The critical period of weed control in forage corn in Birjand region
2011
Mahmoodi, S., Assistant Professor of Birjand University | Mazaheri, D., Professor of Tehran University | Rahimi, A., B.Sc. Staff of Birjand University
The critical period for weed control (CPWC) is the period in the crop growth cycle during which weeds must be controlled to prevent unacceptable yield losses. A field study was conducted in 2006 in the University of Birjand to determine CPWC in Birjand region using a randomized complete design with 14 treatments and three replications. The treatments consisted of two different periods of weed interference, a critical weed-free period and a critical time of weed removal were imposed at V3, V6, V9, V12, V15, and R1 (based on phenological stages of corn development) with a weedy check and a weed-free check. The CPWC was determined by fitting non-linear regression models of Logistic and Gompertz equations to the data in range of 2.5, 5, 10 and 20% of acceptable yield loss levels. The CPWC was from 5- to 15-leaf stage (19-55 DAE) to prevent yield losses of 5%. This period to prevent yield losses of 2.5, 10 and 20% was 4- to 17-leaf stage (14-59 DAE), 6- to 12-leaf stage (25-47 DAE) and 8- to 9-leaf stage (31-36 DAE) respectively. The leaf area index of corn were significantly decreased by weed competition in both weed free and weed infested treatments (P0.01). Results also showed that there was a positive correlation between forage yield and LAI of corn at silking stage when competing with weeds (r
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