Effect of tillage intensity on N mineralization of different crop residues in a
temperate climate
Annemie Van Den Bossche
*
, Sara De Bolle, Stefaan De Neve, Georges Hofman
Department of Soil Management, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
1. Introduction
Agroecosystems in Western Europe are faced with increasing
physical degradation of soil as a consequence of reduced organic
matter content and intensified tillage practices. These concerns
promote research on alternative ways of agricultural production
that reduce soil erosion and balance nutrient inputs with
environmental concerns. Conservation tillage (ConsT) is increas-
ingly being adopted worldwide, mainly because of its role in
protecting the soil from wind and water erosion. However, ConsT is
most practiced for monocultures of grain crops and is only recently
gaining importance in Western Europe. Constraints for ConsT in
Western Europe are on one hand the lack of knowledge about the
effects of ConsT under these specific climatic and soil conditions
and on the other hand the requirement of inclusion of root and
tuber crops in the rotation which seem less suitable for ConsT.
Conservation tillage is any tillage and planting system which
maintains at least 30% of the soil covered with residues after
sowing as to reduce erosion by water (IPCC, 2000). Most of the
residues are left at the soil surface or in the upper few centimeters
of the soil layer with no tillage (NT) or reduced till systems (RT),
whereas with conventional tillage (CT) most residues are buried to
deeper layers by plowing (Burgess et al., 2002).
Nitrogen is one of the nutrients recycled through crop residues.
However, most of the N in crop residues is in organic form and is
not directly available for plant growth. During decomposition of
crop residues, this organically bound N is made available for crop
or microbial growth through N mineralization (Lupwayi et al.,
Soil & Tillage Research 103 (2009) 316–324
ARTICLE INFO
Article history:
Received 21 May 2008
Received in revised form 19 October 2008
Accepted 26 October 2008
Keywords:
Reduced tillage
Crop residues
N immobilization/mineralization
ABSTRACT
To evaluate the effect of tillage intensity on the N mineralization pattern of winter wheat residues, sugar
beet residues, Italian ryegrass and maize residues undisturbed soil samples were taken from six sites
under different tillage management. Site NT
K
had been managed for 10 years under reduced tillage (RT),
whereby the last 4 years the crops were sown using direct seeding (NT). Site RT
CSE
had been managed for
20 years under reduced tillage (RT) and site RT
H
for 3 years. For each site under RT a nearby site under
conventional tillage (CT) was selected (CT
K
,CT
CSE
and CT
H
). On site NT
K
and site RT
CSE
a significantly
higher amount of SOC in the 0–10 cm was accumulated compared to the respective CT sites. Between site
RT
H
and site CT
H
no such significant difference was found. However, the content of microbial biomass C
(MB-C) and the
b
-glucosidase and urease activities were higher on all RT sites compared to the respective
CT sites. This indicates that these microbiological and biochemical parameters seem to be very sensitive
for alterations in management intensity. After 98 days, more N was immobilized under NT
K
than under
CT
K
by adding winter wheat residues (expressed as kg ha
À1
and as % of total added N). This higher
immobilization potential can be explained by a higher microbial activity and a change in microbial
population. Under RT
CSE
and RT
H
net N immobilization of the winter wheat residues was found, but the
pattern was less pronounced than for NT
K
. However, when expressed as % of total N added, N
immobilization of winter wheat residues was higher under CT than under RT, which indicates that high
C:N residues when incorporated, decompose more slowly under RT than under CT. Similar results were
found comparing the N mineralization pattern of maize residues under RT
H
and CT
H
. The residues of sugar
beet and Italian ryegrass at site CT
H
released N more rapidly and to a higher extent, 74.1% and 66.2%,
respectively (expressed as % of total N added) than under RT
H
at the end of the incubation. The slower
mineralization of N rich crop residues under RT compared to CT means that there is less potential risk for
nitrate leaching to occur, which may result in a higher N efficiency in RT compared to CT.
ß 2008 Elsevier B.V. All rights reserved.
* Corresponding author. Tel.: +32 9 264 60 66; fax: +32 9 264 62 47.
E-mail address: annemie.vandenbossche@ugent.be (A. Van Den Bossche).
Contents lists available at ScienceDirect
Soil & Tillage Research
journal homepage: www.elsevier.com/locate/still
0167-1987/$ – see front matter ß 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.still.2008.10.019