2011 Volume 10 Issue 1 Pages 61-67
To determine the sowing and transplanting date to produce a sufficient yield of immature black soybean (Glycine max L. cv. ‘Tankuro’) as a pre-culture crop for summer spinach (Spinacia oleracea L.), we sowed seeds of the soybean plants on various dates (from February 25 to April 9), and compared the plant growth and yield of each crop. The vegetative growth of the soybean plants stopped by the flowering date. To increase the yield of ‘Tankuro’ cultured in the spring, it was therefore important to increase the vegetative growth between sowing and flowering. Because the average temperature in the unheated greenhouse where the plant plug seedlings of soybean were transplanted greatly affected the vegetative growth of the soybean plants, yields differed greatly among years and sowing dates. Our analysis of 3 years of yield and temperature data revealed that a mean temperature of more than 18.8°C in the greenhouse from transplanting to flowering was required to yield 100 kg·a−1 of pods containing two or more seeds. In practice, it would be desirable to transplant soybean after April 15 to avoid low temperatures that would prevent the plants from yielding 100 kg·a−1 of pod weight.
