The researchers found that hemp appeared to be resilient to deficit irrigation, a method of conserving water by using less than what might be considered optimal for maintaining rapid growth (all photos courtesy of B. Hutmacher ).
UCCE and UC Davis research efforts to understand the opportunities and challenges for industrial hemp production in California are increasing.
Since this is a relatively new crop to California breeders and researchers, there is still much to learn about variety selection, the differences between varieties and crops in regions with different soils and climates, best practices for nutrient management, and problems with pests and diseases .
At the university, field research into industrial hemp began in 2019 after the previous year’s Farm Bill declared that the crop should no longer be viewed as a controlled substance but as an agricultural good. Hemp is valued for its fiber and edible seeds; However, in California, it is believed that producing hemp primarily for essential oils, including medicinal cannabidiol (CBD), offers the best economic outlook. The hemp acreage in the US and California rose sharply in 2019 but declined in 2020.
Study on the use of hemp water is expanded
In a study coordinated by Jeff Steiner of the Global Hemp Innovation Center at Oregon State University (OSU), drip irrigation trials are underway in California, Oregon, and Colorado. The research was conducted at the UC West Side Research and Extension Center in Five Points and the UC Davis campus in addition to three locations in Oregon in 2020, with an additional location in Colorado in 2021. These studies were conducted to determine water usage of industrial hemp for CBD production under irrigation regimes ranging from about 40% to 100% of the plants’ estimated water needs, with comparisons of the responses observed at the five sites with different soils, climates and other environmental conditions.
The USDA-OSU-funded study includes photoperiod-sensitive strains, where the flowering response is triggered by shortening the length of the day in mid-to-late summer in central California, and autoflowering strains that do not require shortening the length of the day to flower.
Some of the irrigation treatments require moderate to heavy deficit irrigation to assess the plants’ response to water stress. Deficit irrigation is a method of conserving water by using less than what might be considered optimal for rapid growth.
“This plant appears to be quite robust under deficit irrigation,” said UCCE specialist Bob Hutmacher of UC WSREC.
“We need to find out more about the advantages and disadvantages of plant pollution,” said Hutmacher.
The autoflowering strains tested tend to use less water than the photoperiod sensitive strains because they can be grown in a shorter season. In the San Joaquin Valley, the autoflowering strains in these studies were ready to harvest 75 to 90 days after sowing.
“The water consumption is very specific to the variety,” says Hutmacher. “Autoflowering strains can potentially be grown in spring and harvested in early summer, or planted in late summer and harvested before winter. With a harvest in the short season and with a decent water supply, farmers might consider doubling up on such varieties, which could potentially increase profits. “
Yields were variable but showed great promise for autoflowering strains.
“In our studies, the highest yielding autoflowering strains produced 80 to 90% of the yields of the much larger, photoperiod sensitive plants for the whole season, and some strains may be the same,” he said.
Hemp plant density studies
In collaboration with the Kayagene Company of Salinas, Dan Putnam, UCCE forage plant specialist at UC Davis, and Hutmacher conducted studies with two autoflowering strains in 2019 and 2020 to determine the influence of plant density on plant growth, yield and chemical concentration. Because some of the autoflowering strains are smaller and ripen earlier than many photoperiod sensitive strains, the data in these studies will help determine the tradeoff between higher densities needed to increase yields and higher costs for higher sowing rates.
A primary concern of breeders is to produce a crop that is economical in terms of CBD or other compounds of commercial interest, while complying with regulatory limits for THC (tetrahydrocannabinol), the psychoactive compound in marijuana, a related plant. According to the CDFA, an industrial hemp plant grown in the state cannot have more than 0.3% THC when analyzing plant samples.
“This is a challenge for the breeders. You don’t want to risk a THC level that is too high, ”said Hutmacher. “Farmers need to test to make sure THC is at levels to meet regulations. If it is too high, the CDFA regulations would require that the crop be destroyed. “
Another study uses data from 2019 and 2020 to determine the trade-off between higher densities needed to increase yields and the cost increases from higher sowing rates.
The studies give scientists a chance to evaluate plant-to-plant variation and the effects of flower bud position on THC and CBD levels. The data collected on a range of cultivars with different plant growth habits can help inform both researchers and regulatory groups better when making decisions to monitor the chemical makeup of plants.
Hutmacher and Putnam also work with commercial companies to test lines on site, including Arcadia Biosciences in Davis, Phylos Biosciences in Portland, and Front Range Biosciences in Salinas.
“There are many challenges when it comes to assessing the maturity of these varieties,” Putnam said. “Each variety will ripen at different times, and deciding when is the best time is an important decision. We are still learning about this topic. “
In 2021, variety trials, also coordinated by the OSU’s Global Hemp Initiative Center, will collect data from studies at up to 12 locations from Oregon, Washington, and California in the west to New York, Vermont, and Kentucky in the eastern United States to identify varieties Compare grown for CBD and other essential oils.
“Our participation in these multi-site experiments is important in order to identify the plant reaction in relation to the achieved CBD and THC levels in very different environments and latitudes,” said Hutmacher.
Start of the hemp fertilizer project in 2021
As a new crop in California, little is known about nitrogen needs and how to optimize the use of crops to avoid environmental problems associated with overuse. In 2021, a team of researchers from UC Davis will start a three-year nitrogen management trial supported by the CDFA Fertilizer Research Education Program (FREP). An important part of the project is THC and CBD analysis, an expensive undertaking.
Three companies are providing seeds or clones for the project: Cultivaris Hemp from Encinitas, Kayagene from Salinas and Phylos Biosciences from Portland. Alkemist Labs of Garden Grove donates services for the analysis of plant samples.
“These are incredibly valuable donations to support this project, certainly more than $ 50,000 in donated materials and services from each of these companies,” said Hutmacher. The cooperation with the donors, together with the funds made available by the CDFA-FREP for the experiments, enables the development of environmentally friendly nitrogen optimization information for the producers.