抄録
A field experiment was carried out from October 1999 to September 2001 to establish a cropping system with Italian ryegrass (Lolium multiflorum) and natural-reseeded barnyardgrass (Echinochloa crus-galli) in an abandoned paddy field. Ryegrass was sown in October 1999 and 2000, and barnyardgrass was sown only in October 1999. A split-split plot arrangement was applied with the ryegrass varieties (an early-maturing type (EM) and a mid- to late-maturing type (LM)) as the main plot factors. The subplot factor was barnyardgrass at various sowing rates (100, 200, and 300 g/a). EM and LM were harvested twice and once, respectively, the following spring, and barnyardgrass was harvested twice: once in the summer and once in the autumn in both the EM and LM plots. In both years, the ryegrass yields depended significantly on the variety: the yield of EM was greater than that of LM. The first crop yields of barnyardgrass were affected by the preceding ryegrass varieties: greater yields of barnyardgrass were obtained when EM was the preceding crop than when LM was. The barnyardgrass sowing rate had no significant effect on either the first or the second crop yields. A sufficient number of seeds were produced to naturally establish a sward of barnyardgrass the following year in both the EM and LM plots. To verify the feasibility of this cropping system with ryegrass and barnyardgrass,we applied the system to a small field owned by a cattle farmer. The productivity cost of using this cropping system for grass production, excluding the cost depreciation for farm equipment, was comparable to the price of imported hay.
