Division of Agriculture and Natural Resources
Division of Agriculture and Natural Resources
Division of Agriculture and Natural Resources
University of California
Division of Agriculture and Natural Resources

Research on irrigation and farming practices

Water use optimized to limit leaching
To control nitrate leaching in lettuce, spinach, broccoli and strawberry fields, Mark Bolda, UC Cooperative Extension advisor in Santa Cruz County; Michael Cahn and Richard Smith, UCCE advisors in Monterey County; and Tim Hartz, UCCE specialist in the department of Plant Sciences at UC Davis, are studying the amount of irrigation water applied. For each crop, the scientists are trying to determine the optimum amount of water the plants need to grow quality produce while limiting leaching. For lettuce, they are improving irrigation efficiency by using evapotranspiration data and soil water-holding properties to calculate an irrigation schedule that will maintain desirable crop yields yet minimize deep water percolation. For more information, read the Irrigation and Nitrogen Management article in the Monterey County newsletter.

Adjusting field length can reduce irrigation levels
In his research on how dairy operators can reduce water applications to their crops, Larry Schwankl, UC Cooperative Extension specialist at Kearney Agricultural Research and Extension Center, has found that allowing less water to percolate will reduce impacts on groundwater. With furrow irrigation, the part of the field closest to the water source tends to be overirrigated by the time a sufficient amount of water reaches the far end of the field. Since dairy farms are irrigated with a mixture of nutrient-rich manure water and irrigation water, the head of the field also gets disproportionately more nitrogen. Using shorter fields, he found, is by far the best way to reduce the amount of water applied. “It’s not inexpensive or easy to make this change,” Schwankl said. “Shorter fields make cultural practices more difficult and land is taken out of production.” However, this change can have a dramatic impact: With shorter furrows, water applied per acre was cut nearly in half. In addition, manure water is often added to fresh water as part of dairy irrigation and fertigation practices, so being able to reduce the applied water also significantly reduces the amount of nitrogen applied. For more information, see Schwankl's Irrigation Management website.

Conservation tillage may help farmers use up more nitrogen on dairies
If dairy farmers were able to grow more silage, they might also be able to have more nitrogen in manure and lagoon water taken up and removed in feed materials. Jeff Mitchell, UC Cooperative Extension specialist at Kearney Agricultural Research and Extension Center, and other researchers have been investigating the feasibility of using conservation tillage planting techniques to shorten the intervals between silage crops and to effectively enable triple-cropping as a means to increase annual feed production and nitrogen removal. For more information, see the UC Conservation Agricultural Systems website.

UC helps dairy industry manage nitrogen on the farm
It is common practice for dairy operators to use cattle manure as fertilizer for their silage crops. UC Cooperative Extension advisors throughout California routinely provide reliable information to dairy operators and consultants so they can efficiently manage nitrogen on the farm and comply with pending state regulations. This information includes how to install and calibrate flow meters, how to measure nitrogen levels in manure ponds, how much nitrogen crops need and when they need it, and how to properly sample the crops that are harvested to know how much nitrogen is being removed. “We’ve developed protocols to ensure accurate information gathering, and we can share these with the dairy industry,” said Carol Frate, UCCE advisor in Tulare County. For more information, contact a county UC Cooperative Extension dairy advisor.

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