- Author: Jeannette E. Warnert
Combining low-pressure, overhead sprinklers with conservation tillage may become the new ag production model for the San Joaquin Valley.
This combination of practices is quite common in many irrigated regions outside of California but are relatively new here in the Golden State. However, they may soon be much more important for California producers based on information presented at an evening field tour held on June 10 in Five Points.
This event was coordinated by the Conservation Tillage and Cropping Systems Workgroup and brought together farmers, leading conservation tillage (CT) researchers, and overhead irrigation industry representatives for the over 100 participants in attendance.
“Conservation tillage” is a type of crop management system - such as no-till and strip-till - that leaves crop residues on top of the soil when going from one crop to the next. CT is also a variety of the other “minimum tillage” approaches that reduce the overall number of tillage passes by at least 40 percent of standard tillage systems.
UC Davis researchers Karen Klonsky and Will Horwath have been evaluating the performance of CT tomato and cotton rotations at the University’s West Side Research and Extension Center in Five Points for over 10 years. Horwath, a soil scientist, reported that following eight years of CT farming, soil carbon in the top foot of soil increased by about 23 percent relative to the conventional, tillage-intensive system. That very roughly equates to a greater than 40 percent increase in organic matter.
This is a significant finding as it is the first such outcome in California coming from a long-term study. Klonsky, an ag economist at Davis, reported that tomato yields were about 9 percent higher in the CT versus standard tillage systems.
During the last five years of the study, there have been no yield differences between the tillage systems in the cotton portion of the rotation. There were some establishment problems early on in the experiment that pushed overall cotton yields to 90 percent of those of the standard tillage systems. Fuel use in CT systems was estimated to be 28 percent less than the conventionally-managed systems.
These findings are important and quite timely for San Joaquin Valley (SJV) producers but their significance may even be greater when these practices are added to center pivots or lateral move irrigation systems. With mechanized irrigation, tillage that is typically needed to create and maintain planting beds and furrows that enable surface irrigation are theoretically no longer required. This merging of CT and overhead irrigation technologies was the focus of the second half of the June 10 twilight information event.
Two overhead irrigation studies are currently underway at the West Side Research and Extension Center. One has compared a wheat/corn rotation under overhead irrigation with a conventional, surface irrigation scheme. UC Davis researcher, Jeff Mitchell, reported using 65 percent less water than furrow irrigation but resulted in similar wheat yields.
UC Davis graduate student Brooks Landers also presented information showing higher application uniformities and less deep percolation losses with the overhead system. Following a number of presentations by overhead irrigation company representatives, participants visited the farms of John Diener and Scott Schmidt.
These farmers have used overhead irrigation for about five years to irrigate wheat, corn, onions, sugar beets, alfalfa, cotton and tomatoes. These two West Side farmers got started with overhead irrigation in 2005 when they traveled to Washington State and to meet with center pivot farmers and overhead irrigation company experts.
After meeting with and learning from two Washington farmers who were managing the irrigation of upwards of 8,000 acres all by themselves using automated overhead systems, both Diener and Schmidt returned to their farms and quickly began developing their overhead irrigation management skills. They now use several 135-acre pivots on their farms.
Diener pointed out the precision application and automation aspects of overhead irrigation that allow him or his manager to run his systems using cell phone control. Schmidt pointed out the fact that overhead irrigation is different since you tend to be dealing with the top 18 or so inches of soil and thus irrigation timing and frequency must be carefully finessed.
For more information on these emerging SJV farming technologies, visit the Conservation Tillage and Cropping Systems Workgroup’s website at http://groups.ucanr.org/ucct/, or call Jeff Mitchell at (559) 303-9689. To become a member of the workgroup and receive periodic updates, e-mail Mitchell at email@example.com.