Song Yeob Kim

Long-Term Inorganic Fertilization Effect on the Micronutrient Density in Soil and Rice Grain Cultivated in a South Korean Paddy Field

ABSTRACT Soil fertility exerts a direct influence on the essential micronutrient contents of food crops. The focus in this study was on the role that long-term inorganic fertilization (nitrogen (N), phosphorous (P) and potassium (K)) plays in increasing the micronutrient output of the paddy cropping system. After more than 45 years of inorganic fertilizer application, the combined application of fertilizers (PK > NP > NK) substantially increased As (arsenic), B (boron), Cd (cadmium), Co (cobalt), Cr (chromium), Cu (copper), Fe (iron), Mn (manganese), Mo (molybdenum), Ni (nickel), Se (selenium), V (vanadium) and Zn (zinc) density in the soil and rice grain. Optimized and continuous application of PK fertilizers increased the overall micronutrient densities in rice milling fractions (grain and bran). Micronutrient concentrations were usually the highest in bran. Both grain and bran were rich in Fe, Mn and Zn. Correlation analysis indicated that soil pH and organic matter exert a significant and direct effect on the micronutrient concentration of rice. Although long-term fertilization enhanced the proportion of micronutrients in rice grain, the levels were still much lower than the recommended dietary intake levels for micronutrients. We therefore suggest high consumption levels of brown rice (with micronutrient-dense bran layer) because they may increase the daily intake level of micronutrients and meet the nutritional requirements that people need for sound health.

Effect of molybdenum on nodulation, plant yield and nitrogen uptake in hairy vetch (Vicia villosa Roth)

Abstract Hairy vetch (Vicia villosa Roth) is a leguminous cover crop that is generally used as a green manure to sustain soil health in arable land. Molybdenum (Mo) acts as a cofactor for the nitrogenase (NA) and nitrate reductase (NR) enzymes, which are important for nitrogen (N) fixation, nitrate reduction and N transport in plants. In this study, we applied various doses of Mo to soil to evaluate their efficacy on nodulation, nodule characteristics and biomass production of hairy vetch. Mo application increased the number and size of nodules and NA and NR enzyme activity in hairy vetch. This increase in enzyme activity increased N assimilation and led to higher biomass yield. Plants grown in soil that received 0.5 mg Mo kg−1 showed optimal physical and biochemical properties in nodules, and these properties may explain the increased N fixation in hairy vetch. Higher Mo doses (1.0 mg kg−1) led to the deterioration of nodule structure and, hence, reduced enzymatic activity in plants. The 16S rRNA gene sequencing and cluster analysis showed that the bacterial isolates found in the nodules of hairy vetch roots belonged to the Rhizobiaceae family and shared high sequence similarity with Rhizobium leguminosarum and Agrobacterium tumefaciens. Application of 0.63 mg Mo kg−1 to soil was the optimum dose to maximize the biomass yield of hairy vetch.

Does long-term application of fertilizers enhance the micronutrient density in soil and crop?—Evidence from a field trial conducted on a 47-year-old rice paddy

PurposeTo date, how optimized, long-term fertilizer application affects the concentration of micronutrients in the milling fractions of rice grains (bran or edible grain part) with details of their dietary exposure upon consumption has not been much explored. In this study, we report results from a 47-year-old field experiment conducted in rice paddy.Materials and methodsSoil and rice grain samples were collected from a 47-year-old long-term fertilization field trial (treatments included NPK, compost, NPK + compost, and no fertilizer/control) conducted at Miryang, South Korea. Density of total micronutrients namely As, B, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Se, V, and Zn in soil and rice milling fractions were quantified using ICP-MS and inductively coupled plasma optical emission spectrometry (ICPOES). Concentrations of the exchangeable and water-soluble micronutrients in the soil were also determined by ICP-MS and ICPOES. Potentially bioavailable soil micronutrient levels, micronutrient transfer from soil to rice grain, and dietary intake level of micronutrients by rice consumption were calculated. The correlations between soil properties and crop micronutrient availability were analyzed.Results and discussionIn general, long-term fertilization (NPK + compost > NPK > compost) yielded a significant effect on grain As, B, Co, Cr, Cu, Fe, Mn, Mo, Ni, Se, V, and Zn fortification and promoted bioavailable soil micronutrient density. The highest contributors to micronutrient intake could be rice grains from long-term NPK + compost fertilized plots. However, estimated levels were still lower than the recommended dietary intake levels for micronutrients established by FAO/WHO. From our study, it is important to note that 80% of total micronutrient content (Fe, Mn, Zn, Co, Ni, Se, and V) were concentrated in rice bran. This has important implications for human nutrition and health. Furthermore, correlation analysis indicates that available soil P could be considered a predictor of crop micronutrient intake.ConclusionsOptimized long-term application of compost with NPK fertilizers to soils is a potential grain fortification strategy. Long-term fertilization will not reasonably benefit individuals who consume only white rice, because bran with enriched micronutrients will be removed by milling. We suggest replacing the consumption of white rice by brown rice so that individuals have a better micronutrient intake.

Free Amino Acid Composition of Korean Spinach (Spinacia oleracea) Cultivars as Influenced by Different Harvesting Time

BACKGROUND: There is lack of comprehensive compositional data of the amino acid profile of spinach with regard to different cultivars. A more detailed knowledge in this aspect will be of benefit in the future selection of spinach genotypes with improved nutritional quality.METHODS AND RESULTS: The effects of cultivar type (Jeoncheonhu, Sagyejul, Namdongcho and Mustang) and harvest time (79th, 116th and 145th days after sowing or DAS) on the concentrations of free amino acids in field-grown spinach (Spinacia oleracea) were examined. About 35 different free amino acids were detected and quantified by the amino acid analyzer. Glutamic acid and proline were identified as the major amino acids, while α -aminoadipic acid and α-aminobutyric acid were present in much lower concentrations. Spinach constituted 1468.4 mg/100 g total free amino acids (TAA), of which essential amino acids, neutral/acidic amino acids and sulphur containing amino acids constituted around 15, 45 and 2% of the TAA, respectively. The most limiting amino acids among the leafy vegetables - cysteine was recorded only in Mustang harvested at 116 DAS. Free amino acid contents did not differ significantly among the spinach cultivars and also at different harvest times.CONCLUSION: The data show that, either of the spinach cultivars, preferably Mustang harvested on or after 116 DAS can serve as a significant source of nutritionally relevant amino acids to meet the demand of the growing populations.

Agriculturally relevant microbial community structure in long-term fertilized paddy soils as revealed by phospholipid fatty acid (PLFA) and pyrosequencing analyses

ABSTRACT Evidence linking the direct impact of fertilization on diversity, function and phylogeny of N-fixing and P-solubilizing bacteria in rice ecosystem is lacking. This study using phospholipid fatty acid (PLFA) and 454 pyrosequencing analyses was conducted in long-term fertilized (NP, NK, PK, NPK, compost, NPK + compost) paddy field soil, the objective being to examine the community structure of the functionally important beneficial soil microbial communities. Maximum total PLFAs were observed in organic fertilizer treatments, viz. compost (881.5 ± 11.1 nmol g−1) and NPK + compost (866.5 ± 10.8 nmol g−1). Pyrosequencing revealed that the overall bacterial and eukaryal compositions at phyla level were not significant for all treatments, while the distribution of each phyla differed. Specifically, the major classified bacterial phyla for all treatments were Proteobacteria, Actinobacteria, Cyanobacteria and Firmicutes. Supported by the high throughput sequencing approach we hereby propose that the mechanism of N and P cycling under long-term balanced fertilization in a rice ecosystem is largely governed by microbes, notably by the free living N-fixing and/or P solubilizing heterocystous and/or non-heterocystous cyanobacteria, autotrophic bacteria and heterotrophic bacteria. The current study thus proposes that balanced fertilizers may be used without detrimental effects on rice soils in the long-term.

Determination of Main Indicator for the Changes of Chemical Properties in Greenhouse Soils

BACKGROUND: Changes in Korea`s agricultural soil properties were analyzed at a four-year interval from 1999 to 2002 on a national scale and used as basis for the determination of the appropriate agricultural policy on maintaining food safety and soil quality. The scope of this study ideally requires sampling thousands of paddy, greenhouse, upland and orchard land across the country, however, due to limitations in economic and manpower resources, it was deemed necessary to reduce sampling site to greenhouse soil. In this study, we try to investigate the applicability of cultivated crops as criteria for selecting representing fields in greenhouse soils.METHODS AND RESULTS: Soil samples were collected from red pepper, oriental melon, watermelon and strawberry cultivated soil. Principal components analysis (PCA) was performed on soil chemical properties of the selected fields: pH, electron conductivity (EC), available phosphate (Av-P2O5), organic matter (OM), and exchangeable cation (Ex.-K, Ca, and Mg). Soil chemical properties of oriental melon cultivated soil was separated from red pepper, watermelon, and strawberry cultivated soil on PC1 and red pepper cultivated soil was separated from watermelon cultivated soil on PC2. Position on PC1 was strongly correlated with pH, Ex.-Ca and Ex.-Mg and position on PC2 was strongly correlated with OM and Av-P2O5.CONCLUSION: The soil chemical properties of greenhouse soil was assorted amongst the different crops. Therefore, the cultivated crops as a criteria for the selection of representative field in greenhouse soil would be used in the future.