Ammonium N in manure

Is all the ammonium N shown on the manure analysis available to the crop? It depends on the timing and method of application. Referring back to the N cycle, when manure is applied and not tilled into the soil, the ammonium N is highly susceptible to loss to the atmosphere via ammonia volatilization. On the other hand, if manure is quickly tilled into the soil soon after application, but no crop is present to take up the N (e.g. as with fall applications without cover crops), then the N can be lost through leaching or denitrification, depending on the soil type. As a result, the average availability of ammonium is estimated through the following approach.

• If manure is incorporated in the fall, assume that 100% of the ammonium N is lost, due to leaching or denitrification.
• If manure is applied as sidedress injection into growing row crops (e.g. corn), assume that 100% of the ammonium N is available to the crop.
• If manure is applied in the spring, then the availability of ammonium N depends on how quickly the manure is tilled into the soil. The table, below, outlines the average portion of ammonium N conserved across the range of days before manure is tilled into the soil.

Days until incorporation	% NH4-N availability
1	65
2	53
3	41
4	29
5	17
>5	0

The video clips, below, show three different manure application methods. Click on each photo to run the video and rank the manure application methods from highest to lowest ammonium N availability. To enlarge the movie, click in the upper right corner of the movie image.

Example A	Example B
Spring draghose injection of manure into corn stubble (New York)	Direct manure injection into a growing crop (Netherlands)

Example C

Spring surface application and incorporation of manure within 3 days into corn stubble (New York)

Use the calculator, below, to check the ranking.To do this, assume that you applied 10 tons/acre of manure with 4 lbs NH₄-N/ton.

1. Enter 10 into the "Application Rate" cell.
2. Enter 4 into the "Ammonium-N from Manure Analysis" cell.
3. Switch among the application methods/timings, described above, in the drop down menu.
4. Hit "calculate it!" after you switch to another method/timing.
5. Track the differences in N availability in the box, below.

The calculator can also be used to assess ammonium N availability from manure for other manure types as well as different rates, timings, and methods of application.

The next section focuses on organic N availability from manure.

To read more on this subject: Nitrogen Guidelines for Field Crops in New York (section 3.3).

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