Effect Of Soil Moisture Regimes Research Articles

Soil enzyme activities in heavily manured and waterlogged soil cultivated with ryegrass (Lolium multiflorum)

Extended waterlogging (WL) conditions can alter soil enzyme activities and their role in maintaining healthy soils. We assessed the effects of soil moisture regimes (field capacity [FC] and WL) and phosphorus (P) rates (0, 15, 30, 45 kg available P ha–1) on ( i) soil enzymes and microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass P (MBP); and ( ii) dissolved organic carbon (DOC) and total dissolved nitrogen (TDN). The treatments were tested in a 4-month greenhouse experiment using intact soil columns under annual ryegrass ( Lolium multiflorum). WL decreased the activity of β-glucosidase and acid phosphomonoesterase but increased N-acetyl-β-glucosaminidase in soils. These changes were associated with changes in MBC, DOC, MBN, and TDN, but not MBP. Anoxic conditions in WL soil promote the activity of anaerobes and contribute to the reduction of Fe oxyhydroxides and the release of DOC, TDN, and P in the soil solution. The activity of the extracellular enzymes decreased in WL with additions of slurry indicating adequate supply of C, N, and P. Our results also showed that both enzyme activities and microbial biomass were restricted in the upper soil layer with limited downward movement along the soil profile. We can conclude that since these enzymes control the hydrolysis of cellulose, phosphomonoester, and chitin, soil moisture influences the direction and magnitude of C, N, and P in manured and waterlogged soil cultivated with ryegrass.

Phosphorus Mobility in Heavily Manured and Waterlogged Soil Cultivated with Ryegrass (Lolium multiflorum)

Extended waterlogging (WL) conditions in heavily manured soils can change soil phosphorus (P) dynamics. We assessed the effects of soil moisture regimes (field capacity (FC) and WL) and P rates on (i) dry matter (DM) yield and P offtake of ryegrass, (ii) changes in soil Fe3+, Fe2+, and soil P, and (iii) risk of P leaching. The treatments were tested in a four-month greenhouse experiment using intact soil columns and annual ryegrass (Lolium multiflorum). The DM yield and P offtake were lower under WL compared with FC. The concentration of Fe3+ was 1984 mg kg−1 (0–30 cm) under FC, but 1213 mg kg−1 at 0–5 cm and 2024 mg kg−1 at 25–30 cm depth under WL. The concentration of Fe2+ was 244 mg kg−1 (0–30 cm) under FC, but 2897 at 0–5 cm and 687 mg kg−1 at 25–30 cm under WL. The water extractable P (Pw) was 12.7 mg kg−1 at 0–5 cm and 9.5 mg kg−1 at 25–30 cm under FC, but 8.6 mg kg−1 at 0–5 cm and 10.5 mg kg−1 at 25–30 cm under WL. The P saturation index (PSI) was 27.2% at 0–5 cm and 17.4% at 25–30 cm under FC, but averaged 11.9% at 0–30 cm under WL. We can conclude that extended WL associated with flooding creates reducing conditions in the soil, thus decreasing the concentration of Fe3+, but increasing the concentrations of Fe2+ and the solubility of P which can exacerbate the risk of P loss with runoff and leaching.

Influence of soil moisture regimes, amendments and ageing on nickel availability in soils

In a range of nickel (Ni) spiked soils the effects of soil moisture regimes, amendments and ageing on Ni availability were estimated. The soil was spiked with Ni @ 0, 10 and 25 mg kg-1 soil through its nitrate solution. Lime (5%), farmyard manure (20 t FYM ha-1) and zinc (25 mg Zn kg-1) were added. The treated soil samples were incubated at 35 °C for 1, 45 and 90 days at field capacity and submerged soil moisture regimes. Available Ni was extracted with 0.005 M DTPA extractant and determined by ICP-AES. The results revealed that there was a temporal decrease in the available Ni with ageing and was in the order of 1 day > 45 days > 90 days. The magnitude of decrease in Ni availability was higher with the addition of amendments in the order of lime > FYM > Zn > unamended soil. The decrease in available Ni was further pronounced under submerged moisture regime than under field capacity. The mean per cent recovery of DTPA-Ni in the 10 mg Ni kg-1 spiked treatment decreased from 57.6 after 1 day of incubation to 29.3 and 26.8 after 45 and 90 days of incubation, respectively; whereas in the 25 mg Ni kg-1 spiked soil, per cent recovery of Ni decreased from 60.0 after 1 day of incubation to 29.0 and 25.1 after 45 and 90 days of incubation, respectively. An overall reduction in the mean per cent recovery of DTPA-Ni was observed under submergence as compared to field capacity moisture regime in lime, FYM, Zn amended soils and unamended soil. The results enable us to understand the effect of ageing coupled with different amendments under various moisture regimes on Ni availability and provide useful information to work out the capacity of the soil to serve as a sink for Ni.

Influence of soil moisture regime on the species diversity and biomass of the herb layer of pine forests in the Ural Mountains

Adaptation of plant communities is an important factor for maintaining their functioning and stability in changing conditions. The aim of our research is study of the effect of soil moisture regime on the species richness and biomass of the herb layer for old-growth coniferous forests in the Ural Mountains (Russia). The research has been carried out between 57° 00'N; 60° 15''E and 57° 05'N; 60° 25'E. The studied area is part of the Zauralsky hilly piedmont province, the Southern boreal forest region. Sample plots (0.25 hectares) were laid in pine forests growing in habitats with different moisture regimes: insufficient, optimal (stable), and excessive. The research was conducted in 2010.To determine the herb layer productivity, 10-20 subplots 1x1 m in size were laid on each sample plot. Data analysis is based on the One-way ANOVA and species abundance distributions. It has been established that species richness in extreme (insufficient and excessive soil moisture regime (Cowberry pine forest and Pine forest with shrubs and sphagnum) and optimal (stable) soil moisture regime (Multi-herb pine forest) were found to vary significantly, with soil moisture regime being a statistically significant factor. By contrast, herb layer biomass is maintained fairly stable regardless of the soil moisture regimes. ANOVA showed no significant differences between pine forests growing under different soil moisture regimes. It has been found that biomass is maintained by increasing of the dominant species contribution to the overall biomass and increasing of the approximation function graph slope. At the same time, the parameter β of exponential and power approximating functions is increased and can be considered as an indicator of influencing on forest ecosystems and a measure of their adaptation to insufficient and excessive soil moisture. Thus, species abundance distributions can be used as method to measure the effects of factors that determine forest ecosystem composition and functioning.

The effect of soil moisture regime and biochar application on lead (Pb) stabilization in a contaminated soil

Soil application of biochars has been shown to effectively immobilize potentially toxic elements (PTEs). Soil water regime can also affect PTE availability. No previous studies have examined the interactive effect of biochars and soil water regime on Pb availability. Therefore, this study investigated the effect of high and low temperature (300 and 600°C) biochars derived from cow manure (CB), municipal compost (MB) and licorice root pulp (LB) applied at 3 wt%, under two soil moisture regimes (field capacity (FC) and saturation (ST)) on Pb release kinetics and chemical fractions in a Pb-contaminated calcareous soil. Results showed that CB and MB treatments significantly enhanced Pb stabilization compared to LB, attributed to their favorable chemical properties (high P, ash, carbonate, oxidizable C content and high pH) which could promote Pb conversion into stable chemical fractions. Immobilization of Pb was enhanced under saturated conditions compared to FC by the treatments, which is attributed to increased soil pH, reduction of metal oxides and possible formation of sulfides. The most significantly effective treatments were the CB300, CB600 and MB600 treatments under ST, as indicated by significant decrease in soil Pb mobility factor from 29.1% (CL+FC) to 21.2–22.9%, and 11.7–16.3% increase in non-EDTA-extractable Pb. Results of this study demonstrate that combined application of high ash biochars and soil water saturation significantly enhances Pb immobilization in calcareous soil.

Experimental assessment of influence of soil moisture on the <sup>137</sup>Cs accumulation in shoots of spring wheat

The aim of this research was to analyze the effect of soil moisture regime on the intensity of 137Cs transfer into cereals using spring wheat as a model species. Accumulation of 137Cs in shoots of spring wheat grown on soil substrates differ by water and nutrients content was analyzed. The investigated water regimes were 40 % (insufficient moisture supply), 70 % (optimal moisture supply) and 85 % (excessive moisture supply) of full moisture capacity of the soils; substrates with optimal and low content of essential mineral nutrients were used in the experiment. The plants were grown in a chamber with controlled climate conditions. Increasing water content in the soil from 40 to 85 % of the total moisture capacity significantly reduces the 137Cs content in plants. The shape of the relationship between soil moisture and the soil-to-plant transfer of 137Cs depends on the agrochemical characteristics of the soil. The difference in the radioisotope accumulation in the shoots of wheat grown on extreme water regimes is about four times when substrate with optimum content of nutrients was used. The difference is less than two times when substrate with a low content of essential nutrients was used; moreover, there are no differences between the 70 and 85 % variants on a substrate with low content of nutrients. The revealed dependencies cannot be explained by the change in the share of bioavailable forms of 137Cs in the soil since it does not significantly change in soils with different moisture regimes.

Effect of soil moisture regimes and soil types on incidence of Rhizoctonia bataticola causing dry root rot of chickpea

Effect of different soil moisture regimes and soil types on incidence of Rhizoctoniabataticola causing dry root of chickpea (Cicerarietinum L.). crop were studied during 2018-19 at VNMKV, Parbhani. In present studiesdry root rot disease incidence was higher (range: 80.00 to 74.45 per cent) at the soil moisture level of 55 to 60 per cent. Whereas it was noticed that sandy soil showed highest dry root rot disease incidence followed by sandy loam soil and than the other soil types.

Effect of soil moisture regimes and sources of nutrients on carbon sequestration potential in rice-wheat cropping system

Effect of soil moisture regimes and sources of nutrients on carbon sequestration potential in rice-wheat cropping system

Effect of soil moisture regimes in the early flowering stage on inflorescence morphology and medicinal ingredients of Chrysanthemum morifolium Ramat. Cv. ‘Hangju’

The quality of the traditional Chinese medicine (TCM) is closely related to the climatic conditions of its medicinal plant’s habitats. When Chrysanthemum morifolium Ramat. cv. ‘Hangju’ (Hj) is in the period of flower-bud differentiation, the rainy season also prevails in its original places. In this study, we set three groups of soil moisture regimes (SMR) corresponding to 35%–40% (S1), 65%–70% (S2), 95%–100% (S3) of soil water holding capacity (WHC) and we found for the first time that the effects of different SMR on the inflorescence of Hj in the early flowering stage. With the increase of SMR content, both ray florets (RFs) and disc florets (DFs) are inhibited on inflorescence morphology, especially for DFs. In addition, a CYC2c orthologous gene in “Zaoyang” (ZY, a cultivar of Hj) was identified and sequenced, the phylogenetic analysis showed that this CYCLOIDEA gene in Asteraceae shared duplications which were well-conserved and lineage-specific. Expression analysis showed that HjCYC2c was mainly expressed in RFs, and high SMR condition led to up-regulation. At the same time, our study suggests that FLS gene is a strong candidate as a key factor in Hj for further interaction studies between flavonoids biosynthesis and regulatory factors of floral symmetry. The determination results of medicinal ingredients showed that DFs were more quickly to respond to the SMR variation and produced more medicinal ingredients compared with RFs.

Effect of Soil Moisture Regimes on Growth and Seed Production of Two Australian Biotypes of Sisymbrium thellungii O. E. Schulz.

Sisymbrium thellungii O. E. Schulz is an emerging problematic weed in the northern grain region of Australia. Several different biotypes exist in this region but not all biotypes exhibit the same growth and reproduction behavior. This might be due to local adaptation to the different agro-ecosystems, however, information on this aspect is limited. To determine whether adaptation to water stress was a factor in biotype demographic growth and reproduction behavior, we evaluated the physiological and biochemical responses of two Australian S. thellungii biotypes, selected from high (Dalby) and medium (St. George) rainfall areas, to different pot soil moisture levels corresponding to 100, 75, 50, and 25% of soil water holding capacity (WHC). Averaged across moisture levels, the St. George biotype (medium rainfall area) had 89% greater biomass and produced 321% more seeds than the Dalby biotype. The St. George biotype was less affected by increased levels of water stress than the Dalby biotype. The Dalby biotype produced 4,787 seeds plant-1 at 100% WHC and only 28 seeds plant-1 at 25% WHC. On the other hand, the St. George biotype produced 4,061 seeds plant-1 at 25% WHC and its seed production at 100% WHC was 9,834 seeds plant-1. On a per leaf area basis and averaged across all moisture levels, the St. George had significantly lower net carbon assimilation compared with the Dalby biotype, accompanied by a trend for lower stomatal conductance, which might indicate an adaptation to water stress. Across the moisture levels, the St. George biotype had higher phenolics and total soluble sugar, but free proline content was higher in the Dalby biotype compared with the St. George biotype. Like total soluble sugar, proline content increased with water stress in both biotypes, but it increased to a greater extent in the Dalby biotype, particularly at the 25% of WHC. Branching, flowering and maturity occurred earlier in the St. George biotype compared with the Dalby biotype, indicating relatively faster growth of the St. George biotype, which again seems to be an adaptation to water-limited environments. In conclusion, the St. George biotype of S. thellungii had higher reproductive capacity than the Dalby biotype across all the moisture regimes, which suggests greater invasiveness. Overall, the large size and rapid growth of the S. thellungii population from the medium rainfall area, together with its physiological response to water stress and its ability to maintain seed production in dry conditions, may enable this biotype to become widespread in Australia.

Effect of Soil Moisture Regimes on Seed Iron and Zinc Concentration of Biofortified Bean Genotypes against Malnutrition in Sud-Kivu Highlands

This study investigated the influence of three soil moisture irrigation regimes on concentration of seed iron and zinc content of four biofortified bean varieties promoted for eradication of malnutrition in Sud-Kivu highlands. A field experiment was conducted in the Hogola marsh highlands during two cultural seasons B2013 and B2014. The experiment design was a RCBD with a split plot arrangement where the main plots were 110 m2 and split plots 20 m2. A strategic application of homogenisation of the experimental site’s soil fertility by chemical fertilizers of the type: CaCO3, KCl and DAP was conducted out. Four biofortified varieties (CODMLB001, RWR2245, HM21-7 and RWK10) constituted main factor, while water regimes respectively [bottom of the slope: R1 = 48% soil moisture, at the middle of the slope R2 = 37% soil moisture and at the top of the slope: R3 = 29% soil moisture according to the gradient of humidity] represented secondary factor and seasonality, tertiary factor. The study showed that the concentrations of iron and zinc were highly correlated with soil moisture regimes. The variety HM21-7 demonstrated better adaptability because it showed a low rate of reduction of iron and zinc concentration under the three soil moisture regimes and was therefore best suited to fight malnutrition in the Sud-Kivu province.

Spatial and temporal variability of soil nitric oxide emissions in N-saturated subtropical forest

Acidic subtropical forest soils, receiving high atmospheric nitrogen (N) deposition, are characterized by fast N turnover, making them potential “hot spots” for nitrous oxide (N2O) and nitric oxide (NO) emissions. Production of NO in soils is mediated by microbial nitrification and denitrification and/or chemical decomposition of microbially produced nitrite (NO2 −). In monsoonal forests, soil microbial processes are exposed to strong soil moisture and temperature fluctuations, known to cause pronounced variability in NO emission. We quantified in situ fluxes of NO throughout two summers in the N-saturated TieShanPing forest, Chongqing, SW China. Additional N2O measurements were carried out in the second summer to infer likely source processes. To address spatial variability, fluxes were measured along two transects, one covering well-drained Acrisols on a forested hill slope, and the other hydrologically connected terraces with poorly drained Cambisols situated in a groundwater discharge zone. Hill slope sites emitted on average 48.4 ± 60.6 µg NO–N m−2 h−1 in the relatively wet summer of 2015 and 88.4 ± 94.6 µg NO–N m−2 h−1 in the dry summer of 2016, illustrating the strong effect of soil moisture regime. The NO emission in the groundwater discharge zone, measured in the dry summer of 2016 only, while it was flooded in the summer of 2015, was significantly smaller (26.4 ± 52.7 µg N m−2 h−1). The mean N2O-N emission on the hillslope (18.1 ± 13.9 µg N m−2 h−1) was smaller than NO-N flux, while it was larger (38.3 ± 39.3 µg N m−2 h−1) in the groundwater discharge zone. The temporal variability of the NO flux was largely explained by soil moisture fluctuations, whereas soil organic matter pool sizes contributed most to spatial variability. Hourly measurements showed that the NO flux doubled with 8 °C increase of soil temperature, indicating that soil temperature was another important driver for NO emissions. Our study indicates that acid N-saturated subtropical forest soils are a large source for NO, particularly during dry summers.

Soil moisture legacy effects: Impacts on soil nutrients, plants and mycorrhizal responsiveness

Although most land-plants form associations with arbuscular mycorrhizal fungi (AMF) as a means of optimising nutrient capture, legacy effects of altered soil moisture regimes on plant responses to arbuscular mycorrhizas (AM) have not been studied. As rainfall patters change with climate change, soil moisture legacy effects, and their impact on plants, soil and microbes may become increasingly important. Results of an experiment are presented in which soil was subjected to a range of different soil moisture regimes prior to planting a mycorrhiza-defective tomato mutant and its mycorrhizal wild-type progenitor. There were clear legacy effects of the soil moisture regime prior to planting on soil physicochemical properties, plant growth and nutrition, the formation of AM and mycorrhizal responsiveness. For example, in the Dry treatment the plants were well colonized by AM, there was a clear benefit to the plants in terms of mycorrhizal growth responses and mycorrhizal P responses. In contrast, in the Intermediate treatment AM colonisation was lower, there was little benefit in terms of mycorrhizal responses. Finally, in the Wet and Wet/Dry treatments AM colonization levels were similar (albeit lower) to those in the Dry treatment, but mycorrhizal growth responses were lower and more variable. Together, these results clearly indicate that soil nutrients, plant growth and nutrition and mycorrhizal responsiveness are affected by soil moisture legacy effect. Consequently, as we move into a period where more variable and intense rainfall amounts and patterns have been projected, we need to consider soil moisture legacy effects.

Effects of soil moisture regimes on growth and photosynthesis of the riparian plant Bolboschoenus planiculmis

Plants distributed in riparian regions experience frequent episodes of flooding and drought between years, and hence, riparian plants need to be flood- and drought-tolerant. Riparian plants possess various traits to survive flooding, while their sensitivity to drought has received less attention. To investigate the growth and photosynthetic responses of a riparian species (Bolboschoenus planiculmis) to flooding and drought, plants of this species were subjected to 60-d flooding or drought stress under greenhouse conditions. Growth and photosynthetic traits were measured at the end of the treatments. As well, we determined the efficiency of photosynthetic apparatus in mature leaves. Plants of B. planiculmis adequately adjusted their growth and photosynthetic traits under both flooding and drought conditions. Flooding did not affect the above-ground growth of B. planiculmis. Increased growth of roots and rhizomes and the generation of new tubers suggested a high ability of below-ground lateral growth by capturing resources under flooding conditions. Enhanced photosynthetic capacity, retained leaf pigment concentrations and chlorophyll a fluorescence capacity indicated photosynthetic adaptation to flooding. In contrast, drought significantly decreased the above-ground growth of B. planiculmis, especially the leaves, thereby minimizing water loss due to transpiration. Its increased root to shoot ratio and “phalanx” asexual propagation pattern might enhance soil water uptake ability. Although the functional leaves of B. planiculmis could retain their leaf pigment concentrations, as well as photosynthesis and chlorophyll a fluorescence, the total biomass of plants decreased, which may be a consequence of the reduced leaf area, suggesting adverse effects by drought. Therefore, both growth and photosynthetic responses of B. planiculmis are likely to contribute to the ability of this species to thrive in riparian regions, but remain susceptive to drought.

Effect of Soil Moisture Regimes on Growth and Yield of Mulberry

Effect of three levels of irrigation viz., no irrigation (I0), irrigation once a month (I1) and irrigations twice a month (I2) on some growth attributes and leaf yield and some of its components of five mulberry varieties were studied in field condition. Significant effect of irrigation on relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), and relative leaf growth rate (RLGR) was observed. lrrigation also had significant effect on leaf yield and some of its components. The overall results indicated that twice irrigations in a month with mulberry variety BM-4 could be used for higher leaf yield. Key words: Mulberry; lrrigation; Growth parameters; Leaf yield DOI: 10.3329/bjsir.v45i4.7331 Bangladesh J. Sci. Ind. Res. 45(4), 331-336, 2010

Effect of Soil Moisture Regime and Rice Cultivation on Mineralogical Characteristics of Paddy Soils of Mazandaran Province, Northern Iran, Amol

Effect of Soil Moisture Regime and Rice Cultivation on Mineralogical Characteristics of Paddy Soils of Mazandaran Province, Northern Iran, Amol

Iron plaque enhances phosphorus uptake by rice (Oryza sativa) growing under varying phosphorus and iron concentrations

AbstractBoth solution culture and pot experiments were performed to investigate (a) the effects of external Fe (II) concentrations and forms on the formation of iron plaque on the roots of rice (Oryza sativa) and subsequent P adsorption on iron plaque and shoot P concentrations and (b) the effects of soil moisture regimes on the formation of iron plaque and P adsorption on root surfaces and P accumulation in shoots. The results showed that iron plaque was significantly increased with increasing Fe2+ concentrations in the solution culture. The amounts of P adsorbed on the iron plaque were increased significantly with external Fe2+ concentrations. Although shoot P concentration was not significantly affected by Fe2+ treatment after incubation for 2 days, it was significantly increased in the Fe‐treated plants compared with Fe‐deprived ones after incubation for 4 days. Soil culture experiment showed that the formation of iron plaque on root surfaces was promoted by exogenous iron, with greater amount of iron plaque being formed by addition of ferric hydroxide than of ferric oxide. Phosphorus adsorption on iron plaque also increased with the addition of iron oxides, and increasing soil P increased the amounts of P associated with the iron plaque and shoot P concentration. The amounts of iron plaque were almost sixfold higher under flooding condition than under field capacity condition. Plants pretreated under flooding condition generally had higher shoot P concentrations when they were transplanted to solutions with varying P levels, and this was most pronounced in the treatment with highest solution P concentration. The results suggest that iron plaque acts as a nutrient reservoir for phosphorus in the rhizosphere and helps enhance P acquisition by rice.

Effect of Soil Moisture Regime on Soybean Rhizosphere Activities in Heavy Clay Upland Field Converted from Paddy Field

Effect of Soil Moisture Regime on Soybean Rhizosphere Activities in Heavy Clay Upland Field Converted from Paddy Field

Effects of soil moisture regimes on photosynthesis and growth in cattail (Typha latifolia)

Both waterlogging and water deficiency are major environmental factors affecting plant growth and functioning in many wetland and floodplain ecosystems across North America. Wetland plants possess various characteristics that enable them to survive and function in the intermittently flooded wetland environments, while their sensitivity to drought has received less attention. The present study quantified the photosynthetic and growth responses of cattail (Typha latifolia), an important species of freshwater wetlands, to a wide range of soil moisture regimes. In addition, changes in the efficiency of photosynthetic apparatus following initiation of the treatments were investigated. Under greenhouse conditions, seedlings were subjected to four soil moisture regimes: (1) drained (control), (2) continuous flooding, (3) periodic flooding, and (4) periodic drought. Results indicated that dark fluorescence yield was increased in response to periodic drought, while it showed decreases under continuous flooding. Net photosynthesis and stomatal conductance were enhanced by continuous flooding and periodic flooding. In contrast, these parameters exhibited reduction under periodic drought. In addition, leaf chlorophyll content was adversely affected by periodic drought. Recovery of net photosynthesis was noted, along with enhanced height growth, in both continuously and periodically flooded plants. Meanwhile, continuous flooding enhanced biomass production while periodic drought led to biomass reduction. Periodic drought also contributed to substantial reduction in root growth compared with shoot growth. Therefore, the combined photosynthetic performance and growth responses of cattail are likely to contribute to the ability of this species to thrive in flooded condition but be susceptive to periodic drought.

Natural 15N abundances of inorganic nitrogen in soil treated with fertilizer and compost under changing soil moisture regimes

This study was conducted to examine whether the applications of N-inputs (compost and fertilizer) having different N isotopic compositions ( δ 15N) produce isotopically different inorganic-N and to investigate the effect of soil moisture regimes on the temporal variations in the δ 15N of inorganic-N in soils. To do so, the temporal variations in the concentrations and the δ 15N of NH 4 + and NO 3 − in soils treated with two levels (0 and 150 mg N kg −1) of ammonium sulfate ( δ 15N=−2.3‰) and compost (+13.9‰) during a 10-week incubation were compared by changing soil moisture regime after 6 weeks either from saturated to unsaturated conditions or vice versa. Another incubation study using 15N-labeled ammonium sulfate (3.05 15N atom%) was conducted to estimate the rates of nitrification and denitrification with a numerical model FLUAZ. The δ 15N values of NH 4 + and NO 3 − were greatly affected by the availability of substrate for each of the nitrification and denitrification processes and the soil moisture status that affects the relative predominance between the two processes. Under saturated conditions for 6 weeks, the δ 15N of NH 4 + in soils treated with fertilizer progressively increased from +2.9‰ at 0.5 week to +18.9‰ at 6 weeks due to nitrification. During the same period, NO 3 − concentrations were consistently low and the corresponding δ 15N increased from +16.3 to +39.2‰ through denitrification. Under subsequent water-unsaturated conditions, the NO 3 − concentrations increased through nitrification, which resulted in the decrease in the δ 15N of NO 3 −. In soils, which were unsaturated for the first 6-weeks incubation, the δ 15N of NH 4 + increased sharply at 0.5 week due to fast nitrification. On the other hand, the δ 15N of NO 3 − showed the lowest value at 0.5 week due to incomplete nitrification, but after a subsequence increase, they remained stable while nitrification and denitrification were negligible between 1 and 6 weeks. Changing to saturated conditions after the initial 6-weeks incubation, however, increased the δ 15N of NO 3 − progressively with a concurrent decrease in NO 3 − concentration through denitrification. The differences in δ 15N of NO − 3 between compost and fertilizer treatments were consistent throughout the incubation period. The δ 15N of NO 3 − increased with the addition of compost (range: +13.0 to +35.4‰), but decreased with the addition of fertilizer (−10.8 to +11.4‰), thus resulting in intermediate values in soils receiving both fertilizer and compost (−3.5 to +20.3‰). Therefore, such differences in δ 15N of NO 3 − observed in this study suggest a possibility that the δ 15N of upland-grown plants receiving compost would be higher than those treated with fertilizer because NO 3 − is the most abundant N for plant uptake in upland soils.