Last
month we looked at manure budgets for different counties around the state,
and I got a great question. In those counties where we see robust manure
resources, what can be done to make sure they are using it, striving to be good
stewards, and limit losses of nitrate from crop fields? I always view this
question the same way; is there something we aren’t trusting about the manure
alone to get the job done? In other words, what does the fertility program look
like?
I think one common concern farmers have is how available is
the nitrogen in manure. While the weather conditions in any particular growing
season can vary, the more important factors are the species from which the
manure comes from and the manure management system used. More information on
estimating the nitrogen availability for Iowa conditions can be found in
PMR 1003 – Using manure nutrients for crop production.
A second important area is the potential for loss of the
nitrogen in manure, especially as related to application timing. Nitrogen in
manure starts in either the organic or ammonium form, and while these generally
aren’t susceptible to loss once they are in the soil, under warm conditions,
they can be rapidly converted to nitrate, which makes manure application timing
an important factor for estimating the amount of nitrogen in the soil and
available to support crop production. Recent research has shown, in certain
years, delaying manure application of liquid swine manure from early October
until early November, could increase corn yields 30-60 bushels an acre,
indicating if for some reason manure has to be applied earlier than intended,
yield losses could occur. When farmers see this occurring, it can look like an
availability issue, and cause loss of confidence in manure as a fertilizer
course.
Finally, a third area of concern is uniformity of manure
application and the consistency of manure. The precision age of agriculture has
made farmers more aware of places in the field where yields are inconsistent.
By its nature, manure has variability to it and while new technology, such as real-time
nutrient measurement, may be able to help with this and correct this issue.
Additionally, making sure those nutrients are applied at the correct rate and
uniformly over the field is a critical component of using manure as a
fertilizer, and trusting it will provide what you need, this needs to be done
for both solid
manure and liquid
manure application equipment.
Figure 1. Image of
manifold distribution evaluation
