A survey of weeds of wheat and cotton crops from eight Talukas of district Khairpur (Mir’s) viz. Kingri, Gambat, Khairpur, Sobhodero, Kotdiji, Thari Mirwah, Faiz Ganj and Nara has been carried out during 1999-2002. Twenty three weed species are recorded representing 10 families from wheat, while 36 weed species of 16 families have been reported from cotton.
A floristic account of weed species has been compiled including dichotomous keys to families, genera and species and descriptions. Illustrations of all the species have been made indicating habit and floral parts. Herbarium specimens have been preserved in the herbarium of Shah Abdul Latif University, Khairpur. Scanning electron microscopic study of seed has been carried out, which resulted in the discovery of several taxonomically useful characters to differentiate the species.
All the weed species of both the crops have been categorized as surpassing weeds (SW) which are equal or taller than the actual crop; underneath weeds (UW) are of procumbent, decumbent and prostrate in nature and climbing weeds (CW) which includes climbing, twining, trailing and stoloniferous type of plant species. The SW has constituted 43.47% and 30.55% of species in wheat and cotton crops respectively. UW has been represented by 43.47% in wheat and 52.77% in cotton. Whereas, CW attains 13.4% and 16.66% of species in wheat and cotton crops respectively.
Weed communities have been recorded from various Talukas on the basis of density analysis. The status of weed species based on their frequency is proposed as Assertive (having frequency more than 60%), Ascendant (having frequency of 50-60%), Average (having frequency of 30-49%) and Below Average (having frequency below 30%).
A map of general land has been prepared by using Geographical Information System (GIS) to specify the cultivated and non cultivated areas of district Khairpur in order to show the general trend of cropped and barren areas and to indicate the sampling points. A general concept of area is given delineating Taluka and district boundaries that are supplemented with the preparation of layers for various physical features i.e. main canals, river, roads and towns to portray the base map of the area of interest. Two more views are created to show the density and frequency of some important weeds of wheat and cotton crops in each Taluka, shown in the form of bar and pie diagrams.
A similarity index (SI) of species has been determined. The importance of each family values (FIV) has been compared by calculating an index (FIV) to establish the relative contribution of each family to weed species composition. The most common family representing wheat weeds is Papilionaceae having 56.58 FIV whereas, in cotton the Poaceae is most important with 45.74 FIV.