4 pp., 5 photosApplying organic materials to your land can add beneficial nutrients to the soil. But when too much is applied, or when it is applied incorrectly, organic material can cause environmental problems. This publication will help you select the proper application rate, calibrate equipment so that the correct rate is applied, and learn how location, water, soil and tillage can all affect the process

Harmel, Daren

Lesikar, Bruce J.

Mechell, Justin

Texas A&M University

Composted manure can be applied using a tractor 
and spreader.
pplying organic materials to your land can 
add beneficial nitrogen (N), phospho-
rous (P), potassium (K), micronutrients and 
organic matter to your soil. Organic materials 
can increase the soil’s water-holding capacity, 
improve aeration, decrease erosion, and pro-
mote biological activity in the soil. Organic 
fertilizers can be very beneficial to pastures, 
crops and lawns, but they can contaminate 
surface and groundwater supplies if applied 
excessively or improperly. 
*Extension Assistant, Agricultural Engineering; Agricultural 
Engineer, USDA-ARS, Grassland Soil and Water Research 
Laboratory; Professor and Extension Specialist, The Texas 
A&M System
L-5493
12/07
Justin Mechell, Daren Harmel and Bruce Lesikar*
Land Application
of Organic Fertilizers
or Amendments
Preventing 
Environmental Problems
When too much organic fertilizer is applied 
to land, plants cannot use all of the applied 
nutrients. Then, when rainwater runs off the 
land, it carries these excess nutrients into 
lakes and streams. N and P occur naturally in 
streams and lakes, but excessive concentra-
tions can accelerate eutrophication, a process 
in which dissolved nutrients stimulate the 
growth of aquatic plants and algae and reduce 
the level of dissolved oxygen in the water, 
which can harm aquatic life. 
Organic fertilizers may also contain patho-
gens (disease-causing bacteria or viruses) that 
can be carried into surface water by rainfall 
runoff. Pathogens degrade water quality, 
making it unsuitable for recreational uses and 
greatly increasing the cost of treating it for use 
as drinking water. 
Selecting the Proper 
Application Rate
To prevent environmental problems, the 
most important management practice is to 
develop a nutrient management plan that 
bases application rates on annual soil tests and 
realistic crop yield goals. Fertilizer applica-
tions that exceed soil test recommendations 
waste time and money.
Annual soil tests will tell you the nutrient 
content of your soil. Then you will be able 
to determine how much fertilizer your crop 
needs by subtracting the available soil nutri-
ents from the crop’s total nutrient require-
ment. Remember to base your total nutrient 
requirement on a realistic yield goal. 
Once you know how much supplemental 
N, P and K to apply, test the organic material 
you will use to determine its nutrient concen-
trations. With this information you will be able to 
calculate the appropriate application rate. 
Texas Cooperative 
Extension’s Soil, Water 
and Forage Testing Labora-
tory will analyze soil and 
organic matter samples 
and determine the proper 
application rate for your 
crop. Instructions for using 
this service can be found at 
http://soiltesting.tamu.edu. 
There is a minimal fee.
Remember the following when determining 
application rates for organic fertilizers:
n Apply at rates to meet crop P requirements.
n Apply supplemental N to meet crop N require-
ments at realistic yield goals.
n Split organic fertilizer and supplemental N 
applications so that smaller amounts of nutri-
ents are applied at any one time.
Checking Your 
Application Rate
Calibrate your application equipment periodi-
cally to ensure that it is applying the intended rate. 
Here is a simple method of verifying your applica-
tion rate:
1.  In an area where material can be easily 
applied, spread a tarp or plastic bag on the 
ground and distribute the organic fertilizer 
over the tarp or bag at your normal applica-
tion rate.
2.  Measure and record the length (L) and width 
(W) of the tarp or bag used.
3.  Carefully collect all the material that was 
applied directly on top of your tarp or bag.
4.  Weigh (M) the collected organic material.
Do this procedure at least three times. 
Collect a sample of 
compost for nutrient 
testing.
Use a plastic bag or tarp to 
verify organic fertilization 
rate.
Apply organic fertilizer to  
the bag or tarp and then 
collect and weigh the 
material. 
With the area and weight collected from each 
sample, you can calculate your actual application 
rate (AAR) and determine whether it corresponds 
to your desired application rate. Remember that if 
application rates are to be made on a dry-weight 
basis, the tons per acre (wet basis) should be 
divided by the percent moisture content (MC; 
decimal fraction) to get the correct application rate. 
The example below demonstrates how to determine 
your actual application rate.
Example: Calculating Your Application Rate
Jill needs to apply 2,000 pounds (dry basis) of 
composted manure per acre to achieve the proper 
nutrient balance for her desired crop and yield. To 
check her actual application rate, she has set up the 
test as described above. The tarp she used measured 
36 inches wide (W) by 48 inches long (L). The 
moisture content (MC) of the organic fertilizer is 
5% (0.05).
After each application, Jill weighed (M) the 
sample and recorded the values. The results are as 
follows:
 Sample 1 (M1): 0.5 pounds
 Sample 2 (M2): 0.6 pounds
 Sample 3 (M3): 0.5 pounds 
Using the following four equations, Jill deter-
mined the application rate for each sample.
Sample 1
 M1(lb)      × 6272640 = AAR1(lb/acre) ...... Eq. 1 L(in) × W(in) 
 0.5(lb)       
× 6272640 = 1815(lb/acre)
48(in) × 36(in)
Sample 2
 M2(lb)      × 6272640 = AAR2(lb/acre) ...... Eq. 2 L(in) × W(in) 
 0.6(lb)       × 6272640 = 2178(lb/acre)
48(in) × 36(in)
Sample 3
 M3(lb)      × 6272640 = AAR3(lb/acre) ...... Eq. 3 L(in) × W(in) 
 0.5(lb)       
× 6272640 = 1815(lb/acre)
48(in) × 36(in)
 After determining the actual application rate 
(AAR) for each sample, Jill then takes the average 
of all the samples (Equation 4).
Average Actual Application Rate
AAR1 + AAR2 + AAR3 = AAR(lb/acre) .................. Eq. 4
      3 × (1 – MC) 
 1815 + 2178 + 1815  = 2038(lb/acre)
      3 × (1 – 0.05)
So, Jill’s actual application rate (AAR) is 2,038 
pounds per acre. This value is very close to the 
desired application rate and verifies that Jill’s equip-
ment is properly calibrated.
Other Considerations
Location
In order to protect drinking water, fertilizer 
should not be applied within 150 feet of any private 
water well or within 500 feet of any public water 
well. A 100-foot buffer should be left between the 
application field and nearby streams, lakes or stock 
tanks.
Weather
Take note of current and predicted weather con-
ditions when scheduling the application of organic 
materials. If heavy rain is expected within 48 hours, 
delay the application. Fertilizer applied to wet, fro-
zen or sloping soils is even more likely to be carried 
away from the application site by runoff or erosion. 
Soil
Although nearly any soil can benefit from 
applied organic material, soils that benefit most are 
those with good soil depth, no restricting layer in 
the root zone, a moderate rate of permeability and 
drainage, and a good nutrient-holding capacity. 
Tillage
On cultivated sites, soil should be tilled within 
24 hours of application. Tillage breaks up organic 
material and incorporates it into the soil, which 
decreases the risk of nutrient loss and places 
needed nutrients in the crop root zone. Incorporat-
ing freshly applied organic fertilizer into the soil 
also decreases odors.
Conclusion
Several studies have shown that using animal and 
plant by-products as organic fertilizers is a way to 
benefit from these resources, rather than wasting 
them with other disposal techniques. For the most 
environmentally and economically sustainable 
program:
n Establish a reasonable yield goal.
n Apply organic fertilizers at appropriate rates 
based on fertilizer composition and available 
soil nutrients (as determined by organic and 
soil sample testing).
n Apply nutrients at the time they are most 
needed by crops (approximately 20 days after 
emergence).
n Avoid making a single high-rate application 
(greater than the crop N requirement) because 
it can degrade water quality, even on sites with 
low soil-nutrient levels.
n Do not apply fertilizer or litter just before a 
heavy rain is forecast.
n To further reduce the possibility of water con-
tamination, alternate organic fertilizers with 
commercial (inorganic) N.
For Further Information 
Managing Crop Nutrients Through Soil, Manure 
and Effluent Testing (L-5175), Texas Cooperative 
Extension.
Using Animal Manure and Wastewater for Crops 
and Pastures: Know and Take Credit for Your N, P 
and K (E-47), Texas Cooperative Extension.
Feedyard Manure: A Farmland Fertilizer 
(L-5027), Texas Cooperative Extension.
United States Geological Survey (USGS). 2006. 
“Eutrophication.” Toxic Substances Hydrology 
Program. Available at: http://toxins.usgs.gov/ 
definitions/eutrophication.html
The authors acknowledge the assistance of the 
Texas State Soil and Water Conservation Board, 
soil and water conservation districts in Texas, the 
USDA-Natural Resources Conservation Service, the 
USDA-Agricultural Research Service, and the U.S. 
Environmental Protection Agency, Region VI.
Produced by AgriLife Communications, The Texas A&M System
Extension publications can be found on the Web at: http://AgriLifebookstore.org
Visit the Texas AgriLife Extension Service at http://AgriLifeExtension.tamu.edu
Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national 
origin.
Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, 
in cooperation with the United States Department of Agriculture. Edward G. Smith, Director, Texas AgriLife Extension Service, The Texas A&M System.
5M, New 


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Land Application of Organic Fertilizers or Amendments

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