Home Discussion Forum Nutrient Management Manure Credits

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  • #819

    How can I ensure I am giving my manure enough Nitrogen credits? How does weather affect when N becomes available from fall liquid dairy manure applications?

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    Profile photo of Kevan Klingberg
    Kevan Klingberg

    Assigning Nutrient Credits to Livestock Manure:

    1.  Treat livestock manure like an N-P-K fertilizer.  In the scenario where we consider “starter fertilizer”, you will recognize the phrase – ” I applied 200 lbs/ac of 9-23-30.”  That approach sets us up to define a rate (200 lbs/ac) of a unique product (dry fertilizer mix with an analysis of 9 lbs N – 23 lbs P2O5 – 30 lbs K2O per every 100 lbs of product used) that supplies a total nutrient application of 9 x 2 = 18 lbs N, 23 x 2 = 46 lbs P2O5, and 30 x 2 = 60 lbs K2O per acre..

    2.  Advance the fertilizer mentality to livestock manure.  In a scenario where we consider “fall applied liquid dairy manure”, we can add details as follows: “I surface applied 12,000 gal/ac of liquid dairy manure (traditional consistency, handling & storage) with a nutrient content book value of 7-6-17 per thousand gallons right before soil freeze-up on December 8th.” Similar to the starter fertilizer example, this manure story problem has a rate (12,000 gal/ac) of a unique product (traditional liquid dairy manure with a book value nutrient content of 7 lbs N – 6 lbs P2O5 – 17 lbs K2O per every 1,000 gallons of manure applied) that supplies a total nutrient application of  7 x 12 = 84 lbs N, 6 x 12 = 72 lbs P2O5, and 17 x 12 = 204 lbs K2O per acre.

    3.  Summary.  Whenever we assign nutrient credits to manure, the number one place to start is to define an application rate and a believable nutrient content of the material.  These values can be defined based on a 15 minute conversation between you and your extension ag agent, feed consultant, crop consultant, or co-op agronomist.

    4.  The Marvelous and Complected Nitrogen Cycle; Plus Weather.  Manure is an organic material – recycled grain, forage, protein and water products that are a byproduct of meat and milk production.  The nutrients contained in manure are in many forms, some simple and most complex.  So, when considering a question of how weather impacts manure N availability – think decomposition.  In order for N contained in manure to become available it must go through a biological decomposition of organic matter N into mineral N.  The main pieces of weather that impact decomposition are those that also impact the thriftiness and activity level of soil microbes:  temperature and moisture.  The right temperature and the right moisture at the right time = microbial activity to decompose organic materials into mineral nutrients.  If temperature and moisture are not right………  the decomposition happens either too fast or too slow – putting nutrient availability out of synch with crop needs.

    5.  Fall Liquid Dairy Manure & Weather & Availability.  The goal of fall manure applications should be to supply next year’s crop with a portion of it’s nutrient need.  Hint: in WI, next year’s crop will need the nutrients to be available from May – September.   Fall manure should be applied so that the decomposition process sets in very slowly.  This means waiting until soil temperatures are cooled to 50 degrees or less (mid October), thus slowing the activity of soil microbes.  This allows a small amount of nutrient availability to happen in the fall – and delays the main decomposition to kick in once spring soil temperatures reach 50 degrees (late April).  Similarly, in the event of a cold and wet spring….. the mineralization of organic N could be delayed into late May / early June, thus causing small crops with small root systems to have delayed access to manure nutrients.

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