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Section 13 - Manure Application Rates

This section will help you determine the nitrogen or phosphorus requirements of each field and the amount of manure to apply.

Determination of Manure Application Rates

Field: ___________________

 

1. Field information
Crop: _______________ Crop Year: _____ Number of acres: _____
Soil name/texture: ____________________ Previous crop: _______________

 
 
 

2. Nutrient need
N
P2O5
a) Expected yield: _______________
------ lb/acre -----
b) Nutrient recommendations from soil test report _______ _______
c) Special nutrient need above test recommendations _______ _______
d) Total nutrient need _______ _______

 
 
Nutrient Credits
3. Nutrient credits N (lb/acre)  P2O5
(lb/acre) 
a)Residual soil credit (if not included in 2b above)
b) Irrigation water credit  
c) Organic matter credit (if not included in 2b above)  
d) Previous legume crop
e) Mineralization from previous manure applications
f) Other: ____________________________________
g) Total nutrient credit

 
 
Manure Application Rate
4. Manure application rate N (lb/acre) P2O5
(lb/acre)
a) Total nutrient need (2d) minus Total nutrient credit (3g)    
Recommended nutrient application from manure
Additional fertilizer needed (lbs/acre)
b) Nutrient content of manure
c) Available N from manure
d) Recommended manure application rate

 
 

5. Notes on application methods and timing

 

 

 

 
 

6. Post season follow-up
Actual crop yield: _______________ Total irrigation water applied (in/A): _____ 
Supplemental fertilizers applied: __________ lbs N/A
__________ lbs P2O5/A
Total manure applied (tons/A or 1000 gal/A): ____________________

 

Prepared by: _______________________________

Date: ____________________
 

Manure Nutrient Content and Availability

 

Table A. Nutrient content of solid manures in Colorado (based on 1996 manure survey).

Nutrient content of solid manures in Colorado in lb/ton (fresh weight)
Manure Source Total N P2O5 K2O
Beef
23
24
41
Dairy
13
16
34
Sheep
29
26
38
Horse
19
14
36
Chicken
30
64
39
Llama
31
27
44
Turkey compost
38
80
46
Dairy compost
16
18
37

Table B. Approximate fraction of total N available to plants in the first year after solid manure application (assuming incorporation within 24 hours).

Fraction of total N for Years 1 to 3
Manure SourceFraction of total N available in the first year Fraction of total N available in the second year Fraction of total N available in the third year
Beef
0.4
0.20
0.10
Dairy
0.4
0.20
0.10
Sheep
0.3
0.15
0.08
Horse (with bedding)
0.2
0.10
0.05
Chicken
0.5
0.25
0.12

These tables were developed using data from a survey of Colorado manures done in 1996 and CSU's Best Management Practices for Manure Utilization.  As we increase the sample number in our database of Colorado manures, the table will continually be updated.  For manure types not included in the tables above, use the tables in NRCS Agriculture Waste Management Field Handbook, Chapter 11.

Table 13C. Crediting previous legume crops

Crediting Previous Legume Crops
Legume Crop Nitrogen Credit (lb N/A)

Alfalfa (> 80% stand)

100-140

Alfalfa (60-80% stand)

60-100

Alfalfa (0-60% stand)

0-60

Dry beans

30

Crediting irrigation water nitrate

Because crops take up the majority of the N used during the vegetative growth stages, only water applied during the early part of the growing season can be credited.  Consumptive use during this time period, often referred to as evapotranspiration (ET) , can be used to estimate the amount of water to credit. You should only credit about 60% to 70% of seasonal ET for most crops (no more than 15 inches for corn).  Local NRCS personnel, water districts, or Cooperative Extension offices can provide local values for crop water use (ET) for your area.  With this information, multiply the NO3-N content of the water by 0.23 (an acre-inch of water contains 0.23 lbs of N for each ppm of NO3-N) by the inches of water to obtain the amount of N to credit.

(lbs N/A = acre-inches x 0.23 x ppm NO3-N_)

Example 1: A corn crop used 10 acre-inches of consumptive irrigation water during the vegetative growth (up to tassel). The water contained 15 ppm NO3-N.

10 acre-inches x 0.23 x 15 ppm NO3-N = 35 lb. N/A

Example 2: Seasonal consumptive use (ET) for the area was 21 inches, of which we'll credit 70%. The water contained 21 ppm NO3-N.

(21 acre-inches x 0.70) x 0.23 x 21 ppm NO3-N = 71 lb. N/A

Phosphorus availability

For P, assume that 80% is plant-available.

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