• Journal of Ginseng Research
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• v.14 no.3
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• pp.427-431
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• 1990

To search for substituents of greens, several organic materials such as rice straw, barley straw, corn stem and manufactured compost were applied in a ginseng cultivating field. The yields of six year old ginseng harvested in the rice straw, barley strait and corn stem treated field were similar to or higher than that of the greens treated one. The varied amount of applied substituents resulted in a yield change, but statistical linearity was not found. The growth of ginseng aerial part and soil physicochemical property in the field fortified with these substituents showed similar results to those of the greens treated one. So, it is though that these organic materials can substitute for greens.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.1
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• pp.79-88
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• 1995

A subreflector of an offset dual reflecor antenna system mounted on satelite is analyzed by Uniform Geometrical Theory of Diffraction(UTD). In order to get the total electric field at an observation point, the reflected field and the diffracted fields obtained by UTD are summed. The reflected point and the diffracted points which have to satisfy nonlinear equations are obtained by numerical methods. The numerical results show taht diffracted fields eliminate the discontinuity of reflected fields at the shadow boundary. To show the validity of our results, the field pattern of the symmetric hyperboloidal reflector is computed and compared with S. W. Lee et al.'s results. At various obsevation angles, radiation patterns of offset ellipsoidal subreflectors offseted by a circular corn and by an elliptic corn are obrained, repectivelly.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.518-518
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• 2016

Agriculture is the lifeblood of the economy in Ghana, employs about 42% of the population work force and accounts for 30% of the Gross Domestic Product (GDP). Corn (maize) is the major cereal crop grown as staple food under rain fed conditions, covers over 92% of the total agricultural area, and contributes 54% of the caloric intake. Issues of hunger and food insecurity for the entire nation are associated with corn scarcity and low production. The climate changes are expected to affect corn production in Ghana. This study evaluated variations of corn yields based on different climate conditions of rain-fed area in the Dangbe East District of Ghana. AquaCrop model has been used to simulate corn growing cycles in study area for this purpose. The main goal for this study was to predict yield of corn using selected climatic parameters from 1992 to 2013 using different climate scenarios. The Model was calibrated and validated using observed field data, and the simulated grain yields matched well with observed values for the season under production giving an R squared (R2)of 0.93 and Nash-Sutcliff Error(NSE) of 0.21. Study results showed that rainfall reduction in the range of -5% to -20% would reduce the yield from 1.315ton/ha to 0.421ton/ha (-21. 3%) whereas increasing temperature from 1% to 7% would result in the maximum yield reduction of -20.6% (1.315 to 1.09 ton/ha.). On the other hand, increasing rainfall from 5-20% resulted in yield increment of 68% (1.315-2.209 ton/ha) and decreasing temperature produce 7% increase in yield ( 1.315 to 1.401ton/ha). These results provide useful information to adopt strategies by the Government of Ghana and farmers for improving national food security under climate change.

• Journal of The Korean Society of Grassland and Forage Science
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• v.37 no.1
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• pp.44-49
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• 2017

This experiment was carried out to study the effect of rice black-streaked dwarf virus(RBSDV) infection rate on forage productivity of corn varieties in Cheonan of chungcheongnamdo from 2006 to 2008. Forage corn varieties of 10 were cultivated with first cropping(seeding in the last ten days of April) and second cropping(seeding in the last ten days of May) system in field and tested the infection rates of RBSDV and productivity of forage. The Infection rate of RBSDV was significant difference between corn varieties in middle district of Korea. Resistant corn varieties for RBSDV were 'Kwanganok', 'P3156', 'Kwangpeyongok' and 'P3394' but susceptible varieties were 'Suwon19', 'DK697', 'GW6959' and NC+7117. Dry matter(DM) yield of forage corn according with infection rates of RBSDV in field was significant difference between varieties(p<0.05). DM yield of susceptible varieties, 'Suwon 19', 'DK697' and 'GW6959' was lower about 20% than that of resistant varieties, 'Kwangpeyongok' and 'P3156'. For increasing the productivity of forage corn, recommend of resistant varieties for RBSDV and control of seeding time are very important in middle district of Korea.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.5
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• pp.531-540
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• 2016

The adoption of legume cover crops in no-tillage system can contribute to improve soil fertility by providing several benefits, including reduction in soil erosion, suppression of weed growth and N supply to subsequent crops. We conducted a field study to investigate the effect of cover crops and nitrogen fertilization rates on yield and nitrogen use efficiency of waxy corn (Zea mays L.) in no-tillage upland field. Two legume cover crops, hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnuturn L.) were mechanically terminated with roller in early June. For each cover crop treatment, nitrogen (N) fertilizer was applied at three different rates (145, 72.5 and $0kg\;N\;ha^{-1}$). The growth and yield characteristics of corn were significantly affected by the N fertilization rates in crimson clover plots, which suggest N mineralization from the cover crop residue was not sufficient. In contrast, N fertilization rates had no significant effect on growth and yield of corn in hairy vetch plots, indicating that the amount of N released from the cover crop is large enough to meet most of the N requirement of corn. However, the application of N fertilizer in hairy vetch cover plots resulted in slight increase of crop yield, though not statically significant, and high levels of N concentration in corn plant tissue possibly due to luxury consumption of N. Organic residues on the soil surface in hairy vetch cover plots had substantial amounts of N after harvest, ranging from 100 to $116kg\;N\;ha^{-1}$, which is presumably retained during winter season and released by microbial mineralization in subsequent year. The highest nitrogen yield efficiency was achieved in the plot with hairy vetch cover and no N fertilizer application, followed by the plot with hairy vetch cover and $72.5kg\;N\;ha^{-1}$ fertilization rate. In conclusion, hairy vetch showed better performance in corn productivity as compared with crimson clover. In addition, it was concluded that the application of N fertilizer between 0 and $72.5kg\;N\;ha^{-1}$ in combination with hairy vetch cover crop might be most efficient for corn yield under no-tillage system with climatic and soil characteristics similar to those of the experimental site.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.80-80
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• 2017

Teosinte is now known as a wild variety of corn. It is distributed in Central and South America. It is believed that teosinte contains genes for resistance to flooding because of the climate characteristics of the collected countries. Recent studies have shown that teosinte has the ability to form adventitious roots, to develop aerenchyma tissues of teosinte, and the resistance to toxic substances under flooding soil condition. Therefore, development of corn cultivars to cope with climate change and the growing corn at paddy field in Korea are required to introduce the characteristics of teosinte. However, in order to utilize teosinte resources, preconditions must be settled such as photoperiodic responsibility. Also if the preconditions are studied together with the metabolic level studies, the possibility of utilization will be even higher.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.476-482
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• 2014

In this study, we analyzed the effect of corn growth on the radar backscattering coefficient. At first, we measured the backscattering coefficients of various corn fields using a polarimetric scatterometer system. The backscattering coefficients of the corn fields were also computed using the 1st-order VRT(Vector Radiative Transfer) model with field-measured input parameters. Then, we analyzed the experimental and numerical backscattering coefficients of corn fields. As a result, we found that the backscatter from an underlying soil layer is dominant for early growing stage. On the other hand, for vegetative stage with a higher LAI(Leaf-Area-Index), the backscatter from vegetation canopy becomes dominant, and its backscattering coefficients increase as incidence angle increases because of the effect of leaf angle distribution. It was also found that the estimated backscattering coefficients agree quite well with the field-measured radar backscattering coefficients with an RMSE(Root Mean Square Error) of 1.32 dB for VV-polarization and 0.99 dB for HH-polarization. Finally, we compared the backscattering characteristics of vegetation and soil layers with various LAI values.

• Journal of Animal Science and Technology
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• v.66 no.5
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• pp.949-961
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• 2024

The annual forage crop production system, enclosing silage corn (Zea mays L.) and following cool-season annual forage, can enhance forage production efficiency where available land is limited for pasture production. In this forage production system, successful silage corn cultivation has a significant value due to the great yield of highly digestible forage. However, some untimely planting or harvesting of corn due to changing weather often reduces biomass and feeding values. Therefore, a study was conducted to quantify the corn silage biomass reductions by the deviations from optimum planting soil temperature and optimum growing degree day (GDD). The approximations of maximum corn production were estimated based on field trial data conducted between 1978 and 2018 with early, medium, and late-maturity corn groups. Based on weather data, the recorded planting dates and harvest dates were converted into the corresponding trials' soil temperatures at planting (STP) and the GDD. The silage corn biomass data were regressed against STP and GDD using a quadratic function. The maximum biomass point was modeled in a convex upward quadratic yield curve and the optimum STP and GDD were defined as those values at the maximum biomass for each maturity group. Optimized STP was at 16.6℃, 16.2℃, and 15.6℃ for early, medium, and late maturity corn groups, respectively, while optimized GDD at harvest was at 1424, 1363, and 1542℃. The biomass reductions demonstrated quadratic functions by the departures of STP or GDD. The 5% reductions were anticipated when STP departed from the optimum temperature by 2.2℃, 2.4℃, and 1.4℃ for early, medium, and late maturity corns, respectively; the same degree of reductions were estimated when the GDD departed by 200, 180, and 130℃ in the same order of the maturity groups. This result indicates that biomass reductions of late-maturity corn were more sensitive to the departures of STP or GDD than the early-maturity corn. Therefore, early maturing cultivars are more stable in biomass production in a silage corn-winter annual forage crop production system to enhance forage-based livestock production efficiency.

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.E
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• pp.31-43
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• 1995

Natural emissions of NOx from soils were measured at an agricultural corn field during 3 weeks of growing season in summer (from May to June) 1995. This experiment was conducted in an effort to characterize the role of soil NOx on tropospheric ozone formation in rural atmosphere, and understand the natural NOx emission mechanism with respect to soil parameters. NO fluxes were ranged from 3.1 ng Nm$^{-2}s^{-1}$ to 259.0 ng Nm$^{-2}s^{-1}$, and average NO flux during experimental period was found to be 47.6 $\pm$ 50.6 ng Nm$^{-2}s^{-1}$ with 732 number of data. Diurnal variation of NO flux was shown clearly with daytime maximum and nighttime minimum. NO fluxes were correlated with soil temperature. Exponential soil temperature dependency of NO fluxes was found with 0.0160$^{circ}C^{-1} of k and r^2=0.508$, which agrees well to the value estimated at corn fields in eastern United States. The significant increases of NO fluxes from agricultural soil were detected after applying N fertilizers to soil. THe mechanisms attributed to this are enhanced biological nitrification and denitrification. In the view of rural ozone formation, the roles of natural NO emissions are very essential, especially in NOx - limited region such as southern United States.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.6
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• pp.813-818
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• 2016

Distribution of clay minerals separated from clay fraction of corn fields in Korea has been investigated along with their characterization. Crystalline phases of the clay minerals were identified by powder X-ray diffraction (XRD) pattern, and their relative chemical compositions were analyzed by X-ray fluorescence spectrometry (XRF). The soils were found to have pH 6.4, organic matter $37.2g\;kg^{-1}$, available $P_2O_5$ $599mg\;kg^{-1}$, respectively, and exchangeable K, Ca and Mg were 1.2, 7.3 and $1.8cmol_c\;kg^{-1}$, respectively. Major primary minerals consisted mainly of quartz and mica, and kaolinite and chlorite were identified as major secondary clay minerals. For most of soils, mica phase was identified to be muscovite rather than biotite. The average contents of $SiO_2$, $Al_2O_3$ and $Fe_2O_3$ were 43.7, 23.6 and 8.8%, respectively, although they were different with the locations.