抄録
A 2-year field study was conducted during 2002 and 2003 to determine the impacts of spring sown winter wheat (Triticum spp.) living mulch and soybean (Glicine max (L.) Merr.) planting density on weed control and soybean yield at Hokkaido upland field. The experimental design in 2002 was consisted of 2 wheat sowing densities (0g/m2: MC and 16g/m2: 16M) and 2 soybean planting densities (conventional: CP, 16 plants/m2 and dense: DP, 24 plants/m2) with pre-emergent herbicide application in all plots. The experimental design in 2003 was consisted of 3 wheat sowing densities (0g/m2 and mechanical control to weed: MC, 16g/m2: 16M and 8g/m2: 8M) and 3 soybean planting densities (conventional: CP, 17 plants/m2, sparse: SP, 12 plants/m2 and dense: DP, 28 plants/m2) without herbicide. Soybean yields were lower in the 8M and 16M plots compared with the MC plots. In the DP plots, however, reductions in yield were less significant, especially in 2003. Living mulch showed a remarkable effect on weed control in the DP plots, however, in 2003 the mulch was unable to sufficiently control emergence and development of tufted knotweed (Persicaria longiseta (De Bruyn) Kitag) and Persicaria lapathifolia (L.) S. F. Gray, since the weeds emerged prior to the soil surface being covered by the mulch and soybean leaves. These results indicate that adequate soybean plant density and pre-emergent herbicide application are requirements for weed management and satisfactory yield in soybean production systems that use wheat living mulch.
