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This study was conducted to investigate variations in the stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) of agricultural soils under different land uses (i.e., paddy, upland, and orchard) that subjected to different fertilization management (i.e., 15 N-depleted synthetic fertilizer and 13C- and 15 N-enriched livestock manure and compost application). Soil samples were collected from paddy, upland, and orchard fields in an intensive agricultural area, and forest (pine and oak) soils were additionally included as background soils. The C and N concentrations and isotope ratios of both bulk and water-extractable soil fractions were analyzed. The δ13C and δ15N of agricultural soils were higher than those of forest soils, reflecting repeated manure and compost applications (for both δ13C and δ15N) and higher N loss (for δ15N) in agricultural soils. Among agricultural soils, orchard (− 24.2‰ for δ13C and + 10.6‰ for δ15N) and upland (− 25.4‰ and + 9.6‰, respectively) soils which received higher rates of manure and compost were more enriched with 13C and 15N compared with paddy (− 28.0‰ and + 4.9‰, respectively). Such differences in the isotopic compositions among agricultural soils were also found for water-extractable soil fractions. Our study suggests that δ13C and δ15N of agricultural soils are affected by land use types with different fertilization management, particularly application of 13C- and 15 N-enriched livestock manure and compost. The δ13C and δ15N could be used as chemical indicators to evaluate the effects of the application of manure and compost on soil C and N dynamics.

We compared the patterns of natural abundance of nitrogen (N) isotope ratio (δ15N) of total soil N among cropland, forest, and grassland soils, with special interests in the effects of farming system on cropland and grassland, and climate zone on forest soils, as well as the general effect of land-use change and site disturbance. We analyzed data on δ15N of terrestrial N sources (n = 532), cropland (n = 168), forest (n = 227 for organic and 428 for mineral soil layers), and grassland soils (n = 624). Forest soils had the lowest δ15N (– 1.0 ± 0.2‰ and + 3.1 ± 0.2‰ for mineral and organic soil layers, respectively), reflecting the influence of the 15N-depleted source N and the more closed nature of the N cycle. Tropical forest soil had higher δ15N than other climate zones, reflecting the influence of the high N availability and loss in tropical forests. The low δ15N in subtropical forest soils likely reflected the influence of the high rate of deposition of 15N-depleted N. The δ15N of cropland (+ 5.0 ± 0.2‰) and grassland (+ 6.2 ± 0.1‰) soils was greater with manure than with synthetic fertilizer applications. Soil δ15N was also affected by land-use change and was often increased (followed by progressive decreases) by site disturbance. Land-use type and land management effects on soil δ15N reflect changes in both the N sources and loss, while land disturbance effects are primarily associated with the degree of N loss. We also conclude that subtropical forest soil δ15N is affected by the high rate of atmospheric N deposition.

Lead (Pb) sorption capacity (PbSmax) and distribution in chemical and particle-size fractions of six soils with different physico-chemical properties were investigated to explore the principal properties of soils that affect Pb sorption. A series of experiments of Pb sorption and soil chemical and particle-size fractionation of sorbed Pb were conducted with six soils of different texture, mineralogy, organic matter concentration, cation exchange capacity (CEC), and Fe-Mn concentrations. Soils either developed from volcanic ash or containing smectite showed relatively higher PbSmax than the other soils. Across the soils, clay content, organic matter concentration, and total Fe concentrations were significantly (p

Fly 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. Rice 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. The 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. Our 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.

Fly ash can reduce CO2 emission from soils via biochemical (i.e., inhibition of microbial activity) and physicochemical (i.e., carbonation) mechanisms. This study investigated the effects of fly ash amendment on biochemical and physicochemical reduction in CO2 emission from normal and saline soils. The physicochemical mechanisms of reduction in CO2 emission by fly ash were estimated in a batch experiment with carbonate solution as a CO2 source by the scanning electron microscope (SEM) and inductively coupled plasma analyses. Biochemical mechanisms of reduction in CO2 emission by fly ash were investigated in a 3-day laboratory incubation experiment with normal and saline soils in the absence and presence of fly ash. Finally, the effects of fly ash amendment at a variety rate from 2 to 15 % (w/w) on CO2 emission from normal and saline soils in the presence of additional organic carbon source (glucose) were investigated through a 15-day laboratory incubation study. In the batch experiment with carbonate solution, both the SEM image of fly ash and changes in soluble Ca and Mg concentrations during reaction with carbonate suggested that the formation of CaCO3 and MgCO3 via carbonation was the principal physicochemical mechanism of carbonate removal by fly ash. In the 3-day incubation study conducted to examine biochemical mechanisms of reduction in CO2 emission by fly ash, microbial respiration of saline soil was inhibited (P

Purpose Since substrate quality can influence the C mineralization pattern of compost in soils, proper selection of compost is important in increasing soil organic carbon (SOC) levels. This study investigated the effect of substrate quality of livestock manure composts on compost C mineralization and retention in soils.

Although nitrification plays a key role in the fate of soil nitrogen (N) under global warming, little information is available for the nitrifiers’ response to changing temperatures. Nitrogen isotope fractionation associated with nitrification can be a proxy of nitrifiers’ sensitivity to changing temperature. We hypothesized that the temperature-induced balance between the transport of substrate NH 4 + into the microbial cell (supply) and the intracellular NH 4 + oxidation (consumption) governs the intracellular NH 4 + concentration and then affects nitrification rates and associated isotope fractionations. This study was conducted to understand the microbial response of NH 4 + oxidation to changing temperatures by examining the effect of changing temperature on nitrification rate and apparent isotope fractionation. A batch aerobic incubation was conducted with a sandy loam soil over 150 days at three different soil temperatures: 10, 20, and 30°C. After applying ammonium sulfate, we analyzed the temporal variations in the concentrations and the isotopic compositions of soil inorganic N and calculated nitrification rates and isotope fractionation factors. Net nitrification rate increased with increasing soil temperature, while apparent isotope fractionation factors decreased. The increased net nitrification rate was attributable to both an increase in NH 4 + transport across cell membranes and an increase in intracellular enzymatic activity. Meanwhile, the decreased apparent isotope fractionation suggested that NH 4 + oxidation rate became faster than NH 4 + transport rate, resulting in a decrease in intracellular NH 4 + concentrations. Although intracellular NH 4 + transport and oxidation were not directly measured in this study, it is concluded that NH 4 + oxidation is more sensitive to increasing temperature than NH 4 + transport judging from the apparent N isotopic fractionation associated with NH 4 + concentration changes (mainly by nitrification) under different temperature regimes.

Purpose The chemistry of annual tree growth rings is affected by precipitation pH, and tree rings store information on environmental conditions at the time of ring formation. The purpose of this study was to evaluate the potential use of tree ring chemistry data in estimating historical precipitation pH using the relationship between precipitation pH and tree ring chemistry.

To more efficiently utilize composts as N sources while minimizing the environmental impact, it is necessary to understand the effects of compost type on N mobility in compost-amended soil with different characteristics. The objectives of this study are to investigate the effects of livestock manure composts on N leaching from soils and to identify the principal physicochemical variables of the composts that affect N leaching. A combination leaching-incubation experiment using seven livestock manure composts and three soils (Inceptisol, Ultisol, and Andisol) with different characteristics was conducted for 19 weeks. Leachates were collected periodically and analyzed for various forms of N (NH 4 + , NO 3 − , organic N, and total N). The effects of compost type on N leaching were assessed by analysis of variance and correlation between N leaching amounts and compost variables (pH, total C, total N, C/N, and various forms of extractable N). Initial flush of N leaching at the first leaching event conducted after 1-week incubation was observed probably due to mineralization of readily decomposable N pool; the amount of N leached at 1-week incubation accounted for more than 50% of cumulative amount of N leached through 19-week incubation. Among the various compost variables tested, only total N concentration of compost was significantly (P Ultisol (33.9 to 64.7 mg N) > Inceptisol (12.8 to 31.7 mg N) being affected by soil N availability. The significant effects of compost and soil types suggested that not only soils but also composts characteristics needs to be considered when establishing the compost application guidelines. Particularly when compost characteristics are considered, total N rather than the mineral N concentration of composts can be used to predict the N leaching potential in composts-amended soils.