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1.
《Soil Use and Management》2018,34(3):316-325
Tropical grasses grown as cover crops can mobilize phosphorus (P) in soil and have been suggested as a tool to increase soil P cycling and bioavailability. The objective of this study was to evaluate the effect of tropical grasses on soil P dynamics, lability, desorption kinetics and bioavailability to soya bean, specifically to test the hypothesis that introducing grass species in the cropping system may affect soil P availability and soya bean development according to soil P concentration. Three grass species, ruzi grass (Urochloa ruziziensis ), palisade grass (Urochloa brizantha ) and Guinea grass (Megathyrsus maximus ), were grown in soils with contrasting P status. Soya bean was grown after grasses to assess soil P bioavailability. Hedley P fractionation, microbial biomass P, phytase‐labile P and the diffusive gradient in thin films were determined, before and after cultivation. It was found that grasses remobilized soil P, reducing the concentration of recalcitrant P forms. The effect of grasses on changing the P desorption kinetics parameters did not directly explain the observed variation on P bioavailability to soya bean. Grasses and microorganisms solubilize recalcitrant organic P (Po) forms and tropical grasses grown as cover crops increased P bioavailability to soya bean mainly due to the supply of P by decomposition of grass residues in low‐P soil. However, no clear advantages in soya bean P nutrition were observed when in rotation with these grasses in high‐P soil. This study indicates that further advantages in soya bean P nutrition after tropical grasses may be impeded by phytate, which is not readily available to plants.  相似文献   

2.
As part of a study to simulate plant responses to leaks from pipelines, we injected natural gas into soil at a depth of 1 m in plots of grass, wheat and beans. Measurements of oxygen and methane in soil exposed to gas show that oxygen is depleted significantly to values less than would be caused by simple displacement by natural gas, indicating consumption within the soil by methanotrophic bacteria. Gas concentrations were clustered into two groups: 18% of the oxygen values were less than 1% by volume and 52% of the methane values were less than 5% by volume, indicating a tendency towards either oxygen‐limiting or methane‐limiting conditions. Oxygen depletion was significantly greater in summer. Depletion rates were greatest under grass, and least under wheat. In grass, 36% of the variation in depletion is explained by soil temperature at 10 cm with Q10 = 2.0 over the 0–20°C range. We developed a model that accounts for three gas exchange mechanisms: soil‐air displacement by the injected gas; gas consumption by bacteria; and re‐infusion of the soil atmosphere to account for a net loss of gas volume by consumption. Using this model, we calculate that an average of 37% of the methane was consumed. At initial methane concentrations less than 10% by volume, as much as 100% of the gas was consumed, but consumption efficiency decreased rapidly thereafter. These findings indicate that the soil sink for methane is dynamic and adaptive, acting as a significant constraint on underground methane sources, limited primarily by oxygen availability.  相似文献   

3.
The oxidation of atmospheric methane (CH4) by soil methanotrophic bacteria constitutes the only biological sink for this greenhouse gas. However, anthropogenic activities, in particular N fertilization, often (but not always) reduce this sink, by mechanisms only partly understood. We argue that the difficulty in developing a process-based understanding of the mechanisms involved is, in part, due to complex interactions with environmental conditions and N cycling, in combination with a lack of information on how the involved processes and organisms are organized within soil structure. We have developed a novel method which permits mapping of the spatial distribution of the active soil methanotrophs at a resolution well below 100 μm. In the present study, we applied this technique to a selection of plots from the Park Grass experiment at Rothamsted, UK, to which either no fertilizer, or (NH4)2SO4, NaNO3, or manure were applied for over 150 years. We measured the spatial distribution of CH4 assimilation four times throughout the 2008 growing season, together with field-based measurements of the soil CH4 sink. In general, methanotrophic activity was most pronounced within the top 10 cm of soil, and along the surface of aggregates and pore channels. Soil CH4 oxidation was controlled by soil moisture, with no differences between the plots after correcting for differences in soil moisture within the field site. Exceptions were on the (NH4)2SO4-treated plots in which acidification had occurred due to no or little liming. In these plots, methanotrophic activity was restricted to spots in deeper soil layers, which contributed only little to the sink for atmospheric CH4 due to diffusive limitation of the top soil layers. Our results suggest that spatial distribution of CH4 assimilation is controlled by local concentrations of NH4+ and/or pH within the soil structure. The effect of pH may be direct, or indirect through a reduction in nitrification rates and therefore increased NH4+ concentrations, or indirect through a mobilization of Al3+ which also might reduce methanotrophic activity. The concentration of ammonium ions, and their persistence in soil, will depend on the quantity of N applied, its rate of release through mineralization, and its rate of removal by either plant or microbial assimilation or nitrification. Our findings underline the importance of developing a detailed understanding of the spatial organisation of these processes since this will determine the nature and strength of their interactions. The technique we have shown here provides a powerful tool to achieve this goal.  相似文献   

4.
Tillage and wind effects on soil CO2 concentrations in muck soils   总被引：1，自引：0，他引：1  
Rising atmospheric carbon dioxide (CO2) concentrations from agricultural activities prompted the need to quantify greenhouse gas emissions to better understand carbon (C) cycling and its role in environmental quality. The specific objective of this work was to determine the effect of no-tillage, deep plowing and wind speeds on the soil CO2 concentration in muck (organic) soils of the Florida Everglades. Miniature infrared gas analyzers were installed at 30 cm and recorded every 15 min in muck soil plowed with the Harrell Switch Plow (HSP) to 41 cm and in soil Not Tilled (NT), i.e., not plowed in last 9 months. The soil CO2 concentration exhibited temporal dynamics independent of barometric pressure fluctuations. Loosening the soil resulted in a very rapid decline in CO2 concentration as a result of “wind-induced” gas exchange from the soil surface. Higher wind speeds during mid-day resulted in a more rapid loss of CO2 from the HSP than from the NT plots. The subtle trend in the NT plots was similar, but lower in magnitude. Tillage-induced change in soil air porosity enabled wind speed to affect the gas exchange and soil CO2 concentration at 30 cm, literally drawing the CO2 out of the soil resulting in a rapid decline in the CO2 concentration, indicating more rapid soil carbon loss with tillage. At the end of the study, CO2 concentrations in the NT plots averaged about 3.3% while that in the plowed plots was about 1.4%. Wind and associated aerodynamic pressure fluctuations affect gas exchange from soils, especially tilled muck soils with low bulk densities and high soil air porosity following tillage.  相似文献   

5.
No-tillage (NT) management is a promising method to sequester soil C and mitigate global warming caused by agricultural activities. Here, we report 4 years of continuous soil respiration rates and weekly nitrous oxide (N2O) and methane (CH4) emissions in NT and conventional-tillage (CT) plots in a typical Japanese volcanic soil. Overall, the soil respiration, N2O emission, and CH4 uptake decreased significantly in the NT plot. A difference in soil respiration and N2O emission between the two plots began after the tillage treatment and the incorporation of crop residues and fertilizers, whereas the CH4 uptake did not vary significantly during the fallow period after the treatments. The N2O emission was higher from the CT than from the NT plot during the fall. The overall lower CH4 uptake in the NT than in the CT plot likely resulted from a combination of decreased soil gas diffusivity and higher mineral N content at the soil surface. Higher soil respiration and N2O emission occurred in the NT plot in the summer of 2003 and were plausibly caused by an increase in the soil moisture content that resulted from lower temperatures during July and August; the higher soil moisture must have accelerated the decomposition of organic matter accumulated in the topsoil. These results indicate that NT management is generally effective for the mitigation of the total GWP by reducing soil respiration and N2O emission in temperate regions; however, NT management may increase rather than decrease these emissions when fields experience cool summers with frequent rainfall.  相似文献   

6.
In the context of sustainable soil-quality management and mitigating global warming, the impacts of incorporating raw or field-burned adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) and wheat (Triticum aestivum L.) straw residues on carbon dioxide (CO2) and nitrous oxide (N2O) emission rates from soil were assessed in an Andosol field in northern Japan. Losses of carbon (C) and nitrogen (N) in residue biomass during field burning were much greater from adzuki bean residue (98.6% of C and 98.1% of N) than from wheat straw (85.3% and 75.3%, respectively). Although we noted considerable inputs of carbon (499 ± 119 kg C ha–1) and nitrogen (5.97 ± 0.76 kg N ha–1) from burned wheat straw into the soil, neither CO2 nor N2O emission rates from soil (over 210 d) increased significantly after the incorporation of field-burned wheat straw. Thus, the field-burned wheat straw contained organic carbon fractions that were more resistant to decomposition in soil in comparison with the unburned wheat straw. Our results and previously reported rates of CO2, methane (CH4) and N2O emission during wheat straw burning showed that CO2-equivalent greenhouse gas emissions under raw residue incorporation were similar to or slightly higher than those under burned residue incorporation when emission rates were assessed during residue burning and after subsequent soil incorporation.  相似文献   

7.
Coastal ecosystems represent a potential additional source of the greenhouse gas methane (CH4) that has been insufficiently quantified. Thus, to understand the mechanisms controlling greenhouse gas emissions in these ecosystems, this study investigated CH4 emissions from and the related microbial properties of mangrove soils. Soil and gas samples were collected from several plots at different distances from the seashore in Soc Trang and Ca Mau in Vietnam, and the Sundarbans in India. Soil samples were incubated under different conditions, i.e., anaerobic or aerobic, and the microbial properties of each soil sample with the addition of different amounts of seawater were analyzed. Relatively high CH4 fluxes and production were detected during the aerobic incubation of samples from the seashore plots in Soc Trang and Ca Mau. However, CH4 production was reduced under anaerobic conditions [soil electrical conductivity (EC): 179–289 mS m?1, pH (H2O): 7.45–8.10] compared with aerobic conditions [water content: 38.9–109.2%, EC: 187–299 mS m?1, pH (H2O): 6.86–7.72], but it increased with increasing sulfate concentration, soil EC and cellulase activity and lowering soil pH under anaerobic conditions. Furthermore, mangrove soil with a relatively high level of total organic carbon (C) exhibited relatively high CH4 production when diluted 4-fold with seawater under anaerobic conditions [water content: 38.9–109.2%, EC: 533 mS m?1, pH (H2O): 6.67]. Nearly all of the DNA bands excised from polymerase chain reaction-denaturing gradient gel electrophoresis contained identical sequences related to archaea from the class Halobacteria. The high potential of the seashore plot for CH4 emissions could be due to the enhancement of cellulase activity under the intermittent oxygen supply, which promotes polysaccharide depolymerization and subsequently increases anaerobic methanogenic activities during tidal flooding. This study also indicates that the major archaea responsible for CH4 production require a particular hydrospheric salt concentration and soil pH.  相似文献   

8.
《Soil biology & biochemistry》2001,33(12-13):1613-1623
Methane is an important greenhouse gas and CH4 oxidation in soil represents a significant sink for this gas. High capacity CH4 oxidation potentials and molecular profiles of CH4 oxidizing bacteria in soil were compared for five land-use treatments at a fully replicated experimental site within the Gisburn Forest Experiment, to assess the effects of land-use on both the potential activity of CH4 oxidizing bacteria and their diversity. Forestry land-use was found to have a highly significant effect on CH4 oxidation potentials. Highest CH4 oxidation potentials were found in soils collected under stands of oak, in grassland plots, and in one soil under Norway spruce. A negative relationship between soil water nitrate concentration and CH4 oxidation capacity was evident across the experimental site, with the high nitrate soils under stands of alder exhibiting little or no capacity for CH4 oxidation even at optimal temperature and water content. Molecular profiles indicated that a diverse range of bacteria with the potential to oxidize CH4 were present in all soils, however no clear correlation with CH4 oxidation potential was identified.  相似文献   

9.
There are no reports on the effects of elevated carbon dioxide [CO2] on the fluxes of N2O, CO2 and CH4 from semi-arid wheat cropping systems. These three soil gas fluxes were measured using closed chambers under ambient (420 ± 18 μmol mol−1) and elevated (565 ± 37 μmol mol−1) at the Free-Air Carbon dioxide Enrichment experimental facility in northern China. Measurements were made over five weeks on a wheat crop (Triticum aestivum L. cv. Zhongmai 175). Elevated [CO2] increased N2O and CO2 emission from soil by 60% and 15%, respectively, but had no significant effect on CH4 flux. There was no significant interaction between [CO2] and N application rate on these gas fluxes, probably because soil N was not limiting. At least 22% increase in C storage is required to offset the observed increase in greenhouse gas emissions under elevated [CO2].  相似文献   

10.
Legumes have been shown to increase P uptake of the following cereal, but the underlying mechanisms are unclear. The aim of this study was to compare the effect of legume pre-crops and their residues on the growth, P uptake and size of soil P pools in the rhizosphere of the following wheat. Three grain legumes (faba bean, chickpea and white lupin) were grown until maturity in loamy sand soil with low P availability to which 80?mg P kg?1 was supplied. This pre-crop soil was then amended with legume residues or left un-amended and planted with wheat. The growth, P uptake and concentrations of P pools in the rhizosphere of the following wheat were measured 6?weeks after sowing. In a separate experiment, residue decomposition was measured over 42?days by determining soil CO2 release as well as available N and P. Decomposition rates were highest for chickpea residues and lowest for wheat residues. P release was greatest from white lupin residues and N release was greatest from faba bean residues, while wheat residues resulted in net N and P immobilisation. The growth of the following wheat was greater in legume pre-crop soil without residue than in soils with residue addition, while the reverse was true for plant P concentration. Among the legumes, faba bean had the strongest effect on growth, P uptake and concentrations of the rhizosphere P pools of the following wheat. Regardless of the pre-crop and residue treatment, wheat depleted the less labile pools residual P as well as NaOH-Pi and Po, with a stronger depletion of the organic pool. We conclude that although P in the added residues may become available during decomposition, the presence of the residues in the soil had a negative effect on the growth of the following wheat. Further, pre-crops or their residues had little effect on the size of P pools in the rhizosphere of wheat.  相似文献   

11.
For evaluating the applicability of the soil gradient method as a substitute for CO2‐, CH4‐, and N2O‐flux measurements in steppe, we carried out chamber measurements and determined soil gas concentration at an ungrazed (UG99) and a grazed (WG) site in Inner Mongolia, China. The agreement of the concentration‐based flux estimates with measured chamber‐based fluxes varied largely depending on the respective GHG in the sequence CO2 > CH4 >> N2O. A calibration of the gas‐transport parameter used to calculate fluxes based on soil gas concentrations improved the results considerably for CO2 and CH4. After calibration, the average deviation from the chamber‐based annual cumulative flux for both sites was 11.5%, 10.5%, and 59% for CO2, CH4, and N2O. The gradient method did not constitute an adequate stand‐alone substitute for greenhouse‐gas flux estimation since a calibration using chamber‐based measurements was necessary and vigorous production processes were confined to the uppermost, almost water‐saturated soil layer.  相似文献   

12.
Abstract

To assess their impacts on net global warming, total greenhouse gas emissions (mainly CO2, N2O and CH4) from agricultural production in arable land cropping systems in the Tokachi region of Hokkaido, Japan, were estimated using life cycle inventory (LCI) analysis. The LCI data included CO2 emissions from on-farm and off-farm fossil fuel consumption, soil CO2 emissions induced by the decomposition of soil organic matter, direct and indirect N2O emissions from arable lands and CH4 uptake by soils, which were then aggregated in CO2-equivalents. Under plow-based conventional tillage (CT) cropping systems for winter wheat, sugar beet, adzuki bean, potato and cabbage, on-farm CO2 emissions from fuel-consuming operations such as tractor-based field operations, truck transportation and mechanical grain drying ranged from 0.424 Mg CO2 ha?1 year?1 for adzuki bean to 0.826 Mg CO2 ha?1 year?1 for winter wheat. Off-farm CO2 emissions resulting from the use of agricultural materials such as chemical fertilizers, biocides (pesticides and herbicides) and agricultural machines were estimated by input–output tables to range from 0.800 Mg CO2 ha?1 year?1 for winter wheat to 1.724 Mg CO2 ha?1 year?1 for sugar beet. Direct N2O emissions previously measured in an Andosol field of this region showed a positive correlation with N fertilizer application rates. These emissions, expressed in CO2-equivalents, ranged from 0.041 Mg CO2 ha?1 year?1 for potato to 0.382 Mg CO2 ha?1 year?1 for cabbage. Indirect N2O emissions resulting from N leaching and surface runoff were estimated to range from 0.069 Mg CO2 ha?1 year?1 for adzuki bean to 0.381 Mg CO2 ha?1 year?1 for cabbage. The rates of CH4 removal from the atmosphere by soil uptake were equivalent to only 0.020–0.042 Mg CO2 ha?1 year?1. From the difference in the total soil C pools (0–20 cm depth) between 1981 and 2001, annual CO2 emissions from the CT and reduced tillage (RT) soils were estimated to be 4.91 and 3.81 Mg CO2 ha?1 year?1, respectively. In total, CO2-equivalent greenhouse gas emissions under CT cropping systems in the Tokachi region of Hokkaido amounted to 6.97, 7.62, 6.44, 6.64 and 7.49 Mg CO2 ha?1 year?1 for winter wheat, sugar beet, adzuki bean, potato and cabbage production, respectively. Overall, soil-derived CO2 emissions accounted for a large proportion (64–76%) of the total greenhouse gas emissions. This illustrates that soil management practices that enhance C sequestration in soil may be an effective means to mitigate large greenhouse gas emissions from arable land cropping systems such as those in the Tokachi region of northern Japan. Under RT cropping systems, plowing after harvesting was omitted, and total greenhouse gas emissions from winter wheat, sugar beet and adzuki bean could be reduced by 18%, 4% and 18%, respectively, mainly as a result of a lower soil organic matter decomposition rate in the RT soil and a saving on the fuels used for plowing.  相似文献   

13.
A new sampling technique for measuring the concentrations of trace gases (CH4, CO2 and N2O) in the soil atmosphere from well‐defined depths is described. Probes are constructed from silicone tubing closed with silicone septa on both ends, thereby dividing an inner air space from the outer soil atmosphere without a direct contact. The gas exchanges between the inner and outer atmosphere only by diffusion through the walls of the silicone tube. Tests revealed that the gases N2O, CO2 and CH4 in the enclosed space reached 95% equilibrium with the surrounding atmosphere at 20°C within 7 h or faster. The probe measurements are reproducible: the standard deviation of samples taken from 26 probes stored in the laboratory atmosphere equalled that of a standard gas. The probes can easily be constructed and installed at specified depths in the soil. The method has the following advantages compared with other methods that use spaces with holes in them for gas exchange: (i) the silicone probe enables trace gases to be sampled in wet soils, including ones that are waterlogged or temporarily saturated; (ii) the sampling itself does not create low pressure and hence does not create mass flow in the soil matrix from undefined depths; and (iii) the probe can be made to take samples of gas of any required size. The silicone probes did not show ageing effects during 18 months of use in the field in a mineral soil under grass. The probes yielded comparable results: three probes inserted at 5 cm depth in a uniformly treated 100‐m2 plot provided nearly identical average trace gas concentrations within the measurement period.  相似文献   

14.
淹水土壤有机酸积累与秸秆碳氮比及氮供应的关系   总被引：21，自引：0，他引：21  
有机酸积累和毒害是稻田秸杆还田中受到广泛关注的问题。本文以水稻与小麦秸杆为材料，采用淹水培养研究了甲酸、乙酸、丙酸及丁酸在士壤中的积累及其与秸秆碳氮比、氮肥添加量的关系。结果表明，在不施用氮肥的情况下。随秸秆用量的增加，秸秆处理的有机酸积累均显著增多。与稻秸处理相比，麦秸处理的有机酸（尤其足丙酸）积累量显著较高，土壤溶液中NH4^＋浓度显著较低。加入尿素明显减少有机酸积累，促进CH4排放，但对CO2的排放无显著影响；氮素的影响在麦秸处理中表现的尤为明显。上述结果说明麦秸的高碳氮比增加了无机氮的生物固定，抑制有机酸向CH4转化，从而导致麦秸处理有机酸积累量高于稻秸处理。施用氮肥是减少麦秸还田后有机酸积累的有效措施之一，但此措施将可能促进CH4的排放。  相似文献   

15.
More and more cultivated coastal territories of Syria are being affected by increasing land degradation processes, specifically, by soil erosion due to non‐sustainable soil management. The use of cover crops can be considered an ideal solution to reduce the negative impacts of extreme rainfall events on soil erosion. However, there is no enough information about the main cultivated areas of Syria due to the current conflicts and the very few types of research conducted there. Therefore, the main aim of this research was to assess soil erosion (soil loss and sediment concentration) and hydrological response (run‐off and infiltration) considering the impact of different types of cropping systems on soil organic matter. To achieve this goal, using erosion plots, five grouped natural rainfall events and soil samples were collected, and infiltration measurements were performed between November 2012 and April 2013 (rainy season) on three different cropping systems (wheat, vetch, bean and control) with different sloping gradients (8% and 20%) in Tartous governorate (W Syria). Our results showed a cumulative rainfall amount from 68.8 to 201 mm during the study period. The highest sediment yield was generated in the control and wheat plots, registering 0.468 and 0.368 kg m?2, respectively, with an inclination of 8%. For an inclination of 20%, the control and wheat plots registered 1.145 and 0.967 kg m?2, respectively. In comparison with the control plots, there was a decrease in the total eroded organic matter, which ranged from 0.0579 (control) to 0.0289 (bean) kg m?2 year?1 in the plots with 20% inclination, and from 0.0233 (control) to 0.0069 (bean) kg m?2 year?1 with 8% inclination. To sum up, bean and vetch play an effective role to mitigate soil erosion, delay run‐off and reduce sediment yield. The output of this research provides first insights into the impact of different land uses on soil loss. Also, it could help rural inhabitants and farmers to correctly manage their soils against soil erosion processes.  相似文献   

16.
豆科牧草对黄绵土生态因素影响研究   总被引：2，自引：0，他引：2  
用定位试验方法研究了豆科和禾本科作物对陇东黄绵土生态因素的影响。结果表明:黄绵土坡地养分、泥沙和水的流失量,多年生豆科牧草地最少,未耕裸露地较大,黄豆地最大;土壤酶活性,豆科作物地高于禾本科作物地,苜蓿地>红豆草>裸地>黄豆地;暴雨期拦蓄降水的作用,苜蓿和红豆草大于冬小麦,利用自然资源、同化环境中养分的功能,苜蓿>红豆草>冬小麦,而三者的土壤养分变化没有质的差异。研究证明,多年生豆科牧草对土壤生态和形成良性生态体系具有良好作用。  相似文献   

17.
Legume pre-crops may increase P uptake of the following wheat, but the mechanisms behind this effect are unclear. A rotation study was carried out to assess the concentrations of rhizosphere P pools of three grain legumes and wheat (phase 1) and their effects on P uptake and P pools in the rhizosphere of the following wheat (phase 2). Faba bean, chickpea, white lupin and wheat were grown for 10 weeks in a loamy sand soil with low P availability. The following wheat was grown in the pre-crop soil with and without addition of pre-crop residues. Among the pre-crops, white lupin had the strongest effect on the P pools; it depleted the labile P pools, resin P and NaHCO3-Pi and also the less labile P pools, NaOH-Pi and residual P; whereas the concentration of NaHCO3-Po was higher than that in the rhizosphere of the other pre-crops. White lupin had a smaller biomass compared to faba bean which depleted the P pools to a lesser extent. Phosphorus uptake of the following wheat was greatest in white lupin pre-crop soil. Chickpea increased P uptake of the following wheat when residues were added. In the presence of residues, wheat after legumes depleted labile P pools to a greater extent than wheat after wheat, but this coincided with greater P uptake only in wheat after chickpea and white lupin, which may be explained by the small root biomass of wheat after faba bean. The results show that the greater P uptake of the following wheat induced by pre-crops may be due to two mechanisms: P mobilisation (white lupin) or P addition with legume residues (chickpea). This study further showed that P uptake by a crop is only partly a function of the depletion of P in the rhizosphere; another important factor is the ability to exploit a large soil volume.  相似文献   

18.
Abstract

Humic acids have many benefits for plant growth and development, and these effects may be maximized if these materials are combined with micronutrient applications. In the present study, pot experiments were conducted to evaluate the effects of zinc (Zn) humate and ZnSO4 on growth of wheat and soybean in a severely Zn‐deficient calcareous soil (DTPA‐Zn: 0.10 mg kg?1 soil). Plants were grown for 24 (wheat) and 28 days (soybean) with 0 or 5 mg kg?1 of Zn as either ZnSO4 or Zn humate. Zinc humate used in the experiments was obtained from Humintech GmbH, Germany, and contained 5% of Zn. When Zn was not supplied, plants rapidly developed visible symptoms of Zn deficiency (e.g., chlorosis and brown patches on young leaves in soybean and necrotic patches on middle‐aged leaves in wheat). Adding Zn humate eliminated Zn‐deficiency symptoms and enhanced dry matter production by 50% in soybean and 120% in wheat. Zinc‐humate and ZnSO4 were similarly effective in increasing dry matter production in wheat; but Zn humate increased soybean dry matter more than ZnSO4. When Zn was not supplied, Zn concentrations were 6 mg kg?1 for wheat and 8 mg kg?1 for soybean. Application of Zn humate and ZnSO4 increased shoot Zn concentration of plants to 36 and 34 mg kg?1 in wheat and to 13 and 18 mg kg?1 in soybean, respectively. The results indicate that soybean and wheat plants can efficiently utilize Zn chelated to humic acid in calcareous soils, and this utilization is comparable to the utilization of Zn from ZnSO4. Under Zn‐deficient soil conditions, plant growth and yield can be maximized by the combined positive effects of Zn and humic acids.  相似文献   

19.
The effect of an elevated concentration of atmospheric CO2 and the application rate of nitrogen fertilizers on the microbial biomass and maximum specific growth rate of microorganisms in the soil and rhizosphere was studied in a long-term field experiment involving the growing of sugar beets and winter wheat. It was shown that the treatment of field plots with carbon dioxide at a concentration higher than that in the atmosphere (550 ppm) for three-four years resulted in the formation of a microbial community with a higher maximum specific growth rate and a larger share of R-strategy microorganisms as compared to the soil under the control plants. No reliable differences in the total microbial biomass in the soil under the winter wheat were revealed between the treatments with the ambient and elevated CO2 concentrations; in the soil under the beet plants, a reliable increase in the total microbial biomass at the elevated CO2 concentration was noted only in the close vicinity of the plant roots.  相似文献   

20.
王强盛  刘欣  许国春  余坤龙  张慧 《土壤》2023,55(6):1279-1288
稻田是大气温室气体甲烷(CH4)和氧化亚氮(N2O)的重要排放源, 稻田温室气体减排一直是生态农业研究的热点。目前, 采用水稻品种选择利用、水分控制管理、肥料运筹管理、耕作制度调整以及种养结合模式等方法来减少稻田温室气体排放有较好实践效应, 但不同稻田栽培环境(露地、网室)基础上的稻鸭共作对麦秸全量还田的稻田温室气体排放特征及相关土壤理化特性关联性的影响尚为少见。本研究采用裂区设计, 在两种栽培环境条件下, 以无鸭子放养的常规稻作和麦秸不还田为对照, 在等养分条件下分析麦秸全量还田与稻鸭共作模式对稻田土壤氧化还原电位、CH4排放量、产CH4潜力及CH4氧化能力、N2O排放量及N2O排放高峰期土壤反硝化酶活性、全球增温潜势、水稻产量的影响, 为稻田可持续生产和温室气体减排提供参考。结果表明, 麦秆还田增加了稻田产CH4潜力、提高了CH4排放量, 降低了稻田土壤反硝化酶活性、土壤氧化还原电位和N2O排放量, 整体上导致全球增温潜势上升96.89%~123.02%; 稻鸭共作模式, 由于鸭子的不间断活动提高了稻田土壤氧化还原电位, 降低了稻田产CH4潜力, 增强了稻田CH4氧化能力, 从而降低稻田CH4排放量, N2O排放量虽有提高, 整体上稻鸭共作模式的全球增温潜势较无鸭常规稻田下降8.72%~14.18%; 网室栽培模式显著提高了稻田土壤氧化还原电位, 降低稻田产CH4潜力、CH4氧化能力和土壤反硝化酶活性, 减少了稻田CH4和N2O排放量, 全球增温潜势降低6.35%~13.14%。本试验条件下, 稻田土壤的CH4氧化能力是产CH4潜力的2.21~3.81倍; 相同环境条件下, 稻鸭共作和麦秸还田均能增加水稻实际产量, 网室栽培的所有处理较相应的露地栽培减少了水稻实际产量1.19%~5.48%。本试验表明, 稻鸭共作和网室栽培可减缓全球增温潜势, 稻鸭共作和麦秸还田能够增加水稻实际产量。  相似文献   

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