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1.
Abstract

Soil cores were collected to a depth of 14 m from a Southwest semi‐arid soil amended with either anaerobically digested sludge or inorganic fertilizer. Twenty sections partitioned from each core were characterized for their physical and chemical properties. Denitrification potential was estimated in each core section in the laboratory using the acetylene reduction method. The sludge‐amended soil had significantly higher denitrification rates within and below the root zone than the fertilizer‐amended soil. Additionally, significant correlation values were obtained in both cores between denitrification rates and particle size distribution, moisture, and total organic carbon (C). Sludge applications in semi‐desert soils may add much needed organic C in the soil profile. This additional soluble organic C may help control nitrate (NO3) ground water pollution by providing substrate C for denitrifying bacteria below the root zone.  相似文献   

2.
Abstract

Nitrate leaching losses were estimated using soil core samples from three different locations in a furrow irrigated, N fertilized and sludge amended cotton field. These losses were controlled by irrigation efficiency, as well as sources and quantities of N applied. Statistical comparisons of sample locations and N treatments revealed N treatment to be less significant than the field sampling location. However, sludge amended soils had significantly higher levels of nitrates in the root zone and consequently suffered higher nitrate leaching losses. A NO3‐N profile (30–210 cm) balance indicated that about forty percent (40%) of available NO3‐N was leached below the root zone (0–150 cm) in the upper two‐thirds of the field plots during the pre‐plant irrigation. Whereas, the lower one‐third of the field did not experience significant nitrate losses below the root zone. A one‐dimensional finite difference layered model, was used to estimate the depth of moisture penetration at the field (furrow) locations following pre‐plant irritation. It was concluded that the lower one‐third of the plots received less than 50% of mean plot application (30 cm) water during pre‐plant irrigation.  相似文献   

3.
During freeze-thaw events, biophysical changes occurring in soils can affect processes such as mineralization, nitrification and denitrification which control inorganic N balances in agro-ecosystems. To evaluate the impact of these climatic events on soil biochemical properties, a study was conducted comparing soil denitrification enzyme activity (DEA), dissolved organic C (DOC) and inorganic N levels before and after the winter season in plots under: (1) continuous corn (Zea mays L.) (CC) with annual chisel plow and disking, (2) corn-soybean (Glycine max L.) (CS) rotation with chisel plow every other year prior to planting soybean, and (3) corn-soybean-wheat (Triticum aestivum L.)/hairy vetch (Vicia villosa Roth) (CSW-V) with ridge tillage during the corn and soybean crops, and dairy manure application during the corn year. Soil cores were collected in late autumn and immediately after spring thaw at 0-5, 5-10, 10-15, and 15-30 cm depths. Regardless of management practices, freeze-thaw events resulted in significant (2-10 times) increases in NH4+-N, NO3--N (P<0.001) and DOC (P<0.01) levels at all soil depths. Following freeze-thaw, DEA remained unchanged in the 5-30 cm depth but dropped significantly (P<0.01) in the 0-5 cm soil layer. In that layer, soils which had been chisel plowed during the previous growing season lost 78-84% of the DEA recorded during the fall, whereas in the plots amended with manure during the previous season, the loss of activity was 40-45%. These data indicate that frequent tillage, compared with manure additions, is more conducive to overwinter loss of DEA in surface layers of soils subject to freeze-thaw cycles.  相似文献   

4.
In this study spatial and temporal relations between denitrification rates and groundwater levels were assessed for intensively managed grassland on peat soil where groundwater levels fluctuated between 0 and 1 m below the soil surface. Denitrification rates were measured every 3–4 weeks using the C2H2 inhibition technique for 2 years (2000–2002). Soil samples were taken every 10 cm until the groundwater level was reached. Annual N losses through denitrification averaged 87 kg N ha-1 of which almost 70% originated from soil layers deeper than 20 cm below the soil surface. N losses through denitrification accounted for 16% of the N surplus at farm-level (including mineralization of peat), making it a key-process for the N efficiency of the present dairy farm. Potential denitrification rates exceeded actual denitrification rates at all depths, indicating that organic C was not limiting actual denitrification rates in this soil. The groundwater level appeared to determine the distribution of denitrification rates with depth. Our results were explained by the ample availability of an energy source (degradable C) throughout the soil profile of the peat soil.This revised version was published online November 2003 with corrections to Figure 4 and in February 2004 with corrections to Figure 2.  相似文献   

5.
The relationships between the fluxes of nitrous oxide (N2O) and carbon dioxide (CO2), and their concentrations in the soil air, three different measures of potential denitrification, soil moisture, soil temperature and precipitation were investigated in soils from beneath ryegrass (Lolium multiflorum Lam.), red clover (Trifolium pratense L.) and mixture of ryegrass-red clover stands on a gleic cambisol. Investigations were carried out in order to test the hypothesis that the measure(s) of potential denitrification are good predictor(s) of N2O fluxes and thus may be used in empirical models of N2O emission. Potential denitrification characteristics used in this study involved (i) short-term denitrifying enzyme activity (DEA), (ii) long-term denitrification potential (DP), both determined in soils amended with nitrate and glucose, and (iii) denitrification rate (DR) measured using intact soil cores. Flux measurements were made using cylindrical chambers (internal diameter 31 cm, volume 0.015 m3). The fluxes of N2O and CO2 and many other characteristics showed large spatial and temporal variability. Emissions of N2O from the grass plots were closely related to N2O concentrations in the soil atmosphere at 22.5 cm depth. Most soil properties did not correlate with N2O fluxes. It was concluded that DP was not a good predictor for N2O flux. DEA did not show significant relationship with N2O flux, but it is suggested that if determined in representative, large soil samples, DEA could be a predictor of N2O fluxes; this assumption needs, however, verification. The only potential denitrification characteristic which was significantly related to N2O emission both in grass and clover treatments was DR, which was determined in soil cores.  相似文献   

6.
Abstract

A statistical comparison of data collected from two cotton production fields with a history of either commercial fertilizer or sludge amendments showed significantly different nitrate‐nitrogen (N) concentrations in time and space. The sludge‐amended field had high nitrate concentrations in the root zone (1.5 m) throughout the season. Whereas, the fertilized field showed low nitrate‐N concentrations during the same period. Both fields showed significant increases in nitrate‐N following pre‐plant irrigation events, and significant decreases of nitrate‐N in the root zone during the growing season. Following harvest, the sludge‐amended field had very large reserve of nitrate‐N in the profile. The spatial variabilities, as determined by the % coefficients of variations (CVs) of eight cores per sampling event, of nitrate‐N distributions where large in both fields, 69% and 90% for the sludge and fertilizer field, respectively. The estimated nitrate‐N leaching losses were much higher in the sludge‐amended than the fertilized field. Significant leaching losses in the sludge‐amended field were likely the result of year‐to‐year sludge residue accumulations that mineralize and release nitrate‐N in the zone of incorporation (0–30 cm).  相似文献   

7.
Agricultural soils are a major source of the potent greenhouse gas and ozone depleting substance, N2O. To implement management practices that minimize microbial N2O production and maximize its consumption (i.e., complete denitrification), we must understand the interplay between simultaneously occurring biological and physical processes, especially how this changes with soil depth. Meaningfully disentangling of these processes is challenging and typical N2O flux measurement techniques provide little insight into subsurface mechanisms. In addition, denitrification studies are often conducted on sieved soil in altered O2 environments which relate poorly to in situ field conditions. Here, we developed a novel incubation system with headspaces both above and below the soil cores and field-relevant O2 concentrations to better represent in situ conditions. We incubated intact sandy clay loam textured agricultural topsoil (0–10 cm) and subsoil (50–60 cm) cores for 3–4 days at 50% and 70% water-filled pore space, respectively. 15N-N2O pool dilution and an SF6 tracer were injected below the cores to determine the relative diffusivity and the net N2O emission and gross N2O emission and consumption fluxes. The relationship between calculated fluxes from the below and above soil core headspaces confirmed that the system performed well. Relative diffusivity did not vary with depth, likely due to the preservation of preferential flow pathways in the intact cores. Gross N2O emission and uptake also did not differ with depth but were higher in the drier cores, contrary to expectation. We speculate this was due to aerobic denitrification being the primary N2O consuming process and simultaneously occurring denitrification and nitrification both producing N2O in the drier cores. We provide further evidence of substantial N2O consumption in drier soil but without net negative N2O emissions. The results from this study are important for the future application of the 15N-N2O pool dilution method and N budgeting and modelling, as required for improving management to minimize N2O losses.  相似文献   

8.
Recent studies indicate that soil soluble organic nitrogen (SON) plays an important regulatory role in the soil–plant N cycle. The aims of this study were to identify the vertical distribution of SON and its correlation with N mineralization, nitrification, and amidohydrolase activities, in a soil repeatedly amended with cow manure or chemical fertilizer. For this purpose, soil samples were collected from 0–20, 20–40, 40–60, 60–80, and 80–100 cm depths of a calcareous soil, which has been annually amended for 5 y with cow manure (CM) at two rates of 50 (CM50) and 100 (CM100) Mg CM ha–1 y–1. Treatments with chemical fertilizer (CF) and a control (CT) were also included. Soluble organic N, N mineralization, nitrification rates, as well as L‐glutaminase and L‐asparaginase activities were determined. Both CM50 and CM100 enhanced SON content throughout the soil profile. Nitrogen‐mineralization rate (Nm) was increased at the 0–20 cm depth of the CM100 treatment and remained unaffected at the deeper depths. Nitrification rate (Nn) was significantly higher at the 0–60 cm depth of CM100 compared to CF and CT. L‐glutaminase and L‐asparaginase activities were significantly increased at the 0–40 cm depth in both CM50 and CM100 compared to CF and CT. The amidohydrolase activities could not be detected below 40 cm, regardless of the fertilizer treatments. Our results suggest that SON makes a minor contribution to N mineralization in deep soil layers. It was also concluded that changes in the SON throughout the soil profile were not associated with changes in the N‐transformation rates (Nm and Nn) and amidohydrolase activities. While we conclude that SON is a major N pool in the whole profile of the manure applied soil further investigation is required to characterize SON and to investigate the bioavailability of SON for microbial activity in different soil depths.  相似文献   

9.
Nitrate-N, enriched with 15N, was added to small cores of the 0–10 cm layer of a clay soil. The base of each core was sealed, then water, equivalent to 0, 10, 20 or 30mm of rain, was added to the soil surface. The cores were incubated for 1 week at 10, 20, or 30°C in the presence or absence of wheat straw. The recovery of 15N in the soil mineral-N and organic-N fractions was then measured.No significant losses of 15N were detected in the cores which received 0–10 mm of added water, and in which the soil water content was close to 0.56 g g?1 (?10 kPa). However, 15N losses, assumed due to denitrification, were rapid from cores receiving 20 or 30 mm of water and incubated at 20–30°C. The onset of denitrification was quite sudden as the amount of added water increased from 10 to 20 mm. In this range, a small increment of added water apparently sealed a relatively large volume of soil from atmospheric O2 diffusion. This phenomenon was strongly temperature-dependent since no losses were detected from any cores at 10°C even though the 30mm addition of water produced a thin layer of free water across the soil surface.The addition of straw did not promote denitrification in soil at water contents close to 0.56 g g?1. At high soil water contents, adcling straw increased immobilization of labelled NO3? and so reduced denitrification losses. The response of immobilization to changing soil water and temperature conditions was very different from that of denitrification.  相似文献   

10.
下层土壤反硝化作用的研究   总被引：10，自引：0，他引：10  
在夏玉米生长期间 ,采用乙炔抑制 -原状土柱培养方法研究了北京褐土下层 (15～ 6 0cm)土壤的反硝化作用 ,并探讨影响该层土壤反硝化作用的主要因素。试验结果表明 ,施氮量越高 ,反硝化量越大。随着土壤层次的加深 ,反硝化量呈直线下降 ,但在亚表层土壤 (15～ 30cm)反硝化值仍保持了较高的量 ,约相当于表层的 10 .7%～ 33.5 % ;下层土壤 (15～ 6 0cm)的总反硝化量约相当于表层土壤的 14%～ 51%。加入碳源无论对表层土壤还是下层土壤 ,其反硝化损失氮量大大增加 ,尤其是对下层土壤增加的趋势更为明显。在计算夏玉米季土壤反硝化损失氮量时 ,如果忽略下层土壤的反硝化作用 ,肯定会低估其数值  相似文献   

11.
蔡祖聪 《土壤学报》2003,40(2):239-245
用15N分别标记尿素和KNO3,研究了淹水条件下 ,黄泥土和红壤性水稻土的无机氮转化过程及尿素和KNO3对氮素转化过程的影响。结果表明 ,淹水条件下 ,土壤中存在15NH 4 的成对硝化和反硝化过程。红壤性水稻土15NH 4 硝化只检测到15NO- 2 ,但有反硝化产物15N2 生成 ,因此 ,很可能存在着好气反硝化过程。15NO- 3浓度的下降符合一级反应方程 ,黄泥土的速率常数几乎是红壤性水稻土的 1 0倍。反硝化过程和DNRA过程共同参与15NO- 3的还原。加入尿素提高土壤pH ,增加黄泥土DNRA过程对反硝化过程的基质竞争能力 ,但反硝化过程仍占绝对优势。加入尿素或KNO3改变土壤pH是导致对无机氮转化影响有所不同的主要原因 ,浓度的作用较为次要。  相似文献   

12.
The denitrification potential of the soil horizons between 0- and 90-cm depth of 20 agricultural fields, representative of the most frequent combinations of agricultural crops and soil textures in Flanders (Belgium), and the factors affecting the denitrification potential were studied in the laboratory under controlled conditions. The denitrification potential in the presence of an added soluble C and N source was measured at 15°C after saturation of air-dried soil samples with water. The denitrification potential of the lower horizons was generally negligible compared to the upper horizons. The lower denitrification potential of the deeper horizons could partially be explained by their limited C availability. The denitrification potential of the upper horizons strongly depended on texture. Based on this parameter the soils could be divided into three groups: soils with a high clay content (>30% clay) were characterised by a high denitrification potential (>8.33 µg N g-1 dry soil day-1); soils with medium texture had a medium denitrification potential, between 0.41 and 7.25 µg N g-1 dry soil day-1; and soils with a high sand content (>80% sand) had a low denitrification potential (<2.58 µg N g-1 dry soil day-1). In most cases, extending the saturation period during pre-incubation increased the denitrification potential. Comparison of the denitrification potential of the upper horizons with and without addition of a soluble C source showed that the denitrification potential of the upper horizons of these soils was limited by their percentage of endogenous C. The measured denitrification potentials indicate that denitrification losses in soils high in clay content can be important when NO3 - concentrations are high.  相似文献   

13.
Summary In this study we evaluated the impact of five annual liquid sewage-sludge applications on the organic C and N content of a furrow-irrigated desert soil. Mineralization rates showed that sludge organic matter is mineralized rapidly (65% per year). Resistant residual sludge organic matter accumulation resulted in a theoretical increase in total soil organic C of 0.013% for the single sludge rate or 0.038% for three annual applications. These small additions were not detected in sludged soils at any depth to 270 cm. Similarly, increases in total soil N were not detected at any depth. However, soluble forms of organic C and N did increase in sludged soils relative to the non-sludged soils. In addition, soluble C:N ratios decreased significantly in the sludged soils. Soluble C and N also increased with depth due to leaching. This study therefore shows that applications of liquid sludge onto desert soils could affect the status of underground aquifers with respect to nitrate pollution.  相似文献   

14.
Abstract

Long‐term effects on plant and soil‐profile chemical composition imposed by a residential sewage sludge were studied on an Oxisol from Hawaii. Sludge was applied at 0, 45, 90, and 180 Mg/ha in 1983. An NPK‐fertilized treatment was included for comparison. Sudangrass (Sorghum bicolorL. Moench) was grown as a test crop in the 1983–84 and 1986–87 seasons. Soil samples for chemical analysis were taken in 1987 at three depths: 0–23 cm, 23–46 cm, and 46–69 cm.

Beneficial effects of sludge, measured 3 years after application (beginning of the 1986's planting), were evident by large yield increases on sludge‐amended soils relative to the unamended and the NPK‐fertilized soils. The first cutting produced approximately 5 Mg/ha of dry matter from the sludge treatments, regardless of rate, as compared with 3 and 1.5 Mg/ha from the NPK and the 0 treatments. Regrowths showed similar effect, though less dramatic; average yields were 2.6 Mg/ha with sludge and 1.6 Mg/ha without.

Heavy‐metal concentrations in plants were generally unaffected by sludge applications; probably because (i) heavy‐metal contents of the sludge were low, and (ii) soil pH was increased by sludge.

Remarkable increases in pH, exchangeable Ca and extractable P, and resultant decreases in exchangeable Al, in all three soil layers of sludge‐amended soils suggest that surface application of a low heavy‐metal sludge could serve to correct subsoil acidity and enhance subsoil P availability.  相似文献   

15.
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   

16.
Soils found in semiarid areas of the Mediterranean Basin are particularly prone to degradation due to adverse climatic conditions with annual rainfall <300 mm and high temperatures being responsible for the scant vegetal growth and the consequent lack of organic matter. A three-year field experiment was conducted to test the potential of two organic amendments (sludge and compost) to improve soil quality and plant growth in a semiarid degraded Mediterranean ecosystem. Since little is known about N dynamics in such assisted ecosystems, we investigated the effects of this practice on key processes of the global N cycle. Besides soil chemical and biological parameters and vegetation cover, we measured absolute and specific potential nitrification and denitrification rates and quantified the size of the ammonia oxidising and denitrifying bacterial populations via quantitative PCR (amoA and nirS genes). At the end of the experiment soil fertility, microbial activity and plant growth had improved in treated plots. Amendments increased the amount of ammonia oxidisers and denitrifiers in soil, but the relative proportion of these groups varied in relation to the total microbial community, being higher in the case of ammonia oxidisers but not in the case of denitrifiers. As a consequence, significantly higher potential nitrification and denitrification rates were measured on a global basis in amended soils. Yet specific activities (potential rate/gene copy numbers) were lower for ammonia oxidisers in amended soils and for denitrifiers in sludge treated soils than those observed in control plots. Organic amendments influenced resource availability, the size and the activity patterns of microbial populations involved in long-term N dynamics. Therefore N cycling processes may play a key role to assist sustainable restoration practices in semiarid degraded areas.  相似文献   

17.
Abstract

Fertilizer N recommendations for small grains are frequently based on soil test N but data is limited for irrigated spring wheat. The relative grain yield response of irrigated spring wheat to N as affected by inorganic soil N (NO3‐N and NH4‐N), yield potential and market class was evaluated in thirteen Southern Idaho field experiments involving N rates. Experiments were conducted on silt loam soils from 1978 to 1986. Preplant soil NO3‐N and NH4‐N to a depth of 60 cm and ranging from 27 to 142 kg/ha accounted for approximately 73% of the relative yield variability. NO3‐N and NH4‐N were significantly correlated (r=.72). NH4‐N with NO3‐N did not account for more of the relative yield variability than using NO3‐N alone.

Inorganic N in the first 30 cm and the second 30 cm were significantly correlated (r=.69) but N in the first depth increment accounted for more of the relative yield variability. The linear regression coefficient relating inorganic N in the first 30 cm to relative yield of unfertilized spring wheat was almost twice as high as the coefficient for the second 30 cm increment (.50 vs .27). Results indicate that inorganic N below 30 cm should be weighted differently than N in the first 30 cm when determining the N requirements of irrigated spring wheat.

Yield potential significantly affected the relative yield response to N. The response to N was not significantly affected by spring wheat market class (hard red vs soft white).

For estimating fertilizer N requirements, the results provide little justification for the current widespread practices of (1) using the combined NH4‐N and NO3‐N inorganic soil test N values when NO3‐N alone has as much predictive value and (2) assigning equal weight to inorganic soil N at all sampling depths.  相似文献   

18.
Abstract

City sewage sludge was applied to the surface layer (0–10 cm) of two sandy soils, slightly calcareous with 8.9% CaCO3 and moderately calcareous with 26.7% CaCO3, at the rates of 0, 25, 50, 75, and 100 Mg ha‐1. The effects of sewage sludge and its rates on total soluble salts, pH of soils and concentration and movement of some heavy metals within soils were investigated. Soil samples were packed at bulk density of 1.5 g cm‐3 in PVC columns and incubated for 19 weeks. The results indicated that total soluble salts (EC) of the treated layer increased with increasing sewage sludge rates. Soluble salts also increased with an increase in soil depth for both soils. The pH values of treated layers in two soils decreased with increasing sewage sludge rates. With increasing sewage sludge rates, concentrations of heavy metals [cobalt (Co), nickel (Ni), cadmium (Cd), and leaf (Pb)] increased in the treated layers compared to the untreated layers and their mobility was restricted mostly to the upper 30‐cm depth. Movement of Co and Pb in both the soils was predominately limited up to a depth of 40 cm for Co and 5 cm for Pb below the treated soil layer. Nickel and Cd movement was mostly limited to a depth of 10 cm in slightly calcareous soil and 5 cm in moderately calcareous soil. Metal movement in the respective soils is ranked as Co>Ni=Cd>Pb and Co>Ni=Cd>Pb. The low concentrations of heavy metals and the restricted mobility with soil depth, suggest that this material may be used for agricultural crop production without any toxic effect on plants.  相似文献   

19.
Most published studies related to crop effects on denitrification are not continuous and are based on the growing period. The objective of this work was to evaluate the effect of different amounts of soybean stubble, under different soil moisture contents, on gaseous nitrogen (N) losses by denitrification from an agricultural soil. The following soil moisture treatments were reached by adding distilled water to soil cores of a typic Hapludoll: 50 and 100% of water‐filled porosity space (WFPS). Residue treatments included no application of residues, amendment with 2600 kg ha?1 of soybean residues, and amendment with 5200 kg ha?1 of soybean residues. Cumulative nitrous oxide + dinitrogen (N2O + N2) emissions displayed great variability, ranging between 0 and 581.91 µg N kg?1, which represented 0 to 3.93% of the N residue applied. Under 50% WFPS moisture conditions, statistical differences in cumulative N2O + N2 emissions between residue treatments were not detected (p = 0.21), whereas at saturation conditions, cumulative N2O + N2 emissions decreased with the application of increasing amounts of soybean residues (p = 0.017). Daily and cumulative N2O + N2 emissions significantly increased as soil moisture increased, except at soils amended with 5200 kg ha?1 of soybean residues; this lack of statistical difference was probably due to the immobilization of native mineral N. Under 50% WFPS soil moisture contents, aeration seemed to be the main factor controlling redox conditions, limiting the denitrification process, and preventing differences in N emissions between residue treatments. The application of soybean residues to saturated soils notably decreased N2O + N2 emissions by denitrification through a strong mineral N immobilization into organic and nondenitrifiable forms.  相似文献   

20.
以7年氮肥定位试验地玉米根茬为研究对象,通过把玉米根茬按2%比例与15 cm和45 cm土层深度的土壤混合后田间埋袋的方法,研究长期不同施氮量处理[分别为0 kg(N)?hm?2、120 kg(N)?hm?2和240 kg(N)?hm?2]的玉米根茬(分别用R0、R120、R240表示),在陕西省长武黑垆土中埋藏分解1 a后对土壤碳、氮组分的影响及根茬有机碳的分解特性。与未添加玉米根茬的对照土壤相比,玉米根茬加入能够显著增加各层土壤的微生物量碳、可溶性有机碳和矿质态氮含量,3种施氮量处理间差异不显著。随着分解时间延长,土壤可溶性有机物中结构相对复杂的芳香类化合物比例逐渐增加。分解1 a后,R0、R120和R240根茬的有机碳残留率在15 cm土层中分别为44.4%、35.3%和34.9%,在45 cm土层中分别为53.3%、44.3%和42.5%。R0根茬的碳残留率显著高于R120和R240;玉米根茬在15 cm土层的碳分解率和分解速率常数显著高于45 cm土层。采用一级动力学方程拟合玉米根茬碳残留率变化结果显示,R0、R120和R240根茬有机碳分解95%所需要的时间在45 cm土层比15cm土层分别长3.2 a、2.3 a和1.9 a。氮肥施用量影响玉米根茬在土壤中的分解特性,在评价农田氮肥施用与土壤固碳时,应考虑不同氮肥用量下残茬养分组成及其在土壤中分解的差异。  相似文献   

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