Abstract
1) Experimcnts were undertaken to elucidate the direct or indirect effect of P and N nutrition with solution culture, on the yield components of soybeans which were subjected to low temperature at 15°C for 15 days from the early-to mid-reproductive stage. 2) In order to determine the direct effects of low temperature on the yield components, flowers were allowed to set only in a limited period of flowering, besides a restriction in number on each node, in the first experiment. Pod setting rate and fertile seed percentage were decreased with increased levels of N irrespective of P levels in the low temperature treated plots. The magnitude of damage was closely related to the stage of flower development under low temperature. No significant effect was obtained from P application, P×N and P×T interaction. 3) After the complete removal of the flowers that opened in the first 7 days, comparison of the productivity, or potentiality of compensation was made with subsequent flowers on the plants, which were preconditioned under various levels of N and P combinations for 2 weeks for control plants or for 3 weeks for low temperature treated plots, in the second experiment. The increase in levels of N and/or P which were supplied, prior to the onset of the test flowers, promoted the recovery from the damage and produced more seeds per plant through the increase in number of pods, pod setting rate, number of flowers and fertile seed percentage. The authors are indebted to Mr. Y. Masuo, the chief of first crop division of Hokkaido National Agricultural Experiment Station, for his suggestions with the manuscript.
