Weed Communities And The Eco-niche Of Farmland Under Cultivation Tillage

Farmland weed is an important factor which troubled the development of agricultural production and hindered crop production increased from the beginning of mankind farming that day on.A study showed that low or straw to cover breed weeds,control of weeds in conservation tillage is an important aspect of technology system,which must be taken into account to adopt conservation tillage massly.Through conservation tillage experiment in drylands of the Loess Plateau in Gansu for seven years,the number of weed,cover,fresh weight and other indexes of different farming methods were measured using "W" 5 sampling method.The formula is computed by applying niche width to calculate weeds advantage,niche,species richness,Shannon Weina index,Simpson index,uniformity index,the similarity index,the effect of different farming methods on farmland Weed Community,niche and species diversity are analyzed.The results are as follows:The investigation of weed community in wheat and pea field at the conservation tillage for seven years showed:there were 16 kinds weeds which belong to 10 sections 15 genus such as Kochia scoparia,Chenopodium glaucum,Euphorbia humifusa,Chenopodium album,Artemisia argy,Convolvulus arvensi,Calystegia hederace in wheat field and 12 kinds which belong to 8 sections 11 genus such as Convolvulus arvensi.Kochia scoparia,Euphorbia humifusa,Chenopodium glaucum,Chenopodium album,Calystegia hederace in pea field,in which some of them are annual plants,others are perennial plants.Study on weed community showed that weed kinds in conservation tillage are less than traditional tillage,so which have some function to control weeds appear.Weeds increase slowly when crop growing but rapidly when procreating in different tillages.No-tillage no straw mulch restrains crop to grow in growth prophase but no-tillage straw mulch goes against weed control in prophase compared with traditonal tillage.For seven consecutive years of traditional farming straw up pressure,no-tillage wheat straw mulch on Weeds did not have a significant impact(p＞0.05),but no-tillage pea-straw mulch impact on species richness significantly(p＜0.05).Shannon-Wiener index analysis showed that compared with traditional tillage no-tillage straw mulch and no-tillage are a very significant difference(p＜0.01),and species diversity index reduces,Simpson index,uniformity index have no significant difference(p＞0.05),which showed years of traditional tillage didn't increase species diversity and have not yet formed a single weed population.Important value and relative abundance are coherent basically in conforming main weeds and evaluating the effect of weeds on crop by comparising different tillage methods,only in the treatment of straw up measure Convolvulus arvensi has more difference in vertical niche but the equal degree,frequency degree,desity degree of main weeds have no diffence between fields.So in practical work,only using relative abundace to analyze weeds superiority is possible but must describe the difference of significant extent of weeds community between species.