Research is under way to determine if using cover crops between two annual vegetable crops will improve the soil for future crops. It’s all part of the California Department of Food and Ag Healthy Soils Program—a statewide project.
Amber Vinchesi is a UCANR Vegetable Crops Farm Advisor in Colusa, Sutter and Yuba counties. She works mainly with processing tomatoes but also with growers farming vegetables for seed as well as fresh market vegetables such as honeydew and cantaloupe melons.
Vinchesi is collaborating with California’s Healthy Soils Initiative, a partnership of state agencies and departments led by the CDFA Healthy Soils Project. It’s a combination of innovative farm and land management practices that may contribute to building adequate soil organic matter that may increase carbon sequestration and reduce overall greenhouse gases.
“We have three sites, and the site that I’m working on is focused on winter cover crops between crops such as wheat, tomato or corn, to improve soil health,” said Vinchesi, who is being assisted by her colleague Sarah Light, the agronomy advisor in Sutter, Yuba, and Colusa counties
Other Healthy Soil sites are located in the Delta area, and overseen by Michelle Leinfelder-Miles, UCANR Delta Crops Resource Management Advisor in San Joaquin County. Brenna Aegerter, a UCANR Vegetable Crops Farm Advisor also in San Joaquin County, is working with Leinfelder-Miles. Additionally, Scott Stoddard a UCANR Vegetable Crops Farm Advisor in Merced County has a site.
The cover crop will be vetch, a legume.
“We hope that it will put nitrogen and biomass into the soil,” Vinchesi said. “We’re not sure what the results will be, but we hope it will help with aggregate stability, water infiltration, and even reduce weed density.”
She noted that the trial, which is in the first year of a three-year project, will include two different seeding rates, a high and low rate, and then an untreated control where there’s no cover crop.
“And we’ll do soil testing to see how things change in the soil over time,” she explained.
Jeff Mitchell Has Devoted Career to Conservation No-Till
By Patrick Cavanaugh, Editor
Jeff Mitchell is a Cropping Systems Specialist at UC Davis, based at the Kearney Agricultural Research and Extension Center in Parlier. He has devoted 19 years to improving nitrogen and water use efficiencies in food, feed, fuel and fiber in no-till cropping systems.
His no-till research focuses on soil quality management and potential roles of cover crops and compost in intensive row crop production systems, and the use of cover crop mulches as a means of conserving soil water, suppressing weeds and increasing organic matter in no-till production systems.
He often cites a book called Plowman’s Folly by Edward H. Faulkner, published following the ruinous Dust Bowl. Faulkner dropped an agricultural bombshell when he blamed the then universally used moldboard plow for disastrous pillage of the soil.
This book is the 11th all-time cited, read, or acknowledged a piece of work related to the soil in the history of scientific literature.
“When it was written in 1943, it caused great arguments. The government got involved with the USDA trying to defend the science of the day,” Mitchell said.
The reason the book was so controversial is that it proved that there had been no scientific reason for plowing.
“He was getting in people’s faces by saying, ‘This might not be the way to do it,’ ” Mitchell said. “Faulkner’s stance was embroiling people.”
Mitchell’s work centers on conservation, no-till production of vegetable and cotton crops. The idea is to plant in the crops’ residue, which builds up a rather thick layer of mulch on the bed—leading to reduced water and nitrogen, as well as minimizing weeds.
Mitchell cited several growers in the Midwest and in California that are successfully practicing conservation no-till agriculture. And there is much more recent attention on soils with the Healthy Soils Program (HSP)—stemming from the California Healthy Soils Initiative, a collaboration of state agencies and departments to promote the development of healthy soils on California’s farmlands and ranch lands.
The HSP has two components: the HSP Incentives Program and the HSP Demonstration Projects. The HSP Incentives Program provides financial assistance for the implementation of conservation management that improves soil health, sequester carbon and reduce greenhouse gas (GHG) emissions. The HSP Demonstration Projects showcase California farmers’ and ranchers’ implementation of HSP practices.
“The principles that we are pursuing are allowing growers to keep excellent yields and maybe increase sometimes, cut out some inputs like fertilizers to save money, and to do it with less—less disturbance and fewer operations,” Mitchell explained. “None of this is new. It was 90 years ago when the Natural Resources Conservation Service established the principles of good soil management
Healthy soil holds more water (by binding it to organic matter), and loses less water to runoff and evaporation.
Organic matter builds as tillage declines and plants and residue cover the soil. Organic matter holds 18 to 20 times its weight in water and recycles nutrients for plants to use.
One percent of organic matter in the top six inches of soil would hold approximately 27,000 gallons of water per acre!
Most farmers can increase their soil organic matter in three to 10 years if they are motivated about adopting conservation practices to achieve this goal.
“In 2013, a group of 30 farmers came up with a similar kind of a list,” Mitchell said. “They brainstormed on what would be good soil management, and they came up [with] feed the soil organic matter, reduced disturbance, increased diversity—the same as the NRCS list.”
Mitchell cited a newspaper article published in 1931. “People were finding benefits of cover crops in San Joaquin Valley farming systems. Now with the Healthy Soils Initiative, farmers are trying these techniques and evaluating it. There’s a lot of activity that is going on at many different sites in the state.”
Mitchell’s work at the West Side Research and Extension Center in Five Points on the conservation no-till approach has been with scientific protocol and replicated over 19 years.
“Initially, we would have several systems. In the no-till system, rotations of cotton, transplanted tomato, and a forage crops would grow back to back in a no-till system,” he explained. “Each crop would be planted in the residue of the previous crop. Over the years, the no-till plots have grey residue from last year plantings.”
“Cover crops can also be part of the no-till system, which over the last 18 years have added 34 tons of biomass, which includes 13 tons of carbon per acre to the system, which is a good thing,” Mitchell said. “It adds fuel to the soil biology, but it’s not perfect.”
“My supposition would be that growing cover crops is more completed than people think. I have been at meetings where growers say: ‘are you kidding, I’m not going to grow cover crops because I do not have the water,’” Mitchell noted.
He said he understands the situation in not having enough water. But he explained, “In the winter time, yes there will be evaporation from the soil service every day. Radiation is beating down, and there will be evaporation.”
Evaporation in the cover crop field could be more nuanced. Maybe because the soil surface is shaded out, which would cool the soil, there may not be that much evaporation. The cover crops may increase infiltration of water in the ground, instead of it ponding on the soil surface.
“Yes, there will be some inevitable use of water by growing vegetation in the field in the winter, but it could be less than we think,” Mitchell said.
Mitchell then showed two large aluminum pans of soil. One showed soil dug up in an open field that has been tilled. The other container is soil with crop residue from the non-tilled plots.
He takes a handful of each and drops them into two individual gallon jars within an open metal grid with a few inches of water. This what Mitchell sees every time he does this. The large jar with tilled soil breaks up rapidly with soil particles dropping to the bottom. Within the no-tilled soil jar, the chunk of soil is very stable, with no soil particles breaking off.
“One thing that we are not doing now is looking at the potential benefits of these no-till systems and practices for conserving water and making better use of water that has been achieved in other areas of the world such as South America and the Great Plains and other regions of the United States. They do not have irrigation systems that California has; they have to wait for rainfall.”
“When we do the no-tilled system with lots of residue from back-to-back crops, with cover crops and with no disturbances, you may be able to keep 4 to 5 inches of water in the soil each year compared to a tilled crop.
More information on the Conservation No-Till system can be found here.
Along with working on water issues, Jennifer Lester Moffitt, Deputy Secretary for the California Department of Food and Agriculture, addresses soil quality. Muffin said, “We need to do everything we can do increase water holding capacity so that when do irrigate, when it does rain, we are able to retain that water in the soil. And there are so many additional benefits, I need to look up the exact number, but roughly half the biodiversity of the earth is in the soil.”
While many research budgets have already been stretched thin to deal with the drought, soil research has been funded largely by the healthy soils initiative from the USDA.
Moffitt explained, “Potential state funding sources might be green house gas reduction revenue, but in order to use that money, we would have to show carbon offsets. If we were able to do that, we could show demonstration projects and develop incentives for farmers to sequester carbon, and the impact could be immense. I mean, we have 9 million acres of farmland in the state, and even if we get a small percentage of growers to adopt these practices, we could really make a huge impact.”
Moffitt stated, “You know, I think definitely there are benefits to managing the soil, studying the drought and looking at how we can be more resilient. Particularly for agriculture during drought, maintaining excellent soil health provides a huge benefit–I think a dual benefit–along with mitigating climate change. There’s a whole handful that healthy soils can do.”
Moffitt also mentioned other departments involved in the health soils initiative, “The Department of Conservation is working on this, especially with their Farmland Mapping and Monitoring Program (FMMP).” According to the The Department of Conservation’s Division of Land Resource Protection (DLRP) website, FMMP “produces maps and statistical data for analyzing impacts on California’s agricultural resources. Agricultural land is rated according to soil quality and irrigation status; the best quality land is called Prime Farmland. The maps are updated every two years with the use of a computer mapping system, aerial imagery, public review, and field reconnaissance.”
“CalRecycle,” continued Moffitt, “especially with regard to compost and their goal to reduce green waste in landfills by composting and applying it on agricultural land, is a win-win, all around. Also, the Water Board, Air Resources Board, Department of Water Resources and the land they manage, are really part of a holistic approach.”