- Author: Michelle Leinfelder-Miles
- Author: Brenna Aegerter
Blue-green algae, or cyanobacteria, is a photosynthetic organism that can proliferate, or “bloom”, in waters that are warm and stagnant. It is a concern for human and animal health because it can produce toxins that cause nerve and liver damage. Blue-green algae has been in the news recently. In mid-July, residents of Discovery Bay reported seeing it in the waters of that community. More recently, it has been observed in other Delta waters. While the presence of blue-green algae does not guarantee the presence of toxins, the water around Discovery Bay was tested and confirmed to have the toxin microcystin, and the public has been advised not to enter waters where blue-green algae blooms are observed. Blue-green algae affected waters appear as olive-colored, have surface scums or the appearance of oil slicks, or have green flecks of material. The waters may also have a musty odor.
I was recently asked by a grower if irrigating with water having blue-green algae can damage crops. I have not been able to find much local or statewide knowledge on this, but I have found some pamphlets out of Australia that address this question. I have attached those documents below. Both documents indicate that there is more to learn about whether irrigation water having blue-green algae will affect plants. If there are detrimental effects, they would mostly likely reduce germination or seedling growth, which could ultimately reduce productivity. Another concern for growers is that the blue-green algae could clog irrigation equipment and reduce its efficiency. Because blue-green algae toxins are heat-stabile, it is advised not to use overhead irrigation on crops that are eaten directly, and it is advised that animals not be put on grazed crops (where irrigation water may have touched foliage) for at least seven days after irrigating. The toxins are water soluble, so advice for consumers is to thoroughly wash produce with clean water before consuming, whether eating it raw or cooked.
Luckily, the blue-green algae population should decrease as winter approaches and the weather (and waters) cool down. In the meantime, the State Water Resources Control Board has developed a website (http://www.mywaterquality.ca.gov/habs/index.html ) where the public can see where blue-green algae blooms have been verified and report a bloom that has been encountered. In addition to the website, bloom reporting and information is available by phone (916-341-5357 or toll free at 844-729-6466) or email (CyanoHAB.Reports@waterboards.ca.gov).
- Author: Michelle Leinfelder-Miles
I was speaking with a colleague a few weeks ago about field drainage in the Delta. Our conversation reminded me of a farm visit that I made a couple of years ago. I visited a corn field that was not growing well, and sections of the field had standing water. I consulted with UC Water Management Specialist Emeritus, Terry Prichard, on what this grower could do to improve drainage. I wondered about installing drainage tiles. The irrigation specialist did not recommend installing drainage tiles in the Delta. The high organic matter soils are so fine that the perforations in the tile just plug up. He also did not recommend a deep plow because some Delta soils have a layer of “blue clay.” It is not actually clay but it is anaerobic soil (which is what makes it blue) that has never been near the surface. The irrigation specialist had once visited a field that had been deep plowed and brought up blue clay. The field became completely unmanageable.
What the irrigation specialist did recommend was to dig 4-foot (deep) drain ditches. These would run parallel to the furrows and should be about 500 feet apart. These ditches would connect to another ditch that runs to the main drain of the island. These dimensions are not a prescription for all Delta sites, but they could give landowners a general guide for managing drainage, and in the case of the corn field I visited, make wet fields farmable. Each 4-foot ditch will result in about 10 feet of “wasted” (non-farmed) space, but having these ditches (and keeping them clean) is the only way to get the water out of the soil profile and off the field.
Before any effort is put into digging ditches, it would probably be beneficial, particularly for new landowners, to see from an internet mapping interface if there are any lines in their fields that would indicate past ditches or different soil types. If previous landowners leveled the land, they may have filled in drainage ditches.