• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.14
• /
• pp.123-131
• /
• 1973

1. In order to evaluate the performance of the $F_2$ and $F_3$ generations of $F_1$ varietal crosses which in past trials yielded better than or as high as the recommended double-cross hybrids, eleven yellow and five white-endosperm $F_1$ varietal crosses, their $F_2$ and $F_3$ generations, and the parental open-pollinated varieties together with the standard double-cross hybrids were tested in performance trials in the 1963 wet and 1963-64 dry seasons. The former trials, however, failed due to a strong typhoon that damaged the crop. 2. Net hybrid vigor was highly manifested in grain yield in the $F_1$ varietal crosses, which on the average was 39.9 per cent of the mid-parent yields. Reduction in heterosis was 27.2 per cent in the $F_2$and 30.3 per cent in the $F_3$ generation, respectively. 3. A fairly high degree of reduction in yield occurred in the $F_2$ and $F_3$ generation. On the average, the $F_2$ generation decreased by 17.6 per cent and the $F_3$ by 20.7 per cent. The losses in two generations were exhibited in two levels; four crosses decreased by 10.9 per cent and twelve combinations by 22.0 per cent. The advanced generations of one yellow cross, Cuban Yellow Flint ${\times}$ Hawaiian Flinty Dent, and three white flint crosses, Bicol White Flint ${\times}$ Eto Blanco, College White Flint ${\times}$ Eto Blanco and Bicol White Flint ${\times}$ Nariono 330b, yielded as high as Philippine Hybrid No.1 and Philippine Hybrid No.4, respectively. 4. No significant differences in yield were obtained between the $F_2$ and $F_3$ populations, showing that genetic equilibrium was reached in $F_2$, as may be expected in view of the Hardy-Weinberg law on panmixis. 5. As in past trials, Hawaiian Flinty Dent, a variety, yielded as high as Philippine Hybrid No. 1.

• Korean Journal of Soil Science and Fertilizer
• /
• v.15 no.1
• /
• pp.2-15
• /
• 1982

In this report, a total domestic demand for major commercial fertilizer for crop production in Korea up to 1996 was estimated. The agricultural products and area for demand for both 1982 and 1986 was quoted from the estimate of the 5th Five-year Economic plan. And the demands estimated for 1991 and 1996 reflected possible changes of diet from cereal to meat and their indirect effects on the increase of cereal consumption. As the advanced countries followed, consequently, the demands for soybean, corn and other feed grains were expected to be increased as well as the land for growing those crops. 1. Total annual demands for nitrogen, phosphorus and potassium fertilizers were estimated 1,050,000M/T, 1,110,000M/T, 1,280,000M/T and 1,010,000M/T for the year 1982, 1986, 1991, and 1996 respectively. 2. It was assumed that there would be difficulties in self-sufficiency of grains at the cost of the maximum utilization of land and fertilizers in 1996. 3. It was clear that the increase of the productivity per unit area is possible by improving the conditions of arable land which could resulted a self-sufficiency of food in Korea. As a consequence, the demand for fertilizers at that time would exceed the level of estimates. 4. The recent decrease in demand for commercial fertilizers (currently estimated 850,000M/T) was due to an inadequate application of fertilizers for respective crop reqirement. This inadequacy should be checked and encouraged the consumptions of fertilizers to be increased by supporting the price of grain.

• Journal of Animal Science and Technology
• /
• v.47 no.4
• /
• pp.607-614
• /
• 2005

To determine the optimum fermentation condition, the 50:50 feed mixture of both crushed corn and wet brewer’s grain were anaerobically fermented at various conditions. Three supplementation levels(0, 2%, and 5%) of molasses, five supplementation levels(0, 0.1%, 0.5%, 1.0%, and 2.0%) of yeast and five different incubation temperatures(4$^{\circ}C$, 10$^{\circ}C$, 30$^{\circ}C$, 40$^{\circ}C$ and 50$^{\circ}C$) were tested to determine the optimum fermentation conditions. During fermentation, alcohol concentration, live yeast cell number (LYCN) and pH values of the mixture were analyzed. Alcohol concentrations of the fermented feed mixtures were proportionally increased with increasing level of molasses supplementation. After 24hr fermentation, alcohol concentrations at 0.1%, 0.5%, 1.0% and 2.0% of yeast supplementation was 1.9%, 2.4%, 3.1% and 3.1%, respectively. These results indicate a proportional increase of alcohol concentration with the increasing supplementation of yeast (P<0.05) up to 1%, thereafter showing plateau at 2% supplementation. LYCN was relatively high with more than 0.5% yeast supplementation, whereas the value was significantly low(P<0.05) at 0.1% yeast supplementation. Alcohol production was significantly higher at 30$^{\circ}C$ and 40$^{\circ}C$ than other incubation temperatures (P<0.05), with the highest concentration at 30$^{\circ}C$. pH was rapidly decreased until 24 hours of incubation with steeper decrease at lower temperatures(P<0.05). Based on there results, optimum fermentation conditions for the alcoholic-fermented feed production could be achieved with 5% supplementation of molasses, 1% supplementation of yeast, and 24hr long incubation at 30$^{\circ}C$.

• Korean Journal of Soil Science and Fertilizer
• /
• v.10 no.3
• /
• pp.103-134
• /
• 1977

The physiological and biochemical role of potassium for upland crops according to recent research reports and the nutritional status of potassium in Korea were reviewed. Since physical and chemical characteristics of potassium ion are different from those of sodium, potassium can not completely be replaced by sodium and replacement must be limited to minimum possible functional area. Specific roles of potassium seem to keep fine structure of biological membranes such as thylacoid membrane of chloroplast in the most efficient form and to be allosteric effector and conformation controller of various enzymes principally in carbohydrate and protein metabolism. Potassium is essential to improve the efficiency of phoro- and oxidative- phosphorylation and involve deeply in all energy required metabolisms especially synthesis of organic matter and their translocation. Potassium has many important, physiological functions such as maintenance of osmotic pressure and optimum hydration of cell colloids, consequently uptake and translocation of water resulting in higher water use efficiency and of better subcellular environment for various physiological and biochemical activities. Potassium affects uptake and translocation of mineral nutrients and quality of products. potassium itself in products may become a quality criteria due to potassium essentiality for human beings. Potassium uptake is greatly decreased by low temperature and controlled by unknown feed back mechanism of potassium in plants. Thus the luxury absorption should be reconsidered. Total potassium content of upland soil in Korea is about 3% but the exchangeable one is about 0.3 me/100g soil. All upland crops require much potassium probably due to freezing and cold weather and also due to wet damage and drought caused by uneven rainfall pattern. In barley, potassium should be high at just before freezing and just after thawing and move into grain from heading for higher yield. Use efficiency of potassium was 27% for barley and 58% in old uplands, 46% in newly opened hilly lands for soybean. Soybean plant showed potassium deficiency symptom in various fields especially in newly opened hilly lands. Potassium criteria for normal growth appear 2% $K_2O$ and 1.0 K/(Ca+Mg) (content ratio) at flower bud initiation stage for soybean. Potassium requirement in plant was high in carrot, egg plant, chinese cabbage, red pepper, raddish and tomato. Potassium content in leaves was significantly correlated with yield in chinese cabbage. Sweet potato. greatly absorbed potassium subsequently affected potassium nutrition of the following crop. In the case of potassium deficiency, root showed the greatest difference in potassium content from that of normal indicating that deficiency damages root first. Potatoes and corn showed much higher potassium content in comparison with calcium and magnesium. Forage crops from ranges showed relatively high potassium content which was significantly and positively correlated with nitrogen, phosphorus and calcium content. Percentage of orchards (apple, pear, peach, grape, and orange) insufficient in potassium ranged from 16 to 25. The leaves and soils from the good apple and pear orchards showed higher potassium content than those from the poor ones. Critical ratio of $K_2O/(CaO+MgO)$ in mulberry leaves to escape from winter death of branch tip was 0.95. In the multiple croping system, exchangeable potassium in soils after one crop was affected by the previous crops and potassium uptake seemed to be related with soil organic matter providing soil moisture and aeration. Thus, the long term and quantitative investigation of various forms of potassium including total one are needed in relation to soil, weather and croping system. Potassium uptake and efficiency may be increased by topdressing, deep placement, slow-releasing or granular fertilizer application with the consideration of rainfall pattern. In all researches for nutritional explanation including potassium of crop yield reasonable and practicable nutritional indices will most easily be obtained through multifactor analysis.

• Journal of Aquaculture
• /
• v.5 no.1
• /
• pp.29-67
• /
• 1992

Life cycle and seed production of the freshwater prawn, Macrobrachium nipponense, were studied and the results are as follows : 1. Larval development : Embryos hatched out as zoea larvae of 2.06 mm in mean body length. The larvae passed through 9 zoea stages in $15{\~}20$ days and then metamorphosed into postlarvae measuring 5.68 mm in mean body length. Each zoea stage can be identified based on the shapes of the first and second antennae, exo- and endopodites of the first and second pereiopods, telson and maxillae. 2. Environmental requirements of zoea larvae : Zoea larvae grew healthy when fed with Artemia nauplii. Metamorphosing rate was $65{\~}72{\%}$ at $26{\~}28\%$ and $7.85{\~}8.28\%_{\circ}Cl.$. The relationship between the zoeal period (Y in days) and water temperature (X in $^{\circ}C$) is expressed as Y=46.0900-0.9673X. Zoeas showed best survival in a water temperature range of $26{\~}32^{\circ}C$ (optimum temperature $28^{\circ}C$), at which the metamorphosing rate into postlarvae was $54{\~}72\%$ The zoeas survived more successfully in chlorinity range of $4.12{\~}14.08{\%_{\circ}}Cl.$, (optimum chlorinity $7.6{\~}11.6\;{\%_{\circ}}Cl.$.), at which the metamorphosing rate was $42{\~}76{\%}$. The whole zoeal stages tended to be longer in proportion as the chlorinity deviated from the optimum range and particularly toward high chlorinity. Zoeas at all stages could not tolerate in the freshwater. 3. Environmental requirements of postlarvae and juveniles : Postlarvae showed normal growth at water temperatures between $24{\~}32^{\circ}C$ (optimun temperature $26{\~}28^{\circ}$. The survival rate up to the juvenile stage was $41{\~}63{\%}$. Water temperatures below $24^{\circ}C$ and above $32^{\circ}$ resulted in lower growth, and postlarvae scarcely grew at below $17^{\circ}C$. Cannibalism tended to occur more frequently under optimum range of temperatures. The range of chlorinity for normal growth of postlarvae and juveniles was from 0.00 (freshwater) to $11.24{\%_{\circ}}Cl.$, at which the survival rate was $32{\~}35\%$. The postlarvae grew more successfully in low chlorinities, and the best growth was found at $0.00\~2.21{\%_{\circ}}Cl.$. The postlarvae and juveniles showed better growth in freshwater but did not survive in normal sea water. 4. Feeding effect of diet on zoea Ilarvae : Zoea larvae were successfully survived and metamorposed into postlarvae when fed commercial artificial plankton, rotifers, and Artemia nauplii in the aquaria. However, the zoea larvae that were fed Artemia nauplii and reared in Chlorella mixed green water showed better results. The rate of metamorphosis was $68\~{\%}75$. The larvae fed cow live powder, egg powder, and Chlorella alone did not survive. 5. Diets of postlarvae, juveniles and adults : Artemia nauplii and/or copepods were good food for postlarvae. Juveniles and adults were successfully fed fish or shellfish flesh, annelids, corn grain, pelleted feed along with viscera of domestic animals or fruits. 6. Growth of postlarvae, juveniles and adults : Under favorable conditions, postlarvae molted every five or six days and attained to the juvenile stage within two months and they reached 1.78 cm in body length and 0.17 g in body weight. The juveniles grew to 3.52 cm in body length and 1.07 g in body weight in about four months. Their sexes became determinable based on the appearance of male's rudimental processes (a secondary sex character) on the endopodites of second pereiopods of males. The males commonly reached sexual maturity in seven months after attaining the postlarvae stage and they grew to 5.65 cm in body length and 3.41 g in body weight. Whereas the females attained sexual maturity within six to seven months, when they measured 4.93 cm in body length and 2.43 g in body weight. Nine or ten months after hatching, the males grew $6.62{\~}7.14$ cm in body length and $6.68{\~}8.36$ g in body weight, while females became $5.58{\~}6.08$ cm and $4.04{\~}5.54$ g. 7. Stocking density : The maximum stocking density in aquaria for successful survival and growth was $60{\~}100$ individuals/$\ell$ for zoeas in 30-days rearing (survival rate to postlarvae, $73{\~}80{\%}$) ; $100{\~}300$ individuals/$m^2$ for postlarvae of 0.57 cm in body length (survival rate for 120 days, $78{\~}85{\%}$) ; $40{\~}60$ individuals/$m^2$ for juveniles of 2.72 cm in body length (survival rate for 120 days, $63{\~}90{\%}$) : $20{\~}40$ individuals/$m^2$ for young prawns of 5.2 cm in body length (survival rate for 120 days, $62\~90{\%}$) ; and $10\~30$ individuals/$m^2$ for adults of 6.1 cm in body length (survival rate for 60 days, $73\~100{\%}$). The stocking density of juveniles, youngs and adults could be increased up to twice by providing shelters.