PROCEEDINGS OF THE 18th NITROGEN WORKSHOP
THE NITROGEN CHALLENGE:
BUILDING A BLUEPRINT FOR NITROGEN
USE EFFICIENCY AND FOOD SECURITY
18th Nitrogen Workshop
PROCEEDINGS
Lisbon, Portugal, 30th June – 3rd July 2014
Editor: Cláudia M. d. S. Cordovil
2014
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THE NITROGEN CHALLENGE:
BULDING A BLUEPRINT FOR NITROGEN
USE EFFICIENCY AND FOOD SECURITY
Proceedings of the 18th Nitrogen Workshop
Edited by: Cláudia S. C. Marques dos Santos Cordovil
Lisboa, Portugal, 30th June – 3rd July 2014
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Edited by: Cláudia S.C. Marques dos Santos Cordovil
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Cláudia S.C. Marques dos Santos Cordovil
ISBN: 978-972-8669-56-0
Depósito legal n.º 377 322/14
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Suggested citation: Author(s), 2014. Title. In: Cordovil C. M. d. S. (Ed.).
Proceedings of the 18th Nitrogen Workshop – The nitrogen challenge: building a
blueprint for nitrogen use efficiency and food security. 30th June – 3rd July 2014,
Lisboa, Portugal, pp. nn-nn.
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nor the Editor.
NITROGEN GAS EMISSIONS AND BALANCES
OF ENERGY MAIZE CULTIVATED WITH BIOGAS
RESIDUE FERTILIZER
M. ANDRES, U. HAGEMANN, J. AUGUSTIN
Leibniz Centre for Agricultural Landscape Research (ZALF),
Müncheberg, GERMANY
e-mail: [email protected]
Despite increasing energy maize cultivation in combination with biogas residue
(BR) application, little is known about the impact of this farming system on gaseous
nitrogen (N) losses as well as N balances. However, there is an urgent need to address
these knowledge deficits, since the application of BR is associated with a potentially
higher ecological risk compared to other organic fertilizers. The reasons for this
increased risk are the higher ammonium (NH4+) and total N concentration, the
decreased organic matter (OM) content, and the enhanced pH value of BR compared
with undigested organic fertilizers (Möller and Müller 2012). Our study will make a
major contribution to fill these knowledge gaps by conducting field experiments at two
different study sites in Germany.
Materials and Methods
The field experiments are carried out in the context of the collaborative research
project “Greenhouse gas mitigation potentials in energy maize cultivation to produce
biogas residues” The field site Dedelow, located in the lowlands of Northeast
Germany is characterized by loamy sand (haplic luvisol). The Dornburg site is located
at the eastern periphery of the Thuringian Basin and characterized by very clayey silt
(haplic luvisol). Zea mays was cultivated at both sites. The impact of BR fertilization
was examined by means of five increasing N application levels (50%, 75%, 100%,
125% und 200% N-BR; applied using trail hoses), compared to an unfertilized (0% N)
and a minerally fertilized control (100% N-MIN; site-specific amounts of 160 and 150
kg N ha-1, respectively). Seventy percent of the applied N-BR was assumed to be
plant-available. Nitrous oxide (N2O) measurements at three plots occurred daily
immediately after fertilization and subsequently bi-weekly using the non-flow-through
non-steady-state chamber measurement technique after Livingston und Hutchinson
(1995, Fig. 1). Immediately after BR application, ammonia (NH3) volatilization was
measured intensively using the open dynamic chamber Dräger-Tube method after
Pacholski et al. (2006). To quantify soil N dynamics, soil samples were taken both
three times in spring after fertilization and once in autumn after harvest from 0-30 cm
soil depth. In the laboratory, the sum parameter Nmin was analyzed by means of CaCl2
extraction. Subsequently to drying the harvested plant material, plant N content
(Nharvest) was determined using elementary analysis (VARIO EL III, Elementar GmbH
Hanau). With consideration of the measured N gas exchange as well as the determined
N soil and plant parameters, N balances can be calculated using a simple difference
approach. Values of N output (Nharvest, NN2O_cum and NNH3_cum) are subtracted from N
input values (Nfertilizer, Nmin_spring and Nmin_autumn). All presented results refer to the time
periods 01.04.2011 until 31.03.2012 and 01.04.2012 until 31.03.2013, respectively.
Results and Discussion
At both sites, our results showed small N2O-N losses with maximum cumulative
emissions of 4.9 kg N2O-N ha-1 yr-1 and 3.1 kg N2O-N ha-1 yr-1 in Dedelow and
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Dornburg, respectively. The amount of applied N-BR had a moderate impact on the
N2O emissions. Only very high fertilizer amounts (125% and 200% N-BR) caused
slightly increased cumulative N2O emissions. However, the correlation was attenuated
to a considerable degree by climate-induced inter-annual and seasonal variability of
N2O fluxes (Fig. 2 and 3). Maximum NH3 losses in Dedelow amounted to 28 kg N ha-1
yr-1 and 6 kg N ha-1 yr-1 in 2011 and 2012, respectively. The considerable variability
between these years likely results from differences in the time period between fertilizer
application and incorporation. While it took more than 24 hours to incorporate the
applied BR in spring 2011, the incorporation occurred within two hours following
application in 2012. Thereby, NH3 volatilization was reduced by one fifth (Tab. 1).
Due to immediate incorporation at the treatments 50%-100% N-BR in Dornburg in
2012, a reduction in NH3 losses of one third was achieved compared to 2011. For the
highly fertilized treatments, BR application was split into two doses, with the second
application taking place after planting. As an incorporation of the BR was thus not
possible, the resulting NH3-N losses were comparable to values from 2011 (Tab. 1).
With increasing N-BR amount, N balances tend to increase from strongly negative
values (accumulative deficit) to extremely positive values (accumulative profit) for
treatments receiving high N-BR amounts (Fig. 4). Only applied N amount exceeding
200 kg N ha-1 resulted in accumulative profits, with no differences between field sites
for increasing N levels. It is evident that N balances were more influenced by N uptake
from plants than by gaseous N losses. In order to correctly interpret the N balances, it
is mandatory to integrate other N fluxes into the balance calculation. Apart from soilbased mobilization and immobilization turnover processes and nitrate leaching, this
applies specifically to gaseous N loss in the form of N2. Therefore, in additional
laboratory experiments, we measured the amount of N2-N loss using the Helium
incubation method of Butterbach-Bahl et al. (2002). Our results indicate that N2 may
be a potentially important pathway of N loss, with up to 5% of the total N output lost
as N2, corresponding to 15 kg N ha-1 yr-1.
Conclusions
Our results showed that climatic conditions and incorporation time have a higher
impact on N2O emissions and NH3 losses than the applied N amount. Plant N uptake
affected the N balances more than gaseous N losses, but positive N balances only
occurred when applied N-BR amounts exceeded 200 kg N ha-1. As the results varied
considerably between years, definite conclusion about the effect of BR application as
well as site-specific and climatic effects on gaseous N losses and N balances cannot be
drawn based on only two years of field measurements.
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