SPRING 2017 NEWSLETTER INTRODUCTION

FOCUS ON AGRICULTURE IN THE CHAMPLAIN VALLEY AND BEYOND

  By Jeff Carter, Agronomy Specialist,

Champlain Valley Crop, Soil & Pasture Team

Agronomy and Conservation Assistance Program

Nutrient Management Plan (NMP) classes have been a major emphasis of activity for the past months and 31 farmers completed their NMP through
the UVM Extension goCrop™ classes that were held in Richmond, Middlebury and Pawlet. Statewide, over 70 farmers completed the classes offered by the St. Albans and Middlebury Extension Crop teams so farmers can develop their own crop management plans. There are plenty of field meetings, corn planter clinics, farmer manure trainings, stream floodplain restriction discussions, and buffer workshops going on now and more to come this spring, all geared toward how farmers will adopt practices to meet the Required Agricultural Practices (RAP) rules. Stay updated about current events via e-mail: join our email list at
www.uvm.edu/extension/cvcrops.

Field Research/Demonstration

We will be starting some new projects this year with financial support from the NRCS Vermont Conservation Innovation Grant Program; the Agency of Agriculture, Food and Markets; and the Northeast SARE program to continue our work with local farmers. One study
will start a benchmark program for the economics of growing cover crops and using no-till for crop planting. What is the true cost and benefit of moving to no-till with cover, and then how profitable are you? We need better data about the Vermont farms who have changed to these new crop systems to be sure of the right investments for your particular farm. Starting with a handful of farms who have agreed to provide the details
about their operations, the data from this project will reflect current finances of these conservation practices as they are used here on our soils.

Whole-farm phosphorus (P) mass balance has been around for some time,
but few farms complete the accounting of where the extra P comes from. We have a project to work with several farmers and their feed consultants to collect data on the extent of P imported to local dairy farms. This is good information to have, but really the issue is what to do then? Not all P is leaving the farms, and that is why farmers use the P-Index to better understand the risk of P loss and “plug” any leaks in the farm system.
We will be field testing the new 2017 Vermont P-Index and a new Northeast P-Index on several farms and relate that data to whole-farm P-Mass balances and farm conservation. We will collect data to help farmers with crop management decisions under the revised Vermont P-Index. This will then be used to address the NMP 590 standard, which is the basis for all farm nutrient plans. What to do then if you have a high phosphorus soil test? Another study we have is to evaluate the use of field applications of amendments to reduce soil test P in the field. We will be looking at three types of gypsum, including one with humates, also contrasted with short-paper fiber (SPF). When spring does get here, we
will also see how good the cover crops perform that we planted last fall.

VERMONT RAP RULES
The Vermont Required Agricultural Practices rules affects all farmers this year, and so it affects our Extension work. Focus on Agriculture means a focus on helping you to learn (like Poop Skool) and then figure out the best next steps to take (whatever that is). Give us a call, or just come to the meetings that we host with the Champlain Valley Farmer Coalition.
This is a great way to keep up with new ideas so you can deal with changing times in Vermont agriculture.

Have a question for Jeff?
Jeff Carter (802) 388-4969 ext. 332
jeff.carter@uvm.edu

COVER CROPS: FROM RESEARCH TO REALITY

By Kirsten Workman, Agronomy Outreach Professional

For the last 5 years, our team has had grant funding from the USDA to do research and demonstration projects investigating novel ways of cover cropping in corn silage and soybean systems in Vermont. We started with a small project in 2013 in Ferrisburgh at Deer Valley Farm comparing 2 different cover crop mixtures planted into the standing corn and drilled after harvest. That project was successful and provided us with enough preliminary data to start investigating additional cover crop mixtures and planting timing on a larger basis.

In 2014, we started our NRCS Conservation Innovation Grant, “Better Cover Crop Mixes in Vermont.” This project enabled us to evaluate several three-way cover crop mixtures alongside a winter rye monoculture. The cover crops were planted into standing corn (at V5/V6 growth stage and at tassel) as well as drilled after harvest. Similarly, we interseeded into soybeans at R3-5 and R6-8. As a result, we ultimately evaluated 15 different three-way cover crop mixtures during 29 different planting events for a total of 319 research plots. This work could not have happened without our farm partners. For this project alone, we collaborated with 10 farms on 13 fields in 7 Vermont towns.

So what? you may wonder. These plots provided us with valuable data to share with producers, NRCS staff, technical service providers and agency folks, and that information is helping us make sound recommendations for successful cover cropping in Vermont. However, the true value of this project (and our other cover crop projects) is the ability to enable hundreds of Vermont farmers to witness, learn about and adopt this practice. In this single grant project described above, we were able to do some amazing outreach to farmers. This included 12 field days, 6 presentations, 7 newsletter articles and 5 Across the Fence television episodes. Our field days involved over 200 farmers, 61 agricultural business employees, and 112 agency staff. Our workshops and conferences reached 153 farmers, 81 ag. business employees and 221 agency staff. And while that in itself is a tremendous feat, the real so what is that we have seen exponential increases in the adoption of cover crops in Vermont over the last 3 to 5 years.

According to the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS) data, “Vermont farmers planted a record-setting 25,727 acres of cover crops on more than 2,000 fields in 2016 on approximately 25% of all annual cropland in Vermont. That’s a 58% increase in the acres of protective winter cover crops planted in 2015.” By my count, it is a 250% increase from 2014. While these research and demonstration projects are by no means the sole reason for this impressive rate of adoption, I do believe they are an important piece of the puzzle. Enabling farmers in the Champlain Valley to approach these conservation practices with solid, local information that allows them to be successful. They are able to investigate species, planting methods, potential pitfalls and see for themselves when and if these cover crops make the most sense on their farms, in their soil and weather conditions and with their equipment. And most importantly they are getting the most out of their cover crops by establishing them in a truly effective way, meaning the cover crops are functioning as intended and providing erosion control, taking up manure nutrients, and protecting water quality. In addition, the farmers are figuring out how to do it more profitably, utilizing these cover crops for forage or as a key component in their no-till systems, using less seed and planting it better, and even growing their own seed. Essentially, Vermont farmers are making them an integral part of their farming operations. This is the true meaning of adoption. Not just throwing seed out there because there is cost-share money, but REALLY MAKING IT WORK.

An example of cover crop research plots comparing broadcasting seed on the soil surface versus planting with a no-till grain drill. Both were planted on the same day, after corn silage harvest, on Vergennes clay soil, and received aproximately 4,000 gallons of liquid dairy manure/acre. Pictures were taken about two months after planting and in the following spring.

 

CROP YIELD AND NITROGEN MANAGEMENT IN A COVER CROP, NO-TILL SYSTEM

By Kristin Williams, Agronomy Outreach Professional

We just finished a two-year, multi-farm study on the health of clay soils, funded through a VT Conservation Innovation Grant through the NRCS. Measures of soil health (using Cornell’s soil health test) were not consistent, and we found that comparing practices over time was more informative than comparing field to field. One interesting, and maybe
obvious, lesson was the correlation between soil health practices and crop yields.

So, how do soil health practices influence yield? Research suggests soil health can improve yields. It is important to note our project focused on  demonstration, not replicated research. We compared no-till and conventional/reduced till corn silage on 5 farms with clay fields in our region. A simple t-test revealed no significant difference in yield between no-till (19.1 tons/acre) and conventional (19.2 tons/acre). More importantly, we were able to demonstrate that a farmer can grow no-till without yield losses, and be successful with good management practices. A yield gain might take time as the soil builds up its condition.

We also wondered how cover crop species or mixes might affect corn silage yield. We had an opportunity to use a field where the corn was accidentally killed. We planted 15 different combinations, including 4 single species, 6 two-way mixes, and 5 three-way mixes. This project was a slight anomaly in that the cover crops were planted with a drill in late August, which allowed for a more vigorous production of all cover crops. Radish was a star in the fall, maximizing both phosphorus and nitrogen uptake. We did not measure phosphorus content in the spring, so we do not know how much was retained in the soil. It seems to have allowed
for more available nitrogen in the soil at the time of a pre-sidedress nitrogen test (PSNT), therefore requiring less nitrogen. Surprisingly, legume mix covers had good fall biomass, but that did not translate into more N mineralization.

We applied nitrogen to each plot as per the PSNT recommendation for 20 tons/acre corn silage. At the end of the season, we measured corn silage
yield and compared that to nitrogen applied (see graph). The winter rye plot had a lower corn silage yield and required more nitrogen. Other than the nutrient effect of less uptake and slower decomposition, there may have been a physical barrier created by the standing rye crop, which was particularly vigorous in the spring. However, our three-way mix (winter rye – oats – radish) actually had the highest average corn silage yield, even though it required more N at PSNT time than the pure radish stand.

So, do not go abandoning your winter rye just yet. In fact, we think this three-way mix has promise and we are looking for a mix that gives both fall and spring soil conservation. Radish alone will winter kill, which may be good for mineralization, but not as good for spring soil conservation. Oats also winter kill but provide faster fall soil cover than rye by itself.

When using an over-wintering cover crop, it is clear that timing and success of termination is critical for subsequent crop yields. Nitrogen mineralization may happen later in the season with a plant such as winter rye that has a heavier carbon content. In a no-till system particularly, you may need to adjust your nitrogen rates/timing and put more on upfront. If you are using cover crops, a PSNT seems like a wise investment.

It is also important to remember that soil health is a long game, and it may take time to see the results of your labors with cover crops. We have replicated this project by replanting these cover crops in the fall of 2016, this time planted in September, and will look at this again this coming season.

More info about UVM’s PSNT test can be found at:
go.uvm.edu/getpsnt

Winter 2016-2017 Newsletter Introduction

Focus on Agriculture in the Champlain Valley and Beyond

jeffrey-carterBy Jeff Carter, UVM Ext. Agronomist

Champlain Valley Crop, Soil & Pasture Team Leader

 

We all have learned a lot about using no-till and cover crop farming practices on clay soils over the past few years, and feel good about it because improving soil health for the future really is important. If not, I don’t think you would be farming.

But the fabric of agriculture is a bit tricky as one side pulls the covers off the other, then back, and over and over. Field practices to improve crop yields and water infiltration come back to bite us with reports of fear that this will increase the amount of dissolved phosphorus in the soil, which is exactly what you want for better crops, but not if it leaks out and pollutes Lake Champlain. Now the quilt comes off again and it becomes apparent that the environmental damage may be increased by activities like improving soil health with tile drainage, no-till planting, even cover crop roots that go down into the soil to reduce compaction. All are field practices we promote with confidence that this will solve the “problem”.

Now in a recent report from Farm Journal, Field Agronomist Ken Ferrie discusses how improving soil health increases the concerns about nitrate and water-soluble phosphorus losses down through the soil. But let’s not stop with that part of the equation. This is not a bad thing; it’s just that now farmers need to be even more aware of how their field management practices impact their P losses. And how important the work we do at Extension to compare different cropping system components helps farmers decide what balance of tillage and crop types is right for their farm. One response is to stop if we are afraid; the other is to carefully move ahead with calculated confidence that we are making a positive difference, measure the effect, recognize some new problems, and move ahead.

carter-2016-december-photo-1-crop-smsize
“Wait a minute, I lost my pencil in this preferential flow pathway”.  As the season progresses, clay soils can develop cracks that swell open and then close when the soil gets saturated again in winter.

The Required Agriculture Practices are now here, and we will have a lot of “quilt pulling” as changing one thing like – requiring buffers along ditches – may trigger responses that are counter-productive like installing tile in the whole field and burying those ditches. Which way is better? I’m not sure; just that when the quilt gets pulled off me, I pull back. Switching to no-till corn is a proven way to help soil aggregate structure, greatly reduce soil erosion and reduce fossil fuel use. Yet the reaction is that preferential flow paths through the soil form as a conduit to move manure and P too fast through the soil matrix.

The Vermont Tile Drainage Advisory Group report has been submitted to the Agencies of Agriculture and Natural Resources, and will inform the Secretaries for their joint report to the legislature in January. I participated on that advisory group and the discussions highlighted that these issues are not simply good and bad. Every action, like improving soil drainage, forces a conflict between a current farm business and family sustainability, and the cost of water quality remediation for past indiscretions in our lake that we are faced with fixing.

The only way that we will be able to keep a reasonable perspective is for everyone (both sides of the bed) to continue to be vigilant to maintain a good balance of using our land resources to make money, but keep the water clean. This will never end, as the challenges of farming in Vermont are made more difficult with awareness of how a little P makes such a big problem in the Lake.

I heard a great quote: “there are no wrong turns on the journey, just course corrections when we figure out where we want to go next.” I think we should be focused on learning how to make the best next moves, together, for farming practices that will help us meet the P reduction goals of the Vermont Clean Water Act. I don’t agree with the folks who want to curtail the dairy industry in Vermont with hopes that a different farming model or land use is better. Get active in your local farmer watershed group (there are three in Vt.), come to conferences and workshops we offer to get better at these decisions, speak up so the general public and legislative policy makers hear your voice.

Have a question for Jeff? He can be reached at 802-388-4969 ext. 332 or jeff.carter@uvm.edu

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Stay updated on our events via our blogpage, or via Facebook

A pdf version of our entire newsletter can be viewed here. Our team work is funded through multiple grants and could not be accomplished without our supporters and funders.

Individual newsletter articles can be viewed on the blog below.

Beginning Farmer and Rancher Benefits

By Jake Jacobs

UVM RMA Risk Management Education

USDA has established certain benefits designed to help beginning farmers and ranchers start their operations. These benefits include:

  • Exemption from paying the administrative fee for catastrophic and additional coverage policies;
  • Additional 10 percentage points of premium subsidy for additional coverage policies that have premium subsidy;
  • Use of the production history of farming operations that you were previously involved in the decision making or physical activities; and
  • An increase in the substitute Yield Adjustment, which allows you to replace a low yield due to an insured cause of loss, from 60 to 80 percent of the applicable transitional yield (T-Yield).

How to Apply for Benefits

You must apply for Beginning Farmer and Rancher benefits by your Federal crop insurance policy’s sales closing date. You are required to identify any previous farming or ranching experience and any exclusionary time periods you were under the age of 18, in post-secondary education, or active duty military. Talk to your crop insurance agent for more information.

Cover Crop Guidelines

Recently the Farm Service Agency (FSA), Natural Resource Conservation Service (NRCS) and Risk Management Agency (RMA) worked together to develop consistent, simple and flexible policy for cover crop practices. Search for “Cover Crops and Soil Health” at www.nrcs.usda.gov or contact your local agency for more information.

beginning-farmer
Being a young farmer is challenging enough, but learning about the best options for the business like Sayer Palmer is, can be even more difficult. Contact your crop insurance agent for Beginning Farmer and Rancher benefit information. Photo: Jenn Colby.

 

How Do We Decide When To No-Till Alfalfa?

Nathaniel SeveryConsider the Density and Vigor of Your Cover Crop

By Nate Severy

UVM Ext. Agronomy Outreach Professional

Over the past year there has been growing interest in the farming alfalfa 8242016community in trying to no-till alfalfa hay seedings into winter cover crops as a way of reducing erosion and saving time and fuel.  Come spring, there will be a number of farmers who want to plant then or early summer who will look at their fields wondering “should I plant now, or wait until later?” While we have not yet done any formal research looking at alfalfa establishment under different management systems and the associated economics, there are some clues that may be able to guide us until we have more data.

One clue we can look at when deciding whether to plant in early spring or early summer is cover crop stand density. (Late-summer seeding is also a consideration that we won’t discuss in this article.) We know from helping farmers no-till-renovate pastures/hay fields that a productive and competitive hay field will outcompete your no-till seedlings for light and nutrients.  We should expect this same thing to happen when we have cover crops.

A field was planted to winter rye after corn silage harvest in early September; by December it completely covered the soil surface and was between 4 and 6 inches high.

severy-pic-1-cropped
Dense cover crops like this winter rye can be good for soil conservation, but challenging for no-till planting.

This success was due in part to early planting, full seeding rate, and timely rain. In spring, we expect that this crop is going to take-off and, with proper management, will be very high yielding.  If alfalfa mix were planted into this stand in April without any control methods, will our seedlings be able to compete?  Maybe, but we wouldn’t count on it.  We are not suggesting that a productive stand is bad, as it provides many environmental and economics benefits, but it must be managed correctly.  So, in this situation, we would recommend that before seeding an alfalfa mix, a farmer should either terminate the cover crop, or wait until mid-May and harvest for livestock feed before seeding.  If the field is terminated in April, the alfalfa should be planted with a nurse crop like barley or oats.  If properly killed, the winter rye will be barely noticeable after about a month. If there is no nurse crop, there will be a substantial amount of bare ground which will be susceptible to erosion and weed pressure.

Another field was planted in late September 2015 to winter rye after corn silage harvest. By early April 2016, although the cover crop did protect against erosion, there was still a lot of bare soil.

severy-pic-2-cropped
In contrast to the first picture, a winter rye crop that was lower yielding will be less competition for a no-till crop like alfalfa.

A crop like this can produce high quality livestock feed, but will be very low yielding.  In this type of situation, the farmer can go ahead and plant alfalfa mix.  S/he can terminate the cover crop beforehand, but there should be enough open canopy that the cover crop should not be a problem.  This winter rye can later be mowed for livestock feed, or possibly even left and combined for seed for next fall’s cover crop.

Do you have questions about this work or would like assistance with no-till alfalfa? Contact Nate [802-388-4969 ext. 348, nathaniel.severy@uvm.edu]

Mustard Cover Crops Offer Benefits Beyond Soil Health

RicoBy Rico Balzano

UVM Ext. Agronomy Outreach Professional

 

 

There is growing consensus that cover crops have many environmental and agronomic benefits including reducing soil erosion, adding valuable organic matter, and improving overall soil health. But how do cover crops fit into a weed control program? And how may they effect other soil-borne pests and diseases?

mustad-cover-crop-ready-for-termination-and-incorporation
Mustard cover crop ready for termination and incorporation

In 2015, I received a SARE farmer grant to explore the use of mustard cover crops to help control plant parasitic nematodes*, weeds, and soil-borne diseases. Varieties of two species of mustard (Sinapis alba and Brassica juncea) have been identified as producing chemical compounds known as glucosinolates that have been shown to reduce fungus and nematodes populations when mowed and incorporated into the soil. This process is known as biofumigation.

Six varieties of mustard were trialed to test glucosinolate production and overall biomass yield. The yields were measured by weighing samples in the field, and glucosinolates were measured by a lab at the University of Idaho. The varieties were: Kodiak (Brassica juncea), Pacific Gold (Brassica juncea), Ida Gold (Sinapis alba), Caliente 119 (S.alba and B. juncea blend), Caliente 199 (S.alba and B. juncea blend), and Nemat (Eruca sativa– also a Brassica, bred as a nematode trap crop). They were planted in the spring of 2015 and allowed to grow for 60 days before incorporation and measurements were taken. It was found that ‘Caliente 199’ had the highest biomass yield and highest levels of the glucosinolate sinigrin, a volatile compound that has been shown to have anti-fungal and anti-nematode properties. Interestingly, ‘Ida Gold’ contained another gluscosinolate, sinalbin. This non-volatile compound has shown the ability to inhibit weed seed germination. Unlike Although measurements were not taken, it was observed there was less overall weed pressure in the ‘Ida Gold’ plots. This is similar to observations in trials of ’tillage radish’, another Brassica species. It was not determined whether weed suppression was a result of biofumigation or a dense cover crop outcompeting weeds. Planting rate (density) in other cover crops such as winter rye and oats has been shown to effectively suppress weeds. Further study is needed to determine how planting rates of mustards and other Brassica species effect glucosinolate production, disease suppression, and weed control.

As with any biological control, results can be variable. In trials in Idaho, higher soil moisture improved fungus and nematode suppression, while increasing weed pressure. It is necessary to macerate and incorporate the mustard plants for the glucosinolates to be effective. This can be accomplished by mowing and disking in the plants. For fall planted mustards and Brassicas, freezing and thawing may effectively macerate and release the glucosinolate sinalbin, potentially explaining weed suppression the following spring. Further study is needed to determine how these bio-chemicals and cover crops perform under different management.

*Not all nematodes are detrimental. Many play an important role in soil ecology.

Questions about using mustard cover crops? Contact Rico Balzano [802-388-4969 ext. 338, rico.balzano@uvm.edu]

2017 No-Till & Cover Crop Symposium

cover_graphicUVM Extension Annual No Till & Cover Crop Symposium

Join us on February 16, 2017 at the Sheraton Hotel & Conference Center in Burlington, Vermont

Time: 9:00 am to 4:30 pm

Cost: $80 or $40 for graduate students …lunch, snacks, coffee/beverages included

Register Online: go.uvm.edu/ntcc

Questions about registration can be directed to Karen Gallott [802-388-4969, karen.gallott@uvm.edu]

CCA and Pesticide Credits will be available

Coming Soon: Sponsor link, Brochure, and Graduate Student Poster Session.

The UVM Extension’s Champlain Valley Crop, Soil & Pasture Team & the Northwest Crops & Soils Program invite all farmers and technical advisers to attend this event dedicated to No-Till and Cover Crop systems for field crop growers in our area.  We are welcoming speakers from around the country and from Vermont – including Extension specialists, researchers, farmers and consultants.

Speakers confirmed so far:

  • Dr. John Tooker, Penn State University
  • Mark Anderson, Land View Farms, LLC
  • UVM Faculty & Staff
  • Farmer Panel

To book a room at the Sheraton at the special rate of $109 plus tax, contact the Sheraton at (800)325-3535. Request UVM Extension No Till & Crop Symposium Room Block.  Cutoff Date for special rate is February 3, 2017.

To request a disability related accommodation to participate in this program, please contact Karen Gallott at 802-388-4969 or toll free in  Vermont at 1-800-956-1125 by January 23, 2017 so we may assist you.

Fall 2016 Cover Crop Field Days

Cover Crop Field Day:
Tuesday October 25, 2016
The Champlain Valley Crop, Soils, and Pasture Team will lead a hands-on discussion of benefits cover crop mixes hosted by Chuck Farr and Ashley Farr and families. Farr Farms is a multi-generational dairy operation; Chuck Farr focuses on crop production while his son, Ashley, and his family manages the dairy. Here, we will discuss the many opportunities that winter rye, grown as a seed crop, can offer. We will also take a look at large blocks of 8 different combinations of legumes, brassicas and cereal grains and discuss the benefits and challenges of these systems. We will be looking at cover crops that we drilled with our no-till grain drill.

This cover crop field day is part of a series hosted in conjunction with the UVM Ext. Northwest Crops and Soils Team and the Vegetable and Berry Program.

When: Tuesday October 25, 2016 at 1pm – 3pm
Where: 491 Huntington Rd, Farr Family Farm, Richmond, VT – google maps
RSVP: Register here
or contact Kirsten Workman
at (802)-388-4969 347; kirsten.workman@uvm.edu
See our Fall 2016 Cover Crop Flyer – for a description of all events!
Other Cover Crop Field Days (each day from 1pm – 3pm):
  • October 26, at Foote Brook Farm in Johnson, VT
  • October 27, a tour of cover crops at farms in St. Albans, VT
  • October 28, a look at research plots in Alburgh, VT

Special thanks to the Farr Family.   

To request a disability-related accommodation to participate in this program, contact Susan Brouillette by 10/17/16 at 802-524-6501 or toll-free in VT at 1-800-639-2130 so we may assist you.

IMG_1925

Legumes…

Getting More Out of Your Cover Crop

By Kirsten Workman

UVM Ext. Agronomy Outreach Professional

Vermont farmers are on target to plant over 20,000 acres of cover crops this year.  The majority of these acres will be Mixed species cover crops up closeplanted to winter rye, but there is still time (even now) to get a little more from your cover crop.

Legumes are unique because of their ability to fix nitrogen, utilize that nitrogen themselves reducing fertilizer requirements, and contribute it back to the soil for use by the following crop. Agricultural legumes are plants that are in the family Fabaceae.  Most farmers are familiar with the list of legumes that comprise their forage legume species like alfalfa, clover, and trefoil, or those that are grown for grain like soybeans, peas, lentils and even peanuts. And don’t forget the vegetable legume crops like green beans and snap peas.

Legumes also have a much lower carbon to nitrogen ratio (C:N) than cereal grains, so they decompose quicker making that nitrogen more available to the subsequent crop.  If you have ever plowed down (or killed) a nice stand of alfalfa and then planted corn, then you know just how beneficial a legume in your crop rotation can be.  Legumes can provide over 100 pounds of nitrogen credit per acre, which is why they are often called ‘green manures’.

Rhizobium nodulation seen on pea cover crop roots
Rhizobia nodulation seen on pea cover crop roots

The legumes themselves are not responsible for nitrogen fixation, however.  This happens as a result of a symbiotic relationship between the nitrogen-fixing bacteria that invade the plant root and store nitrogen in root nodules.  The plant provides the bacteria with nutrients and energy, and the bacteria provide the plant with a usable form of nitrogen.  These bacteria, called Rhizobia, are able to take nitrogen gas from the atmosphere (N2) and convert it to ammonia (NH3), which is then converted to ammonium (NH4+) and nitrate (NO3) which are the forms of nitrogen usable by plants.  In order for good root nodulation and maximum nitrogen production, it is important to inoculate your legumes with the appropriate species of Rhizobia bacteria at planting.  Some seed is available pre-inoculated, but many times you will need to apply the inoculant yourself.  Whoever you get your seed from should have inoculant available as well.  Beware, however, inoculants have a short shelf-life and are also species specific.  Using clover inoculant on peas or vetch will not be successful.

Plant Available Nitrogen (PAN)

From D. Sullivan, Oregon State Univ. See Reference below.
Graph 1. PAN from cover crop related to date of cover crop termination. Originally from D. Sullivan, Oregon State Univ. See reference below.

The ability of your legume cover crop to supply nitrogen to your subsequent crop depends on how much biomass and when you terminate the cover crop.  This plant available nitrogen (PAN) becomes available roughly 4-6 weeks after cover crop termination.  Oftentimes, a cereal grain terminated at or beyond the boot stage can actually immobilize nitrogen and create a PAN deficit, making it necessary to increase fertilizer/manure nitrogen applications.  This is because microbes are tying up nitrogen temporarily as they break down the carbon rich material. Conversely, a cover crop terminated too early will provide only minimal PAN.  Below is a simple explanation of the differences between cereal grain and legume cover crops and the implications of when you terminate them.

Table 1 from information in the publication by D. Sullivan referenced below.
Table 1. From information in the publication by D. Sullivan referenced below.

Considerations When Planting Legume Cover Crops

Hairy vetch in bloom

Legume cover crops will need to be planted earlier than cereal grains to survive winter and maximize N production.  For clovers, you’ll want them established by August 15th in Vermont, so this limits them to being interseeded or planted after a cereal grain harvest.  The winter annual legumes can be planted as late as September 1st through 15th, which means you can still plant them after a timely corn harvest.

If you are planting legume cover crops only to replace nitrogen, the economics may or may not pencil out.  Usually in organic systems, this is a preferred practice.  However, when commercial nitrogen fertilizer is $45 for 100 pounds of nitrogen and a legume cover crop could cost you $70 per acre for that same 100 pounds the nitrogen benefit may not be financially rewarding.  Certified organic fertilizer, however, could run you $150 per acre, making the cover crop a wise investment.  However, a legume cover crop is more than just nitrogen, and these additional benefits are harder to quantify.  According to USDA this includes “yield improvements beyond those attributable to nitrogen alone.  These may be due to mulching effects, soil structure improvements leading to better moisture retention and crop root development, soil biological activity and/or enhanced insect populations below and just above the soil surface.” (Clark, SARE).  They are also great soil conditioners, and can provide early weed suppression.

There are many legume cover crops, but the table below gives a list of the most common ones planted in the northeast.

Table 2: Information in this table from Managing Cover Crops Profitably, A. Clark (SARE)
Table 2: Information in this table from Managing Cover Crops Profitably,  A. Clark (SARE)

References:

Sullivan, D. and N. Andrews. 2012. Estimating Plant-Available Nitrogen Release from Cover Crops. Oregon State University Extension Service.

Clark, A. 2007. Managing Cover Crops Profitably. College Park, MD: SARE.

Flynn, R. and J. Idowu. 2015. Nitrogen Fixation by Legumes. New Mexico State Unviersity Extension Guide A-129. 

Carbon to Nitrogen Ratios in Cropping Systems. 2011. USDA Natural Resources Conservation Service.

 Other Resources:

Do you have questions about cover crops? Would you like to conduct a trial on your farm? Contact Kirsten [802-388-4969 ext. 347, kirsten.workman@uvm.edu]