Weed species diversity on arable land of the dryland areasof central Tanzania: impacts of continuous applicationof traditional tillage practices

摘要

This paper presents findings from a studythat assessed influence of continuous application of aparticular traditional tillage practice on weed speciesrichness, diversity and composition and identifiesweed species with positive benefits to the communitiesin semi-arid areas of Mpwapwa district, centralTanzania. In this area farmers apply three differenttraditional tillage practices which are no-till (NT),shallow tillage (ST) and Ridging System (RT). A totalof 36 farm fields were surveyed in 2006/2007 croppingseason where 63 weed species from 26 families wereidentified. Analysis of variance indicated significantdifferences between practices (p < 0.05), with NT practice having highest weed species richness anddiversity. Among the five more prevalent weed speciesappearing, Bidens lineariloba was observed to exist inall the three practices. Community representativesduring focus group discussions indicated 9 weedspecies out of 63 identified to have beneficial uses.These species are Cleome hirta, Amaranthus graeciz-ans, Bidens lineoriloba, Bidens pilosa, Dactylocteniumaegyptium, Launaea cornuta, Heteropogon contortus,Tragus berteronianus and Trichodesma zeylanicum.Their main uses include leaf-vegetable, medicines,fodder and materials for thatching. From this study NThas highest weed species richness and diversity whichtherefore suggests that much more time is needed forweeding in this practice compared to other practicewhich was the farmers' concern. It was also noted thatalthough weed species have negative effects in cropproduction and production costs, they still play a vitalrole in food security and for the health of differentpeople in marginal areas as well as for the completeecosystem including micro and macrofauna.