Winter barley shade suppresses emergenece of Digitaria ciliaris in no-tillage soybean
2004
Kobayashi, H. (National Agricultural Research Center for Tohoku Region, Morioka (Japan)) | Miura, S. | Oyanagi, A.
This study seeks to clarify how a cover ctop over the preceding winter suppresses the emergence of Digitaria ciliaris (Letz.) Koeler, the most important weed in no-tillage soybean in Japan. Winter barley was grown as a cover crop with row spacings of 20 cm, 40 cm, and 60 cm, arid no-tillage soybeans were subsequently grown. Fresh D. ciliaris seeds were sown in cylinders set on the soil surface of all plots the previous autumn. The phenology and the number of D. ciliaris emerging, as well as their spatial distribution in the plots, were compared with those in a plot of no-tillage, continuous soybean without winter crop. In addition, light quality, light intensity, and soil -surface temperature were measured. Most D. ciliaris seedlings from sown seeds emerged before soybean planting in all plots. Its emergence was strongly suppressed in the barley plots. Emergence was more strongly suppressed near the barley rows; it coincided with decreased light intensity, R/FR ratio, and the magnitude of diurnal fluctuations of the soil-surface temperature caused by barley sod. Fewer seedlings of D. ciliaris emerged naturally in the barley plots, particularly near the barley rows, before soybean planting. These results suggest that the preceding winter barley suppressed the emergence of D. ciliaris due to changes in light intensity, light quality, and soil-surface temperature caused by the barley sod.
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