Temperature, radiation, and duration dependence of high soybean yields: Measurement and simulation

Abstract

Information about the relative contribution of various environmental and developmental factors to soybean production can help focus objectives for programs of crop improvement. The growth of high-yielding soybeans ( Glycine max [L.] Merr.) was simulated in order to quantitatively analyze effects of temperature, radiation, and duration of crop growth on seed yield. Data from Saihoku Branch Station, Shinjo, Japan were used for comparison with the simulations. Field data were obtained from fields converted from paddy cultivation by installing drainage tile and from adjacent fields managed as conventional dryland cultivations. Soils on both field types were clayey humic andosols (Dystrandepts). In the model, mean air temperature controlled leaf appearance rate. Sunshine-hours were used as a measure of solar radiation. Observed dates of emergence and harvest maturity were used to estimate the duration of biomass accumulation. Observed values of apparent harvest index (0.576 g seed per g above-ground biomass) were used to calculate the seed yield from simulated biomasses. The model was based on the assumption that these crops did not experience water deficits or nutrient deficiences. Converted paddy fields produced unusually high seed yields (506–649 g/m 2). Simulated yields corresponded with observed high yields for crops at Saihoku Station. Year-to-year variation in temperature, solar radiation and duration of crop growth accounted for a substantial portion of observed annual differences in yield. Year-to-year differences in duration of crop growth on the conventional fields especially influenced the simulated yields. Simulated changes in duration of crop growth on converted paddy fields changed yield at the rate of 5.3 g m −2 day −1.