Kyoto University · Agricultural and Biological Sciences
Professor Tatsuhiko Shiraiwa's research lab focuses on soybean physiology and crop productivity, with a central emphasis on nitrogen dynamics, canopy architecture, and seed yield formation. The lab investigates how genetic differences, plant density, nitrogen fertility, and developmental stages influence nitrogen distribution and dry matter accumulation in soybean canopies. Key research directions include understanding the critical growth stages that determine yield potential and analyzing the partitioning of nitrogen and biomass during seed filling in both old and modern cultivars. The work integrates field experiments with physiological measurements to improve breeding strategies and sustainable crop management.
Figures are computed from collected data and may differ slightly.
The N distribution among leaves in a plant canopy can theoretically have an important influence on crop photosynthetic activity. However, little detailed information is available on the specific leaf nitrogen (SLN, g N m −2 ) distribution in soybean [Glycine max (L.) Merr.] canopies. Experiments were established at Gainesville, FL and in Japan to examine the effects of cultivar, canopy maturity, plant density, and N fertility on SLN distribution. The SLN distribution was measured by dividing can
Seed productivity of old and modern soybean cultivars was analyzed in relation to accumulation and partitioning of nitrogen during seed filling. Four soybean cultivars were grown on a drained paddy field (silty caly loam). Dry weight and nitrogen content were determined for above ground parts weekly from the beginning of seed filling to maturity. The modern cultivars Enrei and Tachinagaha exhibited greater dry matter and nitrogen accumultaions during seed filling and greater seed yield in compar
The critical developmental stage, during which the genotypic difference in yield is determined, was identified by analyzing the correlations between seed yield and seasonal crop dry matter productivity in optimally managed fields in four seasons. The fields (fluvial sandy loam or clay loam) were managed with irrigation, pest and weed control and canopy support to prevent lodging whenever necessary. The tested genotypes included 11 Japanese old and modern cultivars, five US cultivars and one non-
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