Environment-friendly soybean planting system has been being required in the upland field with high slope and heavy rain in summer season. Changes of weed amount and soybean yield by rye cover crop and conservation tillage were investigated. Soil-disturbing at conservation tillage before soybean planting increased numbers and dry weights of weeds germinated in late spring such as Echinochloa crusgalli P. Beauv (barnyardgrass) and Portulaca oleracea L. (common purslane) regardless of herbicide spray even though the weed, Chenopodium ficifolium Smith germinated before soil-disturbing were higher at non-disturbing soil. Higher weed amounts at plots of strip-tillage (30cm rototilling) compared to minimum tillage (10cm rototilling) was mainly due to the weed increase by soil-disturbing. Soybean yields at plots with rye cover crop, particularly early maturity rye cover crop, were lower than those at plots without rye cover crop, which was due to lower soybean seedling stand by heavy rye residue. More researches are required for the higher soybean yield at the minimum tillage with rye cover crop in which weed amounts were low.

Experiments were conducted with aims to (1) estimate the biomass yield potential, (2) characterize the biomass and digestible dry matter production, and (3) reveal the characteristic seedling establishment of a whole crop rice variety, Nogyangbyeo, in dry- and wet-seeded rice. Maximum aboveground total biomass of Nogyangbyeo was 18 t ha-1 in dry-seeded rice and 20 t ha-1 in wet-seeded rice. Biomass yield potential of Nogyangbyeo was lower than that of Dasanbyeo. Comparatively, Nogyangbyeo was straw-dependent and Dasanbyeo was grain-dependent for biomass accumulation. Percentage of digestible dry matter (DDM) was higher in panicles than straw. Digestible dry matter yield was determined mainly by biomass yield rather than DDM percentage. Number of seedling establishment in Nogyangbyeo was 73m-2 in dry-seeded rice and 109m-2 in wet-seeded rice. Poor seedling establishment of dry-seeded Nogyangbyeo in the field condition was the result of low seed germination under low temperature and poor seedling emergence by deep sowing. Low seedling emergence rate of Nogyangbyeo was attributed mainly to slow elongation growth by slow leaf development and partly to mesocotyl and 1st internode lengths, not to genetically defined leaf length. The slow elongation growth of Nogyangbyeo was the same even in the high daily mean temperature of 24~circC . Results suggest DDM yield in rice can be improved simply by increasing biomass and whole crop rice varieties should be adaptable to direct-seeding.

The metabolism of [14~textrmC ] ~textrmGA12 in the Chinese yam (Dioscorea opposita Thunb. var. Tsukune) was examined to determine the identification of endogenous gibberellins. [14~textrmC ] ~textrmGA12 was metabolized to ~textrmGA53 , ~textrmGA44 , ~textrmGA19 , ~textrmGA20 , ~textrmGA1 , ~textrmGA8 , ~textrmGA15 , ~textrmGA24 , ~textrmGA9 , ~textrmGA36 and ~textrmGA4 . Radioactivity of GAs in non C-13 hydroxylation route was five-fold higher than that of early C-13 hydroxylation in analyzed GA-metabolites. Radioactivity of ~textrmGA4 was always four times higher than that of ~textrmGA1 at every feeding time. ~textrmGA1 radioactivity has always a lower level to below 200 DPM. The major pathway of endogenous GA metabolism in seedlings of the Chinese yam might be the non C-13 hydroxylation pathway.

Endogenous ABA and batatasins were first quantified in the stored tubers and bulbils of the Chinese yam, Dioscorea opposita Thunb. cv. 'Tsukune' by GC-MS with comparison of internal standard, and sugar content was also analyzed by HPLC with comparison of external standard. Endogenous ABA content in stored tubers and bulbils was rapidly decreased as storage period prolonged. ABA content of the bulbils was always higher than that of tuber during storage periods. All batatasins of stored tubers and bulbils at 30 days after storage decreased steadily compared to 120 days after storage. On the contrary, batatasin-Ⅲ of the stored tuber and bulbils was only decreased at 60 days after storage. In Dioscorea opposita Thunb. cv. 'Tsukune' like D. japonica, D. alata, and D. bulbifera, may be controlled by endogenous batatasins and ABA, In these compounds, batatasins rather than ABA might be closely related to dormancy-inducing compound during dormancy of the Chinese yam, Dioscorea opposita Thunb. cv. Tsukune.