G1519

Calculating the Value of Manure for Crop Production

This NebGuide provides criteria and guidelines to determine the market value of manure for crop production.


Charles S. Wortmann, Extension Soil Specialist — Nutrient Management
Charles A. Shapiro, Extension Soil Specialist — Crop Nutrition


Manure has value for crop production when it provides nutrients or soil amendments needed for optimum crop yields. Manure does not supply nutrients in balance with crop needs, but has the advantage of slowly releasing nutrients which reduces the risk of nitrate leaching. Manure nutrient content varies widely due to weather conditions, the livestock facility, manure storage systems, the age of manure, and feed composition. Low nutrient concentration due to weathering and dilution with water or soil decreases the value of manure. The organic material in manure also can improve soil productivity by increasing the water infiltration rate and water-holding capacity. On some soils, this gain in productivity may be more than its nutrient value.

The worksheet1 on page 3 is used for calculating the fertilizer value of a manure source for a specific field. It includes the value of needed nutrients for a four-year period and offers the option of including the value of manure nutrients used after that. The value of other benefits of using manure, such as an expected yield increase, can be estimated. An example worksheet is included on page 4. To complete the worksheet you will need one or more recent analyses of the manure to be valued, a recent soil test for the application area, recommendations for nutrients needed for the next and following crops, and current fertilizer prices.

Determining Nutrient Value of Manure

Manure or compost should be applied at or below the rate that meets the nitrogen (N) need of the next or current crop. Applying manure to meet the crop’s nitrogen needs usually results in applying substantially more phosphate (P2O5), potash (K2O), sulfur (S), and zinc (Zn) than is needed by the crop. University of Nebraska–Lincoln recommendations for P2O5, K2O, and Zn are based on meeting crop needs while slowly building soil nutrient levels2,3,4. This is generally the most profitable option for nutrient management. For corn, sorghum, soybean, and sugar beet, research results show no economic benefit to nutrient applications that raise soil test levels higher than 20 ppm phosphorus (P) (Bray-1 P test), 125 ppm potassium (K), and 0.8 ppm zinc. Yields of alfalfa, wheat, and six other crops respond to higher soil phosphorus levels2.

Applying large quantities of nutrients at one time, in excess of recommendations, may be profitable when interest rates are low and nutrients are inexpensive, as may be the case with manure nutrients. A producer receives value from these excess nutrients only if subsequent crops remove the nutrients before more nutrients are applied. This approach is acceptable for relatively immobile soil nutrients like phosphorus, potassium, and zinc, applied where or in a way such that phosphorus is not likely to be transported to surface water, and if total available nitrogen does not exceed crop utilization in year one. Nitrogen released in subsequent years from the organic-N in manure can be credited toward future crop needs.

The organic matter in manure may improve soil productivity and crop yields. For example, manure demonstration plots in Nebraska from 1996 to 2001 produced an average of 7 bu/ac more corn (14 site years) and 2 bu/ac more soybean(6 site years) where manure or manure plus fertilizer was applied compared to fertilizer alone. Soybean in one other site year lost 4.5 bu/ac due to compaction during manure application and incorporation. Line 12 in the worksheet provides a place to include the value of a yield increase. This value is typically between $0 and $60 per acre. Expect less yield increase on fine and high organic matter soil, or if the land has a recent history of manure. Expect greater increase on sandy, eroded, or disturbed soil with no recent manure history.

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1This worksheet is based on a publication from the University of Missouri, Calculating the Value of Manure as a Fertilizer Source (G9330).
2Nutrient Management for Agronomic Crops in Nebraska, University of Nebraska–Lincoln Extension EC155
3Fertilizer Suggestions for Corn, EC117 (August 2009)
4Fertilizer Suggestions for Soybeans, G859 (Revised February 2006)

Manure Testing

Manure varies greatly in nutrient content so recent samples of the manure or effluent to be applied should be analyzed by a laboratory to determine nutrient content.5,6,7 Without a lab test, a “book” value of typical nutrients in manure could be used, but this is not recommended since the actual concentration of one or more nutrients in any manure is often several times more or less than the “book” value.

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5Sampling Manures for Nutrient Analysis, G1450
6Manure Testing: What to Request?, G1780
7Determining Crop Available Nutrients from Manure, G1335

Availability of Manure Nitrogen

Manure nitrogen is mostly in two forms: ammonium nitrogen and organic nitrogen. All ammonium nitrogen is available the first year if it is not lost. Ammonium nitrogen is quickly lost from manure spread in a thin layer and left on the surface of either a feedlot or a field. Cooler temperatures at time of spreading will slow ammonia loss. Ammonium nitrogen is retained once it is incorporated into the soil (Table I) by injection, tillage, or by rainfall or irrigation of one-half inch or more.

Organic nitrogen is slowly released during warm weather by microbial action. From 25 to 50 percent of the organic nitrogen in manure becomes available to crops in the first year (Table II). About 15 percent of the original organic nitrogen in manure or compost is released in year two, 7 percent in year three, and 4 percent in year four. Much of the organic nitrogen in manure is not recovered by crops in the following years.

Table I. Fraction of ammonium nitrogen available this year.
Sidedress Application
      Incorporated
      Sprinkler irrigation
1.00
0.50
   
Preplant Application and Not Incorporated
      Surface - spring or fall 0.00    
Preplant Application and Incorporated
    Temperature at Time of Spreading
      Manure Form Solid Liquid > 50°F Liquid <=50°F
      Not incorporated
      Immediately
      One day later
      Two days later
      Three days later
      Seven+ days later
0.00
0.95
0.50
0.25
0.15
0.00
0.00
0.95
0.70
0.50
0.25
0.00
0.00
0.95
0.70
0.55
0.45
0.40

Table II. Fraction of organic nitrogen available this year.
Beef/Dairy
Solid (e.g. feedlot)
Stored liquid
Compost
0.25
0.35
0.15
Swine
Fresh
Stored liquid
0.50
0.35
Poultry
Deep pit
Solid with litter
Solid without litter
0.45
0.30
0.35

Worksheet Instructions

Line 1: Enter the results of the manure analysis or typical values for this manure.
Line 2: Enter the ammonium nitrogen and organic nitrogen availability factors from Table I and Table II. For fall and early spring-seeded small grains, multiply the organic nitrogen factor by 0.7. For the other nutrients, because most is available the first year and the rest is available the second year, use 1.0 as an availability factor.
Line 3: After calculating available ammonium nitrogen and organic nitrogen, add the two values (Line 3) to get total nitrogen available per unit of manure in the first year.
Line 4: Enter the nutrient recommendations for the next crop. You may enter the average nutrient need for the crop rotation except for nitrogen, which should be that needed or used in year one. If soybean is the next crop, enter 80 lbs of nitrogen. For leguminous hay crops, enter 100 lbs of nitrogen. Sulfur is needed only on sandy soils with less than 1 percent organic matter, low soil test sulfur, and little sulfur in the irrigation water. Soybean is tolerant to low sulfur conditions.
Line 5: The planned manure application rate should be for a similar moisture content to that of the analysis.
Line 6: Total available nitrogen in line 6 should not exceed Total nitrogen on line 4 by more than 20 percent.
Line 7: This is the nutrient need for four years, based on recommendations in line 4. For lower rates of manure applied more frequently, multiply nutrients in line 4 by the number of years between applications.
Line 8:

For each nutrient other than nitrogen, compare the amounts in lines 6 and 7, and circle the smaller of the two amounts. For each nutrient amount circled in line 7, consider giving value to additional amounts as suggested in A through E below.

  A: Future nitrogen release of value: multiply organic nitrogen in line 1 x line 5 x _____. In the blank, use 0.1 if manure is applied before a nitrogen-requiring crop, such as corn or sorghum, in rotation with soybean. Use 0.2 where it is applied before soybean, or continuous corn or grass. Enter zero if the application will be fol- lowed by two or more years of forage legume.
  B: If soil phosphorus is less than 15 ppm Bray-1 or 10 ppm Olsen, up to 250 lbs/ac of additional phosphate can be of value. If soil P is less than 25 ppm Bray-1 or 18 ppm Olsen, up to 150 lbs of additional phosphate can be of value.
  C: If soil potassium is less than 150 ppm, up to 200 lbs/ac additional potash can be of value.
  D: If the soil is sandy and sulfur is less than 10 ppm, up to 40 lbs/ac additional sulfur can be of value.
  E: If soil zinc is less than 1.0 ppm, up to 20 lbs/ac additional zinc can be of value.
Line 9: Add the circled amount in line 6 or line 7 to the additional amounts in line 8, if any, and enter here. These amounts cannot exceed those on line 6. For nitrogen, if manure is applied before a nitrogen-requiring crop, add lines 6 + 8. If not, use only line 8.

TO Worksheet and Sample Worksheet for print out only. (PDF)

TO fillable Worksheet (XLSX)

Acknowledgment

The authors would like to acknowledge Richard DeLoughery, former extension water quality educator, for contributions to a previous version of this publication.

This publication has been peer reviewed.


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