- Author: Giuliano Carneiro Galdi
- Posted by: Gale Perez
Roundup Ready technology incorporates genetic resistance to glyphosate into crops and it's an excellent tool for weed control. Initial screening in the early 2000s found good alfalfa crop safety, and many growers currently rely on glyphosate as the only herbicide. Although using the same herbicide over and over is not a good idea because it may accelerate herbicide resistance in weeds, Roundup Ready alfalfa has been successfully used with few to no concerns regarding crop safety. However, the combination of glyphosate and cold weather may cause crop injury, especially in certain regions.
The problem was first observed in 2014 by Steve Orloff, former UCCE farm advisor in Siskiyou County. A Roundup Ready alfalfa field showed injury after glyphosate application followed by a frost event. The main symptoms were plant stunting, chlorosis, and “shepherd's crook”, in which individual alfalfa stems curl over and die (Figures 1 and 2). Yield reductions were also observed for the first cutting. It was clear to Steve the injury was somehow related to the glyphosate application because a section of the field where the wheel line was sitting was not sprayed and it looked perfectly normal.
Interestingly, the injury seen was very similar to symptoms caused by frost and/or bacterial blight caused by Pseudomona syringae – a bacteria that is present everywhere. The bacteria can exacerbate frost damage due to its protein that mimics a crystalline structure and provides a starting point for ice formation, damaging the plant tissue and serving as an entrance port into the leaves and stems. Once into the plant tissue, colonization leads to infection and symptoms about 7-10 days after the frost event. Symptoms on stems start as water-soaked lesions that extend down one side. Leaves become water-soaked and often are twisted and deformed.
Steve was able to replicate the symptoms in field trials conducted in 2015, 2016, and 2017. The field trials showed yield reductions of up to 0.7 ton/acre in the first cutting in Scott Valley. Crop injury was not observed in a similar field trial conducted in 2014, probably because there was no frost event after glyphosate application. Similar impacts were observed in a trial in the intermountain region near Tulelake, CA; additional yield reductions were observed with higher glyphosate rates (Table 1).
Based on this work, a multi-year project started to investigate the effects of glyphosate rate and application timing during various seasons at 24 sites over five years, measuring the impact on alfalfa crop height and biomass yield. Results were published in the Agronomy Journal in 2023 (Loveland et al, 2023). All sites in this study were in the Intermountain West (California and Utah). Results showed that while summer glyphosate application did not injure alfalfa, spring applications reduced crop height at 76% of the sites and biomass at 62% of the sites. In sites where glyphosate application resulted in crop injury, low (22 oz/A) and high (44 oz/A) rates of glyphosate reduced yields by 0.24 ton/A and 0.47 ton/A, respectively. Data also show that the crop height at glyphosate application influenced the degree of injury (Figure 3), with greater yield reductions at 30 – 40 cm than at 5 to 10 cm height.
As alarming as the possibility of injury might sound, its occurrence and degree are widely variable, and most fields will resume normal growth and yields after first cutting. Figure 4 illustrates this complexity and variability throughout experimental sites where harvest yield and crop height were assessed. Note that the locations represented in the following graph are colder than the San Joaquin Valley and the injury happened after glyphosate applications in the spring.
As of 2024, this type of injury has only been reported in the intermountain west due to its high altitude and cooler weather. However, one field I visited in early February in Firebaugh brought my attention back to the issue. The field was planted in the fall of 2023 and had many of the symptoms described above: plant stunting, typical shepherd's crook, chlorosis, and dead stems. While all these symptoms could be exclusively due to bacterial blight infections or frost, parts of the field where glyphosate application was accidentally skipped looked better.
Current UC IPM weed management guidelines for RR alfalfa recommend rotating herbicides with different modes of action to reduce the development of herbicide resistant weeds and avoid glyphosate overuse during the colder winter months. Second, spray glyphosate when the alfalfa is short (< 2”) when using the higher rate (44oz/A) or 4” when spraying at the lower rate (22oz/A). Third, use the lowest glyphosate rate possible according to the weeds present and their stage of development. Finally, pay attention to the weather forecast. Applying glyphosate before frost events increases the likelihood of crop injury, especially in old stands.
Reference
Loveland, L.C., Orloff, S.B., Yost, M.A., Bohle, M., Galdi, G.C., Getts, T., Putnam, D.H., Ransom, C.V., Samac, D.A., Wilson, R., and Creech, J.E. (2023). Glyphosate-resistant alfalfa can exhibit injury after glyphosate application in the Intermountain West. Agronomy Journal, 115, 1827–1841. https://doi.org/10.1002/agj2.21352.
- Author: Michelle Leinfelder-Miles
- Author: Radomir Schmidt
The term ‘soil health' has become a common term in agricultural research and management. While most of us are familiar with testing soil for chemical properties, like nutrients, salinity, and pH, soil health also considers soil physical characteristics – like compaction, aggregation, and water infiltration – and biological characteristics – like soil respiration, active carbon, and nitrogen mineralization.
These properties influence the soil's ability to function, and enhancing these properties can improve soil functioning to grow crops and produce ecosystem services. We often relate soil health to management practices like crop rotation, cover cropping, reducing tillage, and adding compost because these have been shown to increase soil functioning in agricultural landscapes. They are also some of the practices that are financially incentivized by the CA Department of Food and Agriculture Healthy Soils Program.
There is a regulatory framework for diverting green waste from landfills to make compost. In 2014, AB 1826 was passed in California, which required businesses to recycle organic wastes and jurisdictions to set up organic waste recycling programs to divert green waste from landfills. In 2016, AB 1383 established organic waste reduction targets (75% reduction by 2025, compared to 2014). The bill also required jurisdictions to do education and outreach. Green waste diversion is expected to reduce greenhouse gas emissions by 4 million metric tons per year and increase food recovery by 20 percent. Agricultural land could serve to receive green waste compost recovered by this regulatory framework.
Our project objectives were to learn whether green waste compost improves soil nutrient status or other soil health characteristics, whether it improves alfalfa yield or quality, or if its application affects greenhouse gas emissions from the system. Alfalfa was chosen for this study because it has a large footprint on the state's agricultural landscape and because it has a high phosphorus (P) and potassium (K) nutrient need which compost could help supply. Also, as a ‘high-traffic' crop, alfalfa soils can have poor physical traits (e.g. compaction, water infiltration), which could potentially be ameliorated with compost.
The study was conducted on commercial farms in Yolo and San Joaquin (SJ) counties. The Yolo site had a mineral soil with high clay content (approximately 50 percent clay), and the SJ soil was a mucky clay with high organic matter (approximately 8 percent). We are comparing two green waste compost rates (3 and 6 tons per acre) to the untreated control. Compost applications were annually (2020-2022) surface-applied in the fall/winter ahead of rain.
Our preliminary results indicate no statistically significant differences in total carbon and nitrogen among treatments (Fig. 2). There is a trend, however, for compost to increase carbon at the Yolo site, which is inherently low in organic matter. An interesting observation about the SJ site, where the soil is inherently low in K, is that the compost increased soil K (statistically significant, Fig. 3). The compost analysis showed that the product was roughly 1 percent K. Therefore, the 3-ton compost rate should have added approximately 50 lb of K per acre, and the 6-ton rate approximately 100 lb of K per acre. Based on the amount of change in soil K and the compost analysis, the compost was likely what contributed to the increase in soil K. This appears to be translating into higher tissue K (Fig. 3), and in turn, higher yields (though neither tissue K nor yield are statistically higher than the control, Fig. 4).
Greenhouse gas emissions have not differed among treatments (Fig. 5), indicating that the carbon that is added by the compost is not being respired from the system. There are higher CO2 emissions at the SJ compared to the Yolo site, which we attribute to the inherently higher carbon of the SJ soil. Additionally, we have observed that the soil acts as a methane sink. This is noteworthy because methane is a more potent greenhouse gas than CO2.
Based on our experiences working on this project, we have the following guidance for growers interested in applying green waste compost. While green waste compost is a relatively cheap input, transport cost can be high. In 2021, we estimated that material plus hauling cost was approximately $27/ton and spreading was an additional $10/ton. The highest demand for compost is in the fall. To ensure availability, growers should aim to purchase compost in the spring or summer and store it on-site until fall. Ordering the compost in spring or summer also tends to result in a higher quality product delivered (i.e. less trashy). Timing compost application can be a challenge (i.e. after all harvests but before soil gets too wet), so having the compost already on-site may help in getting it applied more readily. We still have more data to analyzed for this project, so more information will be forthcoming. We want to thank the growers in Yolo and San Joaquin counties for collaborating with us on this project.
- Author: Michelle Leinfelder-Miles
The UC Field Crops, Alfalfa, and Forage Field Day will take place on Friday, September 29, 2023. The field day will take place at the Kearney Research and Extension Center, 9240 S. Riverbend Ave., Parlier, CA 93648. Sign-in and morning refreshments begin at 7:00am, and the field tour tram leaves promptly at 8:00am. There is no registration fee, but please pre-register for the event to help us with our planning. Only preregistered attendees are guaranteed a lunch. CCA continuing education credits (1.0 SW; 1.0 PM; 1.5 CM) and CDFA INMP credits (1.5) have been approved. DPR continuing education credits (1.0) are still pending. The agenda is below and attached to the bottom of this post. We look forward to seeing you at the field day!
Agenda:
7:00 am Sign-in (refreshments provided)
8:00 am Depart for Field Tour
- Sorghum Variety Trials (Grain & Forage) – Jackie Atim, UC ANR
- Sorghum variety trial under deficit irrigation – Jackie Atim
- Dry beans variety selection – Bao Lam Huynh, UC Riverside
- Almond-Alfalfa Intercropping System – Sultan Begna and Lauren Hale, USDA ARS
10:00 am Return from Field Tour
10:10 am New Extension Advisors Introduction – Nick Clark, UC ANR
10:20 am Alfalfa Weed Management – Giuliano Galdi & Jorge Angeles UC ANR
10:40 am Cotton IPM – Ian Grettenberger & Buddhi Achhami, UC Davis
11:00 am Brief: Small Grain and Alfalfa Weed Management – Nick Clark
11:05 am Break
11:15 am Compost Application to Alfalfa – Michelle Leinfelder-Miles, UC ANR
11:35 am Byproducts Trends & Opportunities for the CA Dairy Industry – Jennifer Heguy, UC ANR
11:55 am Lima & Garbanzo Breeding and Dry Bean Heat Stress Testing– Christine Diepenbrock, UC Davis
12:15 pm Lunch
/span>2023 KREC Field Day agenda
- Author: Konrad Mathesius
If you haven't seen the announcements on the UC Small Grains blog, you should be subscribed to the UC Small Grains blog.
Additionally, a friendly reminder to stop by this Thursday for the UC Alfalfa/ Forages and Small Grains Field Day from 7:30 a.m. until 3:30 p.m.
Location: 2400 Hutchison Dr, Davis CA 38.5390, -121.7800
Alfalfa Talks: 8:00 – 10:00
Small Grains Agronomy Topics: 10:00 -12:00
LUNCH will be provided (please register below)
Small Grains Breeding Program Topics: 1:40 -3:00
Agenda: https://ucanr.edu/sites/small-grains/files/383475.pdf
Register: https://surveys.ucanr.edu/survey.cfm?surveynumber=40606
Continuing Education Units (CEUs): 3.5 CCA; 1.5 CDFA INMP (formerly CURES)
Looking forward to seeing you there.
- Author: Michelle Leinfelder-Miles
The annual UC Davis Alfalfa and Small Grains Field Day will take place on Thursday, May 11, 2023 at the Department of Plant Sciences Field Facility (2400 Hutchison Drive, Davis, CA 95616). Registration opens at 7:30am, and the wagons leave for the field at 8am. The event is free and open to the public, but registration is requested. Lunch is sponsored by the CA Crop Improvement Association, and continuing education credits will be available. Directions are as follows:
The field day is located on Hutchison Drive, just west of Davis. Take the Hwy. 113 exit north from I-80, or Hwy. 113 south from Woodland. Exit west on Hutchison Drive. Take a right at the first roundabout, a left at the second roundabout, and the field headquarters is about ¼ mile down in a clump of trees and buildings on the left.
The agenda is as follows:
8:10 Alfalfa Breeding Efforts at UC Davis - Charlie Brummer
8:20 Choosing Varieties for Pest Resistance - Dan Putnam
8:30 IPM and Importance of Management of Insect Resistance in Alfalfa - Ian Grettenberger
8:40 Test your Weed IQ - Identification of Weeds - Brad Hanson
8:55 Use of Compost to Improve Soils in Alfalfa - Michelle Leinfelder-Miles
9:05 Sorghum Projects for Forage and Biofuels - Jackie Atim
9:15 Improving Agronomic and Grain Quality Traits in Sorghum under Well-watered and Drought Conditions - Christine Diepenbrock
9:35 Flood or Drought? Alfalfa Strategies for Coping with California's Future - Dan Putnam
9:45 Teff as an Alternative Summer Forage Crop - Dan Putnam
9:50 Overhead Irrigation Technologies for Improved Efficiency - Isaya Kisekka
10:05 Updates from UC Davis Small Grains Breeding Program - Jorge Dubcovsky
10:20 Effects of Genotype and Environment on Productivity and Quality in California Malting Barley - Maany Ramanan
10:30 California Grain Foundation and Research on Food Use of Triticale - George Fohner
10:40 Small Grain Research Update from Tulelake - Rob Wilson
10:55 Evaluating Digestate and Hydrolysate as Alternative N Sources in Small Grains - Valentina Roel
11:05 Biosolids as a N Fertilizer Source in California Small Grains - Konrad Mathesius
11:15 Helping Farms in the Central Coast get N Scavenging Credits for Cereal Cover Crops - Eric Brennan
11:25 DIY In-field Plant Tissue Tests to Determine N Sufficiency in Wheat - Karla Estrada
11:30 Updates on Small Grain Research and Production in the Central Valley - Mark Lundy
11:45 Tour Small Grain Variety Trials
12:10 Lunch
1:20 Small Grain Breeding Field Day