Evaluation of weed populations under the influence of site-specific weed control to derive decision rules for a sustainable weed management [Elektronische Ressource] / presented by Carina Ritter
Institute of Phytomedicine Weed Science Department University of Hohenheim Prof. Dr. R. Gerhards “Evaluation of weed populations under the influence of site-specific weed control to derive decision rules for a sustainable weed management” Dissertation Submitted in fulfilment of the requirements for the degree “Doktor der Agrarwissenschaften” (Dr.sc.agr. / Ph.D. in Agricultural Sciences) to the Faculty of Agricultural Science presented by Carina Ritter from Heidelberg 2008 This thesis was accepted as a doctoral dissertation in fulfilment of the requirements for the degree “Doktor der Agrarwissenschaften” by the Faculty Agricultural Sciences at the University of Hohenheim on January 30, 2008. Date of oral Examination: April 10, 2008 Examination Committee: Supervisor and Review Prof. Dr. R. Gerhards Co-Reviewer Prof. Dr. W. Claupein Additional Examiner Prof. Dr. W. Kühbauch Vice-Dean and Head of the Committee Prof. Dr. W. Bessei Man muss seine Ideen verwirklichen, sonst wuchert Unkraut darüber. Johann Paul Friedrich Richter (1763 - 1825) Contents Page 1. General Introduction ............................................................................... 1 1.1 State of knowledge.......................................................................................
Institute of Phytomedicine Weed Science Department University of Hohenheim Prof. Dr. R. Gerhards
“Evaluation of weed populations
under the influence of site-specific weed control
to derive decision rules for a sustainable weed management”
DissertationSubmitted in fulfilment of the requirements for the degree “Doktor der Agrarwissenschaften” (Dr.sc.agr. / Ph.D. in Agricultural Sciences)
to the Faculty of Agricultural Science presented by Carina Ritter from Heidelberg 2008
This thesis was accepted as a doctoral dissertation in fulfilment of the requirements for the degree “Doktor der Agrarwissenschaften” by the Faculty Agricultural Sciences at the University of Hohenheim on January 30, 2008.
Date of oral Examination:
Examination Committee:
Supervisor and Review Co-Reviewer
Additional Examiner Vice-Dean and Head of the Committee
Study site ......................................................................................................... 15
2. Population dynamics ofGalium aparineL. andepolAsrucu myosuroidesHUDS. under the influence of site-specific weed management ............................................................................................ 13
Contents
Page
1. General Introduction ............................................................................... 1
1.1.2
Site-specific weed control ................................................................................. 5
3.2.2 Data collection ................................................................................................. 31
3.2.1 Study site ......................................................................................................... 30
3.
Can short-term gains in site-specific weed management be sustained over multiple years? ............................................................................... 28
III
Chapter I
General Introduction
Chapter I General Introduction
1. General Introduction
Agricultural productivity is geared to a high yield and quality level, but pests and diseases
can compromise these objectives; therefore plant protection is needed.
Weeds especially cause heavy losses. They compete for water, light, and nutrients (Wilson
and Wright 1990) and decrease quality and quantity of yield. Weeds cause an increase in
moisture in the field and grain, implicating non-uniform ripening. They hinder harvest
techniques and lead to contamination of harvest grain with weed seeds resulting in
cleaning costs (Koch and Hurle 1978).
Nowadays chemical plant protection is established because of the convenient handling and
the high degree of efficiency. The commencement of chemical weed control goes back to
the 18th century, at that time it was discovered that several chemicals cause a damaging
effect on plants (Hocket al. 1995). The first herbicides 2,4-D and MCPA were developed
in the 1940s for weed control in cereals. Herbicides increasingly replaced the labour–
intensive mechanical weed control. Today around 34 % of worldwide yield is saved due to
chemical weed control (Oerke 2006). However, herbicides represent about 50 % of the
globally used plant protection products (Berger 2002). Pesticide use in European countries
is strictly regulated to minimize any negative side effects for the environment and pesticide
residues in the food chain. In context of the German reduction program for chemical plant
protection, herbicide use needs to be strictly controlled in the future and reduced to the
absolute necessary extent (BMVEL, 2005). Additionally, herbicide resistance must be
prevented, thus sustainable technologies for weed control are needed.
1.1 State of knowledge
1.1.1 Weed distribution in agricultural fields
It is generally known, that the weed seedlings distribution within agricultural fields is
spatially and temporally heterogeneous, weeds often occur in patches of varying size,
whereas other areas in the field are less infested or weed free (Marshall 1988, Thorntonet