‘목양’은 국립식량과학원 벼 육종연구진이 총체 사료용 벼 품종을 육성할 목적으로 2001년 하계에 SR24592-HB2319 를 모본으로 하고 신초형 IR73165-B-6-1-1을 부본으로 교배 하여 계통육종법으로 육성한 품종으로 2010년 12월 농작물 직무육성신품종선정위원회에서 국가목록등재품종으로 선정 됨과 동시에 ‘목양’으로 명명하였다. ‘목양’의 출수기는 보통 기 재배에서 8월 23일로 ‘녹양’보다 8일 정도 늦은 만생종이 다. ‘목양’은 도열병, 줄무늬잎마름병, 오갈병에는 ‘녹양’보다 강하지만, 흰잎마름병, 벼멸구에는 약한 편이다. ‘목양’은 ‘녹 양’보다 탈립에 강하고, 후기녹체성이 우수하였다. ‘목양’은 가소화양분총량(TDN) 함량이 높고 중성세제불용섬유소(NDF) 와 산성세제불용섬유소(ADF)가 낮았다. ‘목양’의 총체수량은 지역적응시험에서 2008년부터 2010년까지 평균 17.7 MT/ha 로 ‘녹양’보다 25% 증수하는 경향을 보였다. ‘목양’은 가소화 양분총량(TDN)은 59.5%였으며 ADF와 NDF가 낮아 상대적 사료가치가 ‘녹양’에 비해 높은 품종이다. ‘목양’의 정조 수량은 보통기 재배에서 5.59 MT/ha로 ‘녹 양’보다 16% 증수되었다. 재배적지는 중부 및 남부평야지 1 모작 지대이다.

The amount of salt to make seed sorting solution of the specific gravity of 1.13 was reconsidered and determined as 3.8 kg salt in 18 L water, which is lower amount than currently used. Five rice cultivars were examined. Percent germination and seedling emergence were not similar. Seedling emergence rate of Japonica varieties, Nampyungbyeo and Daerypbyeo-1 were 87% and 95% under specific gravity of 1.13, respectively. Seedling emergence rate of Tongil type variety, Dasanbyeo was as high as 67% in specific gravity of 1.06. Seedling emergence rate of waxy rice, Hwasunchalbyeo and Aranghangchalbyeo were examined. Seedling emergence rate was 94% in both cultivars in specific gravity of 1.04. Seedling emergence rate was same in specific gravity of 1.08 which is generally used for selecting seed currently. Early growth (plant height, leaf number, and dry weight) were not significantly different by specific gravity within species. In all cultivars except waxy rice, highest seedling emergence rate was observed in specific gravity of 1.13 which is currently used for selection and decreased as specific gravity is lowed. However, considering total amount of seeds in each group of specific gravity, amount of seed in lower specific gravity group is relatively small and total seedling emergence rate within variety dose not show big difference. However, if seeds with low speicific gravity are produced due to the bad grain filling condition and consequently total seed content of low specific gravity increases, results will be differnt. Reduction in total growth and yield could occur. It will be important to comply with the seed sorting criterion of 1.13 for Japonica, 1.06 for Tongil, and 1.04 for waxy rice variety to ensure the maximum rice growth and yield.

The amount of salt to make seed sorting solution for rice of the specific gravity of 1.13 was reconsidered and determined as 3.8 kg salt in 18L water, which is lower amount than currently used. Various rice (Oryza sativa L.) cultivars were used to examine seed specific gravity effect on germination, seedling emergence, and early growth. Percent germination and seedling emergence were not different. Seedling emergence rate of Japonica varieties, Nampyungbyeo and Daerypbyeo-1 were 87% and 95% under specific gravity of 1.13, respectively. Seedling emergence rate of Tongil type variety, Dasanbyeo was as high as 67% in specific gravity of 1.06. Seedling emergence rate of waxy rice, Hwasunchalbyeo and Aranghangchalbyeo were examined. Seedling emergence rate was 94% in both cultivars in specific gravity of 1.04. Seedling emergence rate was same in specific gravity of 1.08 which is generally used for selecting seed currently. Early growth (plant height, leaf number, and dry weight) were not significantly different by specific gravity within species. In all cultivars except waxy rice, highest seedling emergence rate was observed in specific gravity of 1.13 which is currently used for selection and decreased as specific gravity is lowed. However, considering total amount of seeds in each group of specific gravity, amount of seed in lower specific gravity group is relatively small and total seedling emergence rate within variety dose not show big difference. As a result, it is considered that selecting seeds with water (larger than specific gravity of 1.00) instead of salt solution will not make large reduction in seedling emergence rate and have no effects in early growth.

Critical nitrogen concentration (Nc), which is defined as the minimum % N in shoots required to maintain the maximum growth rate of top dry weight (W) at any time, was determined for rice plant. Using two rice varietal groups, japonica varieties and an indica ~times japonica "Dasanbyeo", 18 data points fulfilling the statistical criteria for determining Nc were obtained through eight N-fertilization experiments over two years at Suwon (37~circ 16'N), Korea. Nc dilution curve for each variety was obtained by fitting the Nc-W relationship to power function. However, The critical nitrogen curves for the two variety groups were not different statistically. Thus, a Nc dilution curve was fitted for the Nc data points pooled over the two variety groups and proposed in rice as: Nc=4.08, where W＜1.73 t h a-1 , Nc=5.197 W0.425 3/ (R2 =0.964), where 1.73 t h a-1 ＜W＜12 t h a-l . The Nc for W＜1.73 t h a-l were estimated as a constant value of 4.08%, the mean value of the maximum N concentration for N-limiting condition and the minimum N concentration for N non-limiting condition. The model for Nc is applicable to diagnosing the nitrogen nutrition status during the rice growth period from emergence to heading stage. The Nc curve well discriminated the 144 data points between the N limiting and the N non-limiting groups regardless of varieties, cultural methods, and years.-limiting groups regardless of varieties, cultural methods, and years.