Study on Dryland Weed Species under Different Land Use Patterns in Southwest of Guangxi Province——A Case Study of Longzhou County

Qiujin TAN,Zhenshi QIN,Haisheng CHEN,Dongying XU,Daxuan ZHAO,Xianyang HE,Xiyun HUANG

Agricultural Science Research Institute of South Subtropics of Guangxi,Longzhou 532415,China

Responsible editor:Yingchun YANG Responsible proofreader:Xiaoyan WU

Weed includes all the kinds of plants which were disadvantageous to human activities or deleterious to production spots.It strongly inhibits the growth and development of crops,and it can promote the spread of diseases and pests[1].The size,structural features and dynamic change of the potential weed communities in dryland decide the harm conditions in the future[2-3].In recent years,with the change of cropping system,adjustment of cropping structure,improvement of the integration of water and fertilizer and the long period using of chemical herbicides,the dominant populations of weed in farmland and the community structures had been changed obviously.Dryland weeds have serious damages and effects on the yield and quality of crops[4-5].In abroad,in order to maintain the balance of farmland ecosystem under the condition of changed cultivation system,species,density,distribution and dominant population of weed were widely investigated[6-8]including scientific fertilization,regulation of weed seed bank,reasonable control of weed and reduction the use of chemical herbicide[9-11].In order to master weed community structure,diversity,other dynamic characteristics,occurrence and damage conditions in dryland under different land use patterns in southwest of Guangxi and provide theoretical foundation for scientific prediction of community succession patterns of weeds,scientific and reasonable application of chemical herbicides and efficient control of agroecological system,the writer investigated weed species,density,distribution and dominant population in corn,sugarcane,pineapple,banana and mango fields in Longzhou County during 2013 to 2014.

General Situation in Study Area and the Study Method

General situation in study area

The study area is Binqiao village,Longzhou County,Guangxi Province and belongs to southwest Guangxi,which is located at 22°8′- 22°44′ N and 106°33′-107°12′ E.The highest altitude of the area is 1 045 m and the general altitude is 200 m.It is famous as a basin and belongs to subtropical monsoon climate area.The annual average temperature is 22.3-23.0 ℃;the extremely high temperature is 41.6 ℃and the lowest air temperature is -3.0℃.The sunshine duration is 1 582.7 h and the frost-free period is more than 350 d.The average annual precipitation is 1 304.1 mm and the precipitation period is mainly between June and September.The annual average relative humidity of air is 81%-87%.The northwest of the area is high while the middle-of-south is low.It is mainly consisted of karstic feature stone mountains.There are many small,independent and steep peaks,which belongs to limestone soil weathered from rock during Permian period.

Study method

On the basis of field survey in study area,representative corn,sugarcane,pineapple,banana and mango fields with basically consistent site conditions were selected and fields of each pattern were no less than five.The 0.5 m × 0.5 m square iron wires were adopted for investigation.Weed species,number,height,breadth and cover degree were investigated according to the sampling methods of inverted W-pattern.The density,frequentness and growth condition were investigated with quadrat method[12].The abundance,important value Shannon-Wiener,Simpson and Pielou uniformity of the dominant species of dryland weed were calculated[13].

Results and Analysis

Weed species

According to the investigation results of the five survey points,11 weed species of Gramineae and ten species of Compositae were the main species among the 27 families 54 species(Table1) appeared in the sampling fields.According to the different land use patterns and cultivated crops in the drylands,weeds could be classified into corn field weed,sugarcane field weed,pineapple field weed,banana field weed and mango field weed.There were 20 weed species in sugarcane field,18 weed species in pineapple field,11 weed species in banana field,14 weed species in mango field and 13 weed species in corn field.

Dominant weed species in the dryland under different land use patterns

The dominant weed species and degree of dominance in various drylands were different because of the different planting patterns and ecological environments[14].According to the investigation results,the dryland in Longzhou County formed weed populations with Gramineae,Compositae and Oxalidaceae as the main families(Table2).Bidens bipinnata,Oxalis corniculata,Urena lobata,Roegneria kamoji,etc.were the main weeds in corn fields.The relative abundance,Shannon-Wiener and Simpson of Oxalis corniculata were 0.313,0.294 and 0.026,respectively,which were the biggest.Stellaria media,Emilia sonchifolia and Stenotaphrum helferi were the main weeds in sugarcane fields.The relative abundance,Shannon-Wiener and Simpson of Stellaria media were 0.145,0.255 and 0.014,respectively,which were the biggest.Bidens bipinnata,Oxalis corniculata,Eupatorium odoratum and Silene conoidea were the main weeds in pineapple fields.The relative abundance,Shannon-Wiener and Simpson of Oxalis corniculata were 0.151,0.268 and 0.018,respectively,which were the biggest.Bidens bipinnata,Roegneria kamoji,Oxalis corniculata and Galium aparine were the main weeds in banana fields.The relative abundance of Roegneria kamoji was 0.216,which was the biggest.The Shannon-Wiener and Simpson of Bidens bipinnata were 0.277 and 0.020,respectively,which were the biggest.Oxalis corniculata,Viola inconspicua,Euphorbia prostrata and Bothriochloa bladhii were the main weeds in mango fields.The relative abundance,Shannon-Wiener and Simpson of Oxalis corniculata were 0.200,0.300 and 0.028,respectively,which were the biggest.The relative abundance of the dominant species and dominant populations of weeds in drylands under different land use patterns were relatively high[15].The Pielou uniformity under the five land use patterns were 0.967,0.964,0.947,0.969 and 0.962,respectively.The number and damage degree of the dominant species and populations were over other weeds.It might because of the low drug delivery level or the misuse of herbicides that resulted in the rapid growing of Compositae weeds,Gramineous weeds and other swart weeds.The prevention and treatment are difficult.It could not be controlled by one-time drug delivery while the cost of two times drug delivery was high,which resulted in serious damages of Compositae weeds,Gramineous weeds and other swart weeds which should be treated as the key objects of weed control in Longzhou County.

Table1 Weed species in dry land under different land use patterns in southwest Guangxi

Table2 The dominant species and diversity indexes of dry land weeds

Discussion

Sugarcane was basically planted in the dryland in Longzhou County,southwest Guangxi.In recent years,the income of sugarcane industry decreased under the continuous influences of years of drought.The positivity of farmers was not high.Currently,partial cropping structures were drastically adjusted and the cultivation system was changed.Weeds fight for nutrient,moisture,sunshine and space and produce inhibiting substances to impede crop growth,which not only decrease crop yield and influence the quality of agricultural products but also hamper farm operation and seriously influence agricultural production[16-17].Weed investigation is helpful to construct integrated forecasting system for dryland weeds,to scientifically perform the reform of cultivation system,to implement crop rotation,to increase the input for the basic construction of dryland,to perform deep tillage roundly,to improve ecological environment of dryland and to decrease cardinal number of weeds on the basis of effectively control of weed damage[15].Suggestions were proposed as follows:①Herbicides should be used scientifically; new medicaments with high efficiency,low toxicity and low residual should be studied and developed; the weeding effect of herbicides should be improved to restraint drug resistance of weeds.A certain degree of weed biodiversity should be kept while the weed damage is controlled.②Correlations among the germination of weed seeds,feature of soil seed bank and weed populations under the condition of fertilization should be studied to construct database of weed seed in dryland soil,forecast the population dynamics and community succession of weeds and construct the comprehensive control system of weeds.③Cultivation system should be reformed scientifically;crop rotation should be implemented; ecological and disciplinary management measures for weeds should be formulated;ecological environment of dryland should be improved; the base of weeds should be decreased and weed management should be improved.

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