首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 93 毫秒
1.
Effects of 15 annual applications (from 1979 to 1993) of ammonium nitrate (AN), urea, ammonium sulfate (AS), and calcium nitrate (CN) applied at 168 and 336 kg N ha‐1 to bromegrass (Bromus inermis Leyss.) on soil acidification, and concentration of aluminum (Al), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in soil and in hay were investigated in a field experiment on a thin Black Chemozemic (Typic Boroll) soil in Alberta, Canada. Soil was acidified and the concentration of extractable Al, Fe, and Mn was increased by nitrogen (N) application, but the magnitude varied with N source. Soil acidification was greatest with AS, followed by AN and urea, with no effect of CN. At 336 kg N ha‐1 rate, soil was acidified to a depth of 10, 15 and 30 cm with urea, AN AS, respectively. Soil acidification was also greater at 336 kg than 168 kg N ha‐1. The CaCl2‐extractable Al and Fe in the 0–15 cm layer increased with N application, which closely followed the decrease in soil pH from various N sources. Extractable Al and Fe concentration in the 15–30 cm layer increased in response to reduction in soil pH by AS only, and there was no change in the extractable Al and Fe below the 30‐cm depth by any form of N. The DTPA‐extractable Mn in soil generally changed in response to N application. There was no effect of N source on the DTPA‐extractable Zn and Cu in soil. When soil pH had been lowered from N application, the concentration of Al in hay decreased while Zn concentration increased. The Mn concentration in forage increased markedly in response to reduced soil pH from application of AN, urea and AS. There was no effect of N fertilization on the Cu and Fe concentration in hay. In conclusion, the magnitude of soil acidification, changes in the Al, Fe, and Mn concentrations in soil and changes in the Al, Zn, and Mn concentrations in bromegrass hay varied with N source. The results suggest the need for periodic monitoring of soil pH and consideration of liming costs in the economics of various N fertilizers.  相似文献   

2.
Abstract

Up to 70% applied ammonium‐based nitrogen (N) fertilizers can be lost by volatilization in agricultural soils. The purpose of this experiment was to determine the effects of fertilizer treatment, water potential, and time on volatilization losses in three northern Idaho soils under laboratory conditions maintained at 25°C. A completely randomized block factorial design with repeated measures (3 soils x 4 fertilizer treatments x 2 soil water potentials x 3 replications‐measured at 0,2,4, 8, and 16 d) was utilized in this study. The four fertilizer treatments consisted of 200 kg N/ha applied as: (1) surface‐applied ammonium nitrate (AN), (2) surface applied ammonium sulfate (AS), (3) surface applied urea (Ysur), and (4) incorporated urea (Uinc). Data were analyzed by SAS‐GLM and Omega squared (ω2) values were used to identify the impact of each main effect and interaction. A 4‐factor interaction of fertilizer treatment (NIT) x soil (SL) K water potential (WP) x time of incubation (IT), four‐3 factor interactions, six‐2 factor interactions and four main effects were found to be significant in this study. Due to the number of significant sources of variation, ω2 values were used to assess their relative importance. The soil x fertilizer treatment interaction accounted for 27.3% of the variation in this study. Nitrogen loss after 16 d of incubation from the Usur treatment was 37.8% in the Devoignes silt loam, 18.7% in the Santa silt loam, 4.9% in the Schnoorson silt loam. Volatilization of N from the Uinc and AS treatments was greater in the Devoignes silt loam than the Santa and Schnoorson soils. Conversely, differences in volatilization losses from AN were not observed among the three soils. Fertilizer treatment was the second most important factor accounting for 21.4% of the variability. Losses of 20.5, 2.6, 1.9, and 1.3% were observed for the Usur, Uinc, AS, and AN treatments, respectively. This study demonstrated that: (1) volatilization losses may be significant for surface applications of urea on some Idaho soils; however, incorporation of urea will reduce this hazard, and (2) volatilization losses are minimal when AN and AS are the N fertilizer sources.  相似文献   

3.
Chemical fixation of NH3 to soil organic matter was studied in two Swedish soils with different contents of organic matter: a clay soil with 2.3% C and an organic soil with 36.6% C. 15N‐labelled urea was applied at different rates to both sterilized and non‐sterilized soils. After 10 days, the soils were extracted and washed with K2SO4 and determined for total N and atom% 15N excess. Urea N was recovered as non‐extractable N in sterilized soil corresponding to 9.7% of supplied l5N‐labelled urea in the organic soil and 2.2% in the clay soil. Since no biological immobilization is thought to occur in the sterile soil, this non‐extractable N is suggested to be chemically fixed to soil organic matter. Owing to urea hydrolysis in the clay soil, pH increased from 6.3 to 9.3 and in the organic soil from 5.7 to 6.9 and 8.8, respectively, at the low and high urea supply.  相似文献   

4.
Abstract

The influence of nitrogen (N) fertilization on grass forage yield and quality as well as soil properties may vary with type of N fertilizer and time of application. The effects of 23 annual applications (from 1974 to 1996) of ammonium nitrate (AN) and urea (112 kg N ha‐1) applied in early fall, late fall, early spring and late spring on chemical soil properties and composition of bromegrass hay were evaluated in a field experiment on a thin Black Chernozemic soil located near Crossfield, Alberta, Canada. The influence of N addition, fertilizer type and application time on the soil properties was most pronounced in the 0–5 cm layer and declined in deeper soil layers. Application of N increased extractable ammonium (NH4)‐N, zinc (Zn), and iron (Fe) in the 0–5 cm layer; and sodium (Na), aluminum (Al), and manganese (Mn) in the 0–10 cm layer. But, N addition reduced extractable phosphoras (P) in the 0–30 cm; potassium (K) in the 0–60 cm; and pH, calcium (Ca), and magnesium (Mg) in the 0–5 cm soil layers. There was little effect of N fertilization on nitrate (NO3)‐N in soil. Soil pH, and extractable Ca and Mg in the 0–5 cm layer and Zn in the surface 15‐cm soil depth were lower with AN compared to urea, whereas the opposite was true for Fe, Mn, and Cu in the 0–5 cm layer and Na and Al in the top 15‐cm soil depth. Most of the changes in chemical soil properties due to N fertilization were reflected in elemental concentration of bromegrass hay, except for the increase of P concentration in bromegrass with N fertilization. In bromegrass hay for example, N addition increased total N and Cu with both N fertilizers and Mn and Zn with AN, but it lowered K and Ca with both fertilizers. There was more N and less Na with AN than urea in bromegrass hay. The effect of application time on chemical soil properties and composition of bromegrass hay was much less pronounced than N addition and fertilizer type. In conclusion, both N fertilizers changed chemical soil properties and composition of bromegrass hay, but the effects of 23 annual applications on soil properties were confined to shallow soil layers only. The greater lowering of soil pH with AN than urea may have implications of increased liming costs with AN.  相似文献   

5.
Microbial biomass C and soil respiration measurements were made in 17–20 yr old soils developed on sluiced and tipped coal‐combustion ashes. Topsoil (0–30 cm) and subsoil (30–100 cm) samples were collected from three soil profiles at two abandoned disposal sites located in the city area of Halle, Saxony‐Anhalt. Selected soil physical (bulk density and texture) and chemical (pH, organic C, total N, CEC, plant available K and P, and total Cd and Cu) properties were measured. pH values were significantly lower while organic C and total N contents and the C : N ratio were significantly higher in the topsoil than in the subsoil indicating the effects of substrate weathering and pedogenic C accumulation. Likewise, microbial biomass C, K2SO4‐extractable C, and soil respiration with median values of 786 μg biomass C g–1, 262 μg K2SO4‐C g–1, and 6.05 μg CO2‐C g–1 h–1, respectively, were significantly higher in the topsoil than in the subsoil. However, no significant difference was observed in metabolic quotient between the topsoil and the subsoil. Metabolic quotient with median values of 5.98 and 8.54 mg CO2‐C (g biomass C)–1 h–1 for the 0–30 cm and 30–100 cm depths, respectively, was higher than the data reported in the literature for arable and forest soils. Microbial biomass C correlated significantly with extractable C but no relationship was observed between it and total N, Cd, and Cu contents, as well as plant‐available K and P. We conclude that the presence of the remarkable concentration of extractable C in the weathered lignite ashes allowed the establishment of microbial populations with high biomass. The high metabolic quotients observed might be attributed to the heavy‐metal contamination and to the microbial communities specific to ash soils.  相似文献   

6.
The impact of horticultural management on carbon sequestration in soils has been limited so far to tillage and nitrogen fertilization. Our objective was to evaluate by mathematical modeling the effect of potassium fertilization on CO2 binding in cropland soils. The developed model integrates three subunits: (1) A published simulator of crop dry‐matter (DM) production in response to N, P, K fertilization, but not DM partitioning; (2) a published soil–crop–atmosphere model predicting crop yield and DM partitioning as a function of N but not K fertilization; (3) an original model computing the organic‐inorganic carbon transformations, inorganic‐carbon reactions and transport in soil, CO2 diffusion, and soil carbon sequestration. The model described the K‐fertilization effect on C binding in soil as a function of the soil pH, the Ca2+ concentration in the soil solution, hydraulic properties, air temperature, and crop DM production, and partitioning characteristics. In scenarios of corn (Zea mays L.) growth in clayey soil and wheat (Triticum aestivum L.) in loam soil, the computed K‐induced CO2 sequestration amounted to ≈ 14.5 and 24 kg CO2 (kg K)–1, respectively (0 vs. 100 kg ha–1 K application). The soil CO2 sequestration declined by 8% when corn grew in sandy instead of clayey soil and by 20% when the temperature was 10°C higher than the temperature prevailing in mild semiarid zones. All predicted CO2‐sequestration results were approximately 30‐fold higher than the 0.6 kg CO2 emitted per kg of K manufactured in industry.  相似文献   

7.
Microbial biomass, respiratory activity, and in‐situ substrate decomposition were studied in soils from humid temperate forest ecosystems in SW Germany. The sites cover a wide range of abiotic soil and climatic properties. Microbial biomass and respiration were related to both soil dry mass in individual horizons and to the soil volume in the top 25 cm. Soil microbial properties covered the following ranges: soil microbial biomass: 20 µg C g–1–8.3 mg C g–1 and 14–249 g C m–2, respectively; microbial C–to–total organic C ratio: 0.1%–3.6%; soil respiration: 109–963 mg CO2‐C m–2 h–1; metabolic quotient (qCO2): 1.4–14.7 mg C (g Cmic)–1 h–1; daily in‐situ substrate decomposition rate: 0.17%–2.3%. The main abiotic properties affecting concentrations of microbial biomass differed between forest‐floor/organic horizons and mineral horizons. Whereas microbial biomass decreased with increasing soil moisture and altitude in the forest‐floor/organic horizons, it increased with increasing Ntot content and pH value in the mineral horizons. Quantities of microbial biomass in forest soils appear to be mainly controlled by the quality of the soil organic matter (SOM), i.e., by its C : N ratio, the quantity of Ntot, the soil pH, and also showed an optimum relationship with increasing soil moisture conditions. The ratio of Cmic to Corg was a good indicator of SOM quality. The quality of the SOM (C : N ratio) and soil pH appear to be crucial for the incorporation of C into microbial tissue. The data and functional relations between microbial and abiotic variables from this study provide the basis for a valuation scheme for the function of soils to serve as a habitat for microorganisms.  相似文献   

8.
An incubation experiment was carried out to investigate the interactions of two straw qualities differing in N content and two soils differently accustomed to straw additions. One soil under conventional farming management (CFM) regularly received straw, the other soil under organic farming management (OFM) only farmyard manure. The soils of the two sites were similar in texture, pH, cation‐exchange capacity, and glucosamine content. The soil from the OFM site had higher contents of organic C, total N, muramic acid, microbial biomass C and N (Cmic and Nmic), but a lower ergosterol content and lower ratios ergosterol to Cmic and fungal C to bacterial C. The straw from the CFM had threefold higher contents of total N, twofold higher contents of ergosterol and glucosamine, a 50% higher content of muramic acid, and a 30% higher fungal C–to–bacterial C ratio. The straw amendments led to significant net increases in Cmic, Nmic, and ergosterol. Microbial biomass C showed on average a 50% higher net increase in the organic than in the CFM soil. In contrast, the net increases in Nmic and ergosterol differed only slightly between the two soils after straw amendment. The CO2 evolution from the CFM soil always exceeded that from the OFM, by 50% or 200 µg (g soil)–1 in the nonamended control soil and by 55% or additional 600 µg (g soil)–1 in the two straw treatments. In both soils, 180 µg g–1 less was evolved as CO2‐C from the OFM straw. The metabolic quotient qCO2 was nearly twice as high in the control and in the straw treatments of the CFM soil compared with that of the OFM. In contrast, the difference in qCO2 was insignificant between the two straw qualities. Differences in the fungal‐community structure may explain to a large extent the difference in the microbial use of straw in the two soils under different managements.  相似文献   

9.
Abstract

Ammonia (NH3) volatilization losses from surface‐applied ammonium sulphate (AS), ammonium nitrate (AN), and urea to winter wheat and the effects of the NBPT [N‐(n‐butyl) thiophosphoric triamide], PG (Phospho‐gypsum), and PR (byproduct‐Pyrite) were determined in a field experiment. Effects on grain yield and protein content of the grain were also measured. Total NH3 losses from AS, AN, and urea varied from 13.6–19.5%, 4.4–6.4%, and 3.9–12.0% depending on the compounds and their levels added to nitrogen (N) fertilizers, respectively. The compounds added to AS and AN increased NH3‐N losses with respect to unamended fertilizers (control). On the other hand, while urea treatments with two tons of PG/ha increased NH3 losses, the other compounds decreased the losses. The highest reductions of NH3 loss were observed with NBPT 0.50% and NBPT 0.25% by 63.4% and 52.8%, respectively. Although the effect of nitrogeneous fertilizers on total N losses and protein content of wheat grain was found statistically significant (p<0.01), as the compounds applied with N fertilizers have had no significant effect. Also, a negative and highly significant correlation (r = ‐0.69???) was found between total N loss and protein content of the grain.  相似文献   

10.
With a world population now > 7 billion, it is imperative to conserve the arable land base, which is increasingly being leveraged by global demands for producing food, feed, fiber, fuel, and facilities (i.e., infra‐structure needs). The objective of this study was to determine the effect of varying fertilizer‐N rates on soil N availability, mineralization, and CO2 and N2O emissions of soils collected at adjacent locations with contrasting management histories: native prairie, short‐term (10 y), and long‐term (32 y) no‐till continuous‐cropping systems receiving five fertilizer‐N rates (0, 30, 60, 90, and 120 kg N ha–1) for the previous 9 y on the same plots. Intact soil cores were collected from each site after snowmelt, maintained at field capacity, and incubated at 20°C for 6 weeks. Weekly assessments of soil nutrient availability along with CO2 and N2O emissions were completed. There was no difference in cumulative soil N supply between the unfertilized long‐term no‐till and native prairie soils, while annual fertilizer‐N additions of 120 kg N ha–1 were required to restore the N‐supplying power of the short‐term no‐till soil to that of the undisturbed native prairie soil. The estimated cumulative CO2‐C and N2O‐N emissions among soils ranged from 231.8–474.7 g m–2 to 183.9–862.5 mg m–2, respectively. Highest CO2 fluxes from the native prairie soil are consistent with its high organic matter content, elevated microbial activity, and contributions from root respiration. Repeated applications of ≥ 60 kg N ha–1 resulted in greater residual inorganic‐N levels in the long‐term no‐till soil, which supported larger N2O fluxes compared to the unfertilized control. The native prairie soil N2O emissions were equal to those from both short‐ and long‐term no‐till soils receiving repeated fertilizer‐N applications at typical agronomic rates (e.g., 90 kg N ha–1). Eighty‐eight percent of the native soil N2O flux was emitted during the first 2 weeks and is probably characteristic of rapid denitrification rates during the dormant vegetative period after snowmelt within temperate native grasslands. There was a strong correlation (R2 0.64; p < 0.03) between measured soil Fe‐supply rate and N2O flux, presumably due to anoxic microsites within soil aggregates resulting from increased microbial activity. The use of modern no‐till continuous diversified cropping systems, along with application of fertilizer N, enhances the soil N‐supplying power over the long‐term through the build‐up of mineralizable N and appears to be an effective management strategy for improving degraded soils, thus enhancing the productive capacity of agricultural ecosystems. However, accounting for N2O emissions concomitant with repeated fertilizer‐N applications is imperative for properly assessing the net global warming potential of any land‐management system.  相似文献   

11.
To investigate C and N rhizodeposition, plants can be 13C‐15N double‐labeled with glucose and urea using a stem‐feeding method (wick method). However, it is unclear how the 13C applied as glucose is released into the soil as rhizorespiration in comparison with the 13C applied as CO2 using a natural uptake pathway. In the present study, we therefore compared the short‐term fate of 14C and 15N in white lupine and pea plants applied either by the wick method or the natural pathways of C and N assimilation. Plants were pulse‐labeled in 14CO2‐enriched atmosphere and 15N urea was applied to the roots (atmosphere–soil) following the natural assimilation pathways, or plants were simultaneously labeled with 14C and 15N by applying a 14C glucose–15N urea solution into the stem using the wick method. Plant development, soil microbial biomass, total rhizorespiration, and distribution of N in plants were not affected by the labeling method used but by plant species. However, the 15N : N ratio in plant parts was significantly (p < 0.05) affected by the labeling method, indicating more homogeneous 15N enrichment of plants labeled via root uptake. After 14CO2 atmosphere labeling of plants, the cumulated 14CO2 release from roots and soil showed the common saturation dynamics. In contrast, after 14C‐glucose labeling by the wick method, the cumulated 14CO2 release increased linearly. These results show that 14C applied as glucose using the wick method is not rapidly transferred to the roots as compared to a short‐term 14CO2 pulse. This is partly due to a slower 14C uptake and partly due to slow distribution within the plant. Consequently, 14C‐glucose application by the wick method is no pulse‐labeling approach. However, the advantages of the wick method for 13C‐15N double labeling for estimating rhizodeposition especially under field conditions requires further methodological research.  相似文献   

12.
Recent studies indicate that aerobic rice can suffer injury from ammonia toxicity when urea is applied at seeding. Urea application rate and soil properties influence the accumulation of ammonia in the vicinity of recently sown seeds and hence influence the risk of ammonia toxicity. The objectives of this study were to (i) evaluate the effects of urea rate on ammonia volatilization and subsequent seed germination for a range of soils, (ii) establish a critical level for ammonia toxicity in germinating rice seeds and (iii) assess how variation in soil properties influences ammonia accumulation. Volatilized ammonia and seed germination were measured in two micro‐diffusion incubations using 15 soils to which urea was applied at five rates (0, 0.25, 0.5, 0.75 and 1.0 g N kg?1 soil). Progressively larger urea rates increased volatilization, decreased germination and indicated a critical level for ammonia toxicity of approximately 7 mg N kg?1. Stepwise regression of the first three principal components indicated that the initial pH and soil texture components influenced ammonia volatilization when no N was added. At the intermediate N rate all three components (initial pH, soil texture and pH buffering) affected ammonia volatilization. At the largest N rate, ammonia volatilization was driven by soil texture and pH buffering while the role of initial pH was insignificant. For soils with an initial pH > 6.0 the risk of excessive volatilization increased dramatically when clay content was <150 mg kg?1, cation exchange capacity (CEC) was <10 cmolc kg?1 and the buffer capacity (BC) was <2.5 cmolc kg?1 pH?1. These findings suggest that initial pH, CEC, soil texture and BC should all be used to assess the site‐specific risks of urea‐induced ammonia toxicity in aerobic rice.  相似文献   

13.
Abstract

The effects of various soil properties on ammonia (NH3) volatilization from soils treated with urea were studied by measuring the NH3 evolved when 20 soils selected to obtain a wide range in properties were incubated at ‐0.034 mPa soil moisture potential and 30°C for 10 days after treatment with urea. The nitrogen (N) volatilized as NH3 from these soils represented from 0 to 65% of the urea‐N applied and averaged 14%. Simple correlation analyses showed that loss of NH3 was negatively correlated (P<0.1%) with cation‐exchange capacity, silt content, and clay content and was positively correlated (P <0.1%) with sand content. Loss of NH3 was also negatively correlated with total nitrogen content (P<1.0%), organic carbon content (P<1.0%), hydrogen ion buffering capacity (P<5.0%), and exchangeable acidity (P<5.0%), and was positively correlated with calcium carbonate equivalent (P <1.0%) and with soil pH after incubation with urea (P<1.0%), but was not significantly correlated with initial soil pH or soil urease activity. Multiple linear regression analyses indicated that the amount of urea N volatilized as NH3 from the 20 soils studied increased with increase in sand content and decreased with increase in cation‐exchange capacity. They also indicated that soil texture and cation‐exchange capacity are better indicators of potential loss of urea N as NH3 from soils fertilized with urea than are hydrogen ion buffering capacity or initial soil pH.  相似文献   

14.
Abstract

Chemical transformations of ammonium nitrate (NH4NO3) and urea‐nitrogen (N), at different rates of application, were studied in a Candler (Typic Quartzipsamment) and Wabasso (sandy, Alfic Haplaquod) sand by incubating fertilized surface soil (from 0 to 15 cm depth) samples at 10% moisture content (by weight) in the laboratory at 25±1°C. During the 7 d incubation, the percentage of transformation of NH4‐N into NO3‐N was 33 to 41 and 37 to 41% in the Candler fine sand and Wabasso sand, respectively, at application rates of 1.00 g N kg1. In a parallel experiment, 85 to 96% of urea applied (equivalent to 0.25 to 1.00 g N kg‐1soil) was hydrolyzed to NH4‐N within 4 d in the Candler soil, whereas it required 7 d to hydrolyze 90 to 95% of the urea applied in the Wabasso soil. No nitrification was evident for 30 days in the Candler fine sand which received urea application equivalent to ≥ 0.50 g N kg‐1. In the urea‐amended Wabasso sand, the formation of NO3 decreased as the rate of urea‐N increased. Possible loss of N from NH3 volatilization or inhibition of activity of nitrifiers due to elevated soil pH (8.7 to 9.2) during the incubation of urea amended soils may have caused very low nitrification.  相似文献   

15.
The aim of this study was to examine the effect of the nitrification inhibitor nitrapyrin on the fate and recovery of fertilizer nitrogen (N) and on N mineralization from soil organic sources. Intact soil cores were collected from a grassland field. Diammonium phosphate (DAP) and urea were applied as N sources. Cores were equilibrated at –5 kPa matric potential and incubated at 20 °C for 42 to 56 days. Changes in NH4+‐N, accumulation of NO3–‐N, apparent recovery of applied N, and emission of N2O (acetylene was used to block N2O reductase) were examined during the study. A significant increase in NH4+‐N released through mineralization was recorded when nitrapyrin was added to the control soil without N fertilizer application. In the soils to which N was added either as urea or DAP, 50–90 % of the applied N disappeared from the NH4+‐N pool. Some of this N (8–16 %) accumulated as NO3–‐N, while a small proportion of N (1 %) escaped as N2O. Addition of nitrapyrin resulted in a decrease and delay of NH4+‐N disappearance, accumulation of much lower soil NO3–‐N contents, a substantial reduction in N2O emissions, and a 30–40 % increase in the apparent recovery of added N. The study indicates that N recovery can be increased by using the nitrification inhibitor nitrapyrin in grassland soils at moisture condition close to field capacity.  相似文献   

16.
Research information from a systematic planned study on the effects of vehicular passages and axle load on soil carbon dioxide (CO2) fluxes and soil carbon (C) sequestration under long‐term NT farming is scanty. Therefore, the present study was conducted on an on‐going 20‐year experiment to assess the impacts of variable vehicular passages of a low axle load on soil CO2 emission and soil C sequestration from a no‐till (NT) managed corn (Zea mays L.)–soybean (Glycine max Linneo) rotation in comparison with that a soil under woodlots (soils under natural wooded plantation). The experimental treatment consisted of an empty wagon [0 Mg load for compaction (C‐0; control)] compared with 2 (C‐2) and 4 (C‐4) passages of 2.5 Mg water wagon axle load, applied to the entire plot every year during April/May for 20 consecutive years. Soil samples were obtained in November 2016 to determine the effects of various vehicular passages on C and nitrogen (N) contents and CO2 emissions. Soil CO2 fluxes were measured from November 16, 2016, to May 30, 2017, on the bi‐weekly (November to December and April to May) and monthly (January to March) basis by using high‐density polyvinyl chloride static gas chambers. The soil CO2 fluxes ranged from –1.05 to 9.03 g CO2 m?2 d?1. The lowest soil CO2 fluxes were observed in December coinciding with the minimum soil temperature. In general, daily soil CO2 fluxes were higher under C‐0 than those under other treatments. Vehicular traffic and axle load reduced the cumulative emission of CO2 by 22.6 and 29.8% under C‐2 and C‐4, respectively, compared with that under C‐0 (6.09 Mg ha?1). Soil and air temperatures had a significant positive correlation with the diurnal fluxes of soil CO2 in all the treatments except that under C‐4. Electrical conductivity, soil C and N contents and pools did not differ significantly among the treatments. Further, 2 to 4 passages of vehicles with 2.5 Mg of axle load decreased the soil CO2 emission on Crosby silt loam under NT as compared to that under the control. Therefore, continuous cultivation of row crops with moderate trafficking under NT and residue retention is recommended, and it also reduces the potential of soil CO2 emission while improving the soil organic C pools of well‐drained soils of Central Ohio.  相似文献   

17.
Leaching of dissolved organic matter (DOM) from pastoral soils is increasingly seen as an important but poorly understood process. This paper examined the relationship between soil chemical properties, microbial activity and the losses of dissolved organic carbon (DOC) and nitrogen (DON) through leaching from six pasture soils. These soils differed in carbon (C) (4.6–14.9%) and nitrogen (N) (0.4–1.4%) contents and in the amount of organic C and N that had accumulated or been lost in the preceding 20+ years (i.e. −5131 to +1624 kg C ha−1 year−1 and −263 to +220 kg N ha−1 year−1, respectively). The paper also examined whether between‐soil‐type differences in DOC and DON leaching was a major explanatory factor in the observed range of soil organic matter (SOM) changes in these soils. Between 280 and 1690 kg C ha−1 year−1 and 28–117 kg N ha−1 year−1 leached as DOC and DON, respectively, from the six soils in a lysimeter study, with losses being greater from two poorly drained gley soils. Losses of C and N of this magnitude, while at the upper end relative to published data, could not fully explain the losses at Rawerawe, Bruntwood and Lepperton sites reported by Schipper et al. (2007) . The study highlights the leaching of DOM as a significant pathway of loss of C and N in pasture soils that is often ignored or given little attention in predictive models and nutrient budgeting. Leaching losses of DOC and DON alone, or in combination with slightly increased respiration losses of SOM given a 0.2°C increase in the mean annual soil temperature, do not fully explain long‐term changes in the SOM observed at these sites. When soils examined in the present study were separated on the basis of drainage class, the losses of DOC by leaching were correlated with both total and hot‐water extractable C (HWC), the latter being a measure of the labile SOM fraction. Basal microbial CO2 respiration rates, which varied between 1 and 3.5 µg CO2‐C g−1 soil hour−1 in surface soils (0–75‐mm depth), was also linked to HWC and the quantities of C lost as DOC. Adoption of the HWC method as an approach that could be used as a proxy for the direct measurement of the soil organic C lost by leaching as DOC or respired needs to be examined further with a greater number of soils. In comparison, a poor relationship was found between the hot‐water extractable N (HWN) and loss of DON by leaching, despite HWN previously being shown to be a measure of the mineralizable pool of N in soils, possibly reflecting the greater competition for N than C in these soils.  相似文献   

18.
Abstract

As a means of economic disposal and to reduce need for chemical fertilizer, waste generated from swine production is often applied to agricultural land. However, there remain many environmental concerns about this practice. Two such concerns, contribution to the greenhouse effect and stratospheric ozone depletion by gases emitted from waste‐amended soils, have not been thoroughly investigated. An intact core study at Auburn University (32 36′N, 85 36′W) was conducted to determine the source‐sink relationship of three greenhouse gases in three Alabama soils (Black Belt, Coastal Plain, and Appalachian Plateau regions) amended with swine waste effluent. Soil cores were arranged in a completely random design, and treatments used for each soil type consisted of a control, a swine effluent amendment (112 kg N ha?1), and an ammonium nitrate (NH4NO3) fertilizer amendment (112 kg N ha?1). During a 2‐year period, a closed‐chamber technique was used to determine rates of emission of nitrous oxide (N2O)–nitrogen (N), carbon dioxide (CO2)–carbon (C), and methane (CH4)–C from the soil surface. Gas probes inserted into the soil cores were used to determine concentrations of N2O‐N and CO2‐C from depths of 5, 15, and 25 cm. Soil water was collected from each depth using microlysimeters at the time of gas collection to determine soil‐solution N status. Application of swine effluent had an immediate effect on emissions of N2O‐N, CO2‐C, and CH4‐C from all soil textures. However, greatest cumulative emissions and highest peak rates of emission of all three trace gases, directly following effluent applications, were most commonly observed from sandier textured Coastal Plain and Appalachian Plateau soils, as compared to heavier textured Black Belt soil. When considering greenhouse gas emission potential, soil type should be a determining factor for selection of swine effluent waste disposal sites in Alabama.  相似文献   

19.
Soil of the former lake Texcoco is alkaline saline with pH often >10 and electrolytic conductivity (EC) >70 dS m?1 with rapidly changing water contents. Little is known how fertilizing this area with urea to vegetate the soil would affect emissions of carbon dioxide (CO2) and dynamics of N. Texcoco soil with electrolytic conductivity (EC) 2.3 dS m?1 and pH 8.5 (TEXCOCO A soil), EC 2.0 dS m?1 and pH 9.0 (TEXCOCO B soil) and 200 dS m?1 and pH 11.2 (TEXCOCO C soil) was amended with or without urea and incubated at 40% of water holding capacity (WHC), 60% WHC, 80% WHC and 100% WHC, while emissions of nitrous oxide (N2O) and CO2 and dynamics of ammonium (NH4+), nitrite (NO2?) and nitrate (NO3?) were monitored for 7 days. An agricultural soil served as control (ACOLMAN soil). The emission of CO2 increased in the urea amended soil 1.5 times compared to the unamended soil, it was inhibited in TEXCOCO C soil and was >1.2 larger in soil incubated at 40%, 60% and 80% WHC compared to soil incubated at 100% WHC. The emission of N2O increased in soil added with urea compared to the unamended soil, was similar in TEXCOCO A and B soils, but was <0.2 mg N kg?1 soil day?1 in TEXCOCO C soil and generally larger in soil incubated at 60% and 80% WHC compared to soil incubated at 40% and 100% WHC. The water content of the soil had no significant effect on the mean concentration of NH4+, but addition of urea increased it in all soils. The concentration of NO2? was not affected by the water content and the addition of urea except in TEXCOCO A soil where it increased to values ranging between 20 and 40 mg N kg?1. The concentration of NO3? increased in the ACOLMAN, TEXCOCO A and TEXCOCO B soil amended with urea compared to the unamended soil, but not in the TEXCOCO C soil. It decreased with increased water content, but not in TEXCOCO C soil. It was found that the differences in soil characteristics, i.e. soil organic matter content, pH and EC between the soils had a profound effect on soil processes, but even small changes affected the dynamics of C and N in soil amended with urea.  相似文献   

20.
Urine patches are significant hot‐spots of C and N transformations. To investigate the effects of urine composition on C and N turnover and gaseous emissions from a Danish pasture soil, a field plot study was carried out in September 2001. Cattle urine was amended with two levels of 13C‐ and 15N‐labeled urea, corresponding to 5.58 and 9.54 g urea‐N l–1, to reflect two levels of protein intake. Urine was then added to a sandy‐loam pasture soil equivalent to a rate of 23.3 or 39.8 g urea‐N m–2. Pools and isotopic labeling of nitrous oxide (N2O) and CO2 emissions, extractable urea, ammonium (NH4+), and nitrate (NO3–), and plant uptake were monitored during a 14 d period, while ammonia (NH3) losses were estimated in separate plots amended with unlabeled urine. Ammonia volatilization was estimated to account for 14% and 12% of the urea‐N applied in the low (UL) and high (UH) urea treatment, respectively. The recovery of urea‐derived N as NH4+ increased during the first several days, but isotopic dilution was significant, possibly as a result of stress‐induced microbial metabolism. After a 2 d lag phase, nitrification proceeded at similar rates in UL and UH despite a significant difference in NH4+ availability. Nitrous oxide fluxes were low, but generally increased during the 14 d period, as did the proportion derived from urea‐N. On day 14, the contribution from urea was 23% (UL) and 13% (UH treatment), respectively. Cumulative total losses of N2O during the 14 d period corresponded to 0.021% (UL) and 0.015% (UH) of applied urea‐N. Nitrification was probably the source of N2O. Emission of urea‐derived C as CO2 was only detectable within the first 24 h. Urea‐derived C and N in above‐ground plant material was only significant at the first sampling, indicating that uptake of urine‐C and N via the leaves was small. Urine composition did not influence the potential for N2O emissions from urine patches under the experimental conditions, but the importance of site conditions and season should be investigated further.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号