2012 Volume 81 Issue 4 Pages 397-403
In upland fields converted from paddy field, the dry matter production of soybean in no-tillage (NT) and in conventional tillage (CT) was compared during two years that differed in precipitation. In 2009, when the precipitation during soybean growth period from sowing to flowering stage was higher than in 2010, the length of main stem, the number of nodes on the main stem and the dry matter production after flowering stage in NT soybean were lower than those in CT. Particularly, crop growth rate (CGR) and net assimilation rate (NAR) during the growth period from flowering to pod setting stage in NT was significantly lower than those in CT. This may be because the leaf nitrogen content at the flowering stage in NT was lower than that in CT due to wet damage. In 2009, much precipitation kept the soil moisture content high until the flowering stage. Additionally, the soil moisture content in NT was higher than that in CT in the same growth period. In contrast, CGR and NAR in NT were significantly higher than those in CT in 2010. As a result, there was a significant interaction between tillage treatments and years in CGR and NAR. These results indicated that growth of NT soybean was lower than that of CT when the precipitation from sowing to flowering stage was high.
