- Author: Pershang Hosseini
- Author: Tong Zhen
- Author: Matthew Fatino
- Author: Brad Hanson
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Broomrapes (Orobanche and Phelipanche spp.) are obligate plant parasites with a broad range of agricultural crop hosts. In non-parasitic plant species, seeds generally initiate germination when exposed to favorable conditions of temperature, humidity, oxygen, and, occasionally, light. However, for obligate parasitic plants like broomrapes, a chemical signal from the host plant is essential. Germination of broomrape can only occur under appropriate soil conditions and when the seed receives a strigolactone chemical signal released from the roots of a suitable host. Strigolactones (SLs) are carotenoid-derived hormones that play a crucial role in various aspects of plant growth and development. Fertilizers can regulate the production of these plant hormones (Xie et al. 2010).
Fertilization can improve soil conditions and lead to reduced initiation of broomrape parasitism (Fernández-Aparicio et al. 2016). Studies have shown that heavy infestations of crenate broomrape (Orobanche crenata Forsk.) on faba beans are linked to lower soil fertility (Trabelsi et al. 2017), and parasitism of Egyptian broomrape on tomato occurs more frequently in low-nutrient conditions (Jain and Foy 1992). The application of fertilizers has been reported to suppress the occurrence of other parasitic plants such as Striga (Jamil et al. 2011) and Egyptian broomrape (Phelipanche aegyptiaca) (Jain and Foy 1992). Fertilizers can reduce parasitism and enhance crop tolerance both directly, through toxic effects, and indirectly by improving soil fertility and plant health.
Direct toxic effect of fertilizers
Nutrient management can enhance both resistance and tolerance to broomrape parasitism in crops at the pre-attachment and post-establishment stages. Increasing the levels of nitrogen (N) and phosphorus (P) in the soil through fertilizer application can reduce the germination and subsequent infestation rates of parasitic weeds (Jamil et al. 2011). Ammonium nitrate combined with potassium phosphate or the use of ammonium phosphate alone proved to be effective in reducing parasitism and promoting the growth of tomato plants compared to potassium sulfate (Jain and Foy 1992). The direct inhibitory effects of nutrients on broomrape seeds can occur during the preconditioning, germination, and seedling elongation stages. Preconditioning Egyptian broomrape seeds in the presence ofammonium salts, such as ammonium sulfate or urea, significantly inhibited their germination; in contrast, nitrate did not have the same inhibitory effect (Jain and Foy 1992). Increasing nitrogen rate (ammonium nitrate) decreased seed germination and radicle length of branched broomrape (Irmaileh 1994). Another experiment showed that nitrogen in the ammonium form resulted in greater inhibition than nitrate, and the inhibition mechanism was actually a reduction in radicle elongation rather than inhibition of germination (Westwood and Foy. 1999).
Down-regulating of Strigolactones (SLs)
Fertilization can protect crops from parasitism by downregulating the synthesis and exudation of strigolactones, which are the most potent germination-inducing factors for root parasites (Fernández-Aparicio et al. 2016). Plants release SLs in different situations, including the establishment of symbiotic relationships between plants and certain soil microorganisms (Besserer et al. 2006; Kapulnik and Koltai 2014) and during stress response (Kapulnik and Koltai 2014). It is likely that plants produce strigolactones as a "cry for help," which broomrape exploits to its advantage. The availability of nutrients, particularly nitrogen, can decrease plant stress and subsequently downregulate the production of strigolactones. Effects of N, P, and K deficiencies on SL production showed that both N and P deficiencies enhanced SL exudation in resistant genotypes of faba bean (Trabelsi et al. 2017) and red clover (Yoneyama et al. 2012), while K deficiency had no effect (Trabelsi et al. 2017). A similar positive effect of low phosphate levels on SL production was also observed in tomato (López-Ráez et al. 2008).
In summary, effective nutrient management is a vital strategy in reducing broomrape parasitism and enhancing crop tolerance. By manipulating soil fertility and nutrient availability, it is possible to directly inhibit broomrape development and indirectly protect crops by downregulating strigolactone production. Appropriate fertilization and other stress-reducing management practices can reduce broomrape parasitism.
In addition to the indirect effects on broomrape, researchers in the Hanson lab are investigating the direct toxic effects of various fertilizers on broomrape seeds during three stages: preconditioning, germination, and post-germination (Figure 1). In future studies, we aim to explore the indirect effects of fertilization on broomrape parasitism, focusing on how nutrient management can influence the production of strigolactones and other related mechanisms. The ultimate goal of this work is to determine if manipulating fertilizer form, timing, or rates could directly inhibit branched broomrape and maximize tomato resilience to broomrape parasitism as part of an integrated management strategy.
a | b | c |
Figure 1: Branched broomrape seeds in different treatment conditions:
a) Germination (elongated radicle) observed in the control group.
b) No germination was observed when ammonium phosphate was applied at the germination stage.
c) Elongated radicle changed color when ammonium phosphate was applied post-germination.
References
Besserer, A., Puech-Pagès, V., Kiefer, P., Gomez-Roldan, V., Jauneau, A., Roy, S., ... & Séjalon-Delmas, N. (2006). Strigolactones stimulate arbuscular mycorrhizal fungi by activating mitochondria. PLoS Biology, 4(7), e226.
Fernández-Aparicio, M., Reboud, X., & Gibot-Leclerc, S. (2016). Broomrape weeds. Underground mechanisms of parasitism and associated strategies for their control: a review. Frontiers in Plant Science, 7, 171714.
Irmaileh, B. A. (1994). Nitrogen reduces branched broomrape (Orobanche ramosa) seed germination. Weed Science, 42(1), 57-60.
Jain, R., & Foy, C. L. (1992). Nutrient effects on parasitism and germination of Egyptian broomrape (Orobanche aegyptiaca). Weed Technology, 6(2), 269-275.
Jamil, M., Charnikhova, T., Cardoso, C., Jamil, T., Ueno, K., Verstappen, F., ... & Bouwmeester, H. J. (2011). Quantification of the relationship between strigolactones and Striga hermonthica infection in rice under varying levels of nitrogen and phosphorus. Weed Research, 51(4), 373-385.
Kapulnik, Y., & Koltai, H. (2014). Strigolactone involvement in root development, response to abiotic stress, and interactions with the biotic soil environment. Plant Physiology, 166(2), 560-569.
Trabelsi, I., Yoneyama, K., Abbes, Z., Amri, M., Xie, X., Kisugi, T., ... & Kharrat, M. (2017). Characterization of strigolactones produced by Orobanche foetida and Orobanche crenata resistant faba bean (Vicia faba L.) genotypes and effects of phosphorous, nitrogen, and potassium deficiencies on strigolactone production. South African Journal of Botany, 108, 15-22.
Westwood, J. H., & Foy, C. L. (1999). Influence of nitrogen on germination and early development of broomrape (Orobanche spp.). Weed Science, 47(1), 2-7.
Xie, X., Yoneyama, K., & Yoneyama, K. (2010). The strigolactone story. Annual Review of Phytopathology, 48, 93-117.
Yoneyama, K., Xie, X., Kim, H. I., Kisugi, T., Nomura, T., Sekimoto, H., ... & Yoneyama, K. (2012). How do nitrogen and phosphorus deficiencies affect strigolactone production and exudation?. Planta, 235, 1197-1207.
/table>- Author: Pamela S Kan-Rice
On May 7, scientists from University of California, Riverside, UC Agriculture and Natural Resources, Colorado State University Extension, Kansas State University, University of Arizona, Central Arizona Project, and USDA-Agricultural Research Service will gather with growers in Palm Desert to discuss how artificial intelligence can be used in agriculture.
“Artificial intelligence can be used by farmers to save water, improve fertilizer efficiency and increase productivity,” said Khaled Bali, UC Cooperative Extension irrigation water management specialist and organizer of the workshop. “At this workshop, growers will hear about the latest research on AI technology for agriculture and about the experiences of growers who are already testing it in their fields.”
Speakers and topics will include:
- Raj Khosla, Kansas State University - AI for precision nitrogen and water management in row crops
- Michael Cahn, UC Cooperative Extension - CropManage decision support tool for irrigation and nutrient management
- Daniele Zaccaria, UC Cooperative Extension - Citrus crop water use and open ET in the low desert of California
- Nan Li, UC Riverside - Estimating soil moisture using remote-sensing and land surface parameters in the Central Valley of California.
- Ali Montazar, UC Cooperative Extension - Promises and pitfalls of drip irrigation in desert cropping systems
- Khaled Bali, UC Cooperative Extension - Deficit irrigation strategies for alfalfa in California
- Philip Waisen, UC Cooperative Extension - Environmentally conscious practices for managing soilborne diseases in low desert vegetable production
- Peter Moller, Rubicon Water - On-farm water conservation projects: surface irrigation
- Ronnie Leimgruber, Imperial Valley grower - On-farm water conservation projects: linear move, basin and subsurface drip irrigation
- Rick Benson, Imperial Valley grower - Alternative cropping systems for the low desert region of California: olives and other crops
The workshop will be held at the UCR Palm Desert Center at 75080 Frank Sinatra Drive in Palm Desertfrom 8 a.m. to 3 p.m. on May 7. It costs $30 per person and includes lunch. Register at https://bit.ly/AImay7.
- Author: Kamyar Aram
Autumn is in the air, and while it is still high season for harvest for many crops, shorter days and cooler temperatures inevitably bring to mind that winter prep tasks are not far off. And while the winter is the off-season for most crops in our region, it is definitely the on-season for cover crops. This is because, in California where irrigation water is a premium resource, we typically rely on winter rains to water cover crops. While it is ideal to make plans in advance and get the seed order in ahead of the fall rush, there is still time to think about getting a cover crop in before winter storms settle in.
What are cover crops and what are their benefits?
Cover crops include a wide range of herbaceous plants grown with the primary goal of producing biomass for the soil. They offer many opportunities to address specific soil concerns, in addition to improving and maintaining soil health, in general.
Cover crops can:
- Improve soil physical & biological functions
- Improve water infiltration
- Contribute and retain soil nitrogen
- Allow machinery earlier access to wet fields
- Suppress weeds
- Support pollinators & other beneficial insects
Water infiltration is one of the main issues that motivate growers to plant cover crops in California, as roots open new channels and feed underground life. This is especially helpful in orchards and vineyards where soil compaction is especially difficult to remedy. Cover crops can also contribute significantly to nutrient management, both in the use of nitrogen-fixing legume species, or by just foraging left-over nitrogen at the end of the season and keeping it from leaching out of the soil profile. The organic matter that cover crops contribute also improves soil structure and how much water and nutrients it can hold.
Cover crop types and their applications
Cover crops are often broadly grouped by plant types that differ in their primary benefits. For example, grasses generally produce dense stands with extensive, fine, fibrous roots that improve water infiltration and are excellent at mining nitrogen. They are more amenable to driving on at earlier growth stages, and are usually easy to mow. Legumes can actually add nitrogen to the soil through their symbiosis with bacteria that sequester nitrogen from the atmosphere. Because of their high nitrogen content, their biomass generally decomposes more quickly than other cover crops, which can mean a quicker turnaround in a tight planting schedule. Plants in the mustard family produce deep, thick tap roots that open up the soil, and their flowers are favorites of pollinators and other beneficial insects, but if allowed to mature, their sturdy stems may take more work to chop and more time to decompose.
These different types can be used singly or in combinations. There are mixes that incorporate all three types to "hedge bets" against conditions that might disfavor one or another type, and to take advantage of the way that they can complement one another. Many seed companies have developed their own mixes with characteristics to serve specific needs and circumstances.
2022 Orchard Cover Crop Trial
Cover cropping can be as much art as science, if not more so, which means that experience and experiment are essential. To this end, in the fall of 2022, I teamed up with Tom Johnson of Kamprath Seed and a local walnut grower to test out some different cover crops with the hope to improve water infiltration in the orchard. Our trial included a winter triticale, a hybrid grass known for abundant root production without too much aboveground growth, a mustard “pollinator blend” that included a mix of mustard and radish types, and Kamprath Seed's walnut mix, which includes a full complement of grasses, mustards, and legumes. The grower added a forage, spring triticale, which has more of an upright growth, adding a second triticale type for comparison. It turned out to be a lucky year to have cover crops in the orchard, as it was an exceptionally wet winter, putting many fields feet underwater, especially where infiltration was poor. Overall, all of the cover crop types established rather well in most of the planted rows, though there was a great deal of variation throughout the orchard, showing how conditions can affect the crop. Nevertheless, the walnut mix (with legumes, mustard, and grasses) consistently produced the highest total biomass, even in places where the mustard mix and straight triticale came up somewhat thin (see chart below). This highlights the advantages of diversity, but as Tom pointed out during our spring field day for the trial, results may vary considerably from year to year, and each type or blend will have advantages and disadvantages. You can learn more about the trial and the qualities of different cover crops in a video version of the field day on my YouTube channel.
Getting started with cover crops
If you are inspired, I think it is with good reason. Cover crops are tools with great potential and they really engage farming know-how and problem-solving muscles. As in all new things, it's always best to start small and experiment. There are many resources available for learning the basics or refining your existing knowledge about how to effectively employ and benefit from cover crops. In 2021, UCCE and the Resource Conservation District in Contra Costa County together developed Cover Cropping Opportunities in Specialty Crops, a series of recorded webinars and virtual site visits that explore the world of cover cropping from many different angles. These videos offer a wealth of information, instruction, and demonstrations from experienced practitioners and experts.
In addition, below are listed some other excellent UC resources on cover cropping:
Cover Cropping Opportunities in Specialty Crops video series by Contra Costa County Resource Conservation District and UC Cooperative Extension
Grasses, Mustards, & Legumes: An Orchard Cover Crop Field Day video featuring Tom Johnson of Kamprath Seed by UCCE Specialty Crops in the East Bay/Mt Diablo Region
Covercrops for California Agriculture UC ANR Publication Number 21471
Cover Cropping for Vegetable Production UC ANR Publication Number 3517
Cover Cropping in Vineyards: A Grower's Handbook UC ANR Publication Number 3338
Cover Crop Management in Annual Farming Systems Blog Post by UCCE Agronomy Advisor, Sarah Light
Cover Crop Best Management Practices published by the Almond Board of California in collaboration with UC Davis and UC ANR.
Cover Crops for Walnut Orchards UC ANR Publication Number 21627e
Cover Crop Selection tool by UC ANR SAREP
/span>/span>- Author: Michael D Cahn
CropManage Hands-on Workshop
Bringing Irrigation and Nutrient Management Decision-Support to the Field
Date: Wednesday, March 29th, 2023
9:30 am – 2:30 pm
Location: Animal Services Center
Address: 12425 Monterey Road, San Martin, CA 95046
- Learn how to use CropManage to support irrigation and nutrient management decisions and record-keeping for your crops
- Learn about the latest updates to CropManage
- Learn how CropManage can assist with reporting requirements for Ag Order 4.0
CropManageis a free online decision-support tool for water and nutrient management of vegetables, berry, agronomic, and tree crops. Based on in-depth research and field studies conducted by the University of California Cooperative Extension, CropManage provides real-time recommendations for efficient and timely irrigation and fertilization applications while maintaining or improving overall yield.
At this free workshop, we will provide hands-on training so that you can learn to use the newest version of CropManage. Crops currently supported include many vegetables (carrots, cabbage, celery, broccoli, lettuce, tomato, spinach, etc.), berry crops (raspberry and strawberry), tree crops (almond, walnut, pistachio, prunes, and pear), and agronomic crops (alfalfa and corn). CropManage is also available in Spanish.
Who should participate? Growers, farm managers, other farm staff, crop advisors, consultants, and technical service providers are welcome. The workshop is for both new and current CropManage users. Spanish translation will be available. Lunch will be provided.
What to bring? This is a participatory workshop. Please bring a tablet or laptop computer so that you can follow along and participate in the exercises. Each participant will need a user account for CropManage. Please set up a free user account at https://cropmanage.ucanr.edu/ before the workshop. Please arrive early to set up your laptop or tablet computer on the wifi and get logged on to CropManage.
Registration is free: Please register here
by March 28th, 2023. Seats are limited to the first 40 registrants.
Agenda
9:30 – 10:00 am |
Registration and computer set-up |
10:00 – 10:30 am |
Introduction |
10:30 – 12:00 pm |
Getting started with CropManage |
12:00 to 12:30 pm |
Lunch break |
12:30 – 1:15 pm |
Using CropManage for decision support and record-keeping |
1:15 – 2:00 pm |
Group exercise |
2:00 – 2:30 pm |
Discussion / Q&A / wrap up |
CropManage Hands on Workshop Santa Clara County 2023 English
2023 CropManage Hands on Workshop Santa Clara County Spanish
- Author: Konrad Mathesius
Nitrogen (N) management in small grains has recently managed to capture more attention than usual due to the high cost of N fertilizers. Several researchers from UC and UCCE have been working on projects that can provide growers with some valuable information on various N management options.
Join us next month (Tuesday April 18, 2023, previously March 22, 2023, rescheduled due to wet field conditions) from 8:40 until 10:30 for some quick updates on research. The field site is an experimental trial run by Cameron Pittelkow evaluating the use of digestate and hydrolysate as a N source in small grains.
Additional details below:
Nutrient Management Alternatives in Small Grains: Research Updates
Tuesday April 18, 2023, 8:40 a.m. – 10:30 a.m.
Field located in Solano County (Runge Road between Dixon and Davis, CA)
Click for GPS location: 38.481688, -121.768429
Please RSVP: click here or use the QR code
8:40 a.m. Registration, light refreshments
9:00 a.m. Welcome and Introduction
9:05 a.m. Approaches and tools for in-season N management
Mark Lundy UCCE Small Grains Specialist
9:30 a.m. Evaluating alternative N sources under the CDFA Healthy Soils Program: Digestate and hydrolysate in small grains and future work
Cameron Pittelkow and Valentina Roel, UC Davis Plant Sciences
9:55 a.m. Biosolids as a N fertilizer source in CA: research results and considerations
Konrad Mathesius, UCCE Agronomy Advisor, Yolo, Sacramento, and Solano
10:20 a.m. Discussions, survey, and grower feedback
10:30 a.m. Adjourn
CE Credits
CCA: 1.5 (pending)
INMP/Cures: 1.5 (pending)