Center for Regenerative Agriculture and Resilient Systems

Fava Bean Trial Field Day

Why Study Fava Beans?

Fava bean is an ancient food crop that is extensively grown and consumed around the world. 

Dr. Jingo Hu, research geneticist at USDA, explained that the crop “has many names such as habas, broad bean, fava bean, horse bean, English bean, windsor bean, tick bean, cold bean, silkworm bean. It’s native to the Near East and the Mediterranean basin. It is one of the earliest domesticated crops and is still grown in many regions of the world for use as food, feed, vegetable and a cover crop.”

The top five producing countries of fava beans are China, Ethiopia, Australia, United Kingdom and Germany, while the top four importers of fava beans are Egypt, Norway, Saudi Arabia and Italy. China leads the world in fava bean production, harvesting 902,546 ha and producing 1,803,019 in 2017 alone.

 “The US fava bean germplasm collection of approximately 700 accessions from 60 countries maintained at the Western Regional Plant Introduction Station has high variation at the morphological and molecular levels," Hu said. "According to the Food and Agriculture Organization, the annual harvested fava bean acreage averaged 2.5 million hectares from 2005 to 2010 with an annual production of approximately 4.2 million tonnes.”

In California, fava bean is largely grown as winter cover crop to protect and add nitrogen to soil.

During the Fava Bean Nitrogen Fixation Trial Field Day at Lundberg Family Farms, several speakers taught on the benefits and selection of cover crops for different cropping systems. The talks were followed by a field trial that identified fava bean genotypes with enhanced nitrogen fixation.

An overview

Sarah Light, UCCE Agronomy Advisor, gave a broad overview of cover cropping by listing potential benefits.

Potential Benefits

Cover crops increase:

  • Water infiltration (improved soil structure)

  • Nitrogen for subsequent crops

  • Soil organic matter

  • Food for microbes (carbon)

  • Habitat for beneficial insects

  • Weed suppression

  • Improved accessibility

Cover crops reduce:

  • Soil erosion

  • Nitrogen leaching

  • Pest and disease pressure

Water infiltration and food soil structure are related to microbial activity. Microbes break up organic matter and release compounds that hold aggregates together.

“When we work our soil through some of the necessary on-farm management practices, we’re breaking up our soil aggregates, and that is increasing our soil’s ability to fly away with the wind,” Light said. “Microbial activity and increased carbon hold the aggregates together. Our top soil is our most valuable resources… Soil is a natural resource that we can’t replace… It’s vital for our lives, so we can be able to eat.”

“All life forms rely on carbon, including microbes. That’s the main benefit for so much of soil health, that carbon addition for microbial food.”

Microbes are all about carbon. They eat carbon in the root and create a habitat for themselves where their rhizobial bacteria fix their nitrogen. They need carbon just like humans do. The nitrogen cycle is directly tied to soil carbon and microbial activity. Microbes are responsible for every part of that nitrogen cycle, even converting our synthetic fertilizer.

Nitrogen availability is driven by mineralization, the conversion from organic nitrogen to plant nitrogen. Mineralization is driven by microbes. A low carbon:nitrogen ratio leads plants to rapid decomposition and net release of nitrogen, while a high carbon:nitrogen ratio leads plants to slow decomposition and net immobilization. Ideally, microbes want a diet that’s 24 parts carbon to 1 part nitrogen. When they break up something like a gas that’s higher in nitrogen than their ideal diet, they mine nitrate from the soil profile and use that to break up the carbon.

Fava beans fix nitrogen in their biomass throughout the season. In order to keep the legume from becoming a weed, it is recommended that good management practices be implemented for an optimum system and maximized nitrogen fixation: cut at flowering, maximize biomass, inoculate (especially during year one).

If you want to plant a cover crop, you need to think about what your goals are. If you want to fix nitrogen and have it available for your next crop, legumes are for you. They will reduce nitrogen leaching the least because they have more shallow roots and because they're not mining nitrogen as much. If you're in a high risk area with high soil nitrogen, plant a grass or a mix instead.

Warm and Cool Cover Crops

Margaret Smither-Kopperl, manager, of Lockeford Plant Materials Center spoke about the selection of warm and cool cover crops.

There is essential knowledge for cover crop planning that you need to have:

  • Understand the cropping system

  • When, and for how long is the cover crop window?

  • What equipment is available?

  • Is irrigation available? No or minimal water use is desirable but some planting times will require limited irrigation for germination and establishment.

  • What are the concerns of the producer?

Seasonal Choice for Annual Cover Crops:

Cool Season vs. Warm Season

Cool season:

  • Planted in fall or early spring

  • Will tolerate cold temperatures and some below freezing temperatures

  • Warm temperatures will cause plants to mature and set seed and die

  • Varying degrees of drought tolerance, depending on species and cultivar

Warm season:

  • Planted in spring after danger of frost has passed, may be planted through the summer to early fall

  • Freezing temperatures will kill these crops (winter kill)

  • Tolerate high summer temperatures

  • Varying degrees of drought tolerance, depending on species and cultivar

Some termination methods for cover crops include:

  • Mowing or swathing, leaving chopped material remains as residue on surface

  • Roller crimpers, which are widely used in the midwest

  • Disc under, which can lead to loss of carbon and soil moisture

  • Winterkill (warm season only)

  • Grazing (compatible with NRCS cover crop practice)

  • Chemical herbicide

Management concerns come with both problems and solutions:

Problems and Solutions to Cover Crops


  • Frost damage during bloom

  • Weeds in cover crop

  • Water use of cover crops (although it needs to be taken into consideration that cover crops increase infiltration and capture moisture through dew. Increased soil organic matter increases water holding capacity).


  • Select low growing species, mow cover crops prior to bloom

  • Select species to compete with weeds or mow (clovers, for instance)

  • Use drought tolerant cover crops

  • Use moisture sensors (IWM) to monitor soil moisture. Time for termination can be optimized so that the crop is mowed down at once water is started to be removed from the soil profile.

Smither-Kopperl’s final words of wisdom:

“Cover crop solutions are local. You must think about how cover crops can be integrated into your cropping systems. Speak to other producers, seed company representatives, extension, CCA with experience of cover crops. Don’t worry about growing the perfect cover crop. Consider return on investment, for example: nitrogen added, weed suppression, reduced irrigation, possible regulatory relief. When you find a system that works, build on your success. Incorporate new pants and changes to improve the system if you can. Take into account year to year differences. Last of all, be patient.”

Cover Crops in Orchards

Rory Crowley, Executive VP of Research and Business Development at Nicolaus Nut Company Inc. spoke about cover crops in orchards.

“One of the biggest things that I want to emphasize is the need for patience and balance in these discussions, particularly as it relate to cover crops in orcharding systems and perennial systems. This is by and large a very, very good thing for all growing systems in the central valley, but generally speaking in orchards,” Crowley said.

Crowley farms 700 acres of almonds and walnuts. Nicolaus Nut Company’s mission is to love their neighbor one nut at a time. Their vision is to see a world where agriculture serves the social, environmental and economic good. Their core values are people, planet and product. They aim to cultivate healthy lives, reserve farmland and resources and grow nuts and relationships.

“As part of fulfilling our mission, vision and core values, NNC saw a high potential in cover crop planting,” Crowley said. They believe it may be key to many benchmarks they’re trying to hit environmentally, socially, and economically, including possible significant impacts on:

  • Water use and conservation

  • Bee health, with ultimate impacts on crop pollination and therefore yield

  • Chemical, physical, and biological makeup of soils

  • Nematode reduction

  • Decreased conventional inputs particularly with nitrogen

  • Decreased soil erosion and displacement due to flooding on our ranches

The truth:

  • Cover crops do have potential to store carbon

  • Cover crops can certainly help the honey bees

  • In our experience, cover crop can help improve the soil’s structure and chemical, perhaps even biological components

  • Cover crop has vast potential for water savings but also takes water to grow; nuance is needed in orchards

  • Cover crop can and will affix nitrogen that can possibly begin to dial back use of conventual nitrogen sources

  • Cover crop becoming a pest kind of weed can indeed be a reality for growers

  • The agro-economic analysis of cover crops planting/managing needs much stricter research so we can demonstrate the benefits as it relates to time and cost to plant/manage

  • Just because we have not done something at some time in the past is absolutely no reason why we should not try it now

The bottom line:

“Cover cropping in orchard systems in the central valley of california is highly complex, should be nuanced in many ways, and is largely still in its infancy with regard to the science of the potential benefits in perennial orchard systems in California,” Crowley said.

“Much work has to be done by both the research community and by the growers to establish best management practices, economic analysis of cost/benefit, and how such cover crops can and will make impacts on the various and sundry topics we all want them to solve.

“Still, caution should be sought with regard to not speaking about cover crop as the best thing in the world that will solve all the world’s ills, nor should we discount cover crops out of hand because of its difficulty to implement.

“If you put life into the soil, you will get life out. That is why we farm. For life, socially, environmentally, and economically. Cover crop can be key to life in the orchard contest in our views.”

Fava Bean Benefits to Civilization

Professor Zakeri Hossain of CSU, Chico brought four of his undergraduate students in to finish off the presentation period of the field day. Students Aaron Alvarez, Amanda Cox, Chloe Dugger and Miriam Espinoza, spoke about the ways fava beans benefit civilization.

“It is a staple food for a lot of the developing world. It gives food stability, fights food malnutrition, eases poverty, and increases sustainable agriculture. It is used for animal feeds (pigs, horses, poultry), brick making (straw), cooking (mainly in the Middle East, Mediterranean, China and Ethiopia). It is adaptable, making it one of the easier crops to grow around the world."

“It has several nutritional benefits, including a high concentration of proteins (globulins, albumins, prolamins), thiamin, vitamin K vitamin B-6, potassium, copper, selenium, zing, and magnesium. It also has high levels of folate, iron, manganese, and dietary fiber. It has no saturated fat or cholesterol. The nutrient composition of fava bean seed (per cent) is 24-30 protein, 35-39 total starch (dry basis), 0.25-0.31 cystine acid, 1.48-1.61 lysine, and 0.17-0.19 methionine.”

To learn more about cover crops and fava beans, visit these UCANR resources:

Selecting the right cover crop gives multiple benefits(opens in new window)

Cover crops for walnut orchards (PDF)

Cover cropping for vegetable production, a growers handbook(opens in new window)

Cover cropping in vineyards, a growers handbook(opens in new window)