THE CRITICAL PERIOD OF WEED CONTROL IN GRAIN CORN
2004
Hadi Zadeh, Mohammad Hoseyn | Nuruz Zadeh, Shahram
A study was conducted in Karaj during 2002-04 to determine the critical weed control period in grain corn (Zea mays L.). Treatments included weed free and weed infested period to V3,V6,V9,V13, tasseling and harvest(weed free and weedy check). Treatments were replicated four times in complete randomized block design. Results showed that there was no critical period in first year, but in second year a critical time of weed control in V3 was determined. Removing of weeds during the first week after emergence saved grain yield by 95% at two years. Based on weed infested treatments, corn tolerated weeds until V9 stage (approximately 35 days after emerging), and V3 stage in second year with 5% allowable yield loss. A weed free period until V8-V9 stage (forth week after emergence) is enough to reduce weed dry weight to 95% at both year. Black nightshade (Solanum nigrum L.)at the first year, was dominant weed in weed infested period until V3 (92% of dry weight) and weedy check(50% of weed dry weight). In the second year pigweed and bindweed were dominant. There was no trend for weed number spectra similar to dry weight in weed infested treatments.
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