Weed species composition and distribution pattern in the maize crop under the influence of edaphic factors and farming practices: A case study from Mardan, Pakistan.

Weeds are unwanted plant species growing in ordinary environment. In nature there are a total of 8000 weed species out of which 250 are important for agriculture world. The present study was carried out on weed species composition and distribution pattern with special reference to edaphic factor and farming practices in maize crop of District Mardan during the months of August and September, 2014. Quadrates methods were used to assess weed species distribution in relation to edaphic factor and farming practices. Phytosociological attributes such as frequency, relative frequency, density, relative density and Importance Values were measured by placing 9 quadrates (1 × 1 m2) randomly in each field. Initial results showed that the study area has 29 diverse weed species belonging to 27 genera and 15 families distributed in 585 quadrats. Presence and absence data sheet of 29 weed species and 65 fields were analyzed through PC-ORD version 5. Cluster and Two Way Cluster Analyses initiated four different weed communities with significant indicator species and with respect to underlying environmental variables using data attribute plots. Canonical Correspondence Analyses (CCA) of CANOCO software version 4.5 was used to assess the environmental gradients of weed species. It is concluded that among all the edaphic factors the strongest variables were higher concentration of potassium, organic matter and sandy nature of soil. CCA plots of both weed species and sampled fields based on questionnaire data concluded the farming practices such as application of fertilizers, irrigation and chemical spray were the main factors in determination of weed communities.

Introduction

Weeds are the part of dynamic ecosystems, start off in ordinary environment and become obstacle to the crops (Baker, 1974). Weeds are unwanted plant species emergent in the cultivated crops and grow where they are not needed. Out of 8000 only 250 weed species are important for agriculture world (Holm et al., 1979). Weeds cause great destruction to crops as they increase the costs of different cultural practices, decrease the effectiveness of agricultural equipment and excellence of fertile lands, decrease the germination capability of crops seed due to the phytotoxins or allelochemicals (Algandaby and Salama, 2016). Weeds have some pinpointing characters, such as short seed dormancy, high seed germination rate, environmental plasticity, fast seedling growth and reproductive capability, short span of life cycle, self-compatibility, efficient and well organized methods of seed desperation, manufacturing of diverse types of allelochemicals and tolerance to abiotic and biotic stresses (Baker, 1974, El-Sheikh, 2013). It allows the weed species to survive and grow in different ecological habitats. Due to this weeds are becoming dominant all over the world (Holm et al., 1979, Holm et al., 1977) and damage the local biodiversity (Duke, 1983, Tilman, 2000).

Zea mays is cross pollinated, annual, short day plant of the earth. In Pakistan maize is progressively gaining more significant position in crop husbandry due to its higher yield potential and short development period (Khan et al., 2011a, Khan et al., 2011b, Olsen et al., 2006). The maize crop faces lots of difficulty because the farmers typically give more importance to a small number of cultural practices and ignore other factors resembling as weed control and seed rate. In Pakistan during 2012–13 maize yields 36.581 m ton production in a total of 0.981 m ha cultivated area and in the same year in KPK maize yields 1.468 m ton product in 0.512 m ha cultivation area. A number of weed species that are the tough competitors, compete for existing resources with the maize crop (Al-Shahwan et al., 2016, Gomaa, 2012, Malik et al., 2006). This competition is most grim and significantly decreases maize product at early crop growing period (Mitchell and Tu, 2005).

The present study analyzed the ecological relationship among the distribution of weed communities and their environmental factor in Shahbaz Ghari, District Mardan, Pakistan. It also reveals the weed species types and its distribution pattern, composition and abundance along with the edaphic factor and farming practices that determine the distribution of the weed species and communities in the study area.

Materials and methods

Shahbaz Ghari is a Union Council of District Mardan, Khyber Pakhtunkhwa located on mardan sawabi road having an area of 3956 hac. The people of an area mostly depend on agriculture. Important crop of the area includes Maize and wheat. For the first time the present study was carried out to find out the relationship among weed species, edaphic factors and farming practices in maize crop of Shahbaz Ghari District Mardan during the month of August and September 2014. Different stations were recognized at random intervals on both sides of the road at different distance using quantitative ecological techniques. Quadrat having 1 × 1 m2 size and square shape were placed systematically in the projected area (Shahbaz Garhi) and data collected from different stations (Clements, 1905, Khan et al., 2011a, Khan et al., 2011b, Khan et al., 2012). In each field nine quadrats were positioned and density, frequency, relative density, relative frequency and Importance Values were measured respectively (Curtis and McIntosh, 1950). Associated data i.e., soil data for testing and different methods were based to ask various questions from farmers to collect information concerning farming practices. Weed plant specimens were collected, labeled with tags and pressed in plant presser. After drying the plant specimen were poisoned and mounted on standard herbarium sheets. Specimens were identified using available literature (Ali and Qaiser, 1995, Khan et al., 2014, Khan et al., 2013a, Khan et al., 2013b). The specimens were deposited in the Herbarium of Hazara University Mansehra Pakistan.

Soil collection

A total of sixty-five soil samples were collected up to one feet depth from different fields. These soil samples were placed in plastic bags, brought to laboratory; air dried and ground to form one composite sample. The analysis concerned with the physiochemical properties of these soil samples was carried out in the agriculture research laboratory Mansehra. During soil analysis the soil pH, electrical conductivity (E.C.), organic matter, calcium carbonate concentration, soil texture, phosphorus and potassium parameters were measured. Soil pH and electrical conductivity were measured using 1:5 soil water suspension by pH meter and conductivity meter respectively (Rhoades et al., 1990). Soil texture was determined by the walky-black procedure and texture class was determined with the help of a textural triangle (Adamu and Aliyu, 2012). Organic Matter was determined by the hydrometer method. (Koehler et al., 1984, Nelson et al., 1996).

Data analyses

The data of 585 quadrats were put in MS EXCEL to prepare presence and absence data sheet for Cluster and Two Way Cluster Analysis. The weed data, soil and questionnaire data were analyzed through PC-ORD version 5 to find out the effect of edaphic factor and farming practices on weed species distribution and composition pattern. Through CANOCO software version 4.5 data attribute plots were derived to find out the effect of multivariate environmental, edaphic factor and farming practices on weed species plus the position of indicator species in each region (Khan et al., 2012, Khan et al., 2013b).

Results

A total of 29 weed species were collected from 585 quadrats belonging to 27 genera and 15 families in maize crop of Union Council Shahbaz Garhi District Mardan. Poaceae and Amaranthaceae were the leading families having 4 weed species (13.8%) each. The Cyperus rotundus and Urochloa panicoides are the abundant while Lactuca dissecta and Cucurbita maxima are the less abundant weed species of study area.

Two way cluster analysis

Two Way Cluster analysis (TWCA) derived from presence and absence data sheet (1, 0) by Sorensen measures to classify the pattern of weed species at various regions. Four weed communities identified as a result of grouping of stations of fields which might be obviously seen in two major parts of the dendrogram in Two Way Cluster (Fig. 1).

Figure 1

Two Way Cluster Analysis of 65 maize fields and 29 weed species through PC-ORD.

Environmental gradient

The weed species and environmental data matrix that are with soil data, questionnaire data and questionnaire plus soil data combined were put in CANOCO software version 4.5. It resulted in significant effects of all the environmental variables on weed species composition and diversity. The environmental variables were treated as aspect pH, electrical conductivity, organic matter concentration, calcium carbonate, sand, silt, clay, phosphorous, potassium and textural class. It resulted that there was a little significant effect of first canonical axis and show full significant effect of all canonical axes. Weed species with questionnaire data was analyzed in CANOCO software version 4.5 and significant effects of first canonical axis on weed species composition and diversity were foundv. At last all the weed species are compared with environmental data, questionnaire and soil data through CANOCO software version 4.5 that resulted in significant effects of first and test of all canonical axes with soil and questionnaire variables on weed species composition and diversity of study area (Table 1).

Table 1

Summary table of Canonical Correspondence Analyses (CCA).

Axes	1	2	3	4	Total inertia
Eigen values	0.067	0.051	0.032	0.026	0.638
Species-environment correlations	0.721	0.767	0.680	0.665
Cumulative percentage variance of species data	10.5	18.4	23.4	27.4
Species-environment relation	26.4	46.6	59.1	69.3
Summary of Monte Carlo test (499 permutations under reduced model)
Test of significance of first canonical axis		Test of significance of all canonical axes
Eigen value	0.067	Trace			0.252
F-ratio	4.906	F-ratio			1.250
P-value	0.1100	P-value			0.0220

Classification of weed species communities

Four weed communities identified as a result of grouping of stations or fields. By studying the communities one by one in relation to various soil related variables and different farming practices we can draw the following conclusions.

Celosia – Convolvulus – Euphorbia weed community

The mainly abundant weed species of this community are Convolvulus arvensis, Dactyloctenium aegyptium, C. rotundus, Brachiaria ramosa and U. panicoides with high Importance Values, while at the same time less abundant weed species are Amaranthus blitoides, Achyranthes aspera, C. maxima, Citrullus lanatus and Cynodon dactylon having low Importance Values in the region When field’s data are analyzed by CCA plot, with soil composition data (Fig. 2) it was concluded, the main significant variable of first community are higher concentration of CaCO3, pH and potassium, while CCA plot based on questionnaire data (Fig. 2) shows farming practices such as application of fertilizers (increase in number), chemical spray and early sowing are the main factors in determination of this community. The CCA of both questionnaire and soil data (Fig. 2) reconfirm the validity of our observations that indicates high concentration of CaCO3, pH, potassium and demonstrate more number of irrigation.

Figure 2

Canonical Correspondence Analysis (CCA) diagram showing distribution of 65 fields in relation to various measured environmental variables with questionnaire and soil data respectively.

Data attribute plots using CCA for top 3 indicators species of community – 1 i.e., Celosia argentea with indicator values 45.9 and 26.6, C. arvensis with Indicator value 53.7, 21.2 and Euphorbia prostrata 45.9 and 22.2 in the case of pH and phosphorous respectively. Indicator value of C. argentea is 47.1, C. arvensis with 49.8 and E. prostrata with 42.7 in the case of spray farming practices (Appendix Table A) (Fig. 3).

Figure 3

Data attribute plot (from left to right) of Celosia argentea (1st indicator species), Convolvulus arvensis (2nd indicator species) and Euphorbia prostrata (3rd indicator species) showing its position in respect to different fields and associated environmental variables.

Archyranthes – Ipomea – Physalis weed community

The U. panicoides, C. rotundus, D. aegyptium, B. ramosa and Commelina benghalensis are the most abundant whereas X. strumarium, Physalis angulata, Solanum nigrum, L. dissecta and C. maxima are less abundant weed species of 2nd community. The soil data of community 2 were analyzed through CCA (Fig. 2). It results that the main significant variables are higher concentration of electrical conductivity, potassium and clay nature of soil, while questionnaire data (Fig. 2) concluded higher concentration of moist, application of artificial fertilizers and spray farming practice as compared to others communities. At last CCA plots of both questionnaires and soil data were analyzed (Fig. 2) that again proved the community has high deliberation of electrical conductivity, potassium, clay nature of soil, relevance of artificial fertilizers and chemical spray.

Data attribute plots using CCA for top 3 indicator species of community – 2 i.e., A. aspera, Ipomea purpurea and P. angulata show indicator values of 11.9, 8.6 and 19.9 in the case of electrical conductivity and 11.5, 17.5, 28.1 indicator values of canal irrigation farming practice respectively in the region (Appendix Table A) (Fig. 4).

Figure 4

Data attribute plot (From left to right) of Achyranthes aspera (1st indicator species), Ipomea purpuera (2nd indicator species) and Physalis angulata (3rd indicator species) in relation to various fields, soil and farming practices variables.

Corchorus – Lactuca – Commelina weed community

The most abundant weed species based on Importance Values are B. ramosa, D. aegyptium, C. rotundus, C. benghalensis and U. panicoides. Despite the abundant weed species the I. purpurea, A. blitoides, C. maxima, X. strumarium, and Cannabis sativa are less abundant weed species of community. In light of CCA plot, where we used only soil data (Fig. 2) it is accomplished that the noteworthy variable are sandy nature of soil and organic matter concentration. With help of CCA then questionnaire data (Fig. 2) of community 3 were analyzed which show the main significant variables of the maximum number of irrigation, irrigated by canal and different varieties of maize crop cultivated. Then the CCA of both questionnaire and soil data (Fig. 2) were analyzed that reconfirm each other’s.

The data attribute plots using CCA for top 3 indicators species of community – 3 i.e., Corchorus olitorius, L. dissecta and C. benghalensis show indicator values of 48.9, 11.3 and 41.3 in canal irrigation farming practice and 22.2, 45 and 34.4 indicator values in the case of electrical conductivity environmental variable respectively (Appendix Table A) (Fig. 5).

Figure 5

Data attribute plot (From left to right) of Corchorus olitorius (1st indicator species), Lactuca dissecta (2nd indicator species) and Commelina benghalensis (3rd indicator species) presenting its position with environmental variables and various fields.

Amaranthus – Euphorbia – Parthenium weed community

The top abundant weed species of community four are Boerhavia diffusa, C. rotundus, C. benghalensis, C. arvensis and U. panicoides, while Solanum nigrum, Cassia occidentalis, C. sativa, C. dactylon, and P. angulata are less abundant weed species of the region that show minimum Importance Values. When only soil data were analyzed in light of CCA plot, (Fig. 2) it is concluded that the main significant variables are higher concentration of organic matters and sandy nature of soil. By observing the CCA plot obtained from questionnaire data (Fig. 2) concluded that the community – 4 having significant environmental variables are moist, natural fertilizers, hoeing and tube well irrigation farming practices. Latter on CCA of both questionnaire and soil data (Fig. 2) reconfirm each other and shows higher concentration of natural fertilizers, hoeing, plough and sandy nature of soil as compared to other communities which indicate high concentration of CaCO3, potassium, phosphorus, pH, artificial fertilizers, electric conductivity, and show clay nature of soil.

Data attribute plots using CCA for top 3 indicators species of community – 4 i.e., Amaranthus viridis, Euphorbia hirta and Parthenium hysterophorus show 46.5, 29.5 and 32.4 Indictor values respectively in tube well irrigation farming practice (Appendix Table A) (Fig. 6).

Figure 6

Data attribute plot (from left to right) of Amaranthus viridis (1st indicator species), Euphorbia hirta (2nd indicator species) and Parthenium hysterophorus (3rd indicator species) showing its site in respect with different fields and related environmental variables.

Discussion

In last several years the study of environmental changes is emergent more swiftly as compared to other few disciplines of studies related to the life sciences. Present study revealed 29 weed species belonging to 27 genera and 15 families distributed in 585 quadrats. Amaranthaceae and Poaceae were the dominant families followed by Cucurbitaceae and Asteracece. CCA bi-plot Analysis shows the pattern of weed species composition, its distribution pattern and relation with ecological factors. Tanveer et al. (2013) suggest that the C. arvensis tends to grow better in neutral and slightly acidic soil as compared to alkaline soil environments. Optimum pH range for germination of C. arvensis ranged between 6 and 8 cm. Present analysis showed similar results to Tanveer et al. (2013) that C. arvensis grows more an acidic soil as compared to alkaline nature of a community. C. arvensis is a main problem in cotton, potato, maize, wheat and sugarcane etc (Memon, 2004). It is one of the top harmful weed of the worlds and out of 54 countries it is found in 32 different crops fields (Holm, 1997). Similarly present work also revealed C. arvensis is one of abundant weed species of the region. C. rotundus is growing in farmlands, cultivated fields and grasslands, at the boundaries of forests, sandy seashore, riverbanks and irrigation canal banks (Holm et al., 1977, Wiggins et al., 1971). In the same way our study result C. rotundus was the most abundant weed species of study area present abundantly almost in all communities facing different edaphic factors like higher pH, CaCO3, potassium, electrical conductivity, organic matter concentration, clay and sandy nature of soil. Likewise Swarbrick (1997) also reported that C. rotundus grown well in approximately all type of soil, a wide range of pH, elevation and soil moisture. Present study revealed B. diffusa was abundantly found in regions where higher concentration of organic matters, sandy nature of soil, application of natural fertilizers, hoeing and tube well irrigation farming practice occur. Similarly Low (1991) reported in his book named “Wild food plants of Australia” i.e., B. diffusa is found in dry sandy nature of soils, plus Abeywardana and Hettiarachchi (2001) also reported that B. diffusa is a common weed present in sandy areas, while Chopra (1969) reported that B. diffusa grows all over the warmer region up to 2000 m an altitudinal rang of Himalaya and grows easily in fields following the rainy time of year and in wastelands. Chauhan and Mahajan (2014) reported in a book titled, Recent advances in weed Management i.e., Straw mulch sited in the middle of the two crop rows inhibits the appearance of weed and also adds organic matter to the soil. While in the Philippines a residue of 6 t ha−1 significantly reduced seedling emergence and bio mass of D. aegyptium, Eclipta prostrata, Eleusine indica and L. chinensis. Comparing with Chauhan and Mahajan (2014) the present work resulted community 4 has higher concentration of organic matters and sandy nature of soil which doesn’t allow D. aegyptium to grow abundantly as compared to other communities that contain higher concentration of CaCO3, electrical conductivity, pH, potassium, clay and sandy nature of soil and in addition to application of fertilizers farming practice. In present study C. benghalensis is present in three communities in abundance that exposed moderate moist condition, application of fertilizers and irrigation. Kaul et al. (2002), also resulted that C. benghalensis is a rainy season weed which require moist soil condition for establishment and after establishment it can also survive dry condition. According to Britton et al. (1963) that I. purpurea prefer to grow in rich moist, well drained and sandy loamy soil situation. Similarly our result also show I. purpurea is present in sandy nature of soil, in more number of irrigation fields (moist condition) and in higher concentration of organic matter. It resulted that C. lanatus was present less frequently where higher concentration of pH and potassium take place. In the same way Paksoy et al. (2010) resulted that C. lanatus is grown at different soil textures and pH of 5.0 to 6.5 (low) respectively. Smith (1981) reported that A. aspera weed grown from sea level up to 900 m. In coastal cultivated areas along road sides and frost trails abundantly on rocky seashore, lime stone and grassy slopes. Similarly our study revealed A. aspera weed is grown where higher concentration of CaCO3 present and sandy nature of soil occurred. Costea (1998) reported that A. blitoides can grow on sandy soil, fixed and sand dunes, alluvial sands and can tolerate to a wide range of pH, change able from 4.5 to 8.5, but favor to pH values near to 7. Similarly first community of our study area shows higher concentration of pH and sandy nature of soil which results in A. blitoides to grow less abundantly.

Conclusion

It is concluded that among all the edaphic factors the strongest variables were higher concentration of potassium, organic matter and sandy nature of soil. CCA plots of both weed species and sampled fields based on questionnaire data concluded the farming practices such as application of fertilizers, irrigation and chemical spray were the main factors in determination of weed communities.