Weed Vegetation Analysis and Documentation of Weed Species of Western Zone (Kia Farm) of Tamilnadu

Introduction

Weeds are the plants that grow where they are not desired or unwanted plant species growing spontaneously in crop ecosystem and also on open land areas. It has been estimated that out of 2,50,000 flowering plants, about 8000 species are weeds in the world [8]. In the field, they make a competition with the cultivated plant to make use of nutrients, water, light, and the area. Weed is one of the limiting factors that affect the growth and yield of cultivated plants. They have better characteristics such as a growth ability that is faster than cultivated plants. They flower earlier, run to seed in profusion, and mature ahead of the cultivated plant. Other weed characteristics are the ability to survive under adverse conditions, and they have a very high reproductive capacity. If there are no efforts to control them, they will become harmful. The proper weeding regime for effective and economic weed management needs to be done to obtain high yields and profit. [4]. In sustainable agriculture, farmers need to be aware of the life cycle of the weed species and have knowledge about when and what actions should be taken to control weeds on the cultivated site [7]. Vegetation analysis is used to determine weeds that have a high ability to grow and dominate in a living space. The dominance generally determines whether weeds are important or not. The dominant weed population can later be used as a consideration to make some weed control decisions. With this background the survey was conducted to identify and document the predominant weed species in the KIA farm.

Materials and Method

The survey was conducted at Kumaraguru Institute of Agriculture, Nachimuthupuram, Erode district, Tamil Nadu which is located at 11°49`N Latitude, 77°56`E longitude and with an altitude of 200 m above MSL from April to July 2023.

The survey was aimed to determine the weed types present in the college farm. Sampling was carried out in purposive manners based on the presence of weeds in the cultivated area. The equipment used for this survey was stationery rope, a tally sheet to measure the weed population. The first step of the research was observation of weeds in the campus to know about the areas covered by the weeds.

The sample observation plots were made by purposive sampling with a size of 1 m x 1 m, totaling 20 slots. Randomly selected each 10 sites in North farm and South farm in KIA.  Identification on plant species inside the observation plot is conducted directly based on characteristics and morphological or of every species found. If there are unknown species found, so a herbarium sample is made for further identification [3].

Vegetation analysis was carried out by recording the weed species found in the sample plots and calculating the dominance of weed species by measuring the weed biomass, the above data is then used to calculate the density (D), relative density (RD) frequency (F), relative frequency (RF).The Summed Dominance Ratio (SDR) values were measured to find the dominance of each species found.

D = Certain individual number in an observation plot

                Number of plots where a species found

  F =    ——————————————————— X 100

                  Number of total observation plots

                 Number of individual weed species

 RD =    ——————————————— X 100

                 Total number of weeds

                     The dry weight of weeds of individual species (gm^-2)

  RDw     =                                                                                             X 100

                          Total dry weight of weeds (g m^-2)

                    Relative density + Relative Dry weight (gm^-2)

   SDR =                                                                                       X 100

      2

 Important Values Index  = Relative density + Relative Frequency

D is the number of individuals per unit area or unit volume [3]. RD is the ratio of one type of vegetation density to all vegetation types densities in an area [9]. F is a value that indicates the spread of a vegetation type in a number of sample plots under study [3]. RF is the percentage ratio between the frequency of a vegetation type with the frequency of all vegetation types in the area. IVI shows the ecological importance of a plant species and shows its role in a community so that it is known to be influential or not [1]. SDR is the level of dominance of species in a plant community [5]

Results and Discussion

Weather on Weeds Growth

Weather elements play an important role in exploiting the growth and yield potential of any crop. Weather variability is considered one of the major factors of inter-annual variability of crop growth and yield in all environments. The variations in agricultural production are mostly attributed to the effect of seasonal weather conditions on plant growth. The weather parameters during the survey of the farm are as follows. The Maximum temperature of 37.95º C, Minimum temperature of 20.5º C, Average rainfall of 221.6 mm and  evapotranspiration is 40.8 mm are documented.

Weed flora

Weeds are plants that grow around cultivated plants that can inhibit the growth of crop plants. The presence of weeds causes competition between weeds and cultivable plants for available soil nutrients. From the survey 13 families of weed species have been identified.

The weed flora of the survey was dominated by seven species of grasses Bracharia reptans, Chloris barbata, Cynodon dactylon, Dactylactenium aegyptium, Eragrostis amabilis,  Panicum repens, Perotis indica was the dominating grasses, Acalypha indica, Amaranthus viridis, Boerhavia diffusa, Commelina benghalensis, Cleome viscosa, Euphorbia hirta, Flaveria trinervia, Gomphrena decumbens, Mimosa pudica, Phyllanthus madraspetansis, Phyllanthus niruri,  Parthenium hysterophorus, Ruella tuberosa, Trianthema portulacastrum, Tribulus terrestris, Tridax procumbens are the dominant broadleaved weeds and Cyperus iria,are the only sedges which were conclude from survey of  our farm. The highest percentage of weed species was found in Poaceae family followed by Euphorbiaceae family (Table 1).

Weed density

Different weed species were found on the farm, dominant weed species were then determined by analysing the vegetation. There are 24 species of weeds from 13 families identified which were consisted of 7 no of species belonging to Poaceae, 4 no of species belonging to Euphorbiaceae remaining are from other families. The dominant species in broadleaved weeds compromising mainly Trianthema portulacastrum followed by Phyllanthus niruri, Dactylactenium aegyptium and sedge of Cyperus iria (Table 2)

Frequency

Overall, the presence of a weed species in both the farm is based on the RF classification according to research conducted by [2] [6]. The highest RF value was obtained in Trianthema portulacastrum, Cyperus iria, Cleome viscosa, Dactylactenium aegyptium showing that these four weeds were often found in every observation in both the farm(Table 2)

Important Value Index

The Important Value Index (IVI) is quantitative parameter that can be used to state domination level (dominance level) of certain species in one plant community. The dominant species in one plant community will have a  high important value index, so the dominant species of course would have the highest important value index [2]. In this survey, Trianthema portulacastrum is the species which have the highest important value index of 16.75 (Table 1) respectively. It mean that this plant has the highest level of domination in the observation plots. Whereas Phyllanthus madraspetansis had the lowest IVI of 1.43. (Table 2)

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