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UC researchers collaborate to help rice farmers manage drought, pests, other challenges

New rice crop rotation calculator helps California farmers evaluate financial viability
New rice crop rotation calculator helps California farmers evaluate financial viability

Thanks to a partnership of UC Agriculture and Natural Resources, UC Integrated Pest Management (IPM) and UC Davis researchers, rice growers have a new tool that could potentially help address droughts and other environmental and socioeconomic changes.

A crop rotation calculator provides farmers in the Sacramento Valley – where 97% of California rice is grown – with projections on the economic impacts of transitioning their fields from rice into four less water-intensive crops: dry beans, safflower, sunflower or tomato. The tool gives growers much-needed, science-backed data on whether the practice would make financial sense for their farms.

“I believe more rice growers could benefit from the many advantages of crop rotation, and this new tool is an excellent first step by the UC to help growers look into making such a transition,” said George Tibbitts, a Colusa County rice farmer.

Funded in part by the USDA National Institute of Food and Agriculture, through the Western Integrated Pest Management Center, the calculator fills a major gap in rice research.

“I do think there are people who would have tried rotational crops in the past, but it's just so unknown, we didn't have anything definitive we could give them,'” said Whitney Brim-DeForest, UC Cooperative Extension rice advisor. “This tool gives them preliminary data they can use to make a more informed decision.”


Crop rotation a potential boon to growers, environment

UC Davis doctoral student Sara Rosenberg, UC Davis associate professor of plant sciences Cameron Pittelkow, and Brim-DeForest, along with other members of the UC rice research team, surveyed California rice growers in 2020 on their experiences with and perceptions of crop rotation. Although the practice is rare in the Sacramento Valley (with only an estimated 10% of rice acreage under rotation), some farmers reported benefits that could be crucial in a water-scarce future.

The survey, funded by the Rice Research Board, gave rise to the idea to partner with other experts to develop the calculator as a decision support tool. UC Cooperative Extension Specialist Ellen Bruno joined the collaboration to assist in building the model, and IPM professionals provided their experience to design both the front and back ends of the calculator. “They really brought the vision that we had to fruition,” said Brim De-Forest.

The calculator helps growers determine if rotation can be another option in their “toolbox” of strategies to manage fertilizer price shocks, herbicide resistance and drought. “One of the biggest benefits growers who do rotate describe is their flexibility in times of drought, where they can keep producing on their land when there isn't enough water to grow rice,” Rosenberg said.

According to Brim-DeForest, rotating cropping systems also can allow for the use of different weed control tools, such as different herbicide modes of action, and different cultural controls such as tillage, reducing the chances of selecting for herbicide-resistant weeds – an increasingly pervasive issue in rice systems.

Rosenberg noted that, in some situations – and depending on the crops in rotation – the practice can also disrupt the life cycles of insects and diseases and potentially improve soil structure and increase nutrient cycling and uptake, which may lead to a reduction in inputs such as fertilizer.

The benefits of crop rotation for California rice growers are largely theoretical and anecdotal, however, so the UC rice team is looking to add evidence-based grounding through a variety of studies.

“In California, there is no quantitative data on crop rotation in rice,” said Brim-DeForest. “You'd think after a hundred and some odd years (of UC agricultural research), all the research would have been done, but, no – there's tons still to do.”

More studies are needed on crop rotation according to Whitney Brim-DeForest, UCCE rice advisor
More studies are needed on crop rotation according to Whitney Brim-DeForest, UCCE rice advisor

Tool addresses concerns over cost of rotation

Through interviews with Sacramento Valley growers, researchers found that cost was frequently mentioned as a barrier to trying crop rotation, along with incompatible soil conditions and a lack of equipment, knowledge and experience.

“The results from that Rice Research Board-funded survey indicated that economics were a big part of the reason that growers did not crop rotate,” Brim-DeForest said. “The rotation calculator was seen as a way to provide a decision support tool to assist in making an economic decision about rotation.”

To help clarify those uncertainties, the new calculator tool allows growers to enter baseline information specific to their circumstances – whether they rent or own their own land, whether they contract out the work to plant the rotational crop, and other factors. The calculator then generates potential costs and benefits of staying in rice versus rotating to dry beans, safflower, sunflower or tomato, during the first year and in an “average” year for those crops.

The upfront costs of rotation during “year one” can be daunting. Therefore, the tool only focuses on a short-term profitability perspective. Researchers are currently working on longer term modeling for crop rotation – incorporating the possibility of reduced herbicide use over time, and under different crop yield scenarios, for example – that could significantly change the growers’ calculus.


Project grows new partnerships, collaborations

The rice rotation calculator is an evolving tool that will be continually improved based on user feedback and additional data. Brim-DeForest also said that it could be adapted to other cropping systems such as alfalfa going into another rotational crop.

“This was a great project that helped forge new partnerships between several groups of experts who might not have worked together otherwise,” said Brim-DeForest. “Several other collaborative projects have come out of this one and out of the original rice crop rotation tool.”

The rice calculator tool can be found at:

Other contributors to the project include Bruce Linquist, Luis Espino, Kassim Al-Khatib and Michelle Leinfelder-Miles of UCCE; Amanda Crump of UC Davis; as well as UC IPM team members Chinh Lam, Tunyalee Martin and Hanna Zorlu; and the California rice growers and industry members who participated in the research.

The researchers are also studying cover cropping, which may deliver some benefits of diversification, says UC Davis doctoral student Sara Rosenberg
The researchers are also studying cover cropping, which may deliver some benefits of diversification, says UC Davis doctoral student Sara Rosenberg

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