Agriculture Reference
In-Depth Information
Table 3.7
Methods of non-chemical weed management (after Köpke 2000)
Indirect methods
Direct methods
Crop rotation
competition
complementarity
allelopathy
Mechanical
hand weeding
various ploughs. chisel tines, discs, harrows,
spring tines
rotary hoes
brush weeders
mulching
•
•
•
•
•
•
•
•
Farm hygiene
cleaning of seed supplies
cleaning machinery and tools
Thermal
flame weeders
steam weeders
infrared weeders
•
•
•
•
•
Soil cultiation
tillage (turning/non-turning)
photobiology
Biological
grazing with livestock
classical bio-control
'bio-herbicides', microorganisms as weed
pathogens
•
•
•
•
•
Improement of competitieness
seed quality
morphology and vigour of cultivars
drilling design. density, row distance,
sowing direction
strategic fertilisation and irrigation
•
•
•
•
rotation (>60%). On farms with a high percentage of clover, alfalfa and other mowable crops
(~20%) thistles were not reported as critical. The effective suppression of thistles was as a
result of:
(a) light competition through a fast-growing crop;
(b) root competition; and
(c) continuous destruction of shoots to exhaust the storage of assimilates in the roots (Radics
et al.
2003, Pekrun and Claupein 2004, Lukashyk
et al.
2005).
Therefore in crop rotations with a low level of forage legumes and a high level of cereals,
farmers have to improve crop competition through adequate choice of cultivars (Köpke 2000),
optimised growing conditions and fertiliser banding.
In perennial farming systems such as orchards and grazing enterprises, longer-lived weeds
such as blackberry (
Rubus fruticosus
) and serrated tussock (
Nassella trichotoma
) may be
favoured owing to the lack of ongoing disturbance (Sheppard 2000). Physical removal is
suitable if the infestations are not too great. However, other options for managing perennial
weeds include strategic grazing and biological control (Vere and Holst 1979, Evans and Bruzzese
2003).
Indirect methods
Some of the indirect methods used to manage weeds in organic cropping have been discussed
above. In the sections on rotations and cultural strategies, a range of techniques for controlling
weeds were mentioned including appropriate cropping sequences, growing two or more com-
plementary crops in the same location, careful timing of input applications and strategic
spatial arrangements of crop plants to optimise resource use efficiency and yield. Several other
