Corn- weed Interaction under Different Sowing Dates of Cover Crops

To investigate the effect of planting time of cover crops on corn-weed interaction، an experiment based on randomized complete blocks design with three replications was conducted in Sari Agricultural Sciences and Natural Resources University during growth season of 2010. Treatments consisted of three cover crops (soybean (Glycine max L.)، fenugreek (Trigonella foenum gracum L.) and cowpea (Vigna unguiculata L.)) in two different planting dates (simultaneous with corn and 21 days after planting of corn)، along with two controls (no weeding and weeding). Results showed planting the cover crops soybean، fenugreek and cowpea in the first and second dates reduced by 96، 93، 83، 68، 91 and 97 percent of weeds biomass. Also، these cover crops reduced was density by 90، 85، 64، 52، 81 and 90 percent and weed density، 73، 62، 51، 17، 62 and 80 percent، in all three samplings compared to treatments without weeding، respectively. The lowest yield of corn grain was 5246/1 Kgh-1 in plots with no weeding and the highest was 11853/13 and 11447/4 Kgh-1 in plots with complete weeding and cowpea in the second date of planting، respectively. The results of this research showed that use of leguminous cover crops with suitable management is a good weed management system which increases efficiency of input and brings us closer to sustainable agriculture.