effect of different input management on weed composition, diversity and density of corn field

in order to investigate the effects of input intensity on species diversity, composition and density of weeds in corn (zea mays l.), an experiment was conducted based on a randomized complete block design with three replications at the agricultural research station, ferdowsi university of mashhad, iran during the year 2009. treatments included low input, medium input and high input systems. low input received 30 tonha-1or 30 tonha-1 compost, zero tillage and hand weeding (twice). medium input was based on 15 tonha-1 manure, 150 kgha-1 urea as chemical fertilizer, twice tillage operations and 2, 4-d (1.5 lha-1, at five leaves emergence) as an herbicide and hand weeding (once). high input received 300 kgha-1 urea, four tillage operations and paraquat (2 lha-1, after planting) and 2, 4-d (1.5 lha-1, at five leaves emergence). manure and compost were applied in the planting time. weed samplings were done in three stages (early, mid and late growing season). results indicated that the highest and the lowest weed species diversity and density were observed in low input based on manure and high input systems, respectively. the highest range of weed relative density was obtained for black nightshade (solanum nigrum) with 9.09-75.00%. the highest number of species was observed in low input based on manure. also, management practices affected weed dry matter and diversity indices. the highest and the lowest amounts of weed dry matter were observed in low input based on manure and high input systems, respectively. in the first, second and the third stages of sampling, the maximum and the minimum amounts of margalef index were observed in low input based on manure (with 5.3, 5.4 and 3.3, respectively) and high input systems (with 0.8, 2.3 and 2.6, respectively). in the first, second and the third stages of sampling, the highest and the lowest values of shannon index were observed in low input based on manure (with 0.6, 0.7 and 0.5 respectively) and high input (with 0.1, 0.4 and 0.3 respectively) systems. weed chemical control, intensive tillage operation and high corn density reduced weed number and dry matter in high input only.