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LegumesSoil Health

A New Perspective On A Nitrogen Nightmare

By August 9, 2021September 2nd, 2021No Comments

As if agricultural input costs were not high enough already, the American Farm Bureau is warning producers of a fertilizer fiasco that could poke another hole in U.S. farmers’ piggy banks. The danger is potential duties on imported nitrogen, including the widely used UAN product. Fertilizer costs were already projected to increase by roughly 5% between 2021 and 2022, but the potential tariffs could make that a double-digit increase. Farm Bureau Article

   But you can partially control your own fertilizer destiny by growing a portion of the nitrogen that your next crop will need with late summer and early fall-seeded cover crops.


    If you are following a summer harvested crop of wheat, peas or forage, you have a wide selection of both warm-season legumes (sunn hemp, cowpeas, mung beans, etc..) along with cool-season legumes (peas, vetch, lentils).  These legumes should be a part of a more diverse mix to balance out the C:N ratio for overall soil health.

    For late summer or fall-planted covers, cool-season legumes are the N fixing plants of choice.  These can be divided into two groups: frost tolerant types and winter-hardy types.  Different cool-season legumes will fall into one of these categories based on the location and severity of your winters.

    For example, here in NE and KS, our 4010 spring forage peas (a spring annual) will have more fall growth but will winterkill when we drop into the teens, while winter peas (a winter annual) will have less fall growth but will likely survive the winter and give the majority of their growth in the spring. This is pretty common that winter-hardy varieties make less fall growth than varieties susceptible to winterkill. Depending on your goals, there might be room for both varieties in your planting to gain both fall and spring biomass (and nitrogen fixation).

    In the central Plains, winter-hardy legumes include hairy vetch (the most cold hardy), winter peas, winter lentils, balansa clover and crimson clover. Legumes that ordinarily winterkill in the central US (but may overwinter further south or in California) include faba beans, spring peas, chickling vetch, spring lentils, and chickpeas.

    Here at the farm in Nebraska, we have tested and recorded nitrogen production rates as high as 240# per acre from winter peas and 180# per acre from hairy vetch under ideal conditions.  We think about half of this N will come available for the subsequent corn crop.  Not bad for legumes planted on October 1st!

    Clovers, vetches and peas will likely be in shorter supply and higher demand than past years, so don’t delay if these species are going to be part of your cover crop program. If you would like to learn more about how to use cover crops to replace some of your expensive nitrogen fertilizer needs, just give us a call or send us an email!


  • Dale Strickler

    Dale is an internationally recognized agronomist, agroecologist, speaker and consultant with more than 30 years of experience in agronomy, pasture management, and soil and crop advising while working in academia, for Land-o-Lakes and Green Cover Seed, Dale has developed highly effective crop and grazing systems for numerous farms and ranches with a range of often challenging climates and soil types. Dale has consulted in every region of the USA and as far away as Hungary and South Africa.
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