Control effects of soil-applied herbicides in soybeans sprayed over wheat-residue mulch
2010
Nakayama, S., National Agricultural Research Center for Tohoku Region, Morioka (Japan) | Nakatani, K. | Hamaguchi, H.
To determine the effectiveness of 11 soil-applied herbicides in no-till double-cropping soybeans after wheat, we studied the control effects of these herbicides sprayed over wheat-residue mulch. First, we evaluated the effect of rainfall treatments (0-4 mm),which were applied 24 hr after herbicide application, on the control effects of prometryn-metolachlor (PM) sprayed over 4,000 kg/ha of wheat straw at 0.8+1.2 kg a.i./ha in 1,000 L/ha of water. PM controlled Amaranthus patulus Bertoloni effectively (99%) under all rainfall treatment conditions including no rainfall and no significant difference (p=0.40) was observed in the number of surviving A. patulus plants between the different rainfall treatments. On the basis of the results of the first experiment, we conducted the second experiment under no-rainfall condition to determine the control effects of the 11 herbicides on A. patulus and barnyard millet. The herbicides were sprayed over 6,000 kg/ha of wheat straw at the respective maximum registered doses in soybeans in 1,000 L/ha of water. Wheat straw considerably inhibited the control effects of simazine and diuron on the test plants remarkably (64.5% and 54.7% in wheat-residue plots versus 98.8% and 100% in no-residue plots, respectively). The other nine herbicides controlled the test plants effectively (99%) ; however, in the case of some herbicides, significant differences (p0.05) were observed in the number of surviving plants between residue plots and no-residue plots. Therefore, we concluded that simazine and diuron were less effective than the other nine herbicides in the case of no-till soybeans.
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