- Author: Michelle Leinfelder-Miles
- Author: Brenna J. Aegerter
We began the meeting with “lightning talks” from organizations working on cover cropping and climate-smart agriculture, including UC Cooperative Extension, Contra Costa Resource Conversation District, Community Alliance with Family Farmers, and USDA-NRCS. We then showcased the cover cropping trial that we established in cooperation with Conservation Farms and Ranches. A CDFA Healthy Soils Program grant supports the Delta trial, which is part of a larger effort that includes 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.
This is the second of a three-year on-farm trial to evaluate warm-season, annual legume cover cropping between winter small grain crops compared with a standard dry fallow. Cover cropping is a management practice identified in the Healthy Soils Program as having the potential to improve soil health, sequester carbon, and reduce greenhouse gas emissions. Cover cropping is not a typical practice in the annual crop rotations of the Delta region, however, and summer cover cropping is particularly rare. The Delta is a unique agricultural region with unique environmental challenges. Some soils in the region are subsided due to oxidation of organic matter, and some soils suffer from salinity, having limited ability to leach salts due to low permeability soils and shallow groundwater. Because surface waterways provide water for irrigation, summer cover cropping with a legume has the potential to improve soil tilth at a time of year when the soil would otherwise be fallow and dry with no soil cover.
The soil type across the experimental site is a Valdez silt loam. The trial is approximately 4.5 acres and compares three replicates of two treatments: an irrigated cover crop and a dry, fallow soil in between small grain crops. A cover crop of cowpea (Vigna unguiculata cv. ‘Red Ripper') has been planted in July of 2018 and 2019 after small grain harvest and tillage operations. Irrigation is provided to the cover crop plots only. The cover crop is terminated in the fall ahead of tillage and planting of small grains. Soil properties tested to date include bulk density, salinity (EC), pH, total nitrogen (N), and total carbon (C). We have also evaluated cover crop characteristics and 2019 triticale yield.
Among the soil properties, we have observed essentially no change in bulk density, total C, and total N from the July 2018 baseline condition. We are monitoring salinity and pH semi-annually because we have observed these properties to improve in the cover-cropped plots. After one cover cropping season, salinity increased in both treatments, but it increased more in the dry fallowed plots, averaging 1.22 dS/m from 0 to 12 inches, compared to 0.64 dS/m in the cover crop (CC) treatment. Rainfall during the 2018-19 winter season leached salts in both treatments, but the CC treatment started the 2019 cover cropping season with a lower average rootzone salinity (0-36 in) of 0.78 dS/m, compared to 1.13 dS/m in the dry fallow (No CC) treatment. Soil at this site is acidic, which is typical for the region, but pH was observably higher in the CC treatments.
We made changes to our planting and irrigation scheme in 2019 – changing from flood to sprinkler irrigation – and this has improved cowpea stand in 2019, compared to 2018. There has been a lot of competition from volunteer wheat (2018)/triticale (2019) and weeds, but we decided in both years not to manage these with tillage or herbicides. Both add biomass to the soil, which is an objective of the Healthy Soils Program. Competition, however, likely impedes cowpea growth and nitrogen fixation, and future study should investigate how these soil properties are affected by single-species and mixed cover crop stands. At the end of the first cover cropping season, biomass largely favored the volunteer wheat. Of the total C added to the soil from biomass, the wheat contributed 42-71%, compared to 15-24% from the cowpea, across the three replicate plots. Of the total N added from biomass, the wheat contributed 68-87%, and the cowpea contributed 9-15%. The triticale forage crop (winter 2018-19) yielded 5.4 tons per acre for the CC plots and 6.3 tons per acre for the No CC plots, but there was high variability among subsamples. The overall field averaged approximately 5.5 tons per acre. More detailed methods and results are available in our preliminary report.
In summary, cover cropping, particularly in the warm-season, is not a typical management practice in the annual crop rotations of the Delta region. After the first year of a three-year study, cover cropping had no observed effect on bulk density, Total N, and Total C. We observed better salinity and pH conditions in the cover-cropped plots. Cowpea stand establishment and volunteer grain and weed competition have been the biggest challenges to growing a summer cover crop at this site, and the cover crop was not observed to improve cash crop yield in the following season. We will continue to monitor soil and cover crop properties in 2019 and 2020, and additionally, we will reach conclusions about greenhouse gas (CH4, N2O) emissions, which are being evaluated by our UC Davis colleagues.
This project is financially supported by the California Climate Investments program. We thank Dawit Zeleke and Morgan Johnson of Conservation Farms and Ranches for hosting the trial. We thank Tom Johnson of Kamprath Seed and Margaret Smither-Kopperl and Valerie Bullard of the NRCS PMC for information and advice on cover cropping.
- Author: Michelle Leinfelder-Miles
On Thursday, January 17th, I hosted the annual SJC and Delta Field Crops Meeting in Stockton, CA. I want to thank everyone who attended and provided feedback on the meeting. Your evaluations are critical and inform Cooperative Extension outreach efforts! The presentations from that meeting have now been posted to my website. I encourage you to reach out to the presenters with questions. Also available from my website are full reports of local research trials, including the Delta field corn variety trial. I will make an announcement here on the blog when new reports are available.
UC statewide specialists make their research results available through the Agronomy Research and Information Center (RIC) website. Please check the RIC for information on statewide trials in small grains, alfalfa, dry beans, and other field crops.
We hope you will find this information useful, and we hope you will share your feedback with us so that we may best serve your interests for research and outreach.
- Author: Michelle Leinfelder-Miles
- Contributor: Brenna J. Aegerter
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:
UC Sacramento Valley Field Crops Blog
- Author: Michelle Leinfelder-Miles
On Friday, January 12th, I hosted the annual SJC and Delta Field Crops Meeting in Stockton, CA. The presentations from that meeting have now been posted to my website and are available here. Also available from my website are full reports of local research trials, including the Delta sorghum seeding rate trial and field corn variety trial.
UC statewide specialists make their research results available through the Agronomy Research and Information Center (RIC) website. At the meeting, we had a presentation that referenced the small grains variety selection tool, which was developed using trial data from across the state.
We hope you will find this information useful, and we hope you will share your feedback with us so that we may best serve your interests for research and outreach.
- Author: Michelle Leinfelder-Miles
UC Cooperative Extension will host the SJC and Delta Field Crops Meeting on Friday, January 6, 2017 from 8:00am to 12:00pm. The meeting location is the Cabral Agricultural Center in Stockton (2101 E.Earhart Ave., Stockton, CA 95206).
The agenda is as follows:
8:00am Doors Open, Sign In, and Welcome
8:10am Sorghum Seeding Rates for Optimum Productivity, Michelle Leinfelder-Miles, UCCE, San Joaquin/Delta Counties
8:35m New Pest Advisory: Sugarcane Aphid in California Sorghum, Larry Godfrey, UC Davis
9:05am The Do's and Don'ts of Planting Grain and Forage Sorghum – Why Sorghum is not Corn!, Jeff Dahlberg, UC Kearney Research and Education Center, Parlier
9:30am Update on New Herbicide Options for Established Alfalfa, Mick Canevari, UCCE, San Joaquin County
10:00am BREAK
10:10am Tools for Selecting Small Grain Varieties from UCCE Statewide Trials, Mark Lundy, UC Davis
10:35am Comparing Methods for Estimating Crop Consumptive Water Use in the Delta: Background and Preliminary Results, Kyaw Tha Paw U, Eric Kent, Jenae' Clay, UC Davis
11:00am Nitrogen Mineralization in Soils from the Delta and the Valley, Daniel Geisseler, UC Davis
11:25am Managing Gophers in Alfalfa Fields, Roger Baldwin, UC Davis
11:55am Wrap-up and evaluations
Continuing education (DPR and CCA) will be available. Our programs are open to all potential participants. If you require special accommodations, please contact UCCE San Joaquin County at 209-953-6100. Thank you, and hope to see you at the meeting.