Last week was California Invasive Species Action Week. Guest authors Tunyalee Martin, with the UC IPM Program, and Gene Miyao, farm advisor, describe a parasitic plant that has been found in the Delta. Help in the fight against invasive species by learning more about California Invasive Species Action Week.
Watch out for parasites! Wait, in my tomato field?
Broomrape has quite a rap sheet. Egyptian broomrape, whose first detection in the U.S. in 2014 was in California, is on the federal noxious weed list. Branched broomrape is on the California noxious weed list (A rating = eradication, containment, rejection, or other holding action); on the federal noxious weed list; and is listed as noxious in 10 other states. Broomrape has the potential to damage many economically important crops in California including bell pepper, cabbage, carrot, celery, eggplant, legumes, melons, potato, tomato, and sunflower.
The California Department of Food and Agriculture describes branched broomrape as “terrible” and justifies the A rating because it: 1) could establish itself widely in California, 2) can parasitize many plant hosts (both agricultural crops and many common agricultural weeds), 3) produces many tiny seeds (over 100,000 and only 0.3 mm long) that can easily disperse, 4) has a high potential to harm commercial agriculture, and 5) could also harm rare or endangered wild plants.
As a parasitic plant, broomrape acquires the nutrients and water it needs from the host plant. You might observe symptoms of stunting or yellowing in your crop plants, but broomrape grows and attaches underground, and the only part of broomrape that you may observe above ground are the flower spikes.
If you see this pest, contact your local agricultural commissioner, or for identification, your UC Cooperative Extension office. Use certified seed and clean nursery stock.
USDA-APHIS factsheet for Egyptian broomrape
UC IPM Weed Gallery for branched broomrape
CDFA Pest Rating for branched broomrape
The meeting showcased the UC Davis wheat and triticale variety testing program for the Delta, and presentations were given by UC Cooperative Extension and USDA-NRCS scientists. UCCE Grains Specialist, Mark Lundy, demonstrated a soil nitrate quick test and how it can be used in small grains fertility programs. UCCE Cropping Systems Specialist, Jeff Mitchell, described tillage research taking place at the UC Westside Research and Extension Center and demonstrated how no-till plots had better soil aggregation and tilth than conventionally tilled plots. USDA-NRCS Director, Margaret Smither-Kopperl, described winter and summer cover cropping trials at the Plant Materials Center in Lockeford, CA.
Additionally, Brenna Aegerter and I described an upcoming cover cropping trial that we will conduct on Staten Island. We were awarded a CDFA Healthy Soils Program grant with our farm advisor colleagues in the Sacramento and San Joaquin Valleys – Sarah Light, Amber Vinchesi, and Scott Stoddard – along with Jeff Mitchell and Will Horwath at UC Davis. On Staten Island, we will trial legume cover cropping versus no cover cropping treatments for soil health properties, greenhouse gas emissions, and grain yield from 2018-2020.
The trial will take place in a field that is in small grains (wheat and triticale) rotations, with soil classification Valdez silt loam. Cover cropping will take place in the summer months following the small grains harvest. Initial soil sampling will take place after wheat harvest and subsequent tillage. We will take baseline soil samples, measuring bulk density, pH, salinity, total C and N, aggregate stability, infiltration, and active C (a measure of the carbon available as an energy source for soil microbial communities) in the top foot of soil. At deeper depths, we will also test bulk density and total C. We will soil sample each fall, at the end of the cover crop season, to evaluate changes in soil properties over the three years. Greenhouse gas (N2O and CH4) monitoring will allow comparative evaluations of cumulative emissions between the soil management systems. Small grains yields will also be determined.
We look forward to this trial and will share results as we have them. We want to thank Dawit Zeleke and Morgan Johnson at The Nature Conservancy's Staten Island, Margaret Smither-Kopperl and Valerie Bullard at the USDA-NRCS Plant Materials Center, and Tom Johnson at Kamprath Seed for their collaboration on this trial.
For more information on UCCE or USDA-NRCS programs, please visit the following blogs and websites:
- Author: Jessica Rudnick
- Contributor: Michelle Leinfelder-Miles
Nitrogen (N) fertilizers are widely used in California's agricultural systems to enhance efficiency and crop production, yet there is also growing concern around nitrogen losses from irrigated crop lands that have the potential to impact water quality. Efforts from Cooperative Extension programs have worked to offer growers a toolbox of management practices that aim to increase N use efficiency and decrease any losses from the farm (See Solution Center for Nutrient Management). These management practices help to save growers money, give the crops the appropriate amount of nutrients they need to grow and thrive, while maintaining excellent stewardship of the land and water. UC Davis researchers want to know about how growers use the management practice tools from this toolbox and we're sending a survey out to growers in 2018 to ask them about this.
Our research team is a well-rounded group coming from the Departments of Plant Sciences and Environmental Science and Policy, so that together we can understand what practices are being widely used, what practices have large adoption barriers that we must work together to overcome, which areas across the state will have the most “bang for the buck” when adopting certain practices, and how current outreach, education and incentive programs, as well as regulatory requirements, influence growers' decisions to adopt these practices.
In June 2018, we are sending the survey out to about 4,000 growers in the northern San Joaquin Valley and Sacramento-San Joaquin Delta regions (including Madera, Merced, Stanislaus, San Joaquin, Contra Costa, Alameda, Calaveras, Tuolumne and Mariposa counties) this June. We sent the survey to nearly 2,000 growers in the Sacramento Valley region in spring 2018 and had a high response rate where growers offered a variety of perspectives on their experiences with nitrogen management practices and regulations.
The goal of this project is to understand what education and outreach resources around nitrogen management are useful to growers, where the gaps in resources needed exist, how growers are understanding the new policies that are coming down the pipeline and how we can optimize both the extension and outreach around nitrogen.
We encourage any grower who receives a Nitrogen Management Survey in the mail from UC Davis to please participate in this project. It is important to have broad representation in the data we collect so that we know how to best move forward building programs and resources that support the ever-changing needs of California's growers.
Please contact Jessica Rudnick, a researcher and graduate student on the research team with any comments or questions: email@example.com.
- Author: Michelle Leinfelder-Miles
The 2012-2016 drought was one of the worst droughts in California history, not solely for the lack of precipitation, but also for its length, high temperatures, low snowpack, and water demand. It's probably safe to say that it won't be our last drought – or even our worst – as we look into the future. That said, what can we do in the California alfalfa industry to better manage for drought and the likely salinity impacts from a lack of water?
Water Management during the Growing Season: Dan Putnam wrote a blog article, “Why Alfalfa is the Best Crop to Have in a Drought” (http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=17721), which describes the water use of alfalfa compared to other crops, its adaptations to water-stressed conditions (like being deep-rooted), and ways we can adapt our management in low-water years. In particular, during the growing season, we can optimize water use and alfalfa growth during the early part of the season when yield and quality are highest, and dry down in the later part of the season. Dan's research has shown that the alfalfa will survive and resume growth when moisture conditions become favorable.
Water Management during the Winter Season: In 2013 through 2015, I cooperated with alfalfa growers in the Delta region to understand soil salinity conditions and leaching fractions in fully irrigated fields. I then modelled soil moisture and salinity conditions to understand these conditions during the winter season to help inform our management during the off-season.
Figure 1 (below) shows the daily water balance (precipitation minus crop evapotranspiration, ETc) and the change in soil moisture from field capacity (i.e. soil moisture after free drainage has ceased) at seven alfalfa fields during Winter 2013-14. This figure helps us to visualize why precipitation, particularly in a drought year, is not contributing more to soil moisture for early spring growth or to leaching salts. Total rainfall was approximately 8.2 inches, and for only a few storms (shown as peaks) was there enough precipitation to exceed crop water use (ETc).
The other lines on the graph (labelled Sites 1-7) illustrate the soil moisture deficit from field capacity. Soil moisture is expressed relative to field capacity because a primary interest in this modelling was to understand how much water is available for leaching salts. Until a soil reaches field capacity, we assume the water is held in the soil and not available for leaching. For all sites, the soil was drier than field capacity in the fall after the last cutting and before the first rain event. The lines decrease (i.e. become more negative) until December 1st because crop water use exceeded precipitation, so the crop drew upon soil moisture. On December 1st, there was a rain event that was enough to exceed ETc, so the soil moisture deficit decreased, but soil moisture was still less than field capacity. This trend continued for the remainder of the winter. If there had been enough precipitation to increase soil moisture above field capacity, then water would have been available for leaching, but this did not happen in Winter 2013-14. Precipitation rarely exceeded ETc, and each alfalfa site remained at a soil moisture deficit over the entire winter. In other words, precipitation was never high enough to fill the soil profiles, exceed the soils' field capacity, and leach salts.
Figure 2 (below) represents conditions for water year 2014-15. Total rainfall was approximately 11.8 inches, and precipitation exceeded ETc more frequently than in water year 2013-14. There was a period starting on December 11th where soil moisture exceeded field capacity (for all but Site 5), providing water for leaching. The highest peak on each site's line represents the total water available for leaching after accounting for ETc and filling the soil profile to field capacity. This peak occurred on December 20th and was 0.8, 3.3, 1.1, 1.8, 0, 1.4, and 1.2 inches, for Sites 1-7, respectively. (Site 5 was 0 inches because the soil moisture deficit remained the entire year; thus, zero water was available for leaching.) As this water was available for leaching, we assume that this water drained from the profile, and the lines drop to zero, or field capacity. Beyond December 20th, the daily water balance was never enough to exceed field capacity for any of the sites. (Note: the lines for all sites, except Site 5, overlap after December 20th.) So, no other water was available for leaching over the remainder of the winter season.
Conclusions: The 2012-2016 drought provided limited ability to manage salts with winter rainfall. For seven Delta alfalfa sites, we modelled 0 inches of rainfall available for leaching in Winter 2013-14. We modelled a range of about 0 to 3 inches of rainfall available for leaching in Winter 2014-15, depending on location. As a result, root zone soil salinity decreased in Spring 2015 (data not shown). When winter rainfall is not adequate for effective leaching, however, we need to be creative in our leaching strategies. Leaching during the season may not be advisable for crop health and nutrient management reasons, but we may be able to leverage winter rainfall with irrigation by wetting the soil profile before a rain event. A soil profile that is brought to field capacity with irrigation would likely result in rain water passing through the profile and leaching salts, rather than just soaking into a dry soil. We should also consider field modifications that improve irrigation efficiency prior to planting alfalfa, like increasing on-flow rate, narrowing border checks, or shortening field length, where possible. While drip irrigation in alfalfa is still not widely employed, in those fields that have it, it might be wise to also maintain a surface irrigation system for leaching. Our options are not many, but they could provide some relief when water is scarce.
Figure 1. The daily water balance (i.e. precipitation minus ETc) and the change in soil moisture from field capacity for Winter 2013-14 at seven Delta alfalfa sites. This model shows that there was no water available for leaching. All rainfall was soaked up and held by the soil.
Figure 2. The daily water balance (i.e. precipitation minus ETc) and the change in soil moisture from field capacity for Winter 2014-15 at seven Delta alfalfa sites. This model shows that there was some water available for leaching in mid-December, ranging from about 0-3 inches, depending on location.
- Author: Michelle Leinfelder-Miles
UC Cooperative Extension will host a Small Grains and Soil Health Field Meeting on Tuesday, June 5, 2018, from 9:30am to noon, on Staten Island in the San Joaquin County Delta. The agenda is pasted below and attached. The attached version includes a map and directions. We have applied for CCA continuing education credits, and light refreshments will be provided. RSVP is not required. Hope to see you in the field!
9:30am Meet at Staten Island grain silos to caravan to field trial location (see map below)
10:00am Welcome and Meeting Overview
Michelle Leinfelder-Miles and Brenna Aegerter, UCCE, San Joaquin County
Dawit Zeleke, Conservation Farms and Ranches
10:15am Small Grains Variety Testing – Statewide and Delta Trials
Mark Lundy, UC Davis
10:30am Soil Nitrate Quick Test Demonstration
Mark Lundy, UC Davis
10:45am Introduction to Cover Cropping Project (funded by CDFA Healthy Soils Program)
Michelle Leinfelder-Miles and Brenna Aegerter, UCCE, San Joaquin County
11:00am Cover Crop Trial Results
Valerie Bullard, USDA-NRCS Plant Materials Center
11:15am Demonstrations and Evidence – Why the Hype Over Soil Health Really Matters
Jeff Mitchell, UC Davis
11:30am Walk through small grains trial, participate in soil health demonstrations
12:00pm Wrap-up and evaluations