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: JorgenE.Olesen@agrsci.dk

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