2022 Volume 57 Issue 2 Pages 91-106
To estimate onion yield in the sorghum–onion double-cropping system (DCS) and sweet potato–onion–sorghum–onion crop rotation system (CRS) in comparison with the onion mono-cropping system (MCS), four sets of three-year field experiments (two sets of DCS plus two sets of CRS) were conducted in the southern Kyushu region of Japan. This study demonstrates that in all four sets of field experiments, the onion bulb yields in the first onion cultivation were approximately 20% higher in DCS and CRS than those in MCS; however, when we continued the DCS and CRS to the second and third onion cultivations, the effect of bulb yield enhancement by DCS and CRS over MSC disappeared. The reason the yield-enhancing effect disappeared in the second and third onion cultivations was not clear; hence, further experiments are required with serial measurements of mycorrhizal infection rates and soil nutritional conditions to clarify the effect of DCS and CRS on onion growth and yield in the southern Kyushu region.
