Introduction

From September 2020 to March 2021 the Desert Farming Initiative trialed and monitored eleven varieties of cover crops. The project goals were to understand the timing and establishment of species and degree of maturity for winter survival, investigate the best species and varieties for our climate, and to provide outreach and education regarding soil health management with the use of winter cover crops. This report provides an overview of our practices, each crop’s intended benefits, and its observed performance. Throughout our monitoring, we referred to the UNR Valley Road Weather Station maintained by the Desert Research Institute for information on climactic variables such as temperature and precipitation.
 

Cover Crop Purposes and Challenges

The Desert Farming Initiative is a 3-acre intensive organic farming operation consisting of field row crops and hoop houses. Cover crops are grown to protect the soil from erosion and for maintaining organic matter content and building soil fertility. Although there are many known winter cover crop species that work well in the Northern Hemisphere, in the high desert climate there is a greater challenge to establish and maintain winter cover crops successfully through the season.  Namely, there is very little to no fall precipitation; many irrigation delivery systems are shut down in early to mid-fall; freezing temperatures can persist in early to mid-fall when germination is occurring; and the very cold winter temperatures are not conducive for many winter cover crop species. In addition to climatic variables impacting germination, biomass growth, and mortality, other limiting factors on cover crop success in our area include insect infestation (flea beetles and leaf hoppers), and grazing by geese. Each of these challenges will be assessed in the performance of each crop trialed.
 

Cover Crops Grown

The following table shows all cover crops trialed, the seed used, the date seeded and whether they were grown in the field or a hoop house. Germination success and percent survival are purely qualitative and provide general insight into a crop’s performance.

All crops were seeded with a Jang or EarthWay seeder with the exception of the fava bean which was seeded by hand. These methods are practical on farms of several acres such as ours. All beds had 2-3 drip tape lines installed and lines were moved around to water the entirety of the bed.  After seeding there was little precipitation in the forecast so we irrigated to promote successful germination and allow the crops to establish and put on sufficient biomass. The cover crops in the fields were watered for about an hour and a half on eight separate days between September 24th and October 19th for a total of 18 hours. The cover crops in the hoop houses were irrigated for a total for 7.75 hours between October 22nd and December 10th, also in roughly 1.5 hour increments.

Each crop is discussed in more detail in the following sections.

Discussion of Cover Crops in the Field

Winter Cereal Rye – Leballister Seed

Intended Benefits:

Annual rye grass is a common species used as a cover crop or for winter forage in cold climates and has been grown with success as a winter cover crop in the Great Basin climate.  Its deep roots prevent compaction and improved tilth. It grows rapidly to cover the ground and reduce erosion.

Trial Results:

The winter cereal rye germinated well and grew healthily to about two and a half inches in height. The crop was quite tolerant of extreme low temperatures: 100% of the plants survived through our study with very minimal frost damage. While the rye held up well against the cold and did not have any issue with insects, geese posed a bigger problem. In January, the birds came through and evenly ate all the plants down to a short stubble. Nonetheless, the plants survived and as soon as the geese were no longer present they grew back healthily.  We would have anticipated much more growth and maturity than illustrated in the March 1st picture (below) if the geese were not an issue.  Rye can put on considerable above-ground biomass in late winter and early spring as the temperatures begin to warm and daylight increases, and following our last photo on March 1st it did continue to fill out significantly.

Winter cereal rye on October 22, 2020, January 15, 2021, and March 1, 2021. From high germination, to heavy grazing by geese, to healthy spring growth.

Triticale, Trios 888 – Leballister Seed

Intended Benefits:

Triticale is a hybrid crop species crossed between wheat and rye.  It has been cultivated and grown throughout the Great Basin with similar success as rye in winter. It can produce a thick ground cover before winter dormancy, followed by rapid spring growth. In addition to its benefits of weed suppression and erosion control, triticale prevents leaching of excess soil nitrogen.

Trial Results:

The triticale followed a very similar course to that of the winter rye: it germinated well and remained healthy through the coldest months of the year but was severely grazed by geese. The crop did not experience any insect infestation and had 100% survival through our study. Also similar to the rye, it filled back in quite well as soon as the geese had moved on and continued to grow until terminated.

Triticale on October 22, 2020, January 15, 2021, and March 1, 2021. From high germination, to heavy grazing by geese, to decent spring growth. Growth continued past the March 1 photo.

Camelina – Adaptive Seeds

Intended Benefits:

Camelina is an annual plant in the Brassica family. It is mainly grown for seed oil production but is being trialed as a cover crop in several states. The crop is proving incredibly winter-hardy. Plants provide soil cover and living roots through winter then put forth significant growth in the spring, creating good biomass. Camelina flowers from late April through early May, providing nectar for pollinators. The crop can also reduce leaching of nitrate and total nitrogen from the soil.  

Trial Results:

Camelina was anecdotally one of our highest-performing crops. Germination was excellent, and it was more frost-tolerant than many of the other crops. At least 95% of the plants survived the winter and continued to grow even as temperatures fell and sustained below freezing. By March 1, the plants were about three and a half inches tall, and the plants quickly grew much larger in the warming spring temperatures after the last formal observation for our study. The geese grazed the camelina, but only lightly, showing much higher preference for the triticale and winter rye. Insect pests were not an issue with this crop. As early as January 15 the plants were budding and on March 1 they were beginning to bolt.

Camelina has great potential in Nevada due to its frost tolerance and winter survival, and it can produce a high value seed crop in the early summer, providing farm revenue and soil health benefits to the farmer.

To learn more about Camelina visit this Agricultural Marketing Resource Center online resource.

Camelina: November 12, 2020. While other cover crops were severely impacted by the year’s first freeze on October 23, 2020, the camelina showed only slight damage.

Camelina on January 15, 2021. As temperatures dropped into the teens in December and early January, the camelina showed frost damage, however, it continued to grow and even began to bud.

Camelina on October 22, 2020, December 15, 2020, and March 1, 2021. The crop continued to grow throughout the winter.

Common Vetch, VNS – Great Basin Seeds

Intended Benefits:

Vetch is a popular cover crop in the Legume family, fixing atmospheric nitrogen into plant available forms in the soil, thus increasing crops’ nitrogen uptake in the growing season.  It is a viny plant species, known to be a great weed suppressor with moderate to strong winter survival rates, making it an ideal winter cover crop in most cold climates.

Trial Results:

In our trial, the common vetch had a low germination success rate. The plants reached three inches of biomass height in early October, but died back to around one-and-a-half inches following the first freeze at the end of the month.  The plants remained stunted through the coldest months of the winter and suffered some frost damage. Nonetheless, they all survived and responded well to rising temperatures come March and rapidly increased their biomass. Though our last official observation and photo date was March 1st, by the end of that month the plants had grown significantly, ultimately providing strong biomass and a pollinator-friendly flower.  An earlier seeding date may have produced better germination and more biomass heading into the winter and provided more ground cover through the winter months. The complete survival of vetch through freezing winter temperatures was a big advantage of the crop, and another was its unpalatability to geese. The vetch also did not encounter any insect pest issues.

For more information read: Oregon State University, Common Vetch

Common vetch: October 22, 2020, December 15, 2020, and March 1, 2021

Fava Bean, Sweet Lorane – Adaptive Seeds

Intended Benefits:

Fava beans are notoriously seeded in fall in the Western states for bean production, as a cover crop, or both.  In the last few years, The Great Basin Plant Materials Center in Fallon, NV had strong preliminary results with Fava beans. We chose to trial Sweet Lorane because of its short and stout stature, and smaller bean production, potentially making it more successful against our strong high desert winds. 

Trial Results:

Our fava beans had moderate to low germination, and by October 22 grew to their winter peak height of only around two and a half inches. Although mortality was not seen until January and never rose above 10%, the plants showed significant damage beginning with the first frost. Through the remainder of the study the plants were wilted and yellowing with many dead leaves. The crop did not attract the attention of the geese, although on March 1 leafhoppers were found on the leaves that remained alive. Nonetheless, the insects did not seem to cause much, if any, damage. Although the plants struggled through the winter, by March 1 there were nodules on the roots where they were providing the benefit of nitrogen fixation to the soil, and following the end of our formal monitoring the surviving plants produced significant biomass.  There are many fava bean varieties, and we are optimistic that there is a good variety for our climate and hope to incorporate favas again.

Frost damage on fava bean: January 15th

Fava bean: October 22, 2020 to March 1, 2021

Brassica Mix (40% Nemagon Mustard, 30% Oriental/Common Mustard, 15% Canola, 15% Daikon Radish)

- Leballister Seed

Intended Benefits:

This brassica mix from Leballister seeds has a suite of mustards that provide the same benefits of the Mighty Mustard Mix of suppressing fungal pathogens, reducing nematode pressure, and providing substantial biomass. 

Trial Results:

The brassica mix germinated well and had good initial growth to about three inches in height. The crop was quickly impacted by flea beetles which seemed especially attracted to the mustards in the mix. Following the first freeze around 10% of the crop died. Most mortality was seen in the youngest and smallest plants. It is possible that if the crop were seeded earlier and the plants allowed to establish more before temperatures dropped below freezing there would be better survival. By December 15th about 40% of the mix had died and those surviving were wilted, yellowed, and crisp with frost damage. There was no further mortality, although the 60% of plants that survived never put out more growth and did not provide great ground coverage. Fortunately, this crop did not experience any grazing by geese, which is a benefit on our site.

For more information see: Brassicas and Mustards

Flea beetle and frost damage to brassica mix: November 12, 2020

Brassica mix: October 22, 2020 to March 1, 2021

Mighty Mustard Mix (White Gold Mustard, Kodiak Oriental Mustard, Pacific Gold Mustard)

– Great Basin Seeds

Intended Benefits:

Mighty Mustard Mix is a proprietary blend of three mustard species: White Gold Mustard, Kodiak Oriental Mustard, and Pacific Gold Mustard.  Each mustard species offers a unique benefit to the soil. Two of the mustards contain high levels of glucosinolates which trigger the release of natural compounds called isothiocyanates (ITCs), which function as an efficient natural pesticide, suppress fungal pathogens such as Verticillium, and are highly effective at reducing nematode pressure. The combined benefits of the mix can reduce compaction and produce incredible biomass, providing ample ground cover for erosion control.

Trial Results:

The Mighty Mustard Mix had high germination and rapidly produced great above ground biomass compared to most cover crops trialed.  However, the overall results were poor.  After reaching a peak biomass of three inches in height it was damaged by flea beetle infestation and frost. By January 15th, 2021 roughly 30% of the plants had died from frost damage, while those still living had lost many leaves. The geese present in the field through December and January did not feed on the mustards. On March 1st around half of the crop had died from frost, and the flea beetles first seen in October had returned. Throughout the winter mortality increased while the biomass of the surviving plants decreased.

Frost and flea beetle damage on mighty mustard mix: December 15, 2020

Mighty mustard mix: October 22, 2020 to March 1, 2021

Legume Cover Special Mix (Bell Beans, Common Vetch, Magnus Peas, Dundale Peas)

 - Leballister Seed

Intended Benefits:

Legumes are a special family of plants, with annual, biennial and perennial species that are all known to be used as cover crops in different cropping systems.  Legumes are well known for their ability to fix atmospheric nitrogen into the soil, however they also provide suite of benefits to a cover crop mix: adding organic matter to the soil, attracting beneficial insects when flowering, and increasing ground cover for erosion control.  

Trial Results:

The legume mix trialed had moderate germination and grew well in October, up to its peak height of four inches. After the first frost the crop began to decline. The freezing temperatures had killed a quarter of the plants by November 12, half of them December 15, 80% by January 15, and 85% by March 30. The bell beans in the mix accounted for most of the early die-off and none made it to the end of our study in March. The leaves of the pea plants turned red at the edges: a sign of stress. The legume mix did not have any issues with insects or geese.

Legume mix on October 22, 2020, December 15, 2020, and March 1, 2021. From moderate germination, to worsening frost-kill.

Tillage Daikon Radish - Great Basin Seeds

Intended Benefits:

Radish is a winter annual in the Brassica family, and is a popular winter cover crop in many climates, especially utilized for its ability to break up soil compaction. Radishes are not tolerant of extremely low temperatures (below 25F), however, they are winter cold tolerant in many North American climates. With winter average temperatures increasing in the Reno area, we decided to evaluate if the Daikon Tillage Radish could survive our winters in one of the warmer Great Basin Climates in Nevada.

Trial Results:

Overall, our daikon radish had very poor growth and survival despite high germination. The plants hit their peak biomass in October, growing to about four inches in height, and steadily declined from that point. By October 22nd pest damage (primarily flee beetle) was observed in close to half of the leaves, and by November 12th 35% of the plants had died following the winter’s first freeze (October 23rd) and first snowfall (November 8th). By December half of the plants had completely died, and those alive were in poor condition. In December geese began feeding on other cover crops in our fields but were not interested in the daikon radishes. Virtually zero of the radishes survived through the winter until our final observation on March 1st.  While insect damage was seen early on, the die off can be mainly attributed to frost kill. 

For more information read: Radish: An Introduced Cover Crop for Conservation Use in Montana and Wyoming

Insect damage on daikon radish: October 22, 2020

Daikon radishes had nearly complete die off by January 15, 2021

Daikon radishes were severely impacted by first frost: October 22, 2020 and November 12, 2020

Dwarf Siberian Kale, Forage Kale – Great Basin Seeds

Intended Benefits:

Forage brassicas, like the dwarf Siberian kale in our trial are known to be moderately cold-hardy and can survive many winter climates.  As a cover crop, kale can open up the soil with its tap roots and protect soil from erosion.

Trial Results:

The dwarf Siberian kale had high initial germination and growth, reaching a peak height of four inches tall in October, and the crop did not experience any insect or goose damage. However, the winter’s first frost on October 23, 2020 and first snow on November 8, 2020 killed nearly all of the plants, and by December 12, 2020 there was complete mortality, which we attribute to frost.  We expected the crop to be more cold-hardy, but it proved one of our least successful cover crops of the trial. 

Dwarf Siberian kale: October 22, 2020 to November 12, 2020

Discussion of Cover Crops in the Hoop Houses

Organic Soil Builder Mix (Bell Beans, Magnus Peas, Dundale Peas, Common Vetch, Barley, Oats) & Common Vetch - Leballister Seed

Intended Benefits:

The Organic Soil Builder (OSB) is a common example of a species composition mix. These cover crop blends are often used as a green manure plow down cover crop in many vegetable tillage systems. These systems incorporate cover crop into the soil to increase soil organic matter and available nutrients. While growing, the ground cover provides erosion control and the living roots in the soil provides food for soil microbes and contribute to the formation of soil aggregates.

Trial Results:

The OSB was mixed with common vetch in three beds in a hoop house. Most of the species in the OSB cannot survive the Great Basin winters, therefore we utilize them in the hoop houses.  The plants germinated well, were generally healthy, and grew to more than six inches in height. The pea plants in the mix turned purple-red in the leaves which is a sign of cold stress. Low temperatures inhibit efficient uptake of phosphorus which leads to the discoloration. We encountered a problem in the hoop houses that we did not in the fields: weed competition. Weed pressure was expected due to higher daily temperatures in the hoop houses, allowing for and promoting ideal conditions for many weed species to germinate. Weeds were present throughout the beds, but especially in the sections that were left bare from incomplete germination. In January small birds began entering the hoop houses through gaps in the siding and fed on the cover crop, however, the damage was insignificant. We did not encounter any issues with insects. Overall the crop provided good cover and supported organic processes in the soil of our hoop house though the winter.

Organic soil builder and common vetch: December 15, 2020. Cereals are fed on by birds, and peas are reddening.

Organic Soil Builder and Common Vetch: January 15, 2021           

Legume Cover Special Mix (Bell Beans, Common Vetch, Magnus Peas, Dundale Peas) - Leballister Seed

Intended Benefits:

The legume mix used in the fields was also grown across four beds in a hoop house, providing the same benefits of nitrogen fixation as described above. Legumes have relatively small root systems and are not very fibrous, therefore the crop is easy to terminate and transplant vegetables right over, making them a great choice for no-till systems.

Trial Results:

The mix performed very well in the hoop house. It had high germination and grew to more than seven inches tall. There was no die-off through the winter. Just as they did in the field, the leaves of the pea plants turned red due to the inability to uptake phosphorus at cold temperatures. Leafhoppers were seen on this crop, although they did not cause noticeable damage. We did not experience the same issue of small birds entering the hoop house to feed on this crop despite there being possible points of entry.

Legume Cover Special Mix: January 15, 2021. Growth continued significantly following this photo.

Winter Cover Crop Termination

To terminate the majority of the winter cover crops we used three different methods: hand hoeing, disking, and covering with silage tarp. Crops that did not survive the winter and those with minimal biomass were simply removed by hand with hoes to minimize soil disturbance. For living crops with significant biomass our preferred method of termination is covering with silage tarp as this leaves the soil undisturbed. However, the cost of the tarp can be prohibitive, and we only had enough to use this method on several beds. In the remaining beds we had to resort to disking to terminate the cover crops for spring planting. Apart from these main strategies we tried a few other techniques: the legume mix was mowed down and used as a high-nitrogen input into a compost pile, while the fava beans were crimped by hand and left as a mulch.

Published by: Moe, J, 2021, Winter Cover Crop Trial Report (2020/2021), Desert Farming Initiative, University of Nevada, Reno, Research Report

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