In conventional cropping systems, herbicides are commonly considered as the most reliable tools for weed management in maize. The sustainable use of herbicides requires the knowledge of weed-crop interactions in order to choose the most suitable product and the best period of its application. Particularly important appears, on this purpose, the knowledge of the critical period of weed control (CPWC). The CPWC is defined as the interval when it is essential to maintain a weed-free environment to prevent crop yield loss; its described by two variables of weed-crop competition with weeds: the weed-free period required (WPR) and the length of the tolerated competition (LCT). The research was conducted in Carmagnola (north-western Italy) in 2007 and 2008. In both years weed infestations were mainly composed by CHEAL, POROL, PANDI, ECHCG. In the treatments aimed at the determination of the WPR, plots were maintained free from weeds for growing durations, ranging from 10 to 60 days after emergence (DAE). In the treatments aimed at the determination of the LCT, weeds were let to develop for growing periods from the emergence of the crop up to 60 DAE, and then removed. Season-long weed-free plots and untreated plots were also included as reference. In all trials the treatments were arranged according to a randomized complete block design with 4 replications. Maize was seeded on 30th April in 2007 and on 2nd April in 2008. Crop emerged 11 days after seeding (May 11th) in 2007 and after 20 days (April 22nd) in 2008. In both experiments maize was seeded at a row distance of 75 cm and at an average seed density of 7.4 seed m-2. The weather conditions of the two years were remarkably different, with lower temperature regime and higher rainfall during the early crop stages in 2008. The yield losses recorded in the always infested plots in comparison with the weed-free plots were 44% and 64%, in 2007 and 2008, respectively. Considering an accepted level of yield losses of 2.5%, it was possible to estimate a CPWC, only in 2007, which ranged from 10 to 24 DAE, corresponding to 3-6 leaf stage maize, or 80-213 GDD (Growing Degree Days). In 2008, a proper CPWC was not identifiable, as a weed removal carried out in a specific moment (22 DAE) already resulted in a yield loss lower than 2.5%. The results of these experiments pointed out the need to prevent weed growth during the first 25 days after maize emergence. This was particularly important in early seeded maize and with unfavorable conditions, which limited crop growth and favored weed competitiveness.
Critical period of weed competition in maize in north-western Italy
FERRERO, Aldo;TESIO, FRANCO;VIDOTTO, Francesco
2010-01-01
Abstract
In conventional cropping systems, herbicides are commonly considered as the most reliable tools for weed management in maize. The sustainable use of herbicides requires the knowledge of weed-crop interactions in order to choose the most suitable product and the best period of its application. Particularly important appears, on this purpose, the knowledge of the critical period of weed control (CPWC). The CPWC is defined as the interval when it is essential to maintain a weed-free environment to prevent crop yield loss; its described by two variables of weed-crop competition with weeds: the weed-free period required (WPR) and the length of the tolerated competition (LCT). The research was conducted in Carmagnola (north-western Italy) in 2007 and 2008. In both years weed infestations were mainly composed by CHEAL, POROL, PANDI, ECHCG. In the treatments aimed at the determination of the WPR, plots were maintained free from weeds for growing durations, ranging from 10 to 60 days after emergence (DAE). In the treatments aimed at the determination of the LCT, weeds were let to develop for growing periods from the emergence of the crop up to 60 DAE, and then removed. Season-long weed-free plots and untreated plots were also included as reference. In all trials the treatments were arranged according to a randomized complete block design with 4 replications. Maize was seeded on 30th April in 2007 and on 2nd April in 2008. Crop emerged 11 days after seeding (May 11th) in 2007 and after 20 days (April 22nd) in 2008. In both experiments maize was seeded at a row distance of 75 cm and at an average seed density of 7.4 seed m-2. The weather conditions of the two years were remarkably different, with lower temperature regime and higher rainfall during the early crop stages in 2008. The yield losses recorded in the always infested plots in comparison with the weed-free plots were 44% and 64%, in 2007 and 2008, respectively. Considering an accepted level of yield losses of 2.5%, it was possible to estimate a CPWC, only in 2007, which ranged from 10 to 24 DAE, corresponding to 3-6 leaf stage maize, or 80-213 GDD (Growing Degree Days). In 2008, a proper CPWC was not identifiable, as a weed removal carried out in a specific moment (22 DAE) already resulted in a yield loss lower than 2.5%. The results of these experiments pointed out the need to prevent weed growth during the first 25 days after maize emergence. This was particularly important in early seeded maize and with unfavorable conditions, which limited crop growth and favored weed competitiveness.
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