The effect of cropping systems on production and the environment
Modern agricultural systems greatly influence the environment. In Denmark the emphasis is
particularly on nitrate leaching and greenhouse gas emissions from agriculture. Besides these
environmental issues, sustainable systems also need to fulfil the requirements for quantity and
quality of the agricultural produce.
The project will quantify productivity and environmental impacts of different organic and
conventional cropping systems across a range of soil and climatic conditions. It aims to identify
management measures that can contribute to a sustainable development of the individual
cropping systems.
The effect of cropping systems on production and environment
Harvest of cereals with a well-developed undersown clover as catch crop (photo: Henning C. Thomsen)
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CROPSYS 2007-2010
Modern agricultural systems greatly influence the
environment. In Denmark the focus is particularly on
nitrate leaching and greenhouse gas emissions. An
important issue in this context is also to reduce the
reliance on external resource use, including fossil
fuels and nutrient inputs To be sustainable, agri
cultural systems also need to fulfil the requirements
for quantity and quality of the agricultural produce.
Crop production in organic farming systems relies to
a large extent on soil fertility for nutrient supply and
plant growth. The soil fertility must be maintained
via choice of crop rotation and (green) manuring
practices. Proper management of this to improve
crop yields and reduce emissions environment
requires an indepth understanding of soil processes
and nutrient dynamics and their effects on crops
and weeds.
Long-term crop rotation experiment
A longterm organic crop rotation experiment was
initiated in 1997 at three different locations in Den
mark; in 2005 it was modified to include also a con
ventional system. The three locations represent typical
soils (sand, loamy sand and sandy loam) and climates
for Danish agriculture. The design of the rotations
allows for effects of manure application and catch
crops to be distinguished, and for effects of soil type
and climate to be quantified. Thus, a differentiated
analysis of management strategies can be conducted.
The project exploits this unique longterm experiment
for an integrated study of the productivity and nitro
gen flows in organic cropping systems.
During the period 1997 to 2004 the experimental
factors were 1) proportion of N2fixing crops in the
crop rotation, 2) with (+CC) and without (CC) catch
crop, and 3) with (+M) and without (M) animal ma
nure. Two crop rotations (O2 and O4) with different
proportions of cereals and nitrogenfixing crops in a
fouryear rotation were tested (Table 1). All crops in
all rotations are represented every year in two repli
cates (blocks). From 2005 the design was changed
to include a conventional cropping system (C4) with
Project objectives
The overall goal of CROPSYS is:
to quantify productivity and environmental
impacts of different organic and conventional
cropping systems across a range of soil and
climatic conditions
to identify management measures that
contribute significantly to a sustainable
development of the individual cropping
systems.
The basic hypothesis is that organic cropping
systems can be maintained with high produc
tivity at low environmental impact through
better crop rotation design and management,
as modified by soil type and climate. This will
be achieved through a better description of the
role of soil nitrogen dynamics, soil properties
and crop and weed dynamics in the different
systems, and using modelling and scenario
analyses to integrate and evaluate production
related and environmental indicators of sustain
ability.
Sustainability targets in modern agriculture
a crop rotation similar to the O4 rotation. From
2005 the cuttings in grassclover in O2/+M was no
longer mulched, but removed from the field.
Integrated experimental and modelling approach
The project will apply an integrated experimental
and modelling programme, where measurements of
key indicators of productivity and environmental im
pact and of the underlying processes and dynamic
soil properties are carried out in the longterm crop
rotation experiment. A simulation model and a life
cycle analysis will be used to analyse different man
agement scenarios. The project will produce guide
lines for improving the sustainable development of
organic crop production systems in Denmark.
Rotation system effects on yield and carbon inputs
The inputs of carbon to the soil were highest in crop
rotation O2, in particular where the grassclover
cuttings are mulched and left in the field (Figure 1).
The lowest carbon inputs were obtained in rotation
O4, in particular in the treatment without catch
crops. The higher yields in the conventional systems
(C4) meant the carbon input was higher here com
pared with the comparable organic O4 systems.
Table 1. Structure of the crop rotations.
O2 O4 C4
1st course 1997-2000 S. barley:ley
Grass clover
Winter wheatCC
Pea/barleyCC
Spring oatCC
Winter wheatCC
Winter cerealCC
Pea/barleyCC
2nd course 2001-2004 S. barley:ley
Grass clover
Winter cerealCC
Lupin/barleyCC
Winter wheatCC
Spring oatCC
S. barleyCC
Lupin
3rd course 2005-2008 S. barley:ley
Grass clover
Potato
Winter wheatCC,2
S. barleyCC
Faba beanCC,1
Potato
Winter wheatCC,2
S. barleyCC
Faba beanCC,1
Potato
Winter wheatCC,2
CCCatch crop in the +CC-treatments, 1Pea/barley in 2005, 2S. oats in 2005.
C4/+CC/+M
C4/-CC/+M
O4/+CC/+M
O4/+CC/-M
O4/-CC/+M
O2/+CC/+M
O2/+CC/-M
O2/-CC/+M
0 1 2 3 4 5 0 1 2 3 4 5
Grain yield (Mg DM/ha) Carbon input (Mg C/ha)
Figure 1. Mean annual grain
yield and carbon input as
average of all crops in the
rotations for the period 2005
to 2007 at Foulum, where
the soil is loamy sand.
Cropping system experiment at Foulum
(photo: Erling Nielsen)
The effect of cropping systems on production and the environment CROPSYS 2007-2010
Project leader
Jørgen E. Olesen, University of Aarhus, Department
of Agroecology and Environment
P.O. Box 50, 8830 Tjele, Denmark
Email: [email protected]
Project participants
Margrethe Askegaard, Ilse A. Rasmussen, Per
Schjønning, Søren O. Petersen, Mette Lægdsmand
and Kristian Kristensen, University of Aarhus, Faculty
of Agricultural Sciences
Per Ambus, Technical University of Denmark;
Risø Laboratory for Sustainable Energy
Søren Christensen, Copenhagen University, Faculty
of Science
Selected publications
Askegaard, M., Olesen, J.E. & Kristensen, K. (2005). Nitrate
leaching in organic arable crop rotations: Effects of location,
manure and catch crop. Soil Use and Management 21,
181188.
Olesen, J.E. & Munkholm, L.J. (2007). Subsoil loosening
eliminated plough pan in a crop rotation for organic
farming with mixed effects on crop yield. Soil & Tillage
Research 94, 376385.
Olesen, J.E., Askegaard, M. & Rasmussen, I.A. (2000). Design of
an organic farming crop rotation experiment. Acta
Agriculturae Scandinavica, Section B, Soil and Plant Science
50, 1321.
Olesen, J.E., Rasmussen, I.A., Askegaard, M. & Kristensen, K.
(2002). Wholerotation dry matter and nitrogen grain yields
from the first course of an organic farming crop rotation
experiment. Journal of Agricultural Science, Cambridge 139,
361370.
Olesen, J.E., Hansen, E.M., Askegaard, M. & Rasmussen, I.A.
(2007). The value of catch crops and organic manures for
spring barley in organic arable farming. Field Crops Research
100, 168178.
Rasmussen, I.A., Askegaard, M., Olesen, J.E. & Kristensen, K.
(2006). Effects on weeds of management in newly converted
organic crop rotations in Denmark. Agriculture, Ecosystems
and Environment 113, 184195.
Schjønning, P., Munkholm, L.J., Elmholt, S. & Olesen, J.E. (2007).
Organic matter and soil tilth: Management makes a
difference within 56 years. Agriculture, Ecosystems and
Environment, 122, 157172.
Links
More information is available on the project website at
www.cropsys.elr.dk/uk
About ICROFS
The International Centre for Research in Organic Food Systems (ICROFS) is a “centre without walls” where the research is performed in interdisciplinary collaboration between research groups in different institutions. The centre is an expansion of the former research centre DARCOF, which the Danish Government in 2008 decided to give an international mandate and an international board.
The main purpose of ICROFS is to coordinate and monitor international research in organic food and farming systems in order to achieve optimum benefit from the allocated resources. Further, the aim of ICROFS is to initiate research and create impact of the research results through support and dissemination of high quality research of international standard.
More information at www.icrofs.org
ICROFS