This experiment was conducted to examine the influence of four plant growth regulators on growth, photosynthesis parameters and yield of soybean. To increase dry matter accumulation of seeds, some growth regulators were applied to field grown soybean cv. Sinpaldalkong #2 as determinate type and Muhankong as indeterminate type at dense planting condition. Choline caused significant reduction of stem length, but did not increase seed yield. The number of leaf and total leaf area were showed significant increase in all the treatments, but those increased tremendously in Muhankong treated with ethrel. CO2 assimilation and water use efficiency of a single leaf were showed the highest as 17.2 molm-2s-1 and 9.3 μ mmol mol-1 treated with mepiquat in Sinpaldalkong, respectively. The Photosynthetic rate was closely related to stomatal conductance, transpiration and water use efficiency. Mepiquat treatment mainly produced positive effects on the number of pods, percent of pod setting, number of seeds per pod in two cultivars and also increased their seed yield as compared with control.

‘Yuyeon’, a new ruminant-palatable barley cultivar, was developed from the cross between ‘Suwon311’ and SB86648〔CMB81A-2149 / Saeolbori // Buheung / Gangbori / 5 / Bera-olbori / Horisee-Buheung // bengei / 3 / Olbori-Daechi-Hagane / 4 / T.beared〕by the Honam Agricultural Research Institute (HARI), NICS, RDA in 2006. Among the cross made in 1996, a promising line, SB961012-B-B-1, showed good characteristics in potential forage yield in the yield trial tested in Suwon in 2001. In 2004, it was designated as ‘Suwon 406’ and placed in regional yield trials at five locations around Korea for three years from 2004 to 2006, and was released as the name of ‘Yuyeon’. It belong to maturity group Ⅲ and shows erect leaf type and compact spike with types of hoods. Its heading date was Apr. 27, which was 2 days earlier than that of the check cultivar ‘Olbori’ (‘Sunwoo’), and early dough stage, which was May. 30 which was same date of that of the check cultivar. ‘Yuyeon’ showed weaker winter hardiness, but better resistance to lodging, shattering and BaYMV than those of check cultivar. It showed higher crude protein content, grade of silage quality than those of check cultivar. The average forage yield in the regional yield trial was 10.47 MT/ha, which was 1% lower than that of the check cultivar. Cattles fed with silage from ‘Yuyeon’ (hood type) showed higher feed concentrate requirement (12.9 kg/day/body) and daily weight gain (1.46 kg/day) than those of cattles fed with silage from ‘Olbori’ (rough awn). This cultivar would be suitable for the area whose daily minimum temperature was above -8℃ in January in Korean peninsula.