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1.
Temporal and spatial trends in soil organic carbon stocks following maize cultivation in semi-arid Tanzania,East Africa 总被引:1,自引:0,他引:1
Torben Birch-Thomsen Bo Elberling Bjarne Fog Jakob Magid 《Nutrient Cycling in Agroecosystems》2007,79(3):291-302
Conversion of native ecosystems to agro-ecosystems influences the amount, quality and turnover of soil organic carbon (SOC).
As most agro-ecosystems are not in a steady state in terms of the content of SOC, the time scale and feedback mechanisms of
changes in SOC are highly relevant for predicting future soil fertility and potential rates of soil carbon losses or sequestration.
This paper focuses on changes in land use linked to measured changes in the distribution of total stocks of SOC and the δ13C signature in the upper 0.5 m of cultivated soils in the semi-arid parts of Tanzania. Based on documented land use changes
since 1950s using remote sensing data, 12 sampling sites along two transects were selected to represent semi-natural/natural
savannah and maize fields cultivated for up to five decades. Comparisons between sites representing a chronosequence of well-drained
soils showed that soils cultivated the last 50 years have in average less than 50% SOC compared to soils which have never
been cultivated. Variations between sites were significant and a reduction in SOC could not be established at sites near present
or former villages which have received substantial manure despite a long cultivation history or along a chronosequence representing
wetter and more fine-grained soils. Spatial variations in land use changes were parameterized based on remote sensing data
and successfully validated against sampling sites. Site-specific rates of soil element loss following cultivation were extrapolated
to the study area and uncertainties related to scaling up were discussed. 相似文献
2.
Intensity cultivation induced effects on soil organic carbon dynamic in the western cotton area of Burkina Faso 总被引:1,自引:0,他引:1
Badiori Ouattara Korodjouma Ouattara Georges Serpantié Abdoulaye Mando Michel P. Sédogo André Bationo 《Nutrient Cycling in Agroecosystems》2006,76(2-3):331-339
The soil organic carbon (SOC) dynamic is a key element of soil fertility in savannah ecosystems that form the key agricultural
lands in sub-Saharan Africa. In the western part of Burkina Faso, the land use is mostly linked to cotton-based cropping systems.
Use of mechanization, pesticides, and herbicides has induced modifications of the traditional shifting cultivation and increased
the need for sustainable soil fertility management. The SOC dynamic was assessed based on a large typology of land cultivation
intensity at Bondoukui. Thus, 102 farm plots were sampled at a soil depth of 0–15 cm, considering field–fallow successions,
the cultivation phase duration, tillage intensity, and soil texture. Physical fractionation of SOC was carried out by separating
the following particle size classes: 2,000–200, 200–50, 50–20, and 0–20 μm. The results exhibited an increase in SOC stock,
and a lower depletion rate with increase in clay content. After a long-term fallow period, the land cultivation led to an
annual loss of 31.5 g m−2 (2%) of its organic carbon during the first 20 years. The different fractions of SOC content were affected by this depletion
depending on cultivation intensity. The coarse SOC fraction (2,000–200 μm) was the most depleted. The ploughing-in of organic
matter (manure, crop residues) and the low frequency of the tillage system produced low soil carbon loss compared with annual
ploughing. Human-induced disturbances (wildfire, overgrazing, fuel wood collection, decreasing fallow duration, increasing
crop duration) in savannah land did not permit the SOC levels to reach those of the shifting cultivation system. 相似文献
3.
建立了以KMnO。测定土壤中有机碳的分光光度法。在硫酸介质中,有机碳能快速、定量的还原高锰酸根,在加入有机碳前后,高锰酸钾溶液在波长525nm处的吸光度发生明显变化,且吸光度之差△A与加入的有机碳的浓度成正比。结果表明,有机碳浓度在0.40—28.00mg/L范围内与溶液吸光度差值呈良好线性关系,线性回归方程为△A=0.0466p+0.058(mg/L),相关系数r=0.9987,检出限为0.170mg/a,相对标准偏差(RSD)为0.390%,表观摩尔吸光系数ε=8.39X10^3L/(mol·em)。用于测定国家标准土壤样品中有机碳的含量,相对标准偏差小于2.90%。 相似文献
4.
The significance of soil organic matter (SOM) in sustaining agriculture has long been recognized. The rate of change depends on climate, cropping system, cropping practice, and soil moisture. A 3-yr on-farm study was conducted in two major agro-ecologies (hills with warm-temperate climate and plains with subtropical climate) of Nepal. The soils in warm-temperate climate are Lithic subgroups of Ustorthents with well-drained loamy texture, and in subtropical climate are Haplaquepts with imperfectly drained loamy texture. Farmers’ predominant cropping systems were selected from different cultivation length in addition to a reference sample collected from adjacent virgin forest. The objectives were to examine the effect of cultivation length and cropping system on total carbon, KMnO4-oxidizable soil C, C storage, and C/N ratio in two climatic scenarios: warm-temperate and subtropical. A large difference in KMnO4-oxidizable soil organic C was observed due to the effect of cultivation length and cropping system. However, TC remained similar during the 3-year study. The decrease in KMnO4-oxidizable C due to cultivation was more in the surface layer (43–56%) than in the subsurface layer (20–30%). Total C in uncultivated, < 10-year cultivated, and > 50-year cultivated soil was 22, 13, and 10 g kg−1 in warm-temperate climate and 10, 6, and 5 g kg−1 in subtropical climate, respectively. During the 3-year study period in both climates, large changes in soil C were observed for KMnO4-oxidizable C but not for TC, confirming our earlier work on the usefulness of the KMnO4 oxidized fraction for detecting a relatively short-term increase or decrease in soil C pool. The TC storage in uncultivated, < 10-year cultivated, and > 50-year cultivated soil was 38, 25, and 19 Mg ha−1 in warm-temperate climate and 22, 15, and 12 Mg ha−1 in subtropical climate, respectively. The rice–wheat and maize–potato cropping systems were good in storing soil C of 30 and 20 Mg ha−1 for 0–15-cm soil depth in warm-temperate climate. The rice–wheat cropping system was also good in storing soil C in subtropical climate (19 Mg ha−1) compared with other cropping systems studied. 相似文献
5.
Organic carbon is known to alter crop response to applied phosphorus (P) but that fact has not been incorporated in soil test interpretations. To achieve this objective, field experiments with wheat were conducted for four years on alkaline soils of Punjab, India. The experimental soils ranged from loamy sand to loam in texture, 7.4 to 9.6 in pH, 0.16 to 0.75% in organic carbon (OC) and 2 to 40 mg Olsen extractable P kg–1 soil. Response of wheat to fertilizer phosphorus application was related to the combined effect of Olsen P and soil OC content. At a given Olsen P level, wheat yield was a function of soil OC content. Multiple regression analysis of the data showed that OC content <0.2% did not affect yield significantly. At values >0.6%, OC along with Olsen P accounted for 97% of the variation in yield and there was no response to applied fertilizer P. Yield isoquants for 4 and 5 tons grains ha–1 showed that for a given Olsen P level, as OC content increased the amount of fertilizer P required to achieve a yield target decreased. It was shown that OC may be used to approximate the contribution of organic P mineralization to plant available soil P during a growing season. The reliability of fertilizer recommendations based on Olsen P may be improved on some alkaline soils by consideration of soil OC content. 相似文献
6.
The objective of this study was to elucidate the sorption and desorption behaviors of PCE (Perchloroethylene, C2Cl4) in seven soils with different organic carbon (OC) content. Sorption/desorption kinetic and serial dilution desorption experiments were conducted in batch slurries. The sorption distribution coefficient (K d ) of PCE ranged from 0.60 to 4.66 L kg?1. K d tended to increase as the soil OC increased, but K oc tended to decrease, suggesting that adsorption into the mineral surface was not negligible in soils with low OC. Desorption kinetic data were analyzed by the two-site desorption model. The sorption/desorption of PCE was not reversible over short incubation times due to the presence of a non-desorbable site. The desorbable site fractions of PCE increased and non-desorbable site fractions decreased as the soil OC increased. It is suggested that partition of PCE into soil organic carbon is more reversible than adsorption on soil minerals. 相似文献
7.
Nitrogen and water are both major limiting factors for agronomic production in Africa. The effect of erosion on the availability of N and water for plants is not known for major soils of the tropics. Therefore, a study was conducted to assess erosional effects on N- and water-balance on a Mollic Andosol of 9–17% slope at Lyamungu Agricultural Research and Training Institute (ARTI), Kilimanjaro region, Tanzania. Soil erosion phases were established on the basis of the topsoil depth (TSD) as an indicator of previous erosion: < 15 cm; severely eroded, 16–25 cm; moderately eroded and 26–35 cm; slightly eroded. Fill-in lysimeters (80 cm diameter, 80 cm deep) and field runoff plots (4 × 10 m) were used to monitor evapotranspiration (ET) and seepage, and N losses through erosion, runoff, leaching and plant uptake. Maize (Zea mays var. Kilima) was planted in lysimeters and runoff-plots over two cropping seasons (1995 and 1996). Rainfall and evaporation (E) were measured daily. Sediment samples from runoff plots were analysed for total N, P and C, and water samples from leachate, runoff, and rainfall were analysed for NO3-, and NH4+. There were few effects of severity of past erosion on N and water balance, but the losses of N from the system during the time of observation were very high. More than 100 and 200 kg N ha-1 was lost in 1996 through erosion and leaching, respectively. Removal of N through plant material was about 120 kg ha-1 in 1995 and 60 kg ha-1 in 1996. A net depletion of 125 and 272 kg N ha-1 was observed in 1995 and 1996, respectively. The data show that the traditional system is far from sustainable and yield decline is expected to occur in the coming years unless measures are taken to improve its N balance. 相似文献
8.
Satoshi Nakamura Keiichi Hayashi Hide Omae Tabo Ramadjita Fatondji Dougbedji Hitoshi Shinjo Addam Kiari Saidou Satoshi Tobita 《Nutrient Cycling in Agroecosystems》2011,89(3):375-385
The fertility of sandy soils in the Sahelian zone (SZ) is extremely low. This poor soil fertility is one of the limiting factors of crop production in the SZ. Therefore, it is imperative to improve or to maintain soil fertility through various agricultural management methods. Further, it is well known that soil organic matter plays an important role in improving the physico-chemical properties of these sandy infertile soils. Therefore, it is essential to develop a suitable tool for the appropriate evaluation of soil organic carbon (SOC) dynamics in the SZ. Therefore, the Rothamsted carbon model (Roth-C) was verified in 32 treatments of two long-term field experiments with and without crop residue application. These experiments were performed by ICRISAT. The performance of the model was evaluated by statistical methods using four indices (RMSE: root mean square error, LOFIT: lack of fit, r: correlation coefficient, and M: mean difference). As a result, the predicted SOC values in the case without crop residue management decreased with time in approximately 10 cultivated years. In contrast, in the case with crop residue application, the predicted SOC remained roughly equal to the initial SOC value during the term observed. Mostly, the Roth-C-modelled values agreed well with the actual value. RMSE and LOFIT, the statistical indicators of agreement between predicted and observed values, showed a significant conformity between the predicted and observed SOC values in all the 32 treatments. This fact means that Roth-C can estimate long-term SOC dynamics of several technical options that developed with short-term trials. Moreover the annual carbon requirement for SOC maintaining can be calculate if enough number of cases was estimated. And also analysis of regional carbon dynamics was made possible with using Roth-C model. It will contribute to show the sustainable development in SZ against global warming and other climatic changes. 相似文献
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11.
Dissolved organic carbon loss fluxes through runoff and sediment on sloping upland of purple soil in the Sichuan Basin 总被引:1,自引:0,他引:1
Runoff is a major driver for dissolved organic carbon (DOC) diffusing into aquatic ecosystems. Transport of DOC in runoff is important in the C cycle of soils in an agricultural ecosystem. This study provides a combined dataset on DOC loss pathways and fluxes from sloping upland in the purple soil area of southwestern China. A free-drain lysimeter experiment was conducted to quantify DOC loss through overland flow (2010–2012), interflow (2010–2012) and sediment (2011–2012). Average annual cumulative discharges of overland and interflow were 58.3 ± 3.1 and 289.4 ± 5.4 mm, accounting for 6.8 and 33.8 % of the totals during the entire rainy season, respectively. Average annual cumulative sediment loss flux was 183.5 ± 14.6 g m?2. Average DOC concentrations in overland flow and interflow were 3.44 ± 0.36 and 3.04 ± 0.24 mg L?1, respectively. Average DOC content in sediment was 73.76 ± 4.09 mg kg?1. The relationship between DOC concentration and discharge in overland flow events could be described by a significant exponential decaying function (R = 0.53, P = 0.027). Average annual DOC loss fluxes through overland flow, interflow and sediment were 163.6 ± 28.5, 865.5 ± 82.5 and 9.4 ± 1.5 mg m?2, respectively, and total DOC loss was 1,038.5 ± 112.5 mg m?2. The results suggest that interflow is the major driver of DOC leaching loss on sloping upland. It is shown that interflow is fundamentally important for reducing DOC loss on sloping croplands in the Sichuan Basin and possibly beyond. 相似文献
12.
Katrin Mackenzie Juergen Battke Robert Koehler Frank-Dieter Kopinke 《Applied catalysis. B, Environmental》2005,59(3-4):171-179
The hydrolysis reaction of 1,1,2,2-tetrachloroethane (TeCA) is significantly enhanced by sorption on activated carbon. TeCA is quantitatively transformed into trichloroethene (TCE) at moderate pH values. This transformation is exploited as the basic step of a site-adapted groundwater-cleanup technology. The volatility of TCE is a factor of 23 higher than that of TeCA such that the partially dehydrochlorinated product can be easily stripped out of the groundwater flow. The base-mediated and the neutral dehydrochlorination of TeCA were studied as a function of temperature and pH value in batch and column experiments. Surprisingly, it was found that despite high loadings of the sorbent with TeCA and TCE (≥20 wt.%) the TeCA remains available for the hydrolysis reaction. 相似文献
13.
Nitrogen management in organic farming: comparison of crop rotation residual effects on yields,N leaching and soil conditions 总被引:2,自引:0,他引:2
Manfred Kayser Jürgen Müller Johannes Isselstein 《Nutrient Cycling in Agroecosystems》2010,87(1):21-31
After 3 years of different crop rotations in an organic farming experiment on a sandy soil in northwest Germany, spring triticale
was cultivated on all plots in the fourth year to investigate residual effects on yield, nitrogen (N) leaching and nutrient
status in the soil. Previous crop rotations differed in the way N was supplied, either by farmyard manure (FYM, 100 and 200 kg N ha−1 year−1) or by arable legumes like grass-red clover and field beans, or as a control with no N. Other crops in the rotations were
maize, winter triticale and spring barley. Additional plots had a 3-year grass-clover ley, that was ploughed-in for spring
triticale in the fourth year. Yields of spring triticale were moderate and largest for ploughed-in grassland leys and grass-red
clover and plots that had previously received farmyard manure. The former crop rotation, including grassland break-up, had
a significant effect on most yield and environmental parameters like residual soil mineral nitrogen (SMN) and N leaching and
on the level of available K in the soil. The single crop harvested in the year before spring triticale had a significant effect
on yield parameters of spring triticale, less so on SMN and N leaching in the fourth year and no effect on available nutrients
(P, K, Mg) and pH in the soil. We conclude that the effects of arable legumes were rather short lived while ploughing of 3-year
grassland leys had a profound influence on mineralization processes and subsequently on yield and N losses. 相似文献
14.
Rasmus Einarsson Christel Cederberg Jonatan Kallus 《Nutrient Cycling in Agroecosystems》2018,110(1):25-38
This paper analyzes nitrogen (N) flows on organic and conventional dairy farms in Sweden, and compares three indicators for the N pollution associated with the milk: (1) the farm-gate N surplus, (2) the chain N surplus, and (3) the N footprint. We find that, compared to indicators based on N surplus, the N footprint is a more understandable indicator for the N pollution associated with a product. However, the N footprint is not a replacement for the often-used farm-gate N surplus per unit area, since the two indicators give different information. An uncertainty analysis shows that, despite the large dataset, 1566 conventional and 283 organic farms, there is substantial uncertainty in the indicator values, of which a large part is due to possible bias in estimates of biological N fixation (BNF). Hence, although the best estimate is that conventional milk has 10–20% higher indicator values than organic, it is conceivable that improved estimates of BNF will change that conclusion. All three indicators simplify reality by aggregating N flows over time and space, and of different chemical forms. Thus, they hide many complexities with environmental relevance, which means that they can be misleading for decision-makers. This motivates further research on the relation between N surpluses and N footprints, and actual environmental damages. 相似文献
15.
Temperature effects on soil organic sulphur mineralization and elemental sulphur oxidation in subtropical soils of varying pH 总被引:1,自引:0,他引:1
AFF>Ramesh C. Jaggi Milkha S. Aulakh Randhir Sharma 《Nutrient Cycling in Agroecosystems》1999,54(2):175-182
The increasing sulphur (S) deficiency in soils of several parts of world has led to the use of fertilizer S, an important factor in enhancing the production and quality of crops. Very limited information is available on the use of elemental sulphur (S0) as a fertilizer, its oxidation into SO42- and transformation into organic S in semiarid subtropical soils. We studied the impact of three temperature regimes on the mineralization of soil organic S, and the oxidation and immobilization of S0 in acidic (pH 4.9), neutral (pH 7.1) and alkaline (pH 10.2) subtropical soils of north-western India. Repacked soil cores were incubated under aerobic conditions (60% water-filled pore space) for 0, 14, 28 and 42 d with and without incorporated S0 (500 g g-1 soil). Temperature had profound effects on all three soils processes, the rates of mineralization of native soil organic S, oxidation of applied S0 and transformation of S0 into soil organic S being greatest at 36 °C, irrespective of soil pH. Mineralization of native soil organic S (without added S0) resulted in the accumulation of 39, 66 and 47 g SO42-–S g-1 soil in acidic, neutral and alkaline soil in 42 d period at 36 °C. Of the total mineralization, the majority (62 – 74%) occurred during the first 14 d period. Oxidation rate of added S0 during initial 14 d period at 36 °C was highest in alkaline soil (292 g S cm-2 d-1), followed by neutral soil ((180 g S cm-2 d-1) and lowest in acidic soil (125 g S cm-2 d-1). Of the applied 500 g S0 g-1 soil, 3.2 – 10.0%, 6.8 – 15.4% and 10.0 – 23.0% oxidized to SO42-, and 13.4 – 28.6%, 16.0 – 29.0% and 14.6 – 29.0% were transformed into organic S in 42 d period in acidic, neutral and alkaline soil, respectively. The results of our study suggest that in order to synchronize the availability of S with plant need, elemental S may be applied well before the seeding of crops, especially in acidic soil and in regions where temperature remains low. Substantial mineralization of native soil organic S in the absence of applied S0 and immobilization of applied S0 into organic S suggest that the role of soil biomass as source and sink could be exploited in long term S management. 相似文献
16.
David S. Powlson Penny R. Hirsch Philip C. Brookes 《Nutrient Cycling in Agroecosystems》2001,61(1-2):41-51
Soil is a large sink for organic carbon within the terrestrial biosphere. Practices which cause a decline in soil organic
matter cause CO2 release, in addition to damaging soil resilience and, often, agricultural productivity. The soil micro-organisms (collectively
the soil microbial biomass) are the agents of transformation of soil organic matter, nutrients and of most key soil processes.
Their activities are much influenced by soil physico-chemical and ecological interactions. This paper addresses two key issues.
Firstly, ways of managing, and the extent to which it is possible to manage, soil biological functions. Secondly, the methodologies
currently available for studying soil micro-organisms, and the functions they mediate, are discussed. It is concluded that,
as the world population develops in this new millennium, there will be an increased dependence upon biological processes in
soil to provide adequate crop nutrition for the majority of the world's farmers. Although a major increase in the use of artificial
fertilisers will be necessary on a global scale, this will not be an option for large numbers of farmers due to their poverty.
Instead they will rely on recycling of nutrients from animal and vegetable composts and urban wastes, and biological cycling
from nitrogen fixation and mycorrhizae. The challenge is to select the most appropriate topics for further research. Not all
aspects are likely to lead to significantly improved agricultural productivity, or sustainability within the foreseeable future.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
17.
Electrochemical nucleation of nickel on vitreous carbon electrodes: the influence of organic additives 总被引:1,自引:0,他引:1
R. Albalat E. Gómez C. Müller M. Sarret E. Vallés 《Journal of Applied Electrochemistry》1991,21(8):709-715
The initial stages of the electrodeposition of nickel onto vitreous carbon from ethanol/water chloride solutions was studied in the presence and absence of some organic compounds. The influence of both additives and metal concentration was investigated by cyclic voltammetry, potential step experiments and differential capacity measurements. The role of the additives in the deposition process related to their adsorption, both on vitreous carbon and on vitreous carbon/nickel deposited electrodes, is also discussed. 相似文献
18.
19.
Bromocresol green (BCG) and bromophenol blue (BPB) in acidic and basic forms are used as dispersing agents to suspend multiple-walled carbon nanotubes (MWCNTs) into deionized water. The chemical structures of dye molecules are characterized by ultraviolet-visible-near infrared and nuclear magnetic resonance spectroscopic techniques. The presence of MWCNTs in water is evidenced by Raman spectra and the attachment of dye molecules to nanotubes is suggested by analysis of transmission electron microscope images. All dyes exhibit critical concentrations in dispersing MWCNTs. This may result from the formation of dye micelles, which induces osmotic pressure on MWCNTs and aids nanotube re-aggregation. The critical values of the basic dyes are lower than their acidic counterparts, which can be ascribed to the stronger hydrophilicity of basic dyes. The critical value of basic BCG is lower than basic BPB and this can be attributed to the effect of methyl substitutes in the former. Basic BCG is superior to basic BPB in stabilizing MWCNTs, which may result from the extra steric hindrance provided by the methyl substitutes. 相似文献
20.
Soil organic carbon,total nitrogen and grain yields under long-term fertilizations in the upland red soil of southern China 总被引:13,自引:0,他引:13
A long-term experiment with various fertilizations was carried out during 1990–2006 in a double cropping system rotated with
wheat (Triticum Aestivium L.) and corn (Zea mays L.) in the red soil of southern China. The experiment consisted of eight treatments: non-fertilization (CK), nitrogen–phosphorus
fertilization (NP), phosphorus–potassium fertilization (PK), nitrogen–phosphorus–potassium fertilization (NPK), pig manure
(M), pig manure and NPK fertilization (NPKM), high rates of NPKM (hNPKM), and straw returned with inorganic fertilizers (NPKS).
Applications of manure (i.e., M, NPKM and hNPKM) significantly increased soil organic carbon (SOC) and total nitrogen contents.
Applications of inorganic fertilizers without manure showed small influences on SOC, but resulted in declines of soil total
nitrogen over the long-term experiment. Grain yields were more than doubled under fertilizations for both wheat and corn,
with the highest under the NPKM and hNPKM treatments and the lowest under non-fertilization. Long-term cropping practices
without fertilization or with unbalanced fertilizations (e.g., NP and PK) caused low grain yields. The balanced fertilization
of NPK increased grain yields. However, such practice was not able to maintain high grain yields during the last few years
of experiment. Our analyses indicate that both wheat and corn grain yields are significantly correlated with SOC, total and
available nitrogen and phosphorus. However, the relationships are stronger with total nitrogen (r = 0.5–0.6) than with available nitrogen (r = 0.26–0.3), indicating the importance of maintaining soil total nitrogen in agricultural practice. 相似文献