AgVICE NEWS

PRESS RELEASE - November 30th, 2022

Fall and crop harvest can come early.  With that, producers have started to think about manure application sooner than usual.  These warm fall temperatures set us up for potential nitrogen loss next spring, and with NH3 prices skyrocketing, we need to think about preserving our expensive nitrogen.  

At application, approximately 2/3 of the nitrogen in liquid swine manure is in the ammonium(NH4-N) form.  This means that we have the potential to lose a significant portion of the nitrogen applied early this fall when temperatures are warmer.  Waiting until the ground temperature is at 50 degrees and falling for the season is the best choice.  This will help slow the conversion of the ammonium nitrogen in the manure to the nitrate-nitrogen form, which is more readily leached out of the soil.  

Another option many producers are looking at this fall is to add a nitrification inhibitor to the manure.  The most common product that producers use is nitrapyrin.  Corteva markets it as “Instinct II” for use in manure.  Studies using nitrapyrin in manure and NH3 consistently show it works the best of all the nitrogen stabilizers. 

The poorest performing nitrogen stabilizers are the newer, higher-cost polymer-based inhibitors.  Polymer-based inhibitors work by causing the nitrogen to react with other elements in the soil, to prevent nitrification.  However, when looking at university data, these reactions are not consistent.  We must keep in mind that even when using a well-proven stabilizer, like nitrapyrin, we need to have realistic goals- a product can only do so much, and can only work for so long.  Applying manure extra early in hot weather is pushing the limits of what a stabilizer may be able to provide.  

We would strongly encourage producers who apply manure early this fall to take spring nitrate samples to verify that most nitrogen is still present in the spring.    

Takeaways/key management points for early fall manure application:

1. Add nitrapyrin-based nitrogen stabilizer to manure

2. Inject manure as deeply as possible

3. Focus early application on the heavier, higher organic matter soils - try to avoid early manure application on sandy soils until late fall, or even delay until spring

4. Verify field nitrogen status next year with soil nitrate testing

Crop farmers utilizing manure as a fertilizer source need to pay extra attention to the fertility their manure is providing.  We are seeing decreases in both total nitrogen and phosphorous concentrations of the manure samples that we have submitted so far this fall.  This is not limited to any one certain swine integrator. 

Swine diets affect manure quality

In 2020, many ethanol plants shut down or reduced production. This caused the price of distillers dried grains with solubles (DDGS) to skyrocket.  Many pork producers had to reduce or eliminate DDGS from their finishing diets. Feeding DDGS provides supplemental phosphorus and bulk protein to the pig.

When DDGS are removed as protein source, swine nutritionists utilize other options.  For example, soybean meal and individual amino acids, such as lysine, can be added to the diet. This year, it proved cheaper for many growers to focus on balancing finishing pig diets more closely for individual amino acids, rather than adding more bulk protein like soybean meal.  This strategy means that the pig is much more nutritionally efficient and thus, excretes less wasted protein.  The nitrogen content of the manure is lowered as a result.  Phytase enzyme is also added to diets, which enables pigs to better utilize the phosphorus in the ration.  Phosphorus content of the manure is also lowered, as a result.  

Implications for crop production

How do we ensure that we have enough available nitrogen for the corn plant next year?  If pre-application manure sampling was done, we can increase manure application rates this fall.  However, we need to keep in mind that this may cause excess application of potassium.  Applying excess potassium can result in the corn plant wasting the valuable nutrient through luxury consumption.  In lieu of increasing manure application rates, it is often better to split your nitrogen between commercial sources and manure.  It is recommended that some UAN is applied in the spring, on fall applied manure acres.  UAN rates need to increase as manure nitrogen concentrations decrease.  

For phosphorus, farms with lower P soil test results in a corn-soybean rotation need to be of higher concern.  It is quite possible that manure application this fall will not provide enough phosphorus for both the next years corn crop, as well as the soybean crop to be grown in two years.  

Soil fertility management strategies

1.    Grid sample lower fertility fields on smaller grid sizes

• Use of smaller grids- such as a 2.5-acre grid- allows for precise locating of lower testing areas, and more accurate variable rate prescriptions.

2.    Test manure being applied 

• Crucial for proper nutrient management! 

• We want to see growers taking either a pre-pump core sample, or sample at-pumping sample AFTER the pit has been agitated. 

3. Use multiple nitrogen sources to feed the corn crop

• Adjust your manure application rates to account for at least 50 pounds of spring applied nitrogen.  This can be applied as either UAN with your pre-plant herbicide program, or planter applied starter fertilizer. 

• If using rates above 50#/acre, then NH3 is a good option.     

4.    Variable rate spread commercial P & K only where needed

• For farms that have low testing soils, consider variable rating dry fertilizer to “fill in” the extremely low testing spots to maximize yield. 

• AgVice can create variable rate prescriptions based your GPS manure application maps, to only spread commercial fertilizer on areas that are deficient AFTER manure nutrients are accounted for.  This strategy SAVES you money while helping to MAXIMIZE yield.

When supplementing crops with commercial fertilizer, your MMP and corresponding application records must be recalculated, updated and documented correctly.  Your AgVice agronomist can help you determine a customized crop fertility plan using your manure as the cornerstone of the program, all while keeping you in regulatory compliance.  

We have taken a number of calls on early season manure application already this fall.   The main question we hear is:

“How much nitrogen will be left next spring?”  

This a hard question to answer precisely.  The best advice is to manage your manure the same way that you would your NH3 application.  Wait until the ground temperature is at 50 degrees and falling for the season.  This will help slow the conversion of the ammonium nitrogen in the manure to the nitrate form that is more readily leached out of the soil.   This conversion happens through the nitrification process and this process slows significantly below 50 degrees.  Approximately 2/3rd of the nitrogen in liquid swine manure is in the ammonium(NH4-N) form when applied.  This means that we have the potential to lose a significant portion of the nitrogen applied early this fall when temperatures are warmer.   

From a practical perspective, early fall application is an essential part of swine barn management.  We always accept some N loss, and manage for it rather than trying to avoid it by delaying applications too late into the season.  Here are a few of AgVice’s best management tips for fall manure application:

• Make sure that your Manure Management Plan (MMP) is designed to account for the maximum N loss allowed by law.   This is done by using the highest available yield data source and the correct university data showing the maximum N loss for your application method.   Not all MMP consultants do these things.  Call AgVice for your free MMP review.

• Use a chemical nitrogen stabilizer as a backup plan only.  None of the most widely used stabilizers in manure work consistently according to the vast number of research studies we have seen.  The two most common nitrogen stabilizers marketed are nitrapyrin (sold as Instinct) and a maleic-itaconic copolymer (sold as More Than Manure). 

• Consider moving part of your manure application to spring on lighter sandy type ground.  These fields are the most likely to lose nitrogen in the fall and the least likely to experience compaction problems in the spring.  Spring manure applied on dry soils consistently out-yields fall manure application when compaction is not an issue.  Spring dragline application is an ideal option when available.

• Apply 10-15 gallons per acre of liquid nitrogen in the spring.  This can either be pre-plant or planter applied.  This helps overcome nitrogen loss as well as provide fuel for the corn plant to put roots down farther, to reach manure nitrogen that has moved deeper into the soil profile over time.