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Determining manure application rates

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Before planning for manure applications, consider how the nutrients will be managed for the upcoming crop. Will all the nitrogen (N) be supplied from manure? This will require a higher application rate and will overapply phosphorus (P) and potassium (K) for the crop year. If done too often, there could be environmental consequences when excess P enters waterways.  A lower rate can be used to supply all the P the crop needs. This will allow the manure to be spread over more acres but will require additional N and possibly K to be applied as a commercial fertilizer.

Once you choose a strategy, use the following steps to determine application rates:

  • Step 1: Find the nutrient needs of the crop

  • Step 2: Calculate the actual nutrient availability in the manure

  • Step 3: Divide the answer from Step 1 by Step 2

While this sounds simple, there are slight differences in calculations depending on whether you are basing your applications on N or P needs of the crop or are using liquid or solid manure. The following sections will walk through the calculations for N- and P-based application rates, respectively.

Manure application rate calculations - nitrogen-based

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Manure application rate calculations - phosphorus-based

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Table 1: Amount of nutrients removed in harvested portion of the crop

Data from Minnesota Pollution Control Agency. 2010. Manure management plan, a step-by-step guide
Crop Yield units Crop nutrient removal: N Crop nutrient removal: P2O5 Crop nutrient removal: K2O
Alfalfa Tons (air dry) 50.4 lbs per unit 10.8 lbs per unit 46.2 lbs per unit
Barley (grain) Tons (air dry) -- 0.41 lbs per unit 0.28 lbs per unit
Barley (grain and straw) Bushels -- 0.55 lbs per unit 1.67 lbs per unit
Canola Cwt. -- 1.3 lbs per unit 1.1 lbs per unit
Corn (grain) Bushels -- 0.34 lbs per unit 0.19 lbs per unit
Corn (silage) Tons (as fed) -- 3.8 lbs per unit 7.4 lbs per unit
Edible beans Pounds -- 0.01 lbs per unit 0.03 lbs per unit
Grass or hay pasture Tons (air dry) 27.1 lbs per unit 8.9 lbs per unit 31.3 lbs per unit
Grass/legume Tons (air dry) 43.5 lbs per unit 11.2 lbs per unit 41.3 lbs per unit
Oats (grain) Bushels -- 0.25 lbs per unit 0.16 lbs per unit
Oats (grain and straw) Bushels -- 0.32 lbs per unit 1.31 lbs per unit
Peas Pounds -- 0.01 lbs per unit 0.01 lbs per unit
Potatoes Cwt. -- 0.14 lbs per unit 0.56 lbs per unit
Red Clover Tons (air dry) 45.1 lbs per unit 10.8 lbs per unit 41.1 lbs per unit
Rye (grain) Bushels -- 0.44 lbs per unit 0.31 lbs per unit
Rye (grain and straw) Bushels -- 0.59 lbs per unit 1.25 lbs per unit
Soybeans Bushels 3.5 lbs per unit 0.82 lbs per unit 1.0 lbs per unit
Sugarbeets Tons -- 2.2 lbs per unit 7.3 lbs per unit
Sunflower Pounds -- 0.01 lbs per unit 0.01 lbs per unit
Sweet corn Tons -- 11.0 lbs per unit 13.9 lbs per unit
Wheat (grain) Bushels -- 0.53 lbs per unit 0.3 lbs per unit
Wheat (grain and straw) Bushels -- 0.64 lbs per unit 1.5 lbs per unit

Table 2: Nitrogen availability and loss as affected by method of manure application and animal type.

Year available Broadcast + >96 hours incorporation Broadcast + 12-96 hours incorporation Broadcast + <12 hours incorporation Injection: Sweep Injection: Knife
Beef -- -- -- -- --
1 25% N available/year 45% N available/year 60% N available/year 60% N available/year 50% N available/year
2 25% N available/year 25% N available/year 25% N available/year 25% N available/year 25% N available/year
3 10% N available/year 10% N available/year 10% N available/year 10% N available/year 10% N available/year
Lost 40% N available/year 20% N available/year 5% N available/year 5% N available/year 10% N available/year
Dairy -- -- -- -- --
1 20% N available/year 40% N available/year 55% N available/year 55% N available/year 50% N available/year
2 25% N available/year 25% N available/year 25% N available/year 25% N available/year 25% N available/year
3 15% N available/year 15% N available/year 10% N available/year 15% N available/year 15% N available/year
Lost 40% N available/year 20% N available/year 10% N available/year 5% N available/year 10% N available/year
Swine -- -- -- -- --
1 35% N available/year 55% N available/year 75% N available/year 80% N available/year 70% N available/year
2 15% N available/year 15% N available/year 15% N available/year 15% N available/year 15% N available/year
3 0% N available/year 0% N available/year 0% N available/year 0% N available/year 0% N available/year
Lost 50% N available/year 30% N available/year 10% N available/year 5% N available/year 15% N available/year
Poultry -- -- -- -- --
1 45% N available/year 55% N available/year 70% N available/year n/a n/a
2 25% N available/year 25% N available/year 25% N available/year n/a n/a
3 0% N available/year 0% N available/year 0% N available/year n/a n/a
Lsot 30% N available/year 20% N available/year 5% N available/year n/a n/a

Melissa Wilson, Extension manure management specialist

Reviewed in 2018

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