Rog-Young Kim

Change of Bioavailability in Heavy Metal Contaminated Soil by Chemical Amendment

Crop safety in heavy metal contaminated agricultural field has been a critical issue in Korea and various remediation methods are proposed for minimizing heavy metal transfer from soil to crops. The main objective of this research was to evaluate remediation efficiency of two chemical amendments, lime and steel slag, and to decide extractant for assessing bioavailability of heavy metals. In order to select optimum extractant for evaluating bioavailability of heavy metals, four different single extractants, HCl, DTPA, , , and sequential extraction method were examined. Both chemical amendments showed high immobilization effect for Cd (66%, ) and Pb (74%, ) in soil by HCl extractant. In terms of heavy metal concentration in rice grains, concentrations for Cd (77%, ) and Pb (82%, ) decreased, with addition of chemical amendments. HCl, DTPA, and sequential extractant showed the higher correlation between heavy metal concentration in soil and crops than others. These results indicated that they could be used for assessing bioavailability of heavy metals.

Effect of Suboptimal Nutritional Status on Mineral Uptake and Carbohydrate Metabolism in Tomato Plants

A suitable supply of mineral elements into shoot via a root system from growth media makes plants favorable growth and yield. The shortage or surplus of minerals directly affects overall physiological reactions to plants and, especially, strongly influences carbohydrate metabolism as a primary response. We have studied mineral uptake and synthesis and translocation of soluble carbohydrates in N, P or K-deficient tomato plants, and examined the interaction between soluble carbohydrates and mineral elements. Four-weeks-old tomato plants were grown in a hydroponic growth container adjusted with suboptimal N (0.5 mmol L -1 Ca(NO₃)₂ㆍ4H₂O and 0.5 mmol L-1 KNO₃), P (0.05 mmol L -1 KH₂PO₄), and K (0.5 mmol L -1 KNO₃) for 30 days. The deficiency of specific mineral element led to a significant decrease in its concentration and affected the concentration of other elements with increasing treatment period. The appearance of the reduction, however, differed slightly between elements. The ratios of N uptake of each treatment to that in NPK sufficient tomato shoots were 4 (N deficient), 50 (P deficient), and 50% (K deficient). The P uptake ratios were 21 (N deficient), 19 (P deficient), and 28% (K deficient) and K uptake ratios were 11 (N deficient), 46 (P deficient), and 7% (K deficient). The deficiency of mineral elements also influenced on carbohydrate metabolism; soluble sugar and starch was substantially enhanced, especially in N or K deficiency. In conclusion, mineral deficiency leads to an adverse carbohydrate metabolism such as immoderate accumulation and restricted translocation as well as reduced mineral uptake and thus results in the reduced plant growth.

Understanding of a Korean Standard for the Analysis of Hexavalent Chromium in Soils and Interpretation of their Results

A new Korean standard for the determination of Cr(VI) in soils has been officially published as ES 07408.1 in 2009. This analytical method is based on the hot alkaline digestion and colorimetric detection prescribed by U.S. EPA method 3060A and 7196A. The hot alkaline digestion accomplished using 0.28 M and 0.5 M NaOH solution (pH 13.4) at determines total Cr(VI) in soils extracting all forms of Cr(VI), including water-soluble, adsorbed, precipitated, and mineral-bound chromates. This aggressive alkaline digestion, however, proved to be problematic for certain soils which contain large amounts of soluble humic substances or active manganese oxides. Cr(III) could be oxidized to Cr(VI) by manganese oxides during the strong alkaline extraction, resulting in overestimation (positive error) of Cr(VI). In contrast, Cr(VI) reduction by dissolved humic matter or Fe(II) could occur during the neutralization and acidic colorimetric detection procedure, resulting in underestimation (negative error) of Cr(VI). Futhermore, dissolved humic matter hampered the colorimetric detection of Cr(VI) using UV/Vis spectrophotometer due to the strong coloration of the filtrate, resulting in overestimation (positive error) of Cr(VI). Without understanding the mechanisms of Cr(VI) and Cr(III) transformation during the analysis it could be difficult to operate the experiment in laboratory and to evaluate the Cr(VI) results. For this reason, in this paper we described the theoretical principles and limitations of Cr(VI) analysis and provided useful guidelines for laboratory work and Cr(VI) data analysis.

Toxicity Assessment of Silver Ions Compared to Silver Nanoparticles in Aqueous Solutions and Soils Using Microtox Bioassay

This study was conducted to assess the microbial toxicity of ionic silver solution () and silver nanoparticle suspension () based on the Microtox bioassay. In this test, the light inhibition of luminescent bacteria was measured after 15 and 30 min exposure to aqueous solutions and soils spiked with a dilution series of and . The resulting dose-response curves were used to derive effective concentration (EC25, , EC75) and effective dose (, , ) that caused a 25, 50 and 75% inhibition of luminescence. In aqueous solutions, value of after 15 min exposure was determined to be and remarkably lower than value of with . This revealed that was more toxic to luminescent bacteria than . In soil extracts, however, value of with 196 mg kg-1 was higher than value of with , indicating less toxicity of in soils. The reduced toxicity of in soils can be attributed to a partial adsorption of ionic on soil colloids and humic acid as well as a partial formation of insoluble AgCl with NaCl of Microtox diluent. This resulted in lower concentration of active Ag in soil extracts obtained after 1 hour shaking with than that spiked with . With longer exposure time, EC and ED values of both and decreased, so their toxicity increased. The toxic characteristics of silver nanomaterials were different depending on existing form of Ag (, ), reaction medium (aqueous solution, soil), and exposure time.

Evaluation of Soil and Fertilizer Management Techniques Applied by Farmers in Forcing and Semi-forcing Cucumber Cultivation Facilities

These days, agricultural products cultivated in facilities occupy the highest percentage of agricultural output price. Specifically cucumbers have been one of the crops that farmers prefer to growing, because their prices were high. However, cucumber crop is sensitive to the soil and environments and it requires the exact crop management. In order to establish cultivation techniques for cucumbers, the current situation of cucumber cultivation was surveyed from ten cucumber farmlands; five farmlands of cucumber cultivation in forcing and five of semi-forcing practicing systems, respectably. The soil conditions were alluvial or valley in soil topology, moderately or poorly drainage in soil drainage classes, coarse loamy in soil texture family. Soil was managed with deep plowing combined with application of basal fertilizers such as compost, rice straw, oil cake, wood chip and chemical fertilizer. The whole soil was prepared in uniformly with rotary. Three major nutrients ()of basal application were 815-464-529 kg in forcing and 197-135-151 kg in semi-forcing cultivation. Top dressing of fertilizer was supplied in fertigation system of macro and micro elements in 2~3 day interval with water irrigation. The average yields of cucumbers were with 381,000 thousand won in average gross profit (AGP) in forcing cultivation and with 177,000 thousand won in AGP in semi-forcing cultivation. Cucumber production during the winter season was considered to increase the gross profit because cucumber price tends to stay in high level during this time. The accumulation of soil chemicals like EC, available and exchangeable cations could be controlled by rice straw application. The rice straw application increased soil temperature during the winter season, in exchange of soil air, and in extension of plant roots. In addition, the rice straw application somewhat affected decrease of salts accumulation.

Determination of Exchangeable Cations in Soils Affected by Different Types of Salt Accumulation

Exchangeable cations are often overestimated especially in salt-affected soils due to the presence of high levels of soluble ions in soil solution. Thus, quantitative analysis of the soil exchangeable cation based on ammonium acetate extraction method {(Exch. Cation)total} requires additional process to remove the free ions (pre-washing) in soil with distilled water or alcohol {(Exch. Cation)pw} or subtraction of the soluble ion contents from the total exchangeable cations {(Exch. Cation)ref}. In this research, we compared the three different methods for the determination of exchangeable cations in soils affected by different types of salt accumulation such as the soils from upland, plastic film house, and reclaimed tidal land. In upland soils, non-saline and non-sodic soils, the regular ammonium acetate extraction method did not have any problem to determine the content of exchangeable cations without any additional process such as the pre-washing method or the subtraction method. However, the contents of exchangeable cations in the salt-affected soils might be determined better with the pre-washing method for the plastic film house soils and with the subtraction method for the reclaimed tidal land soils containing high Na.

Chinese Cabbage Growth Effected by Black Vinyl Mulching and Organic Fertilizer Application in Spring Season

Organic fertilizers application has become a popular alternatives to reduce the dependence on chemical fertilizer in Korean farming systems. In this study, we evaluated the nitrogen (N) use efficiency and growth performance of Chinese cabbage grown by black vinyl mulching after application of organic and chemical fertilizers compared with no-mulching. The treatments included chemical fertilizer alone as control (NPK, N- : ), organic fertilizer alone (OF100), 70% organic fertilizer and 30% chemical fertilizer (OF70+N30), and 30% organic fertilizer and 70% chemical fertilizer (OF30+N70), which were all applied in the no-mulching plots and in plots with black vinyl mulching. Daily means soil temperature was higher in the black vinyl mulched treatments throughout the 54 days compared with no-mulched treatments. OF100 with black vinyl mulching gave highest soil inorganic N content. Also, Chines cabbage yield increased 46% by black vinyl mulched compared with no-mulching in OF100 treatment. Without mulching, N use efficiency was, 44, 26, 29, and 27% in NPK, OF100, OF70+N30, and OF30+N70, respectively. However, black vinyl mulching much more effectively increased N use efficiencies by 56, 55, 51, and 39% in the same treatments in the order as mentioned above. Conclusively, combined organic and chemical fertilizers application with black vinyl mulching could be good practical technique to reduce a amount of used nitrogen because of its greater ability to enhance N use efficiency.

Macro and Micro Nutrient Contents in Leaves of Greenhouse-grown Cucumber by Growth Stages

In order to estimate the inorganic nutrient content in cucumber leaves at respective growth stages under greenhouse conditions, we investigated five cucumber farms practicing a forcing cultivation system with nine-month growth period and another five cucumber farms practicing a semiforcing cultivation system with six-month growth period. The cucumber yield in forcing and semiforcing cultivation systems amounted to 14.8 ton and 10.7 ton , respectively. Soils between two different cultivation systems showed no significant differences in pH, organic matter contents and exchangeable cation contents during early growth stage, whereas EC, -N and available contents were higher in soils of semiforcing cultivation systems. Suitable soil temperature was well provided by forcing cultivation. The highest NPK contents in leaves were observed in 60~80 days after planting for forcing systems and in 100 days after planting for semiforcing systems. Thereby forcing cultivation systems showed somewhat higher NPK contents. Ca and Mg contents in cucumber leaves did not significantly change during the growth period in forcing systems, while semiforcing systems showed the highest contents of Ca and Mg in 80~100 days after planting. Fe, Mn and Zn contents in leaves also did not significantly change during the growth period, whereas Mn contents were slightly higher in forcing systems due to lower soil pH. B contents in leaves were higher in semiforcing systems because of higher available B contents in soil.

Effects of Rape Residue as Green Manure on Rice Growth and Weed Suppression

Rape residue as green manure is an emerging alternative of chemical fertilizer to improve soil quality and crop productivity. Objective of this research was to evaluate the effectiveness of rape residue as green manure on reduction of chemical fertilizer and suppression of weed occurrence in rice-rape double cropping system. Greenhouse experiment was conducted with four treatments: the combination of rape residue and three different N application rates (0, 30 and 70% of recommended application rate (7.8 kg N )) and 100% chemical fertilizer as a control. No difference in rice clum length was observed for all treatments, while panicle length was highest in a treatment of rape residue+70% chemical fertilizer (Rape+70%CF). In addition, rice grain weight at a Rape+70%CF treatment increased by 19% compared to the control. This treatment also reduced weed density and biomass by 58 and 53%, respectively, compared to the control. Our results suggest that use of rape residues as green manure is an environment friendly and effective way to reduce chemical fertilizer and to enhance crop productivity in rice-rape double cropping system in Korea.

Changes in Phytoavailability of Cadmium, Copper, Lead, and Zinc after Application with Eggshell in Contaminated Agricultural Soil

Agricultural soils surrounding mine areas in South Korea are often contaminated with multiple metals such as Cd, Pb and Zn. It poses potential risks to plants, soil organisms, groundwater, and eventually human health. The aim of this study was to examine the changes in phytoavailability of Cd, Cu, Pb and Zn after application with calcined eggshell (CES; 0, 1, 3, and 5% W/W) in an agricultural soil contaminated by mine tailings. The contents of Cd, Cu, Pb and Zn in soils were 8.79, 65.4, 1602, and 692 mg kg -1 (aqua regia dissolution), respectively. The experiments were conducted with lettuce (Lactuca sativa L. var. longifolia) grown under greenhouse conditions during a 30-d period. NH₄NO₃ solution was used to examine the mobile fraction of these metals in soil. The application of CES dramatically increased soil pH and inorganic carbon content in soil due to CaO and CaCO₃ of CES. The increased soil pH decreased the mobile fraction of Cd, Pb, Zn: from 3.49 to -1 for Zn with increasing treatment of CES from 0 to 5%. In contrast, the mobile fraction of Cu was increased from 0.05 to 3.08 mg kg -1 , probably due to the formation of soluble CuCO₃ 0 and Cu-organic complex. This changes in the mobile fraction resulted in a diminished uptake of Cd, Pb and Zn by lettuce and an increased uptake of Cu: from 4.19 to -1 dry weight (DW) for Cd, from 0.78 to -1 DW for Zn and conversely, from 3.79 up to 8.21 kg -1 DW for Cu. The increased contents of Cu in lettuce shoots did not exceed the toxic level of > 25 mg kg -1 DW. The mobile contents of these metals in soils showed a strong relationship with their contents in plant roots and shoots. These results showed that CES effectively reduced the phytoavailability of Cd, Pb, and Zn to lettuce but elevated that of Cu in consequence of the changed binding forms of Cd, Cu, Pb, and Zn in soils. Based on these conclusions, CES can be used as an effective immobilization agent for Cd, Pb and Zn in contaminated soils. However, the CES should be applied in restricted doses due to too high increased pH in soils.