Effect of poultry litter application
method on ammonia volatilization
from a conservation tillage system
D.H. Pote and J.J. Meisinger
Abstract: Ammonia (NH3
) volatilization from agricultural fields is important economically
as a direct loss of the valuable crop nutrient nitrogen (N), but it can also be a significant environmental
concern for soil, air, and water quality of nearby ecosystems. As poultry production
has expanded in cropland areas of the southeastern United States, poultry litter has become
a major source of crop nutrients for farmers using conservation tillage systems. However, the
conventional application method of broadcasting poultry litter on the soil surface can allow as
much as 60% of the applied litter N to volatilize as NH3
. To provide management options that
can prevent NH3
losses and help farmers use poultry litter nutrients more efficiently, a research
team at USDA’s Agricultural Research Service developed a prototype tractor-drawn implement
for subsurface application of dry poultry litter in perennial pasture and conservation
tillage systems. When compared to surface broadcasting, previous research showed that subsurface
application of poultry litter decreased odor problems, increased crop yields, prevented
more than 90% of nutrient losses in runoff, and prevented NH3
volatilization from perennial
pasture systems. The current study was conducted to expand our knowledge regarding the
effect of this litter application method on NH3
volatilization from row-crop conservation
tillage systems. For two consecutive summers, field plots with a uniform high-residue surface
cover of chopped wheat straw received about 5,000 kg ha–1 (4,500 lb ac–1) of poultry litter
applied by surface spreading with no incorporation, surface spreading followed by light disking,
or subsurface banding using the prototype USDA ARS applicator. Small mobile wind
tunnels monitored NH3
volatilization for at least five days after each litter treatment. Results
for both years showed that NH3
losses were consistently affected by diurnal variations that
were closely related to the vapor pressure deficit. Compared to conventional surface spreading
of poultry litter, NH3
volatilization decreased an average of 67% when the litter application
was followed by light disking, and decreased an average of 88% when the litter was applied
below the soil surface using the prototype applicator. These data show that subsurface injection
of dry poultry litter can preserve adequate surface cover for conservation needs while
constraining NH3
losses to minimal levels, thus conserving N for row crops and reducing
potential nitrogen losses to the environment.
Key words: ammonia volatilization—conservation tillage—manure application method—
manure nitrogen loss—poultry litter—subsurface application
Ammonia (NH3
) volatilization from agricultural
fields is important economically
to farmers because it is a direct loss of
valuable plant-available nitrogen (N).
However, these NH3
emissions are also a
significant environmental concern because
they contribute to acid rain (Sharpe et al.
2004), soil acidification (van Breemen et al.
1982), and N enrichment of surface waters
(Hutchinson and Viets 1969; Schroder 1985;
Fisher and Oppenheimer 1991). Ammonia is
a chemically active gas that readily combines
with nitrates and sulfates in the atmosphere
to form fine particulate matter, which has
been implicated in human respiratory problems
and led to revised air quality standards in
the United States (Dell et al. 2012; Sommer
and Hutchings 2001). Ammonia loss can
cause additional soil and water problems
by decreasing the N:phosphorus (P) ratio
in manure and accelerating excessive soil P
buildup (Meisinger and Jokela 2000) when
farmers apply extra manure to compensate
their crops for the N that was volatilized
(Marshall et al. 1998). The excess soil P
can be transported by runoff into nearby
aquatic systems where it further accelerates
the eutrophication process (Levine and
Schindler 1989).
Several factors affect the rate at which NH3
is volatilized from animal manure applied to
agricultural fields, including manure composition,
soil factors, application method,
surface cover, and environmental conditions
(Meisinger and Randall 1991; Meisinger and
Jokela 2000; Thompson and Meisinger 2002).
For example, higher NH3
losses occur when
the manure pH value is above 7 (Moore et
al. 2011) and when environmental factors
favor high evaporation rates (Brunke et al.
1988). Thompson and Meisinger (2002)
found that NH3
losses from surface-applied
dairy slurry were 45% for a grass surface,
compared to 29% from bare soil. Pfluke et
al. (2011) also spread liquid dairy manure on
the surface of grass forage plots and observed
during the following 36 hours that NH3
-N
volatilization ranged as high as 59% of total
ammoniacal N (TAN) applied, but found
that surface bandin