RESEARCH FOR

tHermal Weed control In norWay spruce
(PICEA ABIES (l.) H.Karst.) nursery
Gerda Šilingienė, Regina Vasinauskienė, Jonas Račinskas
Aleksandras Stulginskis University, Lithuania
e-mail: g.silingiene@gmail.com
abstract
Growing of economics and new technologies has caused the environment pollution and more intensive use of natural
resources. The principles of stable and balanced forestry became more and more important. Ecologization forests
economy directly and indirectly impacts environment, water, air, landscape. It is not allowed to use chemicals in
ecological farms. In Lithuania the number of ecological farms is growing that is why the new effective ecological
methods are needed to protect seedlings from weeds. Alternative to mechanical control of weed is to use high
temperature. In ecological farms weed control after sowing time is pursued in mechanic, and recently in thermal
way. In thermal weed control the surface of soil remains mechanically undisturbed, the roots of cultural plants remain
undisturbed, too. These features are very important in forest nurseries, where different kinds of tree species are
growing. Seedlings are very small at the beginning of growing, so mechanical weed control is difficult. Thermal weed
control could be a good alternative. Comparable data of 2009-2011 thermal weed control research in Norway spruce
(Picea abies (L.) H. Karst.) nursery is given. The efficiency of destroyed 16 weed sorts using thermal and mechanical
ways of weed control is given. Thermal weed control for short age weeds is 20.3% more effective in comparison with
mechanical way. Mechanical way is 35.2% more effective for perennial weeds. It was detected that in order to control
weeds of different growth stages, it is necessary to use different treatment time of damp water stream.
Key words: thermal weed control, weeds, technology, Norway Spruce.
Introduction
In Lithuania as well as in all European Union
general politics of agriculture and forest sectors is
oriented to ecological farming. The main object of
ecological farming is to improve soil texture, reduce
pollution of heavy metals, and increase stocks of
humus and nutrients in the soil. Numbers of ecological
farms are growing. In the ecological farms weeds after
sowing are exterminated by physical and mechanical
processes such as mechanical removal, harrowing and
inter-row cultivation. Roots of cultural plants grown
are injured when mechanical weeding is carried out.
Mechanical injuries of the over–soil parts of the plants
are also unavoidable, and it reduces productivity
(Lisek, 2001).
More significant attention is given to the
thermal methods. Process of thermal methods could
be different various temperature environments.
Application of thermal weed control processes
increases and utilization of flaming by gas, hot water
and damp water stream procedures spreads out rapidly
(Ascard, 1995; Sirvydas et al., 2003).
Damp water stream is ecological high temperature
environment that can fully replace pesticides. In
the working environment temperature is 100 °C
(Gimbutis, 1993). Process of heat transmission is
very intensive, stream condensation takes place on the
weeds surface and the heat is given. Devices of damp
water stream are very effective (Gimbutis, 1993). The
environments of high temperature water stream do not
allow resisting for the live organisms.
Thermal weed extermination is based on the
thermal energy exchanges and balance in high
FORESTRY AND WOOD PROCESSING
temperature medium. With the plant tissue temperature
raised to over 58 °C, the lethal outcome of the weed
plant is assured. The biological struggle of the plant
against the unusual effect by high temperature
medium takes place, duration of which depends upon
mass of plant tissues involved and the thermodynamic
properties of the thermal medium applied. Plants with
smaller biometric dimensions in damp water stream
reach their value of the lethal level in 0.5–2 s. Plants
with greater biometric dimensions during the same
time undergo thermal stress. As a result, it increases
productivity (Vasinauskiene, 2004). Data in literature
on extermination of various weed plants in high
temperature media were not found.
The aim of the study is to establish efficiency of
mechanical and thermal weeding and the sensitivity
of weeds to high temperature damp water stream
medium.
materials and methods
Analysis of weeds was investigated in the nursery
of Šiauliai Forestry Enterprise. Species structure and
number of weeds was detected in the experimental
patches (0.2 cm x 0.25 cm) which were put on the
Picea abies seedlings according to their nutrition
area (Figure 1). Experimental patches were put as it
is noted in the methodology (Raudonis, 2009). The
experiment was repeated six times.
In the first variant weeds were removed manually
3 times. This is the traditional way of weeding. For
the first time weeds were removed just after mass
shooting in the stage of appearance of the first to
second leaves. Weeds were removed the second and
44 ReseaRch foR RuRal Development 2012