the effects of some cover crops on weeds diversity changes in citrus orchards of northern iran

in order to investigate the effect of different cover crops on density and diversity of weeds, the researcher carried out an experiment in randomized complete block design with seven treatments and three replications for two years (2009-2010) in iran citrus research institute. treatments included planting four cover crops of legumes such as clover (trifolium alexandrinum l.), green bean (phaseolous vulgaris l.), soybean (glycine max l.) and green gram (vigna radiata l.), use of herbicide (paraquat), straw as mulch and control. the results indicated that cover crops are more effective in weeds diversity, therefore; the number of species in the control from seven species, to four species in soybean and mulch, five species of clover, green bean and green gram were reduced, respectively. the objective in cover crops is to decrease weed seed production in soil and to reduce their population. the results indicated that there were significant differences among treatments from weeds density aspect at 1% level that control treatment had the most weeds density and herbicide and green gram treatments, were the lowest. the obtained results showed that vigna radiata l. and glycine max l. were the best treatments in reducing the weeds density and diversity.