Page 51 - Ilmu Tanah

38 The Chemistry and Fertility of Soils under Tropical Weeds

3.1 The Concept of Weeds

Weeds are often defined as unwanted plants, misplaced plants, or plants with
unknown benefits. These definitions show human subjectiveness and thereby the
weed definition is dependent on human background and interest. Therefore,
plants classified as weeds are various. Bridges (1999) mentions this phenomenon
as social perspectives of weeds, therefore, plants determined as weeds for one
society may be important plants for others.
The term weed arises due to human needs. Historicaly, this term is used to
identify dan classify plants not wanted by human in any places like houseyards,
recreation areas, or other places determined what plant are allowed to exist.
Radosevich et al. (1997) states that this view is an anthropogenic concept and,
therefore, weed arises from human views and needs. Weeds are also defined as
plants existing with no values and in general grow fairly fast (Merriam-Webster,
2017). Weed Science Society of America (WSSA) also defines weeds as all
unwanted plants or plants disturbing human activities and interests. Navas (1991)
defines weeds as plants that are able to develop their population so that they are
able to enter particular habitats and depress the main plants ecologically or
esthetically wanted. Ross dan Lembi (2008) defines weeds as plants that are
competitive, persistence, disturbing, and destroying. Therefore, weeds stimulate
human to control. All these views intergrate human views on weeds based on
human interests, particularly related to plants and weeds as components of
ecosystems, particularly ecosystem of agricultural lands.
Out of the above views, it can be concluded that any particular plant can be
classified as weed under specific condition determined by human interests. Any
particular plant is classified as weed not based on where and in what condition this
plant grows. Human perception and interest are more determining and, therfore,
any particular weed is not always classified as weed because its role may be
different depending on condition and situation (Sriyani, 2010).

3.2 Weeds as Pioneer Vegetation

Weeds are competitive and may exist in extreme condition due to their root
excretion like allelopathy and organic acids. Other fact shown by weed researchers
is that most of the important weed in Indonesia and other parts of the world is
included as C-4 plants (Holm et al., 1977 dan Ziska, 2003). This fact is the main

Abdul Kadir Salam and Nanik Sriyani – 2019