Manure Applications Compared
Greg Stewart, OMAFRA
Corn Specialist
Manure
Math
In the process of improving manure use efficiency, the first step is to get
a manure sample that is representative of your manure supply and have it analyzed
for nutrient content. Let’s use an example where the manure analysis tells
you that the total nitrogen content is 50 lbs of N/1000 gallons of manure. This
includes both the organic fraction (20 lbs N/1000 gallons) and the ammonium
fraction (30 lbs N/1000 gallons). The rather stable organic fraction will not
be affected by the method of application as these organic compounds break down
gradually to release nitrogen into the plant-available form. The ammonium fraction
of the manure will start to volatilize into the air as soon as it has been applied
to the field. If this manure was applied in the late fall and incorporated within
24 hours, the OMAFRA estimates indicate that 40% of the total N would be available
to next year’s corn crop. If the application rate is 3000 gallons per acre,
the math looks like this:
3000 gal. x (50 lbs N
/1000 gal.) x .40 = 60 lbs N/ acre (available to corn crop)
This estimate is based on
several assumptions, one of which is the loss of N through ammonia volatilization
in the 24 hour period between application and incorporation. For late fall applications,
this loss is estimated at 25% of the ammonium N in the manure. If the manure
was injected rather than broadcast and incorporated this loss is
assumed to be eliminated. In this example, it would represent reduced nitrogen
losses of about 23 lbs N/acre. Of course, not all of this available nitrogen
will make it to next year’s corn crop, but assume 70% does. If this is
the case, an additional 16 lbs of N would be supplied to next year’s corn
crop. Remember, nitrogen losses from the ammonium form can vary widely with
conditions at the time of manure application. For example, if conditions were
warm (> 25 C) and the soil was dry, the volatilization losses may reach 50%
of the ammonium fraction rather than the 25% used in this example.
Checking it Out
This past summer, a Wellington Soil and Crop Improvement project set out to
compare manure application/injection approaches. This was done by comparing
the amount of ammonia (see Figure 1) that was released after liquid hog manure
was applied. We compared surface broadcast applications to injection systems
where a range of spikes, shanks and s-tines were used to inject or incorporate
the manure (see Figures 2a, b and 3).
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Figure
1. Installing a chamber to measure ammonia losses.
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Figure
2a. Nuhn rotary spike applicator.
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Figure
2b. Manure application on plots with rotary
spike applicator. |
Figure
3. Injection of manure with Nuhn S-tine injector.
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This work showed large reductions in ammonia losses, compared to surface applications (and subsequent incorporation) when the manure was injected behind an S-tine configuration but no improvement when the less aggressive rotary spike system was utilized. See Table 1.
| Table 1. Impact mature application technique on ammonia loss from the soil surface in the week following application. (Wellington County, September 2006) | |
| Manure Application Technique | Ammonia Gas Release (PPM) - cumulative total for one week following application) |
| Surface
Broadcast Incorporated after 6 hours |
47 |
| Surface Broadcast Incorporated after 24 hours |
75 |
| Injected with
Rotary Spike No Additional Incorporation |
108 |
| Injected with
S-Tine No Additional Incorporation |
2 |
Factors
to consider in regard to manure injection systems:
| 1) | Although this particular study did not show an advantage for all injector tool bar designs from an N loss perspective, we were encouraged that a boom style delivery of manure may be useful in increasing spread uniformity. |
| 2) | It does not appear that manure must be buried deep into the soil profile to minimize N losses. A shallow (5-10 cm) injection and covering of the manure appears to prevent most of the N loss. |
| 3) | Like other research, this study validated the concept that direct injection systems may be significantly better at conserving N than a broadcast system with incorporation occurring in the 6-24 hour period. |
| 4) | Odour concerns and the reduction in odour provided by injection may be a significant motivating force for adopting injection technology. |
| 5) | Tillage action of the injection system may be all the tillage (other than leveling, perhaps) that is required for subsequent crop production. |
