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1.
Khalid S. Khan Andreas Gattinger Franz Buegger Michael Schloter Rainer Georg Joergensen 《Soil biology & biochemistry》2008,40(5):1217-1224
An incubation experiment was carried out to investigate whether salinity at high pH has negative effects on microbial substrate use, i.e. the mineralization of the amendment to CO2 and inorganic N and the incorporation of amendment C into microbial biomass C. In order to exploit natural differences in the 13C/12C ratio, substrate from two C4 plants, i.e. highly decomposed and N-rich sugarcane filter cake and less decomposed N-poor maize leaf straw, were added to two alkaline Pakistani soils differing in salinity, which had previously been cultivated with C3 plants. In soil 1, the additional CO2 evolution was equivalent to 65% of the added amount in the maize straw treatment and to 35% in the filter cake treatment. In the more saline soil 2, the respective figures were 56% and 32%. The maize straw amendment led to an identical immobilization of approximately 48 μg N g−1 soil over the 56-day incubation in both soils compared with the control soils. In the filter cake treatment, the amount of inorganic N immobilized was 8.5 μg N g−1 higher in soil 1 than in soil 2 compared with the control soils. In the control treatment, the content of microbial biomass C3-C in soil 1 was twice that in soil 2 throughout the incubation. This fraction declined by about 30% during the incubation in both soils. The two amendments replaced initially similar absolute amounts of the autochthonous microbial biomass C, i.e. 50% of the original microbial biomass C in soil 1 and almost 90% in soil 2. The highest contents of microbial biomass C4-C were equivalent to 7% (filter cake) and 11% (maize straw) of the added C. In soil 2, the corresponding values were 14% lower. Increasing salinity had no direct negative effects on microbial substrate use in the present two soils. Consequently, the differences in soil microbial biomass contents are most likely caused indirectly by salinity-induced reduction in plant growth rather than directly by negative effects of salinity on soil microorganisms. 相似文献
2.
Ingrid Kgel-Knabner 《Geoderma》1997,80(3-4):243-270
Nuclear magnetic resonance (NMR) is a valuable tool for the characterization of soil organic matter and humification processes in soils. This review highlights soil organic matter studies based mainly on solid-state 13C and 15N NMR spectroscopy and some emerging applications, that may provide significant progress in our knowledge on soil organic matter. A major advantage of Nmr spectroscopy is that it can be used as a non-invasive method for solid soil samples or soil fractions. Although resolution is limited, one can obtain an overview on the organic matter structures present in the soil sample. Application of 13C and 15N NMR to soils has, for a long time, been confined to the study of bulk soils or humic extracts for structural characterization. The transformations of soil organic C and N are now being investigated after addition of 13C- and 15N-labelled parent materials to the soil and following their evolution in different C and N pools. With labelling techniques it is also possible to study the interaction of organic pollutants with soil organic matter. Contamination of a soil with man-made additives, such as soot or brown coal dust, can also be detected in soils or individual soil fractions. 相似文献
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N2 adsorption (77 K) was combined with 129Xe nuclear magnetic resonance spectroscopy of adsorbed xenon to characterise soil meso- (2–50 nm) and microporosity (<2 nm). Materials from the Alh and Bt horizons of a Luvisol, the Go horizon of a Gleysol and the Bvs horizon of a Podzol were analysed. Additionally, we examined samples obtained by mixing of H2O2-treated soil fractions with organic soil material (“soil + organic matter” samples). N2- specific surface areas (SBET) and micropore volumes (Vmicro) and areas (Smicro) were markedly affected by the presence of iron oxides in soils. Their removal with dithionite-citrate-bicarbonate (DCB) treatment was accompanied by a significant decrease in SBET and almost complete disappearance of the micropores. The organic carbon (OC) content decreased by 10–35% after the DCB-procedure showing that a certain proportion of the soil organic matter was extracted together with iron oxides. This may point to a close association between carbon compounds and iron oxides, possibly by incorporation of low molecular weight organic compounds into the phase of iron oxides. Such interactions are expected to contribute to the stabilisation of organic carbon in soils. Indeed, as compared to the top horizon (Alh of Luvisol), a higher proportion of organic matter was co-extracted with iron oxides from the subsurface horizons (Bt of Luvisol, Go of Gleysol) characterised by higher amounts of organic carbon resisting oxidation with H2O2. Examination of the mixed “soil + organic matter” samples supports that after addition, organic molecules occupy micropores (evidenced by N2 adsorption) and narrower mesopores of the mineral matter (evidenced by 129Xe NMR). 相似文献
5.
Soil properties may affect the decomposition of added organic materials and inorganic nitrogen (N) production in agricultural soils. Three soils, Potu (Pu), Sankengtzu (Sk) and Erhlin (Eh) soils, mixed with sewage sludge compost (SSC) at application rates of 0 (control), 25, 75 and 150 Mg ha−1 were selected from Taiwan for incubation for 112 days. The aim of the present study was to examine the effects of SSC application rates on the carbon decomposition rate, N transformation and pH changes in three soils with different initial soil pH values (4.8–7.7). The results indicated that the highest peaks of the CO2 evolution rate occurred after 3 days of incubation, for all treatments. The Pu soil (pH 4.8) had a relatively low rate of CO2 evolution, total amounts of CO2 evolution and percentage of added organic C loss, all of which resulted from inhibition of microbial activity under low pH. For the Pu and Sk soils, the concentration of NH4 + -N reached its peak after 7–14 days of incubation, which indicated that ammonification might have occurred in the two soils with low initial pH values. NO3 − -N rapidly accumulated in the first 7 days of incubation in the Eh soil (pH 7.7). The direction and extent of the soil pH changes were influenced by the N in the SSC and the initial soil pH. Ammonification of organic N in the SSC caused the soil pH to increase, whereas nitrification of mineralized N caused the soil pH to decline. Consequently, the initial soil pH greatly affected the rate of carbon decomposition, ammonification and nitrification of SSC. 相似文献
6.
The effect of winter weed control (WWC) management on 14C-atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) mineralization was investigated in an Entic Haplustoll in Argentina. Three WWC managements were selected: Chemical Fallow (CF) and Cereal Cover Crop (CCC), both under no-tillage, and Reduced Tillage (RT) with chisel and moldboard plow. Soil was sampled at two depths: 0–5 and 5–10 cm, to evaluate the soil stratification induced by the tillage system. To distinguish differences in atrazine degradation in soils with and without previous history of atrazine application two crop sequences were selected: continuous soybean [Glycine max L., Merr.] (CS) without previous atrazine exposure, and soybean–maize (Zea mays L.) rotation (SM) with atrazine application every winter and in alternate springs. The release of 14C-CO2 during laboratory incubations of soils treated with ring labelled 14C-atrazine was determined. Soil organic matter (SOM) distribution was determined with depth and among three soil size fractions: 200–2000 μm, 50–200 μm and <50 μm. Previous atrazine application enhanced atrazine degrading microorganims. Atrazine mineralization was influenced by both WWC management and the tillage system. Chemical fallow showed the highest atrazine mineralization in the two crop sequences. Depth stratification in atrazine degradation was observed in the two WWC treatments under the no-tillage. Depth stratification in the content of soil organic C and relative accumulation of organic C in coarsest fractions (200–2000 and 50–200 μm) were observed mainly in no-till systems. Depth stratification of atrazine degrading activity was mainly correlated to the stratification of fresh organic matter associated with the coarsest fractions (200–2000 μm). Atrazine persistence in soil is strongly affected by soil use and management, which can lead to safe atrazine use through selection of appropriate agricultural practices. 相似文献
7.
Long-term cultivation impacts on selected soil properties in the northern Great Plains 总被引：1，自引：0，他引：1
Long-term cultivation impacts soil properties. During the early 1920s a study comparing non-cultivated and cultivated soils was done in eastern SD (Beadle, McCook, Minnehaha, and Union Counties), USA. The objectives of the current study were to: (1) determine the long-term (>80 years) impact of cultivation on selected soil properties; and (2) establish baseline soil data that can be used for future comparisons. Sample sites were located in well-drained summit and upper backslope positions. These topographic positions are strongly influenced by erosion processes from tillage, wind, and water. Previous studies at other locations in the region suggest that one might expect a loss of 10–20 cm of soil in >80 years of cultivation at these topographic positions. In the early 1920s the soils were tested for carbon (C) (total, organic, inorganic), total nitrogen (N), total sulfur (S), total calcium (Ca), total phosphorus (P), total potassium (K), and total magnesium (Mg). The 1920s study sites were resampled at 0–15, 15–50, and 50–100 cm depths and analyzed for C (total, organic, inorganic), N (total, nitrate-N), extractable P, extractable K, delta N (15N/14N or δ15N) for total N, delta C (13C/12C or δ13C) for total C, and pH. Long-term cultivation (>80 years) in the northern Great Plains of the United States has caused many significant reductions in surface soil (0–15 cm) extractable P, extractable K, surface pH, total C, organic C, total N, and δ15N for total N. In addition, the organic C to total N ratio for the 15–50 cm depth of cultivated soils was significantly lower when compared to non-cultivated soils. Cultivation caused significant increases in nitrate-N, delta C, inorganic C, and in the total C to total N and inorganic C to total N ratios (15–100 cm depths). Soil properties varied significantly with increasing soil depth. Soil pH, δ13C for total C, inorganic C, total C to total N ratio, and inorganic C to total N ratio increased significantly as soil depth increased. Nitrate-N, extractable P, extractable K, δ15N for total N, organic C, and total N decreased significantly as soil depth increased. Soil carbon changes at the sample sites are a combined result of differences in the reference surface elevation, carbon mineralization, and redistribution of carbon due to erosion. Changes in soil nutrient levels reflect crop removal, leaching, erosion, and pedogenic processes. 相似文献
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Organic materials responsible for water–repellency in some Australian soils were extracted with an amphiphilic mixture of iso -propanol/15.7 m ammonia (7:3, v:v) in a Soxhlet apparatus, after which the water–repellent soils were rendered wettable. The successful extraction by an organic solvent system indicates that the bulk of hydrophobicity in these soils is not covalently linked to the surface of the sand. The extracted materials restored hydrophobicity on acid washed sands or ignited sands at levels comparable to the original soils.
Spectroscopic and chromatographic examination of the extracted materials indicated that both free and esterified long–chain, 16–32 carbon atom, fatty acids were present with a bimodal distribution showing maxima at C16 and C22 . The 13 C–NMR and infrared spectra of the most hydrophobic extract suggest that hydrophobicity is caused by molecules with extensive polymethylene chains. Calculations with model compounds indicate that at least a close packed monolayer is required before measurable hydrophobicity can be detected with the molarity of ethanol droplet penetration test. 相似文献
Spectroscopic and chromatographic examination of the extracted materials indicated that both free and esterified long–chain, 16–32 carbon atom, fatty acids were present with a bimodal distribution showing maxima at C
9.
This study investigated the effects of mineral-N addition and intensive mixing (analogous to disturbance by plowing) on decomposition of 14C-labelled maize (Zea mays L.) residue and soil organic matter (SOM). Soils were collected from the upper 5 cm of three land use types at Edelweiler, Germany: plow tillage (PT), reduced tillage (RT), and grassland (GL). Soils were incubated for 112 days at 20 °C, with or without 14C-labelled maize residue (4 g DM kg−1 soil), with or without nitrogen (100 mg N kg−1 soil as NH4NO3) and with or without intensive mixing.
The effect of mineral-N on maize residue decomposition differed depending on the stage of decomposition and land use type. Nitrogen accelerated residue decomposition rates in the first 5 days in RT and GL soils, but not in PT soil, and decreased residue decomposition rate in all three land use types after 11 days. At the end of the incubation, N suppressed 14CO2 efflux in RT and PT soils, but not in GL soil. Mineral-N did not increase SOM decomposition independently on the land use types.
Intensive mixing stimulated decomposition of both plant residue and SOM in all three land use types. However, effects were smaller in GL soil than in RT or PT soil, presumably because stronger soil aggregates in GL would have been less affected by mixing and allowed greater protection of SOM and plant residue against decomposition. 相似文献
10.
枸杞产业已成为青藏高原的优势产业,但存在氮肥利用率低、环境污染等问题。适当施用氮肥和硝化抑制剂是减少氮肥气态损失、提高氮肥利用率和降低温室气体排放的有效途径。为探讨枸杞栽培的适宜施肥方式,于2020年在柴达木盆地青海诺木洪农场,以11年生宁杞1号为试验材料开展田间试验,设置4个处理：N267、N133处理分别施用纯氮267、133 kg·hm-2,N267I1.33、N133I0.67处理分别在N267、N133处理施氮量的基础上配施硝化抑制剂—2-氯-6(三氯甲基)-吡啶(nitrapyrin)1.33、0.67 kg·hm-2,研究施氮量和2-氯-6(三氯甲基)-吡啶对施用的15N-尿素在枸杞-土壤系统去向的影响。结果表明,N267I1.33处理枸杞全株的干物质量、吸氮量和植株15 相似文献
11.
Organic matter was extracted with pyrophosphate-NaOH buffer, pH 8.0 from the 02 horizon of a hardwood forest and exposed to 15S-methionine for 18 h to allow the incorporation of the aminoacid into the extract. Compared with other amendments, supplementation of the incorporation medium with Na2SO4 yielded the highest recoveries of the labelled organic matter. This material was chemically recalcitrant, requiring treatment for 6 h at 121°C with 6
NaOH for complete release of the incorporated methionine. A and B horizon soils from several forests were exposed to labelled material following dialysis to remove unlabelled components and a minor 35S-labeIled component. All samples began to release 35S-methionine after 48 h. Further metabolism of this amino-acid included mineralization and conversion to cysteine. A portion of the sulfate-S generated from mineralization was incorporated into organic matter and was recovered only by acid and alkali extraction. 35S-labelled methionine and cysteine were also found in these latter fractions, indicating that these amino-acids had been directly incorporated into organic material during exposure. 相似文献
12.
Long-term management impacts on soil C, N and physical fertility: Part I: Broadbalk experiment 总被引：1，自引：0，他引：1
For many centuries manure application to the soil has been common practice. Organic amendments and fertiliser applications can increase crop yields and soil organic matter (SOM). However, the long-term impacts on soil physical fertility are often neglected. This study was carried out on the Broadbalk Wheat Experiment at Rothamsted, UK, established in 1843 on an Aquic/Typic Paleudalf soil. Application of farmyard manure (FYM), N fertiliser and wheat straw on total organic C (CT), labile C (CL) and non-labile C (CNL), total N (NT), mean weight diameter (MWD) and unsaturated hydraulic conductivity (Kunsat) were studied on wheat (Triticum aestivum) and adjacent woodland and pasture areas. Manure additions, N fertiliser and straw incorporation increased all C fractions, particularly the CL fraction. The addition of 35 t ha−1 year−1 of FYM increased CT to 2.5 times that of the control (no fertiliser) treatment and CL to 5 times that of the control. With highest N application and straw returned, CT increased by 1.3 times and CL by 1.5 times that of the control treatment. There were linear relationships between rate of N fertiliser applied and all C fractions, with the rate of increase almost double with straw than straw removed. Manure application improved MWD, as did high N fertiliser additions with straw returned. Application of N fertiliser only increased MWD and Kunsat (at 10 mm tension) if straw was returned, while the addition of manure resulted in decreased Kunsat. The highest Kunsat rate was on the high N fertiliser, straw returned treatments. The uncropped areas all had high soil structural stability. Similar relationships occurred between all C fractions and NT and MWD for the high C soils, but relationships were much stronger with CL than the other C fractions in the low C soils. These results showed that soils with low C concentration are more reliant on CL for structural stability. 相似文献
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长期施肥下黑土不同团聚体氮组分的植物有效性差异 总被引：1，自引：0，他引：1
16.
Theodore Karyotis Davis D. Onduru Christos Noulas Louis N. Gachimbi Fred N. Muchena 《Soil Science and Plant Nutrition》2005,51(5):645-648
The nutrients status and properties in Kenyan soils (Kiambu, Mbeere Districts) are reported with the aim to elucidate the factors of productivity decline. According to the FAO (1988) system the studied soils were classified as humic Nitisols, haplic Acrisols or luvic Arenosols. The soils were found acidic, as a result of leaching of exchangeable cations and they are poor in organic carbon. Cation exchange capacity was extremely low in the sandy soils of Mbeere. Available phosphorus and exchangeable K+ were low inducing a crucial problem of soil fertility. Among the micronutrients, manganese extracted by DTPA was most abundant element, while micronutrients extracted by 4 M HNO3 ranked as follows: Fe>Mn>Zn>Cu. Copper (DTPA) was low and manganese was extremely high in Kiambu. Iron content varied greatly, while decreased zinc was observed in Mbeere. Nitrogen mineralization over an incubation period of 30 weeks ranged from 54.64 to 145.50 mg kg−1 and represents 4.53–21.09% of the total soil nitrogen. Soil nitrogen was associated to soil organic carbon and was strongly correlated to total soil N. Water harvesting, liming, and improved management of composting and manure are amongst the measures to restore soil fertility. 相似文献
17.
S. Hang M. Nassetta A.I. Caas E.A. Rampoldi M.V. Fernndez-Canigia M. Díaz-Zorita 《Soil & Tillage Research》2007,96(1-2):243-249
The effect of application dose and soil organic matter (SOM) stratification on changes in atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) extractable residues (ER) were investigated. Two soils [Entic Haplustoll (EH) and Typic Hapludoll (TH)] with contrasting SOM content and form and without previous atrazine exposure were selected. Sampling was carried out at two depths: 0–2 and 2–5 cm. Atrazine ER were measured at 0, 3, 7, 14, 28, and 56 days in laboratory incubation. Atrazine concentration recovered 1 h after of its application (Ct0) was used as an index of the soil capacity to reduce the atrazine extractable fraction. SOM stratification was studied by means of physical fractionation. In both soils, the higher OC concentration was found in the 200–2000 μm fraction (OCf 200–2000). Soils differed in terms of the OCf 50–200/OCf 200–2000 ratio. This ratio increased with depth in EH soil: 0.23 (0–2 cm) and 2.00 (2–5 cm). In TH soil, the ratio was 0.80 (0–2 cm) and 0.50 (2–5 cm). The t1/2 values ranged from 9 to 19 days, depending on soil type and atrazine application dose. The upper layer Ct0 and k were higher for higher atrazine doses. Implementation of a split application dose of atrazine may be an effective alternative to extend its half-life in soil solution, as well as involving a lower potential risk of soil accumulation or vertical movement in the soil profile towards deep soil layers and groundwater. 相似文献
18.
The particle density of soil (ρS) represents one of the soil's basic physical properties and it depends on the composition of both the mineral and the organic soil components. It therefore varies for different soils, e.g. within the group of mineral soils, and ranges from 2.4–2.9 g cm−3. Hence, awareness of this variability is important for properties estimated by a calculation involving particle density. Because ρS depends on both the soil's solid mineral particles and soil organic matter composition, we derived a function based on the mixture ratio of these two soil components. This approach represents a further development of earlier investigations dealing with the influence of organic carbon (Corg) on ρS. To parameterise this function, two data sets were used: (1) data from soils with Corg contents between 0% and 54.88% and corresponding values of ρS between 1.49 and 2.72 g cm−3; and (2) data from soils of 17 German long-term experiments contrasting in soil texture and in soil mineral inventory. Data set 1 was used to quantify the influence of soil organic matter on ρS, and data set 2 was used to calculate the influence of mineral matrix on ρS. The soil organic matter has two major influences on ρS: (1) via a mass effect (expressed as a mixture ratio between organic and mineral soil components); and (2) via a quality effect (expressed as calculated changes in particle density of organic soil components). Here, we calculated that with increasing content of soil organic matter (0–100%), the particle density of organic soil components rose from about 1.10 to 1.50 g cm−3, and present possible reasons for this phenomenon. Additionally, we demonstrate that the mineral matrix of the soil affects ρS especially via variations in the mineral inventory, but conclude that differences in particle size distribution of soils were to a lesser extent suitable for describing the influence of the mineral matrix on ρS. Overall, using our approach should generate more realistic values of ρS, and consequently of all calculated parameters which are sensitive to ρS. 相似文献
19.
The relationships of pH to Mn concentrations in equilibrium soil solutions of strongly acid soils (pH < 4.5) were studied. The values of Mn concentrations did not conform to the solubility relationships of MnO2, Mn2O3 or Mn(OH)3. On the othr hand, a significant relationship between pMn and exchangeable Mn (r = 0.636**, N =43) was observed. This suggest that the levels of Mn in solution are primarily controlled by exchangeable Mn in response to pH changes.
Mineral soil samples when air-dried showed a 1.5 to more than 8-fold increase in amounts of NH4Cl-extractable Mn. This increase was not observed in soil samples rich in organic matter (> 5% organic carbon), thus excluding the possibility of release of Mn from the organic fraction of the soil. The increase is considered a consequence of increased solubility of Mn-oxides. 相似文献
20.
长期施肥下三种旱作土壤有机碳含量及其矿化势比较研究 总被引：1，自引：0，他引：1