The growth and yield performance of 19 new com hybrids were evaluated. Results showed that all hybrids had a superior growth performance in the drained-paddy than in the upland field except for daeyul × cheongdo and hyoryeong × cheongdo in plant height, cheongdoyeop × wx-3 in tassel1ength, and cheongdo (black) × wx-3 in number of tassel branch. The same hybrids, except cheongdoyeop × wx-3, obtained lower ear quality in drained-paddy field compared to upland in terms of ear weight, and ear and grain setting length. The highest yield in the drained-paddy and upland fields was obtained in the hybrids ks5wx × ks6wx × cheongdo (1,633.3kg · 10a-1) and daeyul × wx-3 (1,516.7kg · 10a-1), respectively. Highest yield among the wx-3 crosses was obtained in daeyul which was 1,583.3kg · 10a-1 and 1,516.7kg · 10a-1 in drained-paddy and upland field, respectively. For the crosses of wx-8, highest yields were recorded in the cultivar bugye50 (1,466.7kg · 10a-1) and seokgu12 (1,384.6kg · 10a-1) for drained-paddy and upland field, respectively. In the case of cheongdo, highest yields were obtained in ks5wx × ks6wx (1,633.3kg · 10a-1) and seokgu14 (1,111.1kg · 10a-1) for drained-paddy and upland field, respectively. Result also showed that the drained-paddy soil had better physicochemical properties than the upland. The relatively high performance in terms of growth parameters and yield of com hybrids planted in the drained-paddy field is in agreement with the higher organic matter and micro-element content of drained-paddy field.

The study was conducted to evaluate the performance of the popular isoflavone-rich soybean 'agakong' in upland and in drained-paddy fields. Analysis revealed no significant variation in terms of plant height, number of seeds per pod, number of nodes, and 100-seed weight between the two cropping system. Number of pods was significantly higher in paddy field(234.2kg 10a-1) compared to those harvested in the upland field, which was later manifested on the yield where paddy soybeans obtained 278.1kg 10a-1 whereas upland only obtained 179.3kg 10a-1. This observed difference in yield was attributed to the observed higher amount of N in the paddy soil (0.907%) as compared to the upland soil (0.458%). In terms of nutritional content, protein and phytic acid contents were the only parameters that showed significant differences while oil, sugar, reducing power and fatty acids were all comparable in paddy and filed condition. Protein content was higher in upland soil (47.4%) than that of the paddy (44.9%) soil. On the opposite, phytic acid was higher in paddy (2.90%) than in upland (1.09%). This study showed that the yield of soybean is generally a factor of soil N, drained-paddy field production of soybean is comparable to upland-filed production with the benefit of increasing phytic acid content while maintaining its nutritional value.

Naturally occurring soybean isoflavones are known to be influenced by various genetic and environmental conditions. Growth, yield, and isoflavone content were determined in four different cultivars of soybean grown under drained paddy and upland fields. Most of growth characteristics and yield components of four different soybean cultivars harvested in drained paddy field were greater than those in upland field, regardless of cultivar. By means of high performance liquid chromatography, total daidzein and genistein contents of soybean in drained paddy field were increased up to 40 and 35%, respectively, compared with those in drained paddy field. Besides isoflavone contents, the growth and yield of soybean were significantly affected by cultivar and field conditions, indicating the necessity of genetic program for soybean cultivars appropriate to drained paddy field conditions. In conclusion, converting paddy field into upland may effectively improve soybean cropping system, especially in terms of isoflavone increment under paddy field conditions.