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Fertilizer Management

Natural Gas and Nitrogen Fertilizers

There is concern about the increased cost of nitrogen (N) fertilizers for the 2004 production year by producers and consultants. Nitrogen is essential for plant growth, but soils typically do not supply sufficient quantities for maximum and economic production of non-legume crops. In Mississippi, N fertilizer normally is used in cotton, corn, rice, grain sorghum, pasture, and forage production.

Natural gas accounts for 75 to 90 percent of the cash cost per ton of N fertilizer manufactured. Hydrogen from natural gas is combined with atmospheric nitrogen to synthesize anhydrous ammonia that can be used as fertilizer or further processed into other fertilizer products. Nitrogen fertilizer supplies and prices have been an issue since a 400% increase in natural gas prices in the winter of 2000-01. Natural gas prices decreased after that spike, but have recently (2003-04) climbed to new, higher levels due to a variety of factors.

Common ammonia based fertilizers available in Mississippi are:

anhydrous ammonia, 82 - 0 - 0,
ammonium nitrate, 33 or 34 - 0 - 0,
urea, 46 - 0 - 0,
UAN solutions, 28 - 32 percent nitrogen,
ammonium sulfate, 21 - 0 - 0,
ammonium polyphosphate solutions, 10 - 34 - 0 or 11 - 37 - 0,
monoammonium phosphate, 11 - 48 - 0,
diammonium phosphate, 18 - 46 - 0.

Manufacture of these fertilizers begins with natural gas. This listing also includes some fertilizers widely used for their phosphate content or as starter fertilizers.

Mississippi row crop producers commonly use UAN solutions as their nitrogen fertilizer due to its stability in our warm, humid climate and ease of handling. Ammonium nitrate is the most common nitrogen source for pasture and forage producers. The ammonium polyphosphates are often used as starter fertilizers in the state. Urea and ammonium sulfate are also used in Mississippi crop production.

What to do?

Below are some factors to use in examining your situation and assessing alternatives.

1. Develop a Nutrient Management Plan approach.

The first reaction to higher N prices may be to cut back N use, but remember that N fertilization has a tremendous effect on yields and production efficiency. Nutrient management plans have long been used in animal agriculture production areas to evaluate nutrient sources, levels, and needs, and to develop an economically and environmentally sound system of providing plant nutrients. Use this approach to systematically evaluate your production system and develop a cost-effective soil fertility management program.

2. Evaluate your non-nitrogen nutrient and lime needs by soil testing

Efficiency through good management is critical to getting the best return from investment in fertilizers. Nitrogen fertilizer use is most efficient when soils are not acid and other fertilizer elements are not limiting crop growth or soil microbial activity. Nutrient planning for efficiency begins with soil testing. The test results include indications of plant available phosphorus (P), potassium (K), magnesium, calcium, and other nutrients. The soil test results will also have the pH of the sample, and a lime requirement, if there is one.

The MSU-ES Soil Testing Laboratory does not routinely test for N because soil N levels fluctuate in our warm, humid climate. Recent research in Mississippi has found that soil test N is very variable within fields. The lack of discernible patterns confounds research attempts to calibrate and correlate soil test N levels with fertilizer application rates of N, subsequently making interpretations suspect. Northern and some western states with colder, drier climates have had success using soil N testing as a management tool.

Mississippi State University Extension Service crop N recommendations provided with the results of the soil test are crop and soil specific. They are based on research here and surrounding states. The recommendations are reviewed periodically for potential updates by Extension Service Specialists and Experiment Station Scientists.

3. Test the nutrient content of any animal manure used in your system

Animal manures are an important part of many Mississippi production systems, particularly for forages and pastures. For effective management, the manure should be tested for nutrient content annually.

4. Evaluate commercial N fertilizer purchases on cost per nutrient pound

Nitrogen fertilizers purchasing decisions should be based on the cost per pound of nutrient. Following is an example calculation.

Note: to compare price per pound of nitrogen in different materials:

(Price per ton of fertilizer)/(2000 x material N content as decimal value)

Example 1:
UAN at $185 per ton with 32% N content
($185/ton) / (2000 lbs/ton x 0.32 N) = $0.289/lb N or $0.29 cents per pound of N

Example 2:
Ammonium nitrate at $250/ton with 33% N content ($250/ton) / (2000 lbs/ton x 0.33 N) = $0.379/lb N or $0.38 cents per pound of N

5. Credit or consider N contribution by legumes

Legumes such as soybeans obtain N from the atmosphere through a symbiotic relationship with bacteria. If N fertilizer prices or supply are problematic for producers, soybean production is a viable alternative. It has been difficult to differentiate subsequent crop response to soybeans in Mississippi to either residual N from the legume, or to a rotation effect.

6. Manage wisely

A Nutrient Management Plan is simply a budget. Use the soil test results and recommendations, manure analysis (if applicable), and realistic yield goals to determine an action plan. Since efficient N use depends on balanced fertility, address liming needs first, based on the soil test results. Liming leads to more efficient use of native nutrients as well as P and K fertilizers.

7. Use BMP's

Best Management Practices are cost-efficient operation methods that ensure that fertilizers are used effectively with minimal impact on the environment.

• Use realistic yield goals
  Use average crop yields from the past 3 to 5 years, then add 10% for a realistic projection of the production potential on your soils, using your production management, in your climate area.
  
  

• Use the most suitable nitrogen fertilizer source, depending upon the crop, application method, and climatic conditions
  Some fertilizers work better in certain situations due to climate and soil conditions. For example, anhydrous ammonia is lost due to incomplete soil sealing when soils are wet.
  
  

• Price fertilizers on the cost per pound of nutrient
  This is the best way to compare cost of nitrogen among equivalent sources.
  
  

• Use proper application techniques
  Use the correct technique for the particular situation. Refer to the specific commodity pages for more particular information.
  
  

• Maintain and calibrate application equipment
  Improperly maintained and poorly set equipment 'steal' crop input dollars. Make sure owned equipment is properly working and calibrated. Confirm with custom applicators that they have calibrated the equipment.
  
  

• Avoid application to surface waters.
  Care must be taken to avoid direct application to any surface streams.
  
  

• Time application properly for the crop
  Nitrogen use efficiency is best when applied close to the time of crop uptake. We hear reports every year of N application to fields for cotton several weeks prior to planting. These increases the probability of N loss from the field, and may necessitate supplemental N fertilizer later in the growing season.
  
  

• Control soil erosion
  Nutrients move when soil particles move. Using soil conservation keeps soil and nutrients where they can be utilized by growing crops.
  
  

• Properly control water flow
  Nitrogen movement in the landscape is closely linked to water movement. Slow water down when appropriate by conservation practices, or speed water movement when appropriate.
  
  

• Use cover crops, and maintain crop residue on the soil surface
  Cover crops reduce the likelihood of N movement in the landscape by 'scavenging' N left in the soil profile after the previous crop. Using the residual N increases cover crop dry matter production, thus enhancing soil quality attributes such as soil organic matter levels and tilth.

Frequently Asked Questions

Why is my corn stunted and purple?
How do I use poultry litter in my forage nutrient management program?
What happens to nitrogen fertilizer in soils?
How can I use nutrient management to maximize forage production? (pdf)

Publications

MSUcares Soils/Fertilization publications

Soil Sampling Information:
IS346 Soil Testing for the Farmer
IS1294 Soil Testing for the Homeowner
P2078 Soil Sampling in Reduced Tillage
IS1614 Soil and Broiler Litter Testing Basics

Plant Nutrients and Liming:
IS372 Soil pH and Fertilizers (horticulture)
IS1584 Interpreting Soil Tests (horticulture)
IS767 Nitrogen in Mississippi Soils
IS871 Phosphorus in Mississippi Soils
IS894 Potassium in Mississippi Soils
IS1587 Limestone Relative Neutralizing Value
IS1620 Useful Nutrient Management Planning Data
P1466 Using Fluid Fertilizers
P2311 Soil pH and Trees
B1129 Economics of Variable Rate Fertilization
P2208 Using Dairy Lagoon Effluents as Fertilizer
IS1635 Using Poultry Litter in Forage Production

Specific Crop Nutrient Management:
P1622 Cotton
IS873 Soybean
I1341 Rice
IS1225 Grain Sorghum
IS1169 Forages
IS411 Ornamental Trees

Other Fertilizer Information

Crops Require Sulfur - May 2004 Delta Farm Press
Non-traditional Soil Additives and Fertilizers - April 2004 Delta Farm Press
Nitrogen Cycle: Potash and Phosphate Institute
Nitrogen Fertility
Phosphorus Fertility
Acidity and Liming
Soil Testing
The Fertilizer Institute
Potash and Phosphate Institute
Crop Decisions Magazine
Better Farming Radio Broadcast 2/6/01 (requires Real Player)
Nutrient Management
Best Fertility Management Practices