa acreage, but this trial suggests that SDI may deserve wider adoption: not only does it increase water use efficiency, it can even increase total alfalfa yields due to more uniform soil wetting and better weed control. However, alfalfa SDI systems face a big problem from a small pest: pocket gophers love to make their homes in alfalfa fields, and they readily chew through the underground plastic tubing. (Field day attendees witnessed several puddles caused by gopher damage.)
A key step in irrigating efficiently is knowing how much water the crop needs to keep up with evapotranspiration (ET). Many California farmers schedule irrigation according to real-time ET data from their nearest CIMIS weather station. Data from a farmer’s own field can be considerably more accurate, but on-farm ET measurements are too costly for most farmers. A new technology called surface renewal (developed by the Hub’s own Andrew McElrone and others) may help change this. These lower-cost ET sensors, now commercialized by Tule Technologies, are on display at the Russell Ranch alfalfa trial.
These are only a few examples of the research presented at the 2016 Russell Ranch field day. Other researchers discussed the water-energy nexus in the context of groundwater well pumps; remote sensing of crop water stress; and creating soil maps to inform groundwater recharge. The Climate Hub aims to keep up with these innovations and help get the word out to farmers who are dealing with climate variability and change on the ground.
All photos by Amber Kerr.