UC scientists presented recent additions to the growing body of research on conservation tillage in California at the second annual Twilight Conservation Tillage and Cropping Systems field day Sept. 8, demonstrating progress in agricultural systems that will help farmers cut production costs, reduce soil disturbance and save water.
UC scientists and their partner farmers are conducting research that address the current needs of the San Joaquin Valley agricultural industry and research that is looking to the future by anticipating changes that may need to be negotiated in coming decades.
During the field day at UC's West Side Research and Extension Center in Five Points, Calif., participants visited two primary research areas. The first is the longest-standing conservation ag system study in California, where a cotton/tomato rotation has been farmed for 12 years running. The plots include standard tillage with and without cover crops and conservation tillage with and without cover crops.
“This might be the most-visited research field in California,” said Jeff Mitchell, UC Cooperative Extension vegetable crops specialist and chair of the CT workgroup. “Many students and scientists have conducted research here.”
For example, scientists have been able to quantify significant improvements in soil quality with the use of cover crops and conservation tillage. UC Davis soil biochemist Will Horwath reported that conservation tillage combined with an off-season cover crop has increased the soil carbon content close to five tons per hectare.
“Is that significant?” Horwath asks. “Yes. In 10 years, we have almost doubled the soil carbon content.”
Because of the valley’s dry, hot climate, the native soils are typically very low in carbon, which is a characteristic of low soil quality. Carbon in the soil acts as a glue, helping reduce wind erosion.
“There are more than 17,000 center pivots in the state of Nebraska, and it is estimated that there are somewhere between 300 and 500 pivots currently in use in California, the No. 1 ag state in the nation,” Mitchell said. “This situation is changing rapidly.”
Overhead irrigation is efficient, automated, allows for diverse cropping and, with soil residues from conservation tillage, permits uniform infiltration.
Four users of overhead irrigation shared their experiences with overhead irrigation at the field day. West side farmer John Deiner said mechanized irrigation has significantly reduced labor input in his agronomic crops while boosting crop yields.
“Our corn grew two to three feet taller under the pivot,” he said.
Will Taylor of King City grows potatoes for In and Out Burger under center pivots. He said his yields are 20 percent higher when using the overhead irrigation system.
“Once you overcome challenges,” Taylor said, “they’re awesome.”
He demonstrated their ease of use by bringing along his 9-year-old son Liam, whom he said can already manage the machine.
Darryl Cordova of Denair uses overhead irrigation in a hilly area on the east side of the valley.
“What used to take three guys six hours of moving pipe is now done with a push of a button on my cell phone,” Cordova said.
Scott Schmidt, who farms across the street from the West Side Research and Extension Center, said he has learned how to successfully use overhead irrigation and conservation tillage from the “school of hard knocks.”
“Most of the problems have been self-inflicted wounds,” Schmidt said. But now, he calls the system “flawless.” “We have seven pivots that I operate remotely from my phone.”
The Conservation Tillage and Cropping Systems Workgroup has launched a new radio podcast to provide farmers information about adopting conservation tillage techniques at their operations.
After 10 years of experimentation, researchers at the University of California’s Westside Research and Extension Center in Five Points, Calif. have worked out a number of the “kinks” in conservation tillage (CT) practices for cotton and tomato rotations.
“Completely new crop production paradigms pose inherent challenges and risk and the adoption of these new systems is not easy,” reports UC Davis research team leader Jeff Mitchell.
The team, composed of Will Horwath, Karen Klonsky, Wes Wallender and Randy Southard out of UCD, Dan Munk and Kurt Hembree out of local Fresno County Cooperative Extension office, and Anil Shrestha from Fresno State, has made steady progress over the years and their research is now shedding light on a number of promising practices for these two stalwart San Joaquin Valley (SJV) crops.
The first few years of the team’s work in CT farming systems weren’t too encouraging. The standard tillage methods initially were better in terms of yield. Mitchell and colleagues, however, didn’t become discouraged as they knew that conservation tillage has been used in other parts of the country – mainly in the Midwest and Southeast – with success and yields comparable to those achieved using conventional, intensive tillage. However, these areas of the U.S. traditionally experienced much soil erosion due to a lack of protective soil cover during their rainy, establishment period for their crops. The cropland in the San Joaquin Valley is much different from that of the Midwest and Southeastern U.S. It has generally been leveled for surface irrigation and concerns about soil erosion have not been a major driver for conservation tillage practices in the SJV. In recent years, however, increased fuel prices, labor needs and dust regulations have provided the incentives for renewed interest in conservation tillage.
A variety of “minimum tillage” approaches that put together various tillage operations – such as ripping, disking and ring-rolling – are now being widely used throughout the central SJV, according to Mitchell. These approaches, however, simply rely on combining tillage passes and do not necessarily reduce the overall volume of soil that is disturbed. There have been no cropping systems developed and used in the SJV to evaluate the capability of the more classic forms of CT management, such as no-tillage and strip-tillage to further reduce production costs or to increase soil carbon sequestration over time, as has been reported in other regions where these more severe forms of CT are used.
Additionally, because successful CT systems such as no-till and strip-till have been widely used in other parts of the country for a number of the crops commonly produced in the SJV, the research team reasoned that the principles of conservation tillage should work here as well. Most CT is currently employed in production regions with higher rainfall or with growing-season precipitation. The semi-arid SJV annually receives only about 7 inches of rainfall and thus agriculture relies largely on surface or gravity irrigation. Surface irrigation would likely be more difficult across or through residues that tend to accumulate in CT fields and this has been one of the things studied by the team.
The long-term tillage systems work of this team began in 1999 to evaluate CT tomato and cotton systems with and without winter cover crops. It has evaluated impacts of these practices on yield, production costs and soil carbon. The first four years of cover crops didn’t see any increase in total soil carbon, but rather, a shift in the distribution of the carbon throughout the profile was detected. The amount of carbon in the topsoil (0-6”) increased and the carbon in the subsoil (6”-12”) decreased. However, after eight years of following these four systems, the conservation tillage with cover crop (CTCC) had significantly more organic matter and the standard tillage without a cover crop (STNO) – the type that is most used in the San Joaquin Valley – had the lowest amount.
For the first year, the cover crops were irrigated up, but after that, they relied on winter rainfall for moisture and, as could be predicted, the amount of cover crop biomass produced and surface residue generated covered a greater percent of the area with greater rainfall. The conservation tillage plots had 10 times the ground covered than the standard tillage plots.
Yields for tomatoes after the first two establishment years of the CT systems were almost 10 percent higher than the standard tillage system and the cover crop systems were almost 6 percent than the non-cover crop systems. The tomato yields were comparable to the typical yields (9-year average = 36.8 tons/ac) in Fresno County. Cotton production, however, presented a different story. In the last four years of the continuing conservation tillage and cover crop study, the cotton yields were not significantly different between the standard tillage method and the conservation tillage method, but earlier in the study, difficulties with cotton stand establishment resulted in generally lower cotton yields in the CT systems.
About half the number of tillage passes were used in the CT systems relative to the standard till practices. For tomatoes without a cover crop, tillage passes went from 19 to 11. For cotton, tillage passes went from 19 for the standard tillage down to 11 using CT. That’s almost a 50 percent reduction of tillage passes for tomatoes and a 40 percent reduction in cotton.
There are many benefits that may be gained from both conservation tillage and cover cropping and a growing number of Valley farmers are now beginning to develop successful systems using these practices at a commercial scale. More information on this research and these systems is available at the Conservation Tillage and Cropping Systems Workgroup’s website at http://ucanr.org/ct.
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.
Discussions have been initiated toward the formation of the California Overhead Irrigation Alliance. The alliance will be a diverse group of farmers, private sector representatives, university and other agency folks interested in developing and extending information on overhead, mechanized irrigation systems here in California. The group will hold a “founders’ meeting” on Friday, Oct. 1, in Five Points.
Because of the obvious connections and possible benefits of merging or coupling overhead mechanized irrigation with conservation tillage crop production approaches, it makes good sense for the Conservation Tillage and Cropping Systems Workgroup to be involved with this emerging initiative.
"It remains to be seen what form a partnership between the workgroup and the alliance might take, but as options become clearer and more focused, I’ll try to pass on additional information on what is being considered so that we might discuss things together," said Jeff Mitchell, the Conservation Tillage and Cropping Systems Workgroup chair.
Several UC scientists are already involved in overhead mechanized irrigation research and extension efforts at the UC West Side Research and Extension Center, but if others are interested in learning more about this overall endeavor or our ongoing work in this arena, please call Mitchell at (559) 303-9689.