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McClain County

Will Pasture Legumes Eliminate My Need to Purchase Nitrogen Fertilizer?

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The cost of nitrogen fertilizer can be one of the biggest expenses to forage production. This has many producers wondering if there is a cheaper way of producing the forage they need for their grazing animals.

The cost of nitrogen fertilizer can be one of the biggest expenses to forage production.  This has many producers wondering if there is a cheaper way of producing the forage they need for their grazing animals. Some are looking at legumes as a way of bridging the gap in the production of their grass pastures since they have reduced nitrogen fertilizer inputs.

   Legumes have the ability to produce their own nitrogen with the help of a bacteria that lives on their roots. This bacteria has the ability to convert nitrogen from the air into a useable form for the plant. Most of this nitrogen is taken in by the legume plant itself and is used in the production of above ground forage and for growth of its roots. Nitrogen credits attributed to legumes can be as high as 200 lbs of N per acre for white clover, 110 lbs. for red clover and 100 lbs per acre for crimson and arrowleaf clovers. The legume plant itself is using most of this N production for its own growth, while providing high quality forage to the grazing animal.

Contrary to popular opinion, very little of this nitrogen leaks out from the roots and is available for grass growth. We do receive some nitrogen recycling from legumes in animal urine and manure, but about 50% of this nitrogen is lost through volatilization and is not available for forage grass uptake. In a pasture that has been in legume production for several years, there will however be decaying roots and bacteria nodules that will provide nitrogen to the soil that is available for the grass crop to use. The amount returned to the soil by this decomposition varies greatly with the previous year’s production of legumes. The nitrogen credit to that soil can vary from 20 to 50 pounds of N per acre from decaying plant root material and recycled animal waste.

So are legumes a good way of reducing the need for fertilizer inputs? The answer to that is yes, but not because it puts large amounts of N in the soil for your grass to use. What is does is replace the grass production you used to get with nitrogen fertilization with high quality legume production, which is probably better for your grazing animals in the long run.

Will it reduce your cost of production? Well that depends. In order to grow legumes, your soil will have to have the proper ph, phosphorus and potassium levels in order to survive and thrive. If your pastures fertility is not in good enough shape to produce legumes and you are not willing to spend the time, money and effort to get them established properly, then don’t waste your time buying expensive legume seed. Without the proper soil fertility environment, your legume stand will not survive.  Also, remember that legumes are broadleaf plants and therefore will limit your weed control options on your pastures.

Using legumes in a balanced forage system will in the long run save you on nitrogen inputs and will provide your grazing animals with high quality forage. It will take some proper management in order for legumes to work well over the long haul. Start by getting a soil test before jumping head long into a legume forage system. Then pick a legume that is adapted to our growing conditions here in McClain County.  If you are then willing to commit to the increased management levels, legumes may be a viable way to reduce your dependence on fossil fuel based nitrogen fertilizer.


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