• Korean Journal of Soil Science and Fertilizer
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• v.42 no.3
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• pp.167-171
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• 2009

An attempt was made to provide the most reasonable fertilizer recommendation for radish crop based on soil analysis data and yield response to the N, P, K fertilizers, which was obtained from field experiments on 2004 in highland, 850 meters above the sea level. Optimum times of NPK application to past application amount based on soil test were 0.90-0.77-0.50 for radish. The adjusted NPK recommendation models of highland soil were made by adding the application times to past application methods which were based on chemical properties of soil. The revised models for fertilizer application were recommended to decrease the amount of N, P, K by 10-23-50% for radish in highland. In application to total cultivation area, 2,546ha for radish, saving amounts of NPK fertilizers with these adjusted recommendation in comparison with past application levels will be 244.4 tons for radish. Using the optimal application amounts for radish, we will can reduce agricultural pollution without affecting crop yields.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.1
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• pp.64-70
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• 2001

To verify the newly developed decision assisting expert system for nitrogen fertilizer application NES to Illinois cornfields, a couple of N rate studies from Dr. Howard and five Illinois Agricultural Experiment Stations were applied. Four types of recommendations including the current Illinois recommendation, Hoeft recommendation, NES, and maximum economic recommendation were compared with each other for the crop yields, profits, recovery rate, and N losses to cornfields. The N rate of NES recommendation, considering productivity index (PI), soil organic matter content (SOM), and pre-sidedressing nitrate concentration (PSNT) level, was the lowest in comparison to those of other recommendations. However, N recovery rate in NES was generally higher and the resulting N loss was lower than others. But, adherence to the recommendations may also reduce farmers income if environmental expense did not considered. Therefore, NES will be more effective by adding the factors including environmental expense, tillage systems, crop rotation, and other agricultural management parameters.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.3
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• pp.150-161
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• 2017

This study was conducted with the data of monitoring on soil chemical properties of rice paddy soils in Gyeongbuk Province. The selected soil chemical properties were analyzed every 4 year from 1999 to 2015. The soil pH measured in 2015 was higher than pH 6.0, which was 0.3-0.4 pH unit higher than data until 2007 survey year. The mean content of organic matter was greater than $24g\;kg^{-1}$ since 2003, but 35% of soil samples remained below the recommended level ($20-30g\;kg^{-1}$) in 2015. The mean concentration of available phosphate was maintained at $40mg\;kg^{-1}$ higher than the upper recommendation level ($80-120mg\;kg^{-1}$), and more than 40% of paddy soils tested were found to have less than the recommendation level during the survey period. The exchangeable K concentration ranged from 0.25 to $0.39cmol_c\;kg^{-1}$. Exchangeable Ca showed an average at the optimum range ($5.0-6.0cmol_c\;kg^{-1}$) during the monitoring period. Exchangeable Mg decreased linearly ($0.02cmol_c\;kg^{-1}\;year^{-1}$) from $1.55cmol_c\;kg^{-1}$ as of 1999 to below the lower level of the recommendation range ($1.5-2.0cmol_c\;kg^{-1}$). The amount of available $SiO_2$ was increased significantly from 2011 to over the recommendation level (${\geq}157mg\;kg^{-1}$). It was revealed that the soil chemical properties of rice paddy fields was influenced by topology, soil texture, type and region as result of principal component analysis or cluster analysis. Therefore, an assessment on chemical properties of rice paddy soils should be performed to consider various soil physical conditions and agronomic practices such as fertilization, cropping system, and so on. Because of the high variability of nutrient levels across Gyeongbuk Province, nutrient management based on soil fertility test is required by respective farm land unit.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.4
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• pp.388-392
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• 2016

The objectives of fertilizer recommendation are to prevent the application of excessive fertilization and to produce target yields. Also, optimal fertilization is important because crop quality can be influenced by fertilization. In this study, yields and fertilizer use efficiency of Taro (Colocasia esculenta Schott) were evaluated in different level of NPK fertilization. N, P and K fertilizer application rates were 5 levels (0, 50, 100, 150, 200%) by practical fertilization ($N-P_2O_5-K_2O=180-100-150kg\;ha^{-1}$), respectively. In the N treatment, the yields of Taro tuber were about $33Mg\;ha^{-1}$ from 90 to $360kg\;ha^{-1}$ N fertilization. However, the ratio of tuber to total biomass decreased with increasing N fertilization rate. In the P and K treatments, yields of Taro tuber were the highest at $150kg\;ha^{-1}$ fertilization. Fertilizer use efficiency was decreased by increase of N and K fertilization. Crude protein of Taro tuber was the highest at practical fertilization. Sucrose content of tuber was influenced by phosphate application.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.4
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• pp.383-396
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• 1992

In order to find out the reasons for the excessive accumulation of certain fertilizer elements in arable land in Korea, which may be a detrimental factor for her sustainable agriculture in the future, total requirement of fertilizers were estimated from the huge number of soil test data obtained throughout the country using the fertilizer requirement models based on the soil analysis data and the concepts of multi nutrient factor balance or starter fertiliazer. The total fertilizer requirements estimated based on the present soil fertility status were much less than those estimated from the suspected cropping area of various crops cultivated depending on the conventional fertilizer recommendation for each crops or the actual amount of fertilizer elements consumed through National Agricultural Cooporative Federation(NACF). The excessive accumulation of certain fertilizer elements in arable land in Korea must be due to excessively high dose of chemical fertilizers as well as those farm wastes such as animal wasts produced unexpectedly in large amounts or crop residues. And it is suggested that the improved fertilizer recommendation must be developed in consideration both with the soil fertility status and the amounts of nutrient removal by each crop, and that the high analyzed complex fertilizers commonly used by farmers must ugently be developed in a form containing low P and K with Mg and slow release type N for the better balanced management practices of soil fertility by farmers arid for their practices of sustainable agriculture.

• Korean Journal of Soil Science and Fertilizer
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• v.15 no.2
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• pp.101-109
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• 1982

An attempt to determine the optimum levels of P and K fertilizers application for Tong-il lines (indica${\times}$Japonica) was made with the data obtained from the farm fields during 1976 to 1979. The detailed interpretation to obtains relationships between fertilizer recommendation of P and K with their balance with Ca and Mg contents in soil were made using yield data obtained in 1977. The results were summarized as follows : 1. The optimum rates of P and K fertilizer application varied with the kinds of paddy soils showing the ranges of 6.6-11.4 kg/10a for P (as $P_2O_5$) and 7.0-11.3 kg/10a for K (as $K_2O$). The amounts of optimum fertilizers increased in the order of unmatured soil, normal soil, sandy soil, saline soil, poorly drained soil for P, and unmatured soil, poorly drained soil, sandy soil, normal soil, saline soil for K. 2. The yield increment at the optimum levels of P and K in comparison with no fertilizer application were 3,5-7.5% for P and 2.1-9.1% for K. The effectiveness of P was greatest in the unmatured soils and that of K was greatest in the poorly drained soils, and in the saline soil, that of P and K was relatively high. 3. According to relationship between relative yield index and soil testing value, the critical $P_2O_5$ contents which showed the yield response in soil were about 100 ppm for normal soil and 200ppm for sandy soil. That of exchangeable K/Ka+Mg ratio in soil were about 0.08 for normal paddy soil and over 0.08 for sandy soil, and those for poorly drained soils were not obtained in the ranged below 0.08. 4. The regression equations of fertilizer recommendation for different soils were obtained between the available $P_2O_5$ in soil or ratio of K to base including Ca and Mg in soil (x) and the amount (Y) of P and K fertilizers applied. The equations for phosphorus recommendation were Y=11.27C-0.048x for normal paddy soil and Y=13.383-0.061x for sandy soil, and those for potassium recommendation were Y=9.526-0.569x for normal paddy soil, Y=11.727-1.004x for sandy soil, and Y=12.574-0.558x for poorly drained soil, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.6
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• pp.594-597
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• 2014

Crop yields depend on the limiting factor of crop growth; Liebig law of minimum. Identifying the kind and the necessary amount of the limiting factor is essential to increase crop yield. Although nitrogen is the most essential nutrient, N application does not always bring about yield increases when other elements are limiting in rice cultivation. Two experiments were compared to elucidate the effect of soil testing on rice yield response to N level. The one was an experiment about yield response of 3 rice cultivars to 7 levels of N application, which was conducted from 2003 to 2004 in 25 farmer's fields without ameliorating soil conditions by soil testing and the other was a demonstration experiment on N fertilizer recommendation equation by 0, 0.5, 1.0, and 1.5 times of N recommended level in 5 soil types from 30 fields after ameliorating soil conditions by soil testing. The N response patterns of the experiments conducted without soil testing showed a Mitscherlich pattern in some cultivars and soil types, but did not in the others. The N response patterns of the demonstration experiment showed a Mitscherlich pattern in all soil types. Because these results indicated that N was the minimum nutrient in the demonstration experiment by ameliorating soil conditions with soil testing, but not in the other experiment without soil testing, the supply of minimum nutrients by soil testing could increase the efficiency of N-fertilization.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.1
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• pp.55-63
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• 2001

N fertilizer recommendations to optimize with consideration to maximum crop yields, maximum profits, and minimum N losses to ground or runoff water, an advisory system. Nitrogen Expert System (NES), was developed. The system was to estimate the optimal rate of N fertilizer application cornfields in Illinois. NES was constructed using Smart Elements, a knowledge-based system that manages the expertise of human experts. NES was reinforced by addition of the effect of a productivity index (PI), soil organic matter content (SOM), and pre-sidedressing of nitrate concentration (PSNT) to the optimal N fertilizer recommendation. NES contains 49 rules, 1 class, 14 objects, and 2 properties. NES was successfully operated, showing N recommendations with inputs of three soil properties including PI, SOM, and PSNT. NES can reduce N loss to the environment, but adherence to the recommendations may also reduce farmers income. Therefore, NES will be more effective by evaluating both environmental damage assessment and other economic agricultural management parameters and other soil physico-chemical parameters.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.2
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• pp.74-82
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• 2004

This study was conducted to estimate the optimum application rate of fertilizer N based on $NO_3-N$ concentration in soils for tomato (Lycopersicon esculentum Mill.) cultivation in plastic film house. Tomato plants were cultivated with and without fertilizer in twelve soils which have different concentrations of $NO_3-N$ ranging from 46 to $344mg\;kg^{-1}$. Dry weight (DW) of above-ground part of tomato with no fertilizer ranged from 28.9 to $112.5g\;plant^{-1}$, depending on N-supplying capability of soils. The soil $NO_3-N$ was positively correlated with DW ($r=0.83^{**}$) and N uptake ($r=0.78^{**}$) by tomatoes in no fertilizer treatment, and negatively correlated with fertilizer effciencies resulted from the differences of DW and N uptake between fertilized and non-fertilized plot. The relationships between soil $NO_3-N$ concentration and DW, N uptake, and fertilizer efficiency were analyzed to determine the critical levels of soil $NO_3-N$ for tomato cultivation. The limit critical levels of soil $NO_3-N$ were estimated to be more than $280mg\;kg^{-1}$ for no application of fertilizer N and to be less than $50mg\;kg^{-1}$ for recommended application of fertilizer N. These critical levels of soil $NO_3-N$ were nearly the same as those calculated from regression equation between electrical conductivity(EC) and soil nitrate for critical levels of EC in recommendation equation of fertilizer N for tomato under the plastic film house by NationaI Institute of Agricultural Science and Technology. Consequently, the optimal application rate of ferdilizer N for tomato cultivation in the soils containing $NO_3-N$ concentration between $280mg\;kg^{-1}$ and $50mg\;kg^{-1}$ was estimated by the equation Y = -0.4348X＋121.74, where Y is the percent(%) to the recommended application rate of N fertilizer and X is the soil $NO_3-N$ concentration ($mg\;kg^{-1}$).

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.3
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• pp.37-44
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• 2020

The Project supporting organic fertilizer started in 1999 as a national policy. In farmhouse, over application of mixed organic compound fertilizer(OC) caused salt accumulation in plastic film house soil. To replace inorganic fertilizer with OC fertilizer, this study was investigated the effect of OC application on yield and soil chemical properties for lettuce cultivation in plastic film house. The OC fertilizer was applied at 50(OC50+N50), 100(OC100), and 150(OC150) % level of the basal amount of nitrogen fertilizer in soil testing recommendation. And these were compared to NPK(nitrogen, phosphat, and potash fertilizer) and PK treatment. The yield of lettuce in OC100 was similar to that of NPK treatment. In OC 50, 100 and 150 treatments, pH had a tendency to increase than that of NPK treatment. Nitrate nitrogen(NO₃-N) and electrical conductivity(EC) were similar to NPK treatment. These showed that nutrients from OC fertilizer were less likely to accumulate in soil than NPK. Also, use efficiency of nitrogen in OC100 treatment were similar to NPK treatment. These results suggest that OC application as the basal dressing at the 100% level could be best to prevent a nutrient accumulation of soil and to increase the yield and commercial quality for lettuce.