“There is more than one way to skin a cat,” is a famous
phrase telling us other options exist. It’s also a phrase murmured by this
husband to Mrs. Manure when the initial plan for the day’s home renovation
project hits an unexpected snag. However, the same idea applies when we think
about capturing manure value, there is more than one way to achieve it.
In particular, I’d like to take a quick look at two
approaches today, the bigger, faster, approach designed to reduce the cost of
application per gallon and then side-dressing manure. The truth is, both have
advantages and challenges to capturing manure value. Understanding the
challenges of each is important to determine what may work best for you and your
farm. While there are many considerations, today I’m going to focus on some of
the economics behind value. To get started, I’ll be working on some of the
concepts I first discussed in Manure
Application Logistics – Rate and Cost,
where I looked at how the application rate we are using impacts the cost of
manure application rate.
To make this comparison, I’m going to consider a 4,800-head
swine farm, which will generate about 1.75 million gallons of manure a year, or
enough to cover about 695 acres (approximately 60 lb N/1,000 gallons and
applying 150 lb N/acre). At this farm, we’d have an application rate of about 2,500
gallons per acre.
For illustrative purposes, I’m going to ballpark $500,000 in
equipment costs (pumps, hose, drags, and a toolbar), but that is dependent on
what you are using. In the case of swine manure, let’s assume we have a 30-foot
bar and can drive through the field at 7 mph. This means they can cover an 0.42
acres per minute and to get 2,500 gallons per acre the flow rate would be about
1,060 gpm. This means to get all 1.75 million gallons applied would take 27.5
hours and assuming the crew was about 50% efficient, it would take about 55
hours overall. Just for fun, let’s assume run time costs about $500 an hour
(tractors, fuel, wear and tear, etc.). If we figure a 5-year equipment life and
1.75 million gallons is about 10% of the total gallons they apply every year,
then our cost for manure would be about $37,500 or about $0.021 a gallon of
manure applied or about $0.36 per pound of N applied.
Figure 1. Manure application in the fall using drag line equipment and thinking about travel speed to lower application cost.
Now we need to do the same thing for a side-dressing type
scenario. I’m going to keep the equipment cost the same and assume setup time
remains the same at 27.5 hours (since I’ll have the same number of sets), but since
we are side-dressing we are going to have to drive slower, here I’m going to
assume a travel speed of 3 mph. At this speed, we will cover 0.18 acres a
minute, or manure application will take 64.3 hours or 92 hours overall. Making
the same assumptions as above for cost, that is $500 per hour in variable
expenses and $0.006 in fixed expenses, per gallon for a cost of around $55,925
or $0.032 per gallon. This amounts to about $0.54 per pound of nitrogen.
When you look at these numbers it may be easy to say that
the first case is maximizing manure value as the price per unit of nitrogen
delivered to the field is cheaper, but there is a timing impact on how
efficiently this nitrogen can be used by the plant. While I don’t have data on
side-dressing manure and the impact it has on value, we do have data from the
last two years on how three different application timings (early fall, late
fall [50 degree soils and cooling], and spring manure application) impacted
corn yield. While not a perfect comparison, they give us some idea of what the
potential yield increase may be. In that study, we saw late fall versus early
fall worth 45 bushels an acre on average, while moving to spring manure
application versus late fall application was worth 33 bushels per acre. Given
the weather and soils at that site, these are probably a bit higher than we’d
see in much of Iowa, but provide a starting point to the conversation.
Figure 2. Side dressing manure, slows our gallon per minute rate, but what does it do to value?
The 33 bushels an acre we saw in that study, at $3 a bushel
corn, would be worth $99 an acre. This improved timing added approximately
$0.66 of value from the nitrogen applied. Thinking of this in a slightly
different way, by changing timing we estimated a change in the cost of nitrogen
delivery in these systems of $0.18 a pound increase, meaning the return on
investment using the data we have, was about 3.6-to-1.
