Proceedings World Bioenergy 2010

INTERCROPPING OF REED CANARY GRASS, PHALARIS ARUNDINACEA L., WITH LEGUMES CAN CUT
COSTS FOR N-FERTILIZATION
Cecilia Palmborg and Eva Lindvall
Department of Agricultural Research for Northern Sweden, SLU
90183 Umeå, Sweden
ABSTRACT: In a field experiment close to Östersund in mid Sweden reed canary grass was intercropped with barley,
Alsike clover, Trifolium hybridum L., red clover, T. pratense L., goats rue, Galega orientalis L. or a combination of red
clover and goats rue. There were also three fertilization treatments: A: Recommended amounts of N, P and K. B:
Recommended amounts of P and K and half amount of N. C: Sewage sludge application before sowing (establishment
year) and recommended amounts of P and K and half amount of N. The biomass was lower where reed canary grass had
been undersown in barley, and higher with full N-fertilization than with half N-fertilization. However there were no
significant differences between legume intercrops with half N-fertilization and pure reed canary grass with full Nfertilization.
Alsike clover was the most productive legume, followed by red clover. The amount of nitrogen fixed by the
legumes was less with full N-fertilization (29 kg/ha as a mean) than with half N-fertilization (38 kg/ha). Intercropping
with legumes could substitute half of the N in fertilization but similar experiments in other parts of Sweden has shown
that there is a higher risk of weed problems.
Keywords: autumn harvest, spring harvest, bioenergy crop, energy grass
1 INTRODUCTION
Cropping systems that will provide our future energy
for society need to be sustainable in many ways. The
system should use nutrients efficiently, the system should
need a minimum of input of fossil fuels for machinery
and transport and the system should bind at least as much
carbon to the soil as is respired from the soil. Reed
canary grass harvested in spring fulfills these criteria [1].
However, to make the cropping profitable without heavy
subsidies, costs must be cut. This paper focus on the
possibilities to cut fertilization costs by intercropping
between reed canary grass and legumes and by
fertilization with sewage sludge.
The legumes take some of their need for nitrogen
from nitrogen fixation by symbiotic bacteria in their root
nodules. Some of this nitrogen then can be transferred to
the accompanying grass via decomposing legume litter
both above and below ground. Reed canary grass as an
energy crop is always grown in monoculture. There have
been few experiments with intercropping with legumes.
The only experiment that has studied intercropping in a
system with spring harvest a Lithuanian study by
Jasinskas et. al [2]. In that study there was no Nfertilization
in the intercrops and this favored the legumes
that increased from year to year and the third year they
comprised 28-56 % of the crop. In our experiment we do
not take away all fertilizers in order to favor reed canary
grass and keep legumes as a minor component or the
sward.
2 MATERIALS AND METHODS
A field experiment was established in Ås close to
Östersund in mid Sweden (latitude 63 o 14’ longitude
14 o 34’) in july 2008. Reed canary grass was intercropped
with Alsike clover, Trifolium hybridum L., red clover, T.
pratense L., goats rue, Galega officinalis L. or a
combination of red clover and goats rue. There are also
monoculture reed canary plots established alone or
undersown in barley that was harvested as a whole crop,
a strategy to get an income from the crop the first year.
There are also three fertilization treatments: A:
Recommended amounts of N (40 kg/ha first year and 100
kg/ha second year), P (20 kg/ha first year) and K (40
kg/ha first year and 50 kg/ha second year). B:
Recommended amounts of P and K and half amount of
N. C: Sewage sludge application before sowing
(establishment year) and recommended amounts of P and
K and half amount of N. The experiment has a split-plot
design with fertilization treatment on the main plots and
species mixtures on the sub-plots (2.8 x 9 m), and it is
randomized in four replicate blocks.
In the end of August 2009, 50 x 50 cm plots, 50 cm
from the edge of the big plots were harvested by hand
cutting in autumn 2009. The biomass was sorted in each
sown species and weeds and the dry weight of each
fraction was determined. The sown species were milled
and N% and the proportions of the stable isotope 15 N
were analyzed on an ANCA-SL coupled to a Sercon 20-
20 IRMS (Sercon, United Kingdom). The data were used
to calculate the nitrogen fixation using both the
difference method and the 15 N natural abundance method
[3]. In October, larger plots (1.5 x 7.5 m) were harvested
with a plot harvester. However, since this harvest was
interrupted by snow, only 2/3 of the plots were harvested.
The harvested material was put back on the plots and
collected and weighed again in May 2010 to determine
winter losses.
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