• Korean Journal of Soil Science and Fertilizer
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• v.15 no.1
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• pp.34-48
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• 1982

1. Production and consumption of chemical fertilizers in Korea could be divided into five different phases of total imports, setting up fertilizer plants, self-sufficiency in production, net export, and diversification in compound fertilizers. Currently the nation has production capacity of 800 thousand M/T of nitrogen, 400 thousand M/T of phosphate ($P_2O_5$) and 200 thousand M/T of potash ($K_2O$). 2. Yearly consumption increased every year, since 1964, 28,000 M/T N, 7,700 M/T $P_2O_5$, and 7,500 M/T $K_2O$ until 1972, when the increase jumped by eight times for $P_2O_5$ and seven times for $K_2O$ for the following 3 years in anticipation of their short supply. Now total consumption has been more or less stabilized at the level of 450 thousand M/T N, 220 thousand M/T $P_2O_5$ and 180 thousand M/T $K_2O$ for the last 7 years. 3. Current operation rate of fertilizer plants is around 80% throughout the whole industry, after going through several different levels depending on demand at times. 4. Fertilizer export started in 1967 and reached a peak of 150 thousand nutrient ton in 1972, about 20% of total production, before temporarily stopping due to over-demand for next three years. The export resumed again in 1976 rise to the all time high of 670 thousand nutrient ton in 1980, almost half of total production, and then started to decline due to higher price of petroleum since then. 5. The decline in fertilizer export appears to be accelerated because several countries, in South-Eastern Asia, traditional export market for Korean fertilizers, started to build their own plants, since 1980, based on their raw materials of especially petroleum. 6. Current consumption in Korea is about 30 nutrient Kg per 10a, equivalent to that in Western European countries, partly due to new high-yielding rice varieties and extensive cultivation of fruit trees and vegetables. Additional fertilizer demand in future can be anticipated in reclaimed land for growing grass and forestry.

• Korean Journal of Environmental Biology
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• v.31 no.4
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• pp.471-477
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• 2013

Biochar amendment to agricultural soil is regarded as a promising option to mitigate climate change and enhance soil quality. It could sequester more carbon within the soil system and increase plant yield by changing soil physicochemical characteristics. However, sustainable use of biochar requires comprehensive environmental assessment. In this sense, it is important to measure additional greenhouse gas emission from soils after biochar addition. We investigated emissions of $CO_2$, $N_2O$, and $CH_4$ from incubated soils collected from rice paddy and cultivated grassland after amendment of 3% biochar (wt.) produced from rice chaff. During incubation, soils were exposed to three wet-dry cycles ranging from 5~85% soil gravimetric water content (WC) to investigate the changes in effect of biochar when influenced by different water levels. The $CO_2$ emission was reduced in biochar treatment compared to the control at WC of 30~70% both in rice paddy and grassland soils. This indicates that biochar could function as a stabilizer for soil organic carbon and it can be effective in carbon sequestration. The $N_2O$ emission was also reduced from the grassland soil treated with biochar when WC was greater than 30% because the biochar treated soils had lower denitrification due to better aeration. In the rice paddy soil, biochar addition resulted in decrease in $N_2O$ emission when WC was greater than 70%, while an increase was noted when WC was between 30~70%. This increase might be related to the fact that available nutrients on biochar surface stimulated existing nitrifying bacterial community, resulting in higher $N_2O$ emission. Overall results imply that biochar amendment to agricultural soil can stabilize soil carbon from fast decomposition although attention should be paid to additional $N_2O$ emission when biochar addition is combined with the application of nitrogen fertilizer.

• Journal of The Korean Society of Grassland and Forage Science
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• v.11 no.3
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• pp.189-194
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• 1991

This experiment was carried out to investigate the effect of pure mineral nitrogen fertilization on dry matter yield and to determine the amounts of advisable mineral nitrogen according to difference of annual precipitations in permanent grassland. The results obtained were as follows: 1. Only PK-fertilizing without additional mineral nitrogen application produced 6. 9 tonlha of annual dry matter yields on average in relatively wet years that was higher than in rel. dry and normal years under 3-cut system by 0. 7 and 0.6 ton DMIha, respectively. 2. Due to the lesser rainfall the nitrogen-efficiency was substantially higher with heavy dressing of nitrogen fertilizer. The absolute differences in yield between rel. dry and wet years were 0.4 and 0.7 ton DMIhalyear respectively when dressed with 90 and 120 kgN/ha/cut at 4-, 5- and 6-cut systems, whereas at 3-cut system differences around 1.3 and 1.1 ton Dhllhalyear respectively were recorded. 3. In rel. dry years the most efficient N-dressing rates per ha and year tended to be slightly higher than in rel. wet and normal years. Particularly at 5-cut system 4-7 kg/ha/cut of more nitrogen fertilization was required in order to obtain the highest overyields. 4. The N-dressing rates needed to maintain a nitrogen-efficiency of 8 to 16 kg DM/kg N tended to be stronger particularly at high cut system, and also in rel. dry years higher dressing rates were required that in rel. wet and normal years.

• Journal of Crop Science and Biotechnology
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• v.10 no.1
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• pp.33-38
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• 2007

Nitrogen management at the panicle initiation stage(PI) should be fine-tuned for securing a concurrent high yield and high quality rice production. For calibration and testing of the recommendation models of N topdressing rates at PI for target grain yield and protein content of rice, three split-split-plot design experiments including five rice cultivars and various N rates were conducted at the experimental farm of Seoul National University, Korea from 2003 to 2005. Data from the first two years of experiments were used to calibrate models to predict grain yield and milled-rice protein content using shoot fresh weight(FW), chlorophyll meter value(SPAD), and the N topdressing rate(Npi) at PI by stepwise multiple regression. The calibrated models explained 85 and 87% of the variation in grain yield and protein content, respectively. The calibrated models were used to recommend Npi for the target protein content of 6.8%, with FW and SPAD measured for each plot in 2005. The recommended N rate treatment was characterized by an average protein content of 6.74%(similar to the target protein content), reduced the coefficient of variation in protein content to 2.5%(compared to 4.6% of the fixed rate treatment), and increased grain yield. In the recommended N rate treatments for the target protein content of 6.8%, grain yield was highly dependent on FW and SPAD at PI. In conclusion, the models for N topdressing rate recommendation at PI were successful under present experimental conditions. However, additional testing under more variable environmental conditions should be performed before universal application of such models.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.18 no.4
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• pp.63-71
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• 2015

Recently the roof gardening has become very popular and even on the apartment-veranda and on the roofs in high buildings many kinds of vegetables and berries are cultivated. And the demand of the nutritional supplement for the effective plant growth is also increasing. The general urban conditions are to be adapted for plant growth. A different hygroscopic and temperature-conditions after regions, sunshine and wind have strong influences on the plant growth and usually it is not optimal enough. It is because why a nutritional condition in soil for plant growth so important and essential. The usual compound-soil or -fertilizer cannot offer enough quantities of nutrients for plant growth and additional soil conditioner becomes more necessary. There are many kinds of soil conditioners like hydrogel in the market and we studied on Geohumus, Montigel and Geko, which are widely used in Europe and other countries. Water absorption and microbial immobilization with effective microorganisms were tested and compared. The EM solution was identified as bacteria, fungi and azotobacter etc. and they were immobilized at the soil conditioners at first. And the cultivated and immobilized at the soil conditioners EM-solution was added to the plant soil. 1 g of the soil conditioners absorbed ca. 20 g of water. The plant grew 10 cm more, got 3 times more branches and 2 times more fruits in the soil with soil conditioners immobilized with microorganisms. With water addition the plant with both conditions in the soil could stay fresh in comparison to without soil conditioners.

• Journal of The Korean Society of Grassland and Forage Science
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• v.15 no.3
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• pp.164-168
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• 1995

A field experiment was carried out to determine the effects of nitrogen (N) fertilization levels after first harvest (0, 30, 60, 90 and 120 kglha) during spring season on the gms growth, dry matter (DM) yield, nutritive value, and efficiency of DM production per N kg applied in orchardgrass meadow. Additional N was applicated at early spring (70 kg), after second harvest (50 kg), and after fourth harvest (30 kg/ha) in all treatments, 1990. Growth and DM yield of orchardgrass at second harvest were significantly increased with increasing level of N after first harvest (P<0.05), but no yield differences were observed between application of N 60, N 90, and N 120 kg. The efficiency of DM increment per N kg applied was rapidly decreased with increasing level of N; that was 14.8, 12.0, 10.7 and 4.7 DM kg/N kgha in the plot of N 30, N 60, N 90 and N 120 kg, respectively. The content and yield of crude protein of orchardgrass at second harvest were significantly increased with increasing of N (P<0.05), ranged h r n 11.0% (N 0 kg) to 16.8% (N 120 kg), and from 195.0 kg (N 0 kg) to 508.2 kglha (N 120 kg), respectively. However, the content of neutral detergent fiber was not affected by N level after first harvest. From the above results, it is suggested that application of N fertilizer after first harvest was very effective for regrowth and nutritive value of orchardgrass during spring season, and the proper amount of N after first harvest was 60-90 kglha in this experiment.

• Journal of the Korean Society of Food Culture
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• v.23 no.6
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• pp.737-747
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• 2008

This study was conducted to investigate the perception and understanding parents had regarding environment friendly agricultural products being used for school foodservice. A trained practitioner surveyed 221 parents of children at elementary schools in Daejeon using a questionnaire, after which the resulting data were analyzed by a Chi-square test. Overall, the parent's responses regarding the foodservice were positive. However, most of the parents do not participate (65%) in the school foodservice if they work, and those that do participate primarily work as meal service aides (58.1%). Parents indicated that the work of urgent field of inspection on food materials (69.9%), and the reason of an agreement (98.2%) for them were the students' health (68.4%). In addition, most parents were positive about the possibility of replacing foods used in the school with environment friendly products (51.6%) and felt that the government should pay the additional expense associated with their replacement. Furthermore, the majority of the parent's surveyed felt that children should be supplied with vegetables (54.9%) purchased directly from farms. The parents' satisfaction with the meal service (25.1%) was lower than that of the students (54.1%). The reason for the satisfaction reported by the parents was concern regarding the health of their children (53.3%). In addition, the majority of the parents (47.3%) responded that environment friendly agricultural products differ from general agricultural products because insecticides and fertilizer were not used. The main objection parents had to using environment friendly products was their cost (59.1%), and most parents felt that a realistic solution to this problem was unified purchase (41.4%). Besides, a problem when replacing with them was the expensive price (38.1%) and true or false (37.7%), and the students' satisfaction (59.5%) was selected the most in an effect of using them, diversity of the product (39.1%) and price reduction (32.6%) for a solution of the increase of using them.

• Journal of Microbiology and Biotechnology
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• v.34 no.2
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• pp.407-414
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• 2024

Phosphorus is an essential but non-renewable nutrient resource critical for agriculture. Luxury phosphorus uptake allows microalgae to synthesize polyphosphate and accumulate phosphorus, but, depending on the strain of algae, polyphosphate may be degraded within 4 hours of accumulation. We studied the recovery of phosphorus from wastewater through luxury uptake by an engineered strain of Synechocystis sp. with inhibited polyphosphate degradation and the effect of this engineered Synechocystis biomass on lettuce growth. First, a strain (∆phoU) lacking the phoU gene, which encodes a negative regulator of environmental phosphate concentrations, was generated to inhibit polyphosphate degradation in cells. Polyphosphate concentrations in the phoU knock-out strain were maintained for 24 h and then decreased slowly. In contrast, polyphosphate concentrations in the wild-type strain increased up to 4 h and then decreased rapidly. In addition, polyphosphate concentration in the phoU knockout strain cultured in semi-permeable membrane bioreactors with artificial wastewater medium was 2.5 times higher than that in the wild type and decreased to only 16% after 48 h. The biomass of lettuce treated with the phoU knockout strain (0.157 mg P/m²) was 38% higher than that of the lettuce treated with the control group. These results indicate that treating lettuce with this microalgal biomass can be beneficial to crop growth. These results suggest that the use of polyphosphate-accumulating microalgae as biofertilizers may alleviate the effects of a diminishing phosphorous supply. These findings can be used as a basis for additional genetic engineering to increase intracellular polyphosphate levels.

• Korean Journal of Soil Science and Fertilizer
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• v.14 no.4
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• pp.219-223
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• 1982

The results of study on the yield and absorption of N and K applied to the chinese cabbage (Brassica pekinensis) which was grown at comparatively infertile red-yellow soil in the fall of 1980 are summerized as below. 1. The optimum quantities of potash to be applied for the autumn chinese cabbage is suggested in the range of 15kg-20kg/10a, $K_2O$. 2. Combined treatments of N and K showed a positive interaction by promoting the effect of the other element. The increase of Nitrogen absorption from the additionally applied 10kgs of nitrogen on top of 15kg N/10a showed only 16 per cent at potash minus plot, while that of potash applied plot showed 60 per cent. The cabbage yield increase therefor, at high rate of nitrogen only was 1,700kgs per 10 are over low rate of nitrogen, while high nitrogen plus potash treatment produced additional 2,200kgs over the low rates of N and K. 3. Additional 10kgs of nitrogen applied on top of 15kgs N/10a resulted in increasing soil potassium uptake; 4kgs of soil potassium was additionally absorbed at potash applied plot and 6.5kgs at potash minus plot. 4. Utilization of applied potash was greater at low rates of N, and K application (each 15kgs of N and $K_2O$ per 10a) where 77 per cent of applied potash was utilized, while high rates of N and K application (each 25kgs of N and $K_2O$ per 10a) showed 44 per cent of potash utilization rate. Lower utilization of applied potash at high rate of nitrogen application is due probably to greater uptake of soil potassium. 5. N and K contents in the chinese cabbage are 0.17-0.20% and 0.35-0.43% respectively and these were not statistically correlated with the yields.

• Korean Journal of Environmental Agriculture
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• v.29 no.1
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• pp.12-19
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• 2010

Optimum nitrogen fertigation level by soil testing was determined on the growth and yield of eleven-year-old 'Campbell Early' (Vitis labrusca L.) grapevine in a sandy loam soil from 2005 to 2007. Fifty percent of the annual application of the nitrogen rate (195 kg/ha/yr) was top-dressed as basal fertilizer in all treatments, and the remainders were drip-irrigated with fertigation rate at 25 (12.5% of total N, N 1/4 level of the remainder), 50 (25% of total N, N 1/2 level), and 100 mg/L (50% of total N, N 1 level) in intervals of twice (2.1 mm/times) a week for 12 weeks, and the effect of N drip fertigation was compared to control which the N remainder was applied with surface application as an additional fertilizer. The results showed that chlorophyll content reading in SPAD value and N contents of leaves increased as nitrogen fertigation level increased. Also observed was the growth of the internode and stem diameter of shoots which were longest at N 1/2 level among the treatments conducted both in 2005 and 2006. It was also noted that yield of the fruit was different every year, where average yield for three years was recorded highest in N 1/4 level, and lowest in N 1 level compared to control(surface application). Soluble solid content and titratable acidity of fruit juice were also not significant during the treatments, the maturation of fruits tended to be retarded in N 1 level. The study proved that N 1/4 (N 25 mg/L) levels of fertigation based on soil testing was most efficient in obtaining optimum yield and also, fertigation of grapevine at open field condition reduces the use of nitrogen fertilizer.