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1.
Soil properties and C dynamics in abandoned and cultivated farmlands in a semi-arid ecosystem 总被引:1,自引:0,他引:1
Fayez Raiesi 《Plant and Soil》2012,351(1-2):161-175
Background and Aims
Land abandonment might be an alternative management for restoring soil conditions and C from prolonged cultivation and agricultural practices. In the present study, the influence of 18–22?years of land abandonment on soil properties, C dynamics and microbial biomass was evaluated in closely situated wheat and alfalfa farmlands, and abandoned lands on calcareous soils, Central Iran.Methods
Soil properties of the 0–15 and 15–30?cm depths from abandoned lands were compared to those from conventionally cultivated lands (i.e., continuous wheat–fallow and alfalfa–wheat rotation) common in calcareous soils of Central Zagros Mountains.Results
Soil bulk density in the 0–15 and 15–30?cm layers decreased significantly while total porosity increased significantly in abandoned lands. Generally, soil aggregate stability tended to increase within the abandoned fields owing to increased water-stable macro-aggregates. Soil organic C (OC) contents (g kg?1) and pools (Mg ha?1) in the 0–15?cm soil layer increased significantly in abandoned lands compared with cultivated lands, with no effect in the 15–30?cm soil layer after 18–22?years of land abandonment, suggesting the restoration of C is pronounced in the upper 0–15?cm soil depth . The total C accumulation in abandoned lands was 7.0?Mg?C?ha?1 for the entire sampling depth (0–30?cm) over the 18–22?years of land abandonment, which was 26% greater relative to cultivated lands. Carbon mineralization (Cmin) followed a trend similar to organic C, whereas C turnover (Cmin/OC ratio) was slightly greater in wheat fields. However, soil microbial biomass C (MBC) did not vary considerably among the three land uses.Conclusions
In brief, improvements, albeit slowly, in soil properties of the top layer with the cessation of cultivation indicated that land abandonment may result in enhanced soil C sequestration, and would maintain fertility and productivity of the farmlands of semi-arid climates. 相似文献2.
Background and aims
The impacts of atmospheric nitrogen (N) deposition on terrestrial ecosystem processes remain controversial, mostly because of the uncertainty regarding the fates of deposited N. We conducted a 16-week simulated deposition study to experimentally trace N in a greenhouse plant-soil system.Methods
Using a two-way factorial design, we added (15NH4)2SO4 solution twice a week to pots containing different soil organic matter (SOM) content and with or without a live plant (Salix dasyclados). The recoveries of 15N in soil, plant biomass, and leaching solution were quantified.Results
We found most 15N was retained in soil (18.0–59.2%), with significantly more 15N recovered from high-SOM soils than from low-SOM soils. Plant presence significantly increased 15N retention in soil. Plant biomass accounted for 10–20% of the 15N input, with proportionally more 15N assimilated when plants were grown in low-SOM soils. Leaching loss of 15N was relatively low (10–17%).Conclusion
Our study suggests that SOM content and plant presence significantly affect the fates of deposited N. Indeed, N would be preferentially retained in soils with high SOM content and live plant, while plants would assimilate more deposited N when grown in low SOM soils. Global biogeochemical models thus need to incorporate such soil-specific N retention and plant N assimilation. 相似文献3.
Sean D. Mason Mike J. McLaughlin Caroline Johnston Ann McNeill 《Plant and Soil》2013,373(1-2):711-722
Background and aims
Recent research has demonstrated the high accuracy of a new method for assessment of plant available P in soil called diffusive gradients in thin-films (DGT). The process of P released by additions of bicarbonate to soil samples simulating common soil P tests is yet to be assessed by the new method (DGT). The aim of this study was to identify the pools of soil P extracted by soil test methods (DGT, Colwell and resin) by comparing, in 32P–labelled soils, the specific activity (SA) of phosphorus extracted by common soil test extracts with the SA of wheat plants grown in a range of agricultural soils from southern Australia.Methods
Wheat (cv. Frame) was grown for 4 weeks in 14 soils that were labelled uniformly with carrier-free 32P. The specific activity (SA) of P (MBq 32P kg 31P?1) in each soil test extract was compared to the SA of P in the wheat plants.Results
The SA of P in plants were similar to P extracted by the Colwell extractant in only 4 of the 14 soils; while SA in plants and extractants corresponded in 10 of the soils for the resin method and in 12 of the soils for the DGT method. Phosphorus in the Colwell and resin extract solutions had significantly lower SAs compared to P in the plants for 10 and 4 of the soils, respectively, indicating greater extraction of non-labile P sources (unlabelled 31P). Phosphorus in the DGT extractant had significantly lower SA than the plants for 1 soil and in 1 soil the SA was higher. Overall, across all soils, 25 % of P extracted by the Colwell method was non labile compared to 9 % and 2 % for the resin and DGT methods, respectively.Conclusion
The new DGT method for extraction of soil P has the potential to accurately predict occurrences of P deficiency because it generally extracts the same pool of labile soil P accessed by wheat plants, while methods using bicarbonate solution (e.g. Colwell, Olsen) or water (resin) at wide soil:solution ratios are more likely to measure more non-labile forms of P in soil. 相似文献4.
Yuping Wu Sarah Kemmitt Rodger P. White Jianming Xu Philip C. Brookes 《Plant and Soil》2012,352(1-2):51-63
Aims
To determine if the soil microbial biomass in a 60?year fallow soil of the Highfield Ley-Arable Experiment at Rothamsted Research, UK, had maintained its ability to mineralise soil organic matter and added substrates compared to biomasses in a grassland and arable soil of the same experiment.Materials and methods
Three soils of the same type: a 60 y permanent fallow, arable and grassland, were incubated (25°C, 40% WHC) with and without 1. a labile substrate (yeast extract, C/N ratio 3.6) or 2. more resistant ryegrass, (< 2?mm, C/N ratio 14.6). Measurements included biomass C, ATP, PLFAs and substrate C mineralization.Results
Mean biomass C and ATP concentrations were:grassland.arable.fallow, as expected. However, substrate C mineralization was less in the grassland than fallow soil, opposite to that expected. Microbial biosynthesis efficiency (measured as biomass C and ATP) was similar in all soils. However, microbial community structure differed significantly between soils and treatments.Conclusions
The extent of mineralization of both substrates were unrelated to initial microbial community structure, size or soil management. Thus, the biomass in the fallow soil maintained full metabolic capacity (assessed by CO2-C evolution) compared to permanent arable or grassland soils. 相似文献5.
Aims
We investigated whether changes in respiratory C fluxes, soil CO2 efflux, or root exudate quantity or quality explained differences in growth rates between closely related clones of Pinus taeda (L.).Methods
A factorial design with two clones, fertilized and control treatments, and four sequential harvests was installed in a greenhouse for 121 days.Results
The two clones did show significant differences in respiratory C fluxes, soil CO2 efflux, and root exudation quantity and quality. While the clones also differed in growth rates, the C fluxes assessed in this paper did not explain how seedlings were able to allocate more C to stem growth in the months following fertilizer application. Changes in root exudation were not consistent with reduced heterotrophic soil CO2 efflux, which does not appear to be a plant-mediated process.Conclusions
These results indicate that if single genotypes are deployed over large land areas in plantations, dramatic differences between clonal plant-soil interactions may require consideration in ecosystem C budgets. Further, the range of belowground fluxes observed implies that genotype-specific C allocation may make some clones better able to exploit a given resource environment than others. 相似文献6.
Aluminum tolerance of wheat does not induce changes in dominant bacterial community composition or abundance in an acidic soil 总被引:1,自引:0,他引:1
Chao Wang Xue Qiang Zhao Rong Fu Chen Hai Yan Chu Ren Fang Shen 《Plant and Soil》2013,367(1-2):275-284
Aims
Aluminum-tolerant wheat plants often produce more root exudates such as malate and phosphate than aluminum-sensitive ones under aluminum (Al) stress, which provides environmental differences for microorganism growth in their rhizosphere soils. This study investigated whether soil bacterial community composition and abundance can be affected by wheat plants with different Al tolerance.Methods
Two wheat varieties, Atlas 66 (Al-tolerant) and Scout 66 (Al-sensitive), were grown for 60 days in acidic soils amended with or without CaCO3. Plant growth, soil pH, exchangeable Al content, bacterial community composition and abundance were investigated.Results
Atlas 66 showed better growth and lower rhizosphere soil pH than Scout 66 irrespective of CaCO3 amendment or not, while there was no significant difference in the exchangeable Al content of rhizosphere soil between the two wheat lines. The dominant bacterial community composition and abundance in rhizosphere soils did not differ between Atlas 66 and Scout 66, although the bacterial abundance in rhizosphere soil of both wheat lines was significantly higher than that in bulk soil. Sphingobacteriales, Clostridiales, Burkholderiales and Acidobacteriales were the dominant bacteria phylotypes.Conclusions
The difference in wheat Al tolerance does not induce the changes in the dominant bacterial community composition or abundance in the rhizosphere soils. 相似文献7.
Background and Aims
Crop residues are important for the redistribution of alkalinity within soils. A net increase in pH following residue addition to soil is typically reported. However, effects are inconsistent in the field due to confounding soil processes and agronomic practises.Methods
A column experiment investigated the effects of canola, chickpea and wheat residues, differing in alkalinity content and C:N ratio, on soil pH changes in a Podosol (Podzol; initial pH 4.5) and Tenosol (Cambisol; initial pH 6.2) under field conditions.Results
Residues (10 g dry matter kg-1 soil; 0–10 cm) increased soil pH, and temporal changes in alkalinity depended on the residue and soil type. Alkalinity was generated via abiotic association reactions between H+ and added organic matter and via ammonification and decarboxylation processes during decomposition. Alkalinity from canola and chickpea residues moved down the soil profile (10–30 cm) and was attributed to nitrate immobilisation and organic anion decomposition by soil microbes.Conclusions
The application of residues to acid and moderately acid soils increased the pH of both topsoil and subsoils, which persisted over 26 months. Maximal increase of pH observed at 3 months was correlated with the concentration of excess cations in the residues. 相似文献8.
H. L. van Asperen A. M. C. Bor M. P. W. Sonneveld H. J. Bruins N. Lazarovitch 《Plant and Soil》2014,374(1-2):779-792
Background and aims
In the Central Negev hills (Israel) many ancient terraced wadis exist, which captured run-off and caused gradual soil aggradation, which enabled agricultural practices. In these terraces, dark colored soil horizons were observed, containing charcoal, as can be found in Terra Preta soils, suggesting higher fertility compared to natural soils. The aim of our investigation was to investigate these anthropogenic soils and to study the effects of charcoal and ash addition on soil properties and crop growth.Methods
We investigated 12 soil profiles, focusing on possible differences between light and dark colored soil horizons. We also investigated the effects of amendment of charcoal and ash on the growth of wheat (Triticum Aestivum L.) in a 40-day pot experiment involving two water regimes.Results
Results show that charcoal content in light and dark horizons were both low (<0.2 %), but significantly lower bulk densities were found in dark colored horizons. In the crop experiment, charcoal addition resulted in decreased crop growth, while, in the water deficit regime, ash addition resulted in increased crop growth.Conclusions
Considering the observed charcoal and the results from the crop experiment, we hypothesize that, in ancient run-off capturing agricultural systems, ash was purposefully added as fertilizer. 相似文献9.
Effects of condensed tannins in conifer leaves on the composition and activity of the soil microbial community in a tropical montane forest 总被引:1,自引:0,他引:1
Background and aims
Condensed tannins, a dominant class of plant secondary metabolites, play potentially important roles in plant-soil feedbacks by influencing the soil microbial community. Effects of condensed tannins on the soil microbial community and activity were examined by a short-term tannin-addition experiment under field and laboratory conditions.Methods
Condensed tannins were extracted from the leaves of a dominant conifer (Dacrydium gracilis) in a tropical montane forest on Mt. Kinabalu, Borneo. The extracted tannins were added to soils beneath the conifer and a dominant broadleaf (Lithocarpus clementianus) to evaluate the dependence of the response to tannin addition on the initial composition of the soil microbial community.Results
Enzyme activities in the field tannin-addition treatment were lower than in the deionized-water treatment. Carbon and nitrogen mineralization were also inhibited by tannin-addition. The fungi-to-bacteria ratio after tannin-addition was higher compared with the distilled-water treatment in the laboratory experiment.Conclusions
Based on our results, we suggest that the higher concentration of condensed tannins in the leaf tissues of Dacrydium than in those of Lithocarpus is a factor influencing the microbial community and activity. This may have influences on subsequent plant performance, which induces plant-soil feedback processes that can control dynamics of the tropical montane forest ecosystem. 相似文献10.
Tao Zhang Yongfu Li Scott X. Chang Peikun Jiang Guomo Zhou Juan Liu Lin Lin 《Plant and Soil》2013,367(1-2):249-261
Background and aims
Land-use change often markedly alters soil carbon (C) and nitrogen (N) pool sizes with implications for climate change and soil sustainability. The objective of this research was to study the effect of converting paddy fields to Lei bamboo (Phyllostachys praecox) stands on soil C and N and other nutrient pools as well as the chemical structure of soil organic C (SOC) in the soil profile.Methods
Soils (Anthrosols) from four adjacent paddy field–bamboo forest pairs with a known land-use history were sampled from Lin’an County, Zhejiang Province. Soil water soluble organic C (WSOC), hot water soluble organic C (HWSOC), microbial biomass C (MBC), readily oxidizable C (ROC), water soluble organic N (WSON), and other soil chemical and physical properties were determined. Soil organic C functional group compositions were determined by 13C-nuclear magnetic resonance (NMR).Results
Concentrations of soil available P, available K, and different N forms increased (P?<?0.05) by the land-use conversion. Higher concentrations of SOC and total N (TN) were observed in the subsoil (20–40 and 40–60 cm soil layers) but not in the topsoil (0–20 cm layer) in the bamboo stands than in the paddy fields. The storage of SOC and TN in the entire soil profile (0–60 cm) increased by 56.7 and 70.7 %, respectively, after the land-use change. The increases in the SOC stock of the three soil layers were 11.0, 14.3, and 9.5 Mg C ha?1, respectively. The conversion decreased WSOC concentrations in the subsoil but increased the ROC concentration in the topsoil. Solid-state NMR spectroscopy of soil samples showed that the conversion increased (P?<?0.05) the O-alkyl C content while decreased the aromatic C content, alkyl C to O-alkyl C ratio (A/O-A), and aromaticity of SOC.Conclusions
Conversion of paddy fields to bamboo stands increased soil nutrient availability, and SOC and TN stocks. Effects of land-use change on C pools and C chemistry of SOC varied among different soil layers in the profile. The impact of the land-use conversion on soil organic C pools was not restricted to the topsoil, but changes in the subsoil were equally large and should be accounted for. 相似文献11.
Sarah M. Shannon Jonathan T. Bauer Wendy E. Anderson Heather L. Reynolds 《Plant and Soil》2014,382(1-2):317-328
Aims
Non-native shrubs are important invaders of the Eastern Deciduous Forest, dramatically altering forest structure and functioning. Study of invasion mechanisms in this system has emphasized aboveground processes, and plant-soil feedbacks are relatively unexplored as a mechanism of shrub dominance. We tested whether plant-soil feedback in this habitat is affected by competition and whether arbuscular mycorrhizal fungi (AMF) are involved in plant-soil feedback.Methods
We used a standard two-phase plant-soil feedback experiment run concurrently for each of three invasive shrub species, measuring feedback effects on AMF colonization, aboveground biomass, and the responses of native plant species in greenhouse mesocosms.Results
Lonicera maackii and Ligustrum vulgare reduced AMF colonization of native roots, both with legacy effects (prior growth in soil) and direct effects (current growth in soil). Elaeagnus umbellata grown with natives left a legacy of increased AMF colonization of native communities.Conclusions
Our results suggest that woody invasive species can alter the AMF associations of native plants even after the invasive is no longer present. Such consequences merit study with other native species and where environmental factors, such as light availability, might be expected to compound the effects of changes in AMF. 相似文献12.
Jian Jin Caixian Tang Roger Armstrong Clayton Butterly Peter Sale 《Plant and Soil》2013,368(1-2):315-328
Aims
The efficient management of phosphorus (P) in cropping systems remains a challenge due to climate change. We tested how plant species access P pools in soils of varying P status (Olsen-P 3.2–17.6 mg?kg?1), under elevated atmosphere CO2 (eCO2).Methods
Chickpea (Cicer arietinum L.) and wheat (Triticum aestivum L.) plants were grown in rhizo-boxes containing Vertosol or Calcarosol soil, with two contrasting P fertilizer histories for each soil, and exposed to ambient (380 ppm) or eCO2 (700 ppm) for 6 weeks.Results
The NaHCO3-extractable inorganic P (Pi) in the rhizosphere was depleted by both wheat and chickpea in all soils, but was not significantly affected by CO2 treatment. However, NaHCO3-extractable organic P (Po) accumulated, especially under eCO2 in soils with high P status. The NaOH-extractable Po under eCO2 accumulated only in the Vertosol with high P status. Crop species did not exhibit different eCO2-triggered capabilities to access any P pool in either soil, though wheat depleted NaHCO3-Pi and NaOH-Pi in the rhizosphere more than chickpea. Elevated CO2 increased microbial biomass C in the rhizosphere by an average of 21 %. Moreover, the size in Po fractions correlated with microbial C but not with rhizosphere pH or phosphatase activity.Conclusion
Elevated CO2 increased microbial biomass in the rhizosphere which in turn temporally immobilized P. This P immobilization was greater in soils with high than low P availability. 相似文献13.
Plant-soil interactions in Mediterranean forest and shrublands: impacts of climatic change 总被引:4,自引:0,他引:4
Background
In the Mediterranean climate, plants have evolved under conditions of low soil-water and nutrient availabilities and have acquired a series of adaptive traits that, in turn exert strong feedback on soil fertility, structure, and protection. As a result, plant-soil systems constitute complex interactive webs where these adaptive traits allow plants to maximize the use of scarce resources.Scope
It is necessary to review the current bibliography to highlight the most know characteristic mechanisms underlying Mediterranean plant-soil feed-backs and identify the processes that merit further research in order to reach an understanding of the plant-soil feed-backs and its capacity to cope with future global change scenarios. In this review, we characterize the functional and structural plant-soil relationships and feedbacks in Mediterranean regions. We thereafter discuss the effects of global change drivers on these complex interactions between plants and soil.Conclusions
The large plant diversity that characterizes Mediterranean ecosystems is associated to the success of coexisting species in avoiding competition for soil resources by differential exploitation in space (soil layers) and time (year and daily). Among plant and soil traits, high foliar nutrient re-translocation and large contents of recalcitrant compounds reduce nutrient cycling. Meanwhile increased allocation of resources to roots and soil enzymes help to protect against soil erosion and to improve soil fertility and capacity to retain water. The long-term evolutionary adaptation to drought of Mediterranean plants allows them to cope with moderate increases of drought without significant losses of production and survival in some species. However, other species have proved to be more sensitive decreasing their growth and increasing their mortality under moderate rising of drought. All these increases contribute to species composition shifts. Moreover, in more xeric sites, the desertification resulting from synergic interactions among some related process such as drought increases, torrential rainfall increases and human driven disturbances is an increasing concern. A research priority now is to discern the effects of long-term increases in atmospheric CO2 concentrations, warming, and drought on soil fertility and water availability and on the structure of soil communities (e.g., shifts from bacteria to fungi) and on patching vegetation and root-water uplift (from soil to plant and from soil deep layers to soil superficial layers) roles in desertification. 相似文献14.
Fanqiao Meng Jennifer A. J. Dungait Xuan Zhang Minyi He Yanbin Guo Wenliang Wu 《Plant and Soil》2013,373(1-2):755-764
Aims
Pulse labeling of crops using 13C is often employed to trace photosynthesized carbon (C) within crop-soil systems. However, few studies have compared the C distribution for different labeling periods. The overall aim of this study was to determine the length of the monitoring interval required after 13C-pulse labeling to quantify photosynthate C allocation into plant, soil and rhizosphere respiration pools for the entire growing season of maize (Zea mays L.).Methods
Pot grown maize was pulse-labeled with 13CO2 (98 at.?%) at the beginning of emergence, elongation, heading and grainfilling growth stages. The routing of 13C into shoot and root biomass, soil CO2 flux and soil organic carbon (SOC) pools was monitored for 27 days after 13C-pulse labeling at the beginning of each growth stage.Results
The majority of the 13C was recovered after 27 d in the maize shoots, i.e., 57 %, 53 %, 70 % and 80 %, at the emergence, elongation, heading, and grainfilling stages, respectively. More 13C was recovered in the root biomass at elongation (27 %) compared to the least at the grainfilling stage (3 %). The amount recovered in the soil was the smallest pool of 13C at emergence (2.3 %), elongation (3.8 %), heading and grainfilling (less than 2 %). The amount of 13C recovered in rhizosphere respiration, i.e. 13CO2, was greatest at emergence (26 %), and similar at the elongation, heading and grainfilling stages (~16 %).Conclusions
At least 24 days is required to effectively monitor the recovery of 13C after pulse labeling with 13CO2 for maize in plant and soil pools. The recovery of 13C differed between growth stages and corresponded to the changing metabolic requirements of the plant, which indicated labeling for the entire growth season would more accurately quantify the C budget in plant-soil system. 相似文献15.
Aims
Along a gradient of diminishing heavy metal (HM) concentrations formed by local inclusions of uranium mine soils into non-contaminated cropland, duplicate 1-m2 plots of 3 winter wheat cvs. (Akteur E, Brilliant A, and Bussard E) were established at 3 positions within a winter rye (cv. Visello) culture. It was the goal to determine permissible soil HM concentrations tolerated by cereal cvs. with variable excluder properties, and regulatory mechanisms which optimize the concentrations of essential minerals and radionuclide analogues in viable seeds from geologically related soils with diverging HM content.Methods
Total metal concentrations / nitrogen species in soils, shoots, and mature grains were determined by ICP-MS / spectrophotometry, and Kjeldahl analyses.Results
No non-permissible concentrations in grains of the 4 cereal cvs. were caused by elevated but aged total soil resources (mg kg-1 DW) in As (156); Cu (283); Mn (2,130); Pb (150); and in Zn (3,005) in the case of Bussard although CdCuZn elicited phytotoxicity symptoms. Uranium (41) contaminated grains of Akteur and Brilliant but not of Bussard and Visello due to their excluder properties. The concentration in Cd (41) had to be reduced to 20/2 mg kg-1 for the production by excluder cvs. of fodder/food grains. Cultivars excluding both HM and radionuclide analogues such as BaCsSr synchronously were not identified. Whereas plant tissue concentrations in the metalloprotein-associated elements CdCoCuMnNiZn rise and fall generally with Norg, grains of the wheat cvs. differed too little in Norg to designate variations in their metal acquisition rates solely as protein-regulated. Wheat grains confined nevertheless the concentrations in Cu to 11–14 mg kg-1 although the respective soil concentrations varied by factor 19. Grain deposition in CaFeMn(Zn) and in nuclides followed the same rules.Conclusions
It is hypothesized that cereals down-/up-regulate grain:soil transfer rates from soils with excessive/deficient trace metal resources to equip viable seeds with an optimum but not maximum in essential minerals. Positive correlations between metal concentrations in planta to those in soil can thereby be lost. 相似文献16.
Timothy J. Fahey Joseph B. Yavitt Ruth E. Sherman Peter M. Groffman Guoliang Wang 《Plant and Soil》2013,367(1-2):379-389
Background and aims
Trees allocate a high proportion of assimilated carbon belowground, but the partitioning of that C among ecosystem components is poorly understood thereby limiting our ability to predict responses of forest C dynamics to global change drivers.Methods
We labeled sugar maple saplings in natural forest with a pulse of photosynthetic 13C in late summer and traced the pulse over the following 3 years. We quantified the fate of belowground carbon by measuring 13C enrichment of roots, rhizosphere soil, soil respiration, soil aggregates and microbial biomass.Results
The pulse of 13C contributed strongly to root and rhizosphere respiration for over a year, and respiration comprised about 75 % of total belowground C allocation (TBCA) in the first year. We estimate that rhizosphere carbon flux (RCF) during the dormant season comprises at least 6 % of TBCA. After 3 years, 3.8 % of the C allocated belowground was recovered in soil organic matter, mostly in water-stable aggregates.Conclusions
A pulse of carbon allocated belowground in temperate forest supplies root respiration, root growth and RCF throughout the following year and a small proportion becomes stabilized in soil aggregates. 相似文献17.
Aims
Despite our current understanding of plant nitrogen (N) uptake and soil N dynamics in arable systems, the supply and demand of N are infrequently matched as a result of variable seasonal and soil conditions. Consequently, inefficiencies in N utilisation often lead to constrained production and can contribute to potential environmental impacts. The aim of this study was to examine the influence of plant residue quality (C/N ratio) and extent of residue incorporation into soil on temporal changes in soil mineral N and the associated plant N uptake by wheat in the semi-arid agricultural production zone of Western Australia.Methods
Oat (Avena sativa); lupin (Lupinus angustifolius) and field pea (Pisum sativum) were incorporated into a Red-Brown Earth using varying degrees of mechanical disturbance (0 to 100% residue incorporated). Soil samples for inorganic N (NO 3 ? and NH 4 + ) profiles (0?C50?cm), microbial biomass-C (0?C50?cm) and plant N uptake were taken throughout the growing season of the subsequent wheat (Triticum aestivum) crop. Grain yield and yield components were determined at harvest.Results
Despite observed treatment effects for plant residue type and soil disturbance, fluctuations in inorganic N were more readily influenced by seasonal variability associated with wet-dry cycles. Treatment effects resulting from residue management and extent of soil disturbance were also more readily distinguished in the NO 3 ? pool. The release of N from crop residues significantly increased (p?=?0.05) with greater soil-residue contact which related to the method of incorporation; the greater the extent of soil disturbance, the greater the net supply of inorganic N. Differences in microbial biomass-C were primarily associated with the type of plant residue incorporated, with higher microbial biomass generally associated with legume crops. No effect of residue incorporation method was noted for microbial biomass suggesting little effect of soil disturbance on the microbial population in this soil.Conclusions
Despite differences in the magnitude of N release, neither crop type nor incorporation method significantly altered the timing or pattern of N release. As such asynchrony of N supply was not improved through residue or soil management, or through increased microbial biomass in this semi-arid environment. N fluxes were primarily controlled by abiotic factors (e.g. climate), which in this study dominated over imposed agricultural management practices associated with residue management. 相似文献18.
Aim
To determine, for arable land in a temperate area, the effect of tree establishment and intercropping treatments, on the distribution of roots and soil organic carbon to a depth of 1.5 m.Methods
A poplar (Populus sp.) silvoarable agroforestry experiment including arable controls was established on arable land in lowland England in 1992. The trees were intercropped with an arable rotation or bare fallow for the first 11 years, thereafter grass was allowed to establish. Coarse and fine root distributions (to depths of up to 1.5 m and up to 5 m from the trees) were measured in 1996, 2003, and 2011. The amount and type of soil carbon to 1.5 m depth was also measured in 2011.Results
The trees, initially surrounded by arable crops rather than fallow, had a deeper coarse root distribution with less lateral expansion. In 2011, the combined length of tree and understorey vegetation roots was greater in the agroforestry treatments than the control, at depths below 0.9 m. Between 0 and 1.5 m depth, the fine root carbon in the agroforestry treatment (2.56 t ha-1) was 79% greater than that in the control (1.43 t ha?1). Although the soil organic carbon in the top 0.6 m under the trees (161 t C ha?1) was greater than in the control (142 t C ha?1), a tendency for smaller soil carbon levels beneath the trees at lower depths, meant that there was no overall tree effect when a 1.5 m soil depth was considered. From a limited sample, there was no tree effect on the proportion of recalcitrant soil organic carbon.Conclusions
The observed decline in soil carbon beneath the trees at soil depths greater than 60 cm, if observed elsewhere, has important implication for assessments of the role of afforestation and agroforestry in sequestering carbon. 相似文献19.
William S. Cuddy Brett A. Summerell Michelle M. Gehringer Brett A. Neilan 《Plant and Soil》2013,370(1-2):317-332
Background and aims
This study investigated the effect of cyanobacterial inoculants on salt tolerance in wheat.Methods
Unicyanobacterial crusts of Nostoc, Leptolyngbya and Microcoleus were established in sand pots. Salt stress was targeted at 6 and 13 dS m?1, corresponding to the wheat salt tolerance and 50 % yield reduction thresholds, respectively. Germinated wheat seeds were planted and grown for 14 (0 and 6 dS m?1) and 21 (13 dS m?1) days by which time seedlings had five emergent leaves. The effects of cyanobacterial inoculation and salinity on wheat growth were quantified using chlorophyll fluorescence, inductively coupled plasma-optical emission spectrometry and biomass measurements.Results
Chlorophyll fluorescence was negatively affected by soil salinity and no change was observed in inoculated wheat. Effective photochemical efficiency correlated with a large range of plant nutrient concentrations primarily in plant roots. Inoculation negatively affected wheat biomass and nutrient concentrations at all salinities, though the effects were fewer as salinity increased.Conclusions
The most likely explanation of these results is the sorption of nutrients to cyanobacterial extracellular polymeric substances, making them unavailable for plant uptake. These results suggest that cyanobacterial inoculation may not be appropriate for establishing wheat in saline soils but that cyanobacteria could be very useful for stabilising soils. 相似文献20.
Amending soils of different texture with six compost types: impact on soil nutrient availability, plant growth and nutrient uptake 总被引:1,自引:0,他引:1