Weed control by hairy vetch (Vicia villosa LOTH.) in shikoku area - vegetation test and field survey in 1993 to 1997

摘要

Hairy vetch (Vicia villosa LOTH. ), a winter-annual legume, produces a viny vegetation with a large biomass, and has been widely used as green manure, forage, hay or silage in U. S.A. Due to its prostrate nature covering the soil surface, hairy vetch is also utilized for weed control as a useful understory cover plant in various orchards To confirm the suitability of this winter crop and to apply it over broad areas in Shikoku island, we carried out a vegetation test in the experimental field of Shikoku National Agricultural Experiment Station (SNAES) and a field survey using a variety of fields including orchards, abandoned paddy fields, fallow fields, and grasslands in 1993 to 1997. The results obtained from five-year field trials are as follows (Information supplied by the farmers, based on field questionnaire, is also outlines). 1) Due to the scant top growth of hairy vetch during cold weather, Gramineae or other weeds such as, Lamium amplexicaule L. or Capsella bursa-pastoris Medik. dominated in winter. After March, however, hairy vetch showed rapid growth and produced a large biomass covering the total area of the upland field tested. The weed suppression effect of hairy vetch persisted until early July. 2) Biomass of hairy vetch harvested in May was the same as or higher than that of the other leguminous crops or winter cereals including white clover (Trifolium repens L. ), crimson clover (T. incarnaytum L. ), oat (Avena satire L. ) or rye (Secale cereale L. ). 3) Growth injury due to continuous cropping was not observed during 1993 to 1997. Plowing or tillage before and after sowing carried out to destroy the first flush of weeds and prepare the seed bed resulted in a satisfactory dry matteryield of hairy vetch with a maximum yield of 800 kg/10a. 4) When italian ryegrass (L.mulliflorum Lam. ) or Brassica grew prior to hairy vetch in the last cool-season the growth of autumn-sown hairy vetch was markedly inhibited, and therefore brought about a remarkable flush of weeds in the spring. 5) Dry matter yield of hairy vetch increased by mixed cropping with gramineous grasses. In contrast, the yield of most of the cereal mixtures decreased compared with mono-cultivation. 6) Hairy vetch showed good growth also in abandoned paddy fields with a highly clayey moist soil, and was more effective in weed suppression and in biomass production than clover or Chinese milk vetch. 7) In rice cultivation, the effectiveness of hairy vetch plowed into the paddy fields as green manure was not as conspicuous as reported in corn or sorghum fields in U. S. A. 8) When hairy vetch was seeded on hilly land or orchards in the foot hill area, previous weeding using herbicide or mower was especially effective for obtaining better germination and stands of hairy vetch. 9) In most of the Shikoku area, hairy vetch started flowering from early to mid- May and produced mature seeds in June. Volunteer hairy vetch plants were more observed in fallow or infertile soil than in well-managed fertile fields. 10) Vegetation of hairy vetch in slope land fields significantly affected the community and biomass of weeds growing below the plot of this viny legume. Among the weeds, growth of Compositae such as Sonchus oleraceus L. or Artemisia princeps was severely suppressed by the above vegetation of hairy vetch on the slope, strongly suggesting the allelopathic action of hairy vetch. 11) Attack of shoot of hairy vetch by high densities of aphids (Aphisis gossypii) was observed both in the experimental field of SNAES and abandoned paddy field of Zentsuji city from April through May in 1997. Above-ground parts of hairy vetch were seriously injured and killed by convergent aphids, but the damage did not spread over the field, possibly due to the subsequent occurrence of associated predatory insects, lady beetles. 12) Viruses (CYVV and BYMV), which cause mosaic symptoms and veinal necrosis on the shoot of broad bean (Vici