Sang-Sun Lim

Nitrogen transformations and ammonia volatilization losses from 15N-urea as affected by the co-application of composted pig manure

Co-application of composted manure (compost) and urea is considered an environment-friendly fertilization practice; however, the high urease activity in compost may stimulate NH3 volatilization and cause N loss from co-applied urea. To test the above hypothesis, we investigated the fate of urea co-applied with compost in a loam-textured soil through two laboratory incubation experiments. Urea (150 mg N kg-1) was co-applied with 0, 4.9, 9.8, and 14.6 g of compost (oven-dry basis) kg-1 of soil, designated as treatments UC0, UC1, UC2, and UC3, respectively. Co-application of compost and urea enhanced urea hydrolysis and increased the 1st order rate constant of urea hydrolysis from 0.047 h-1 in the UC0 to 0.139 h-1 in the UC3 treatments. Soil pH increased from 7.0 for UC0 to 7.6 for UC3, leading to greater NH3 volatilization (up to two times more) in the soils receiving 9.8 g kg-1 or more of compost. Compost co-application also increased the immobilization of urea-derived N, probably because the organic matte...

Fertilizer and Organic Inputs Effects on CO 2 and CH 4 Emission from a Soil under Changing Water Regimes

BACKGROUND: Agricultural inputs (fertilizer and organic inputs) and water conditions can influence and emission from agricultural soils. This study was conducted to investigate the effects of agricultural inputs (fertilizer and organic inputs) under changing water regime on and emission from a soil in a laboratory incubation experiment. METHODS AND RESULTS: Four treatments were laid out: control without input and three type of agricultural inputs (, AS; pig manure compost, PMC; hairy vetch, HV). Fertilizer and organic inputs were mixed with 25 g of soil at 2.75 mg N/25 g soil (equivalent to 110 kg N/ha) in a bottle with septum, and incubated for 60 days. During the first 30-days incubation, the soil was waterlogged (1 cm of water depth) by adding distilled water weekly, and on 30 days of incubation, excess water was discarded then incubated up to 60 days without addition of water. Based on the redox potential, water regime could be classified into wetting (1 to 30 days), transition (31 to 40 days), and drying periods (41 to 60 days). Across the entire period, and flux ranged from 0 to 13.8 mg /m/day and from 0.4~1.9 g /m/day, and both were relatively higher in the early wetting period and the boundary between transition and drying periods. During the entire period, % loss of C relative to the initial was highest in HV (16.4%) followed by AS (8.1%), PMC (7.5%), and control (5.4%), indicating readily decomposability of HV. Accordingly, both and fluxes were greatest in HV treatment. Meanwhile, the lower flux in AS and PMC treatments than the control was ascribed to reduction in generation due to the presence of oxidized compounds such as , , , and that compete with precursors of for electrons. CONCLUSION: Green manure such as HV can replace synthetic fertilizer in terms of N input, however, it may increase emission from soils. Therefore, co-application of green manure and livestock manure compost needs to be considered in order to achieve satisfactory N supply and to mitigate and emission.

Kinetic Responses of Soil Carbon Dioxide Emission to Increasing Urea Application Rate

BACKGROUND: Application of urea may increase CO2 emission from soils due both to CO2 generation from urea hydrolysis and fertilizer-induced decomposition of soil organic carbon (SOC). The objective of this study was to investigate the effects of increasing urea application on CO2 emission from soil and mineralization kinetics of indigenous SOC. METHODS AND RESULTS: Emission of CO2 from a soil amended with four different rates (0, 175, 350, and 700 mg N/kg soil) of urea was investigated in a laboratory incubation experiment for 110 days. Cumulative CO2 emission (Ccum) was linearly increased with urea application rate due primarily to the contribution of urea-C through hydrolysis to total CO2 emission. First-order kinetics parameters (C0, mineralizable SOC pool size; k, mineralization rate) became greater with increasing urea application rate; C0 increased from 665.1 to 780.3 mg C/kg and k from 0.024 to 0.069 day -1 , determinately showing fertilizer-induced SOC mineralization. The relationship of C0 (non-linear) and k (linear) with urea-N application rate revealed different responses of C0 and k to increasing rate of fertilizer N. CONCLUSION(s): The relationship of mineralizable SOC pool size and mineralization rate with urea-N application rate suggested that increasing N fertilization may accelerate decomposition of readily decomposable SOC; however, it may not always stimulate decomposition of non-readily decomposable SOC that is protected from microbial

Soil and Compost Type Affect Phosphorus Leaching from Inceptisol, Ultisol, and Andisol in a Column Experiment

A column leaching experiment using three soils (Inceptisol, Ultisol, and Andisol) and seven livestock manure composts that had different characteristics was conducted for 19 weeks to investigate the interactive effects of composts and soils on the phosphorus (P) leaching potential of compost-amended soils and to identify the principal variables that affect P leaching. Cumulative total P leaching (TPcum) tended to increase with increasing total and available P concentration in the soils. Among various compost properties, total P concentration was positively correlated with TPcum from the compost-amended soils, except for the Andisol, which has a high P-sorption capacity. There was no significant relationship between TPcum and water-extractable P concentration of the composts, suggesting that total P rather than inorganic P concentration of composts may be successfully used in predicting P leaching potential from compost-amended soils except for soils that have a high P-sorption capacity, as in Andisol.

The Role of Organic Amendments with Different Biodegradability in Ammonia Volatilization during Composting of Cattle Manure

This study was conducted to investigate the roles of co-existed organic materials (OM) with different biodegradability in composting of cattle manure in terms of emission and volatilization. Either sawdust (SD, low biodegradability) or rice bran (RB, high biodegradability) was mixed with cattle manure at a various rate and the amounts of emission and volatilization were determined periodically during 4 weeks of composting. Percentage of dry matter loss during the composting period was also calculated. The amount of emitted increased with increasing rate of OM and was significantly (P immobilization and thus decrease concentration that is susceptible to ammonia volatilization. Binding of on to phenolic compounds of SD may also contribute to the decrease in concentration. Meanwhile, as RB has a relatively low C/N ratio, remineralization of immobilized could increase concentration as high as the level for the occurrence of ammonia volatilization. Therefore, our study suggests that OM which is resistant to biodegradation can reduce volatilization largely by physico-chemical pathways across the entire composting period and that easily biodegradable OM can retard volatilzation via microbial immobilization in the early period of composting followed by rapid remineralization, leading to substantial volatilization of in the middle stage of composting.

Fly ash and zeolite amendments increase soil nutrient retention but decrease paddy rice growth in a low fertility soil

PurposeFly ash (FA) and zeolite (Z) are known to increase nutrient retention in paddy soils through the immobilization of phosphorus (P) by FA and nitrogen (N) by Z. However, there is a possibility that the co-application of the amendments may hamper rice growth due to reduced availability of the nutrients. This study was conducted to investigate the effects of the co-application of FA and Z on soil N and P availability and rice growth.Materials and methodsRice was cultivated in soils without the amendment (control) and with the amendment: FA alone, Z alone, and both FA and Z. Tiller number, dry matter (DM), rice uptake of N and P, and soil N and P concentrations were determined.Results and discussionThe application of FA and Z increased N and P concentrations in the soils; however, such increased nutrient retention did not translate to DM increases. Results suggested that reduced mobility of nutrients hampered tillering in the early growth period, eventually leading to a reduction in DM accumulation at the harvest. Due to the nutrient limitation caused by FA and Z, the rice grown with both FA and Z did not survive at the harvest.ConclusionsOur study shows that the application of FA and Z does not always improve rice growth due to nutrient limitation, especially in a low fertility soil. Furthermore, the co-application of FA and Z should be avoided, as the negative impact of FA or Z on nutrient limitation became more severe when FA and Z were co-amended.

Sand Mixing Improved Chloroform Fumigation Efficiency in the Determination of Microbial Biomass Carbon of Water-Saturated Soils

Sand mixing effects on chloroform fumigation–extraction (CFE) efficiency in the determination of soil microbial biomass carbon (MBC) of water-saturated soils were investigated in two soils with different soil organic C (SOC) contents. Sand mixing increased (P < 0.001) MBC by up to 20% and 107% for the soil with low and high SOC values, respectively, suggesting that the creation of water-empty macropores by sand mixing improved chloroform fumigation efficiency. This study demonstrates that sand mixing is a feasible measure to improve CFE efficiency for the determination of the MBC of water-saturated soils, particularly for soils with a high SOC.

Fly Ash Application Effects on CH 4 and CO 2 Emission in an Incubation Experiment with a Paddy Soil

To estimate potential use of fly ash in reducing and emission from soil, and fluxes from a paddy soil mixed with fly ash at different rate (w/w; 0, 5, and 10%) in the presence and absence of fertilizer N () addition were investigated in a laboratory incubation for 60 days under changing water regime from wetting to drying via transition. The mean flux during the entire incubation period ranged from 0.59 to with a lower rate in the soil treated with N fertilizer due to suppression of production by that acts as an electron acceptor, leading to decreases in electron availability for methanogen. Fly ash application reduced flux by 37.5 and 33.0% in soils without and with N addition, respectively, probably due to retardation of diffusion through soil pores by addition of fine-textured fly ash. In addition, as fly ash has a potential for removal via carbonation (formation of carbonate precipitates) that decreases availability that is a substrate for reduction reaction (one of generation pathways) is likely to be another mechanisms of flux reduction by fly ash. Meanwhile, the mean flux during the entire incubation period was between 0.64 and , and that of N treated soil was lower than that without N addition. Because N addition is likely to increase soil respiration, it is not straightforward to explain the results. However, it may be possible that our experiment did not account for the substantial amount of produced by heterotrophs that were activated by N addition in earlier period than the measurement was initiated. Fly ash application also lowered flux by up to 20% in the soil mixed with fly ash at 10% through removal by the carbonation. At the whole picture, fly ash application at 10% decreased global warming potential of emitted and by about 20%. Therefore, our results suggest that fly ash application can be a soil management practice to reduce green house gas emission from paddy soils. Further studies under field conditions with rice cultivation are necessary to verify our findings.

Relationship between stability degree and chemical indices of livestock manure composts

Principal chemical indices of compost associated with compost stabilization were investigated using relationship between stability degree (SD) and chemical indices including pH, electrical conductivity (EC), total C, extractable C, decomposability, total N, NH4+, NO3−, molar ratio of NH4+ to NO3−, C/N, total P, and soluble P of various composts. Compost SD was positively (p<0.05) correlated with pH and C/N, and negatively (p<0.05) with EC, total N, and molar ratio of NH4+ to NO3−. However, the correlation with pH, C/N, and total N were in contradiction to other studies that reported an opposite relationship to ours, probably due to different properties of initial composting materials. Therefore, the present study in conjunction with other studies suggest that EC and the molar ratio of NH4+ to NO3− are the chemical indices closely associated with stabilization of composts regardless of composting materials.

Introducing trees to agricultural lands increases greenhouse gas emission during spring thaw in Canadian agroforestry systems

The role of agroforestry systems in mitigating greenhouse gas (GHG) emission from agricultural soils during spring thaw (early April to mid-May) has been poorly studied. Soil CO2, CH4 and N2O fluxes were measured from treed areas and adjacent herblands (areas without trees) during spring thaw in 2014 and 2015 at 36 agroforestry sites (12 hedgerow, 12 shelterbelt and 12 silvopasture) in central Alberta, Canada. Fluxes of those GHGs varied with agroforestry systems and land-cover types. We found greater CO2 emission (P < 0.001) and CH4 uptake (P < 0.05), but lower N2O emission (P < 0.01) in the silvopasture than in the hedgerow and shelterbelt systems, with no difference between the last two systems. Treed areas in general had greater CO2 emissions (P < 0.001) and CH4 uptake (P < 0.01), and lower N2O emissions (P < 0.001) than the herblands. Soil temperature, moisture content, organic C content and soil available N concentration affected GHG fluxes. The global warming potential (GWP) was greater (P < 0.05) in the silvopasture than in the hedgerow or shelterbelt systems over the two spring thaw seasons examined, and greater (P < 0.05) in the treed areas than in the herblands during the cool spring in 2015. However, the GWP per unit soil organic C was lower in the treed areas (0.004-0.101%) than in the herblands (0.005-0.225%). As compared to previously reported mean growing season GHG emission (15.4 g CO2-eq m-2 day-1), the GWP of these land uses during spring thaw was small (<5% of the annual GWP) due to the short spring period (6 weeks) and the small GHG emission (2.5 g CO2-eq m-2 day-1). Although GHG emissions during spring thaw were small compared to those in the growing season, they should not be ignored.