In Africa, weeds are the most universal of all crop pest. In agriculture, when a plant grows where it is not wanted, it is considered a weed and has negative impact on the activities of economic interest. Weeds when introduced from other environment, adapts and begin to reproduce enough to occupy the space of native species and bring about changes in natural ecological processes, tending to become dominant after the required time for adaptation. Besides competing for water, light and nutrients, weeds can also impair physical space. The phytosociological survey is defined by a group of ecological assessment methods in order to provide a comprehensive view of both the composition and the distribution of plant species in a certain community (Concenco et al., 2013). Phytosociological surveys are useful as tools to shed light on the dynamics of weed species and their interaction in arable fields. The methods, however, are the most diverse as several indexes and coefficients are available, depending on the literature used as a reference by a given author. Basic care should be taken when sampling and describing the plant community. Even classical references miss some important aspect of phytosociological studies. To come to a valid conclusion, one must choose the most suitable and ecologically based methods, since cultured environments have a relatively distinct group of selection factors compared to the natural environments.
Weed composition in crops or plantation varies from region to region and season to season as established by Tyagi (2005). The primary objective of weed surveying is to accurately identify and delineate land populations of invasive weeds. Information is collected and compiled into maps showing the distribution and severity of the infestations. A standard system of weed surveying and mapping is necessary to provide consistently reliable information that can be compared from year to year.