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1.
Protected cultivation, mainly represented by plastic-film mulching, has greatly improved crop production worldwide since the 1950s. However, despite its widespread use in tropical USA, Europe and China, its use in sub-Saharan Africa is not widespread. A field experiment was conducted using cocoyam (Colocasia esculenta L. Schott) to evaluate the effects of two tillage systems (tilled and no-till) and plastic-film mulch (black and clear plastic-film mulch) on soil properties and cocoyam growth and yield in 2003 and 2004 planting seasons on a Typic paleudult in southeastern Nigeria. The experiment comprised six treatments and was laid out in the field using randomized complete block design replicated three times. Results showed that 70–80% of the corms emerged 7–8 days (21 days after planting [DAP]) earlier in both tilled and no-till plastic-film mulched plots when compared to the unmulched plots. At later stages of crop development, the plants in the tilled black plastic-film mulched plots were taller by 61–67% than those in the unmulched no-till plots, which had the lowest plant height (27–30 cm). At 98 DAP, there were no significant treatment differences in leaf area index (LAI) between tilled and no-till mulched plots with LAI of 15.5–19.8. However, LAI was reduced in both unmulched plots by 35–54% when compared to the mulched plots. On the average soil temperature was higher in plastic-film mulched plots than that under plots without mulch by about 2 °C. Results show significantly lower soil bulk density (between 1.10 and 1.26 Mg m−3) in both tilled clear and black plastic-film mulched plots when compared to the corresponding no-till clear or black plastic-film mulched plots (1.40–1.45 Mg m−3). For the two seasons studied volumetric water content (VWC) in tilled black plastic-film mulched plots were significantly higher than VWC in other mulched plots by between 10 and 38% in 2003 and between 17 and 30% in 2004. At harvest (270 DAP) the highest corm yield was obtained in tilled black plastic mulched plots (29.1 Mg ha−1). This was higher (P = 0.05) than yields obtained in no-till, no mulch plots by 72%. Yields were also higher in tilled black plastic mulched plots when compared to tilled clear plastic mulched plots, no-till black plastic mulched plots and no-till clear plastic mulched plots by 29, 47 and 59%, respectively. These findings suggest that plastic mulched plots provide a better soil environment for cocoyam than unmulched plots and that tilled mulched plots especially tilled black plastic mulched plots provide superior edaphic environment for cocoyam when compared to other treatments used.  相似文献   

2.
Tillage effects on near-surface soil hydraulic properties   总被引:1,自引:0,他引:1  
The processes for the formation of porosity are thought to differ between tilled and non-tilled cropping systems. The pores are created primarily by the tillage tool in the tilled systems and by biological processes in non-tilled systems. Because of the different methods of pore formation, the pore size distribution, pore continuity and hydraulic conductivity functions would be expected to differ among tillage systems. The objective of this study was to determine effects of three tillage systems — mold-board plow (MP), chisel plow (CP), and no-till (NT) — on hydraulic properties of soils from eight long-term tillage and rotation experiments. Tillage effects on saturated and unsaturated hydraulic conductivity, pore size distribution, and moisture retention characteristics were more apparent for soils with a continuous corn (CC) rotation than for either a corn-soybean (CS) rotation or a corn-oats-alfalfa (COA) rotation. Pore size distributions were similar among tillage systems for each soil except for three soils with a CC rotation. The MP system increased volume of pores >150 μm radius by 23% to 91% compared with the NT system on two of the soils, but the NT system increased the volume of the same radius pore by 50% on one other soil. The NT system had 30 to 180% greater saturated hydraulic conductivity than either the CP or MP systems. The NT system with a CC rotation showed a greater slope of the log unsaturated hydraulic conductivity; log volumetric water content relationship on two of the soils indicating greater water movement through a few relatively large pores for this system than for either the CP or MP systems.  相似文献   

3.
Information regarding the evaluation of tillage effects on soil properties and rainfed wheat (Triticum aestivum L.) cultivars of Iranian fields is not available. Therefore, this research was conducted in Sanandaj (west of Iran) using a randomized complete block design in a split-plot arrangement. Three types of tillage including conventional tillage (moldboard plow to soil depth of 30 cm plus disk harrow twice), minimum tillage (chisel plow to soil depth of 15 cm plus disk harrow once) and no-tillage are assigned to the main plots. Wheat cultivars (Sardari and Azar2) were randomly distributed within the subplots in each tillage system. Results showed that the greatest bulk density and cone index were found in the minimum tillage and no tillage systems. The highest rate of grain yield was obtained in the minimum tillage system. The grain yield of Sardari cultivar (1624.1 kg ha?1) was significantly greater than that of Azar2 (1572 kg ha?1). Minimum tillage improved soil physical properties and wheat growth compared with the other tillage systems. No tillage increased microbial biomass carbon and bacteria number in soil compared with the other tillage systems. We conclude that using minimum tillage for Sardari cultivar will be more effective compared with other treatments.  相似文献   

4.
This research concerns the influence of no tillage (NT) or conventional tillage (CT) and a ryegrass (Lolium multiforum Lam.) cover crop in a cotton (Gossypium hirsutum L.) production system on soil and ryegrass microbial counts, enzyme activities, and fluometuron degradation. Fluorescein diacetate hydrolysis, aryl acylamidase, and colony-forming units (CFUs) of total bacteria and fungi, gram-negative bacteria, and fluorescent pseudomonads were determined in soil and ryegrass samples used in the degradation study. Fluometuron (14C-labelled herbicide) degradation was evaluated in the laboratory using soil and ryegrass. The CT and NT plots with a ryegrass cover crop maintained greater microbial populations in the upper 2 cm compared to their respective no-cover soils, and CT soils with ryegrass maintained greater bacterial and fungal CFUs in the 2–10 cm depth compared to the other soils The highest enzymatic activity was found in the 0–2 cm depth of soils with ryegrass compared to their respective soils without ryegrass. Ryegrass residues under NT maintained several hundred-fold greater CFUs than the respective underlying surface soils. Fluometuron degradation in soil and ryegrass residues proceeded through sequential demethylation and incorporation of residues into nonextractable components. The most rapid degradation was observed in surface (0 to 2 cm) soil from CT and NT–ryegrass plots. However, degradation occurred more rapidly in CT compared to NT soils in the 2 to 10 cm depth. Ryegrass cover crop systems, under NT or incorporated under CT, stimulated microbiological soil properties and promoted herbicide degradation in surface soils.  相似文献   

5.
Information regarding the evaluation of long-term tillage effects on soil properties and summer maize growth after winter vetch in western Turkey is not available. Therefore, this study was conducted for 5 years with three types of tillage including conventional (mouldboard plough) and conservation (rototiller and chisel). Results indicated that tillage had no significant effect on penetration resistance, except at the bottom of 20 cm soil depth where it was higher in mouldboard plough than in rototiller and chisel. Bulk density in the topsoil of 10 cm decreased with the degree of soil manipulation during tillage practices. Rototiller caused significantly higher root, leaf and stems biomass and plant height than the other systems. The root dry weight was higher in the topsoil of 10 cm than at the bottom of this soil depth for all systems. The highest root dry weight was found in fourth year of chisel, but the lowest was recorded in the same year of plough, especially at the bottom of 20 cm due to higher penetration. Rototiller improved soil properties and maize growth compared to other systems in 2 of 5 years. We concluded that using rototiller for maize after winter vetch will be more effective compared with other systems.  相似文献   

6.
To study the effect of different soil tillage practices and the consequences of soil deformation on the functioning of the pore system, we performed unsaturated leaching experiments (by applying a suction of −10 kPa) on undisturbed soil columns from the Ap-horizon of a luvisol derived from glacial till (agricultural site at Hohenschulen, North Germany). We compared two different tillage practices (conventionally tilled to 30 cm depth, and conservational chiselled to a depth of 8 cm-Horsch system) with respect to soil strength, pore connectivity and their effect on the fate of surface-applied fertilisers. The soil strength was measured by determining the precompression stress value (PCV). The conventionally tilled topsoil had a PCV of 21 kPa at a pore water potential of −6 kPa, while the conservation treatment resulted in a slightly higher PCV of 28 kPa, suggesting a slowly increasing soil strength induced by the formation of aggregates under reduced tillage practice.

The leaching experiments were modelled using the convection dispersion equation (CDE) and a modified version of the mobile–immobile approach (MIM), which included three water fractions: mobile, immobile and totally immobile water. From the CDE mobile water fractions (θm) ranging from 47 to 67% were found, and θm was slightly higher in the ploughed seedbed compared to the conservation-tilled one. This could be due to higher aggregation in the latter one. Dispersivities were relatively large, ranging from 44 to 360 mm, but no difference was found for the treatments. The MIM could simulate the drop in concentration when leaching was interrupted, but overall did not improve the simulation, despite the larger number of fitting parameters.

Compacting the soil with loads of 70 kPa prior to the leaching experiment did not affect solute transport in the conservational tilled soil. In the conventional-tilled soil, however, the dispersivity decreased and the mobile water content increased compared to the non-compacted soil, suggesting that the former one is less prone to deformation by mechanical loads.  相似文献   


7.
The effects of tillage implement distrubance on the physical properties of soil have been widely studied. However, because soil properties resulting from the use of a given implement vary due to implement factors (depth and speed of tillage) and soil factors (water content, texture, residue cover, etc.), soil properties for a given operation are difficult to visualize, let alone predict. This report summarizes the ranges of selected soil property responses observed in previous tillage studies and identifies factors that must be considered in developing useful models to predict the effects of tillage on soil properties that are related to soil and water conservation. Considered are soil mechanical properties (surface micro-relief, aggregate size distribution and bulk density) and hydraulic properties and processes (water retention, saturated conductivity, infiltration and evaporation). For future literature reports on tillage to be useful for developing comprehensive relationships between tillage and soil properties, the reports should include information on: soil classification, texture, water content (or time of precipitation), bulk density, mechanical impedance and organic matter concentration; tillage method, depth and speed of operation; previous crop, including availability of crop residues; and previous soil management history (compacted soil, irrigated or dryland, etc.).  相似文献   

8.
Soil tillage practices can affect soil hydraulic properties and processes dynamically in space and time with consequent and coupled effects on chemical movement and plant growth. This literature review addresses the quantitative effects of soil tillage and associated management (e.g., crop residues) on the temporal and spatial variability of soil hydraulic properties. Our review includes incidental management effects, such as soil compaction, and natural sources of variability, such as topography. Despite limited research on space–time predictions, many studies have addressed management effects on soil hydraulic properties and processes relevant to improved understanding of the sources of variability and their interactions in space and time. Whether examined explicitly or implicitly, the literature includes studies of interactions between treatments, such as tillage and residue management. No-tillage (NT) treatments have been compared with various tillage practices under a range of conditions with mixed results. The trend, if any, is for NT to increase macropore connectivity while generating inconsistent responses in total porosity and soil bulk density compared with conventional tillage practices. This corresponds to a general increase in ponded or near-zero tension infiltration rates and saturated hydraulic conductivities. Similarly, controlled equipment traffic may have significant effects on soil compaction and related hydraulic properties on some soils, but on others, landscape and temporal variability overwhelm wheel-track effects. Spatial and temporal variability often overshadows specific management effects, and several authors have recognized this in their analyses and interpretations. Differences in temporal variability depend on spatial locations between rows, within fields at different landscape positions, and between sites with different climates and dominant soil types. Most tillage practices have pronounced effects on soil hydraulic properties immediately following tillage application, but these effects can diminish rapidly. Long-term effects on the order of a decade or more can appear less pronounced and are sometimes impossible to distinguish from natural and unaccounted management-induced variability. New standards for experimental classification are essential for isolating and subsequently generalizing space–time responses. Accordingly, enhanced methods of field measurement and data collection combined with explicit spatio-temporal modeling and parameter estimation should provide quantitative predictions of soil hydraulic behavior due to tillage and related agricultural management.  相似文献   

9.
Soil degradation, decrease in soil's actual and potential productivity owing to land misuse, is a major threat to agricultural sustainability and environmental quality. The problem is particularly severe in the tropics and sub-tropics as a result of high demographic pressure, shortage of prime agricultural land, harsh environments, and resource poor farmers who presumably cannot afford science based recommended inputs. Tillage methods and soil surface management affect sustainable use of soil resources through their influence on soil stability, soil resilience, and soil quality. Soil stability refers to the susceptibility of soil to change under natural or anthropogenic perturbations. In comparison, soil resilience refers to soil's ability to restore its life support processes after being stressed. The term soil quality refers to the soil's capacity to perform its three principal functions e.g. economic productivity, environment regulation, and aesthetic and cultural values. There is a need to develop precise objective and quantitative indices of assessing these attributes of the soil. These indices can only be developed from the data obtained from well designed and properly implemented long-term soil management experiments conducted on major soils in principal ecoregions.  相似文献   

10.
Field experiments were conducted on a silty clay loam (Typic Hapludalf) during 1988–1990 to study the effect of tillage practices, such as puddling (P), compaction (C) and non-puddled dry tillage (NP) with four rates of lantana (Lantana camara L.) residue incorporation (0(M0), 10(M1), 20(M2) and 30 (M3) t ha−1), on soil physical properties and yield of rice. Greatest water retention was noticed under PM3, followed by CM3 and NPM3. The soil penetration resistance was lowest for NPM3, followed by PM3 and CM3. Puddled treatments either with or without residue impeded infiltration as compared with C and NP. Puddled treatments either with or without residue had higher soil as well as flood water temperature. Residue addition invariably reduced the ploughing energy required after rice harvest; however, among puddling and compaction treatments, puddling consumed less energy. The rice grain yields under puddled treatments were significantly higher than under C and NP irrespective of residue addition.  相似文献   

11.
A review of tillage systems in Latin America revealed that considerable research on this topics has been done and much is currently in progress. Results of most of this tillage research, however, have not been published in international refereed journals, thus making it difficult to assess the current state of the art on this topic. A high percentage of tillage research results has not been published at all. In general, conservation tillage practices, that is, those commonly referred to as no-till and minimum till, had higher bulk densities in the surface soil, but lower macroporosities, infiltration rates and crop yields as compared with conventional tillage, which was typically disk plowing. Chisel plowing and subsoiling, deep tillage practices whose action extends below the usual depth of disk plowing, usually decreased mechanical impedance, improved root penetration and increased crop yields. Soil loss from cropped land was usually greatest under conventional tillage unless mulch was applied to the soil surface. We believe that some form of tillage practice that mixes the surface soil layer will have to be incorporated from time to time into any tillage system to maintain soil conditions adequate for sustained continuous cropping.  相似文献   

12.
Tillage systems and soil properties in North America   总被引:6,自引:0,他引:6  
This paper reviews current knowledge on the range and extent of various tillage systems used in North America with special reference to the effects on soil properties, the erosion hazard and water quality. The increasing adoption of conservation-tillage systems since their introduction in the early 1960s follows an enhanced awareness of the increasing risks of soil erosion and non-point source pollution and the high cost of fuel with conventional tillage. Most “conventional tillage” systems encompass complete inversion tillage along with several secondary and tertiary tillage methods. In contrast, conservation-tillage systems involve streamlining various farm operations, thereby reducing the frequency and intensity of the soil manipulative operations. Reduction in tillage intensity has been accompanied by the development of rotations and cropping systems, methods of surface and internal drainage, fertilizer technology and pest management alternatives.

The status of antecedent soil physical properties is an important factor affecting the choice of tillage systems. Important soil physical properties governing the choice of tillage systems include soil wetness and anaerobiosis, soil temperature and soil structure including its susceptibility to compaction, crusting or erosion. Tillage systems affect soil physical, chemical and biological properties. Among drastic tillage-induced changes in soil properties are bulk density, infiltration rate, aggregation and aggregate size distribution, soil organic carbon and nutrient profile, microbial activity and species diversity, and the population of earthworms. Macropores and biochannels are usually more prevalent in conservation-tillage than conventional-tillage systems. Conservation tillage induces stratification of soil organic matter and related nutrients, enhances the activity of soil fauna and leads to acidification. The magnitude of these changes depends on the soil type, the cropping systems and the type of conservation tillage adopted. Soil organic carbon and nutrient stratification are generally more pronounced in coarse-textures than in clayey soils. Conservation tillage is also associated with greater biomass pool size. The latter affects the nutrient response curves of the soil. Nitrification and denitrification are other important processes affected by tillage systems.

The widespread adaption of conservation-tillage systems, although beneficial in controlling off-site sedimentation, has raised concerns about the potential for increased leaching of nutrients and pesticides to groundwater. Important pollutants associated with conservation tillage are nitrate and pesticides. Some studies have shown little effect of tillage on losses of pesticides. Conservation tillage may suppress crop yields, especially on heavy textured soil with poor internal drainage and in those prone to soil compaction caused by vehicular traffic.  相似文献   


13.
This paper defines tillage, indicating that as it is mostly a physical concern of the soil, it has not been studied as much as chemically related soil properties. Tillage in shifting cultivation is also reviewed. Different tillage systems in a number of east African Countries namely Tanzania, Malawi, Botswana, Kenya, Zambia and Uganda are reviewed. The types of tillage in their respective soils are discussed in each Country. Uganda's tillage practices for the main food crop (banana) are discussed, pointing out the crop's rooting system in relation to the heavy, relatively fertile soils, where the bananas are mostly grown. The paper distinguishes between tillage to avoid soil compaction and tillage to reduce soil crusting or hardening and concludes that more research should be carried out on tillage practices relating to heavy soils as it affects the different types of crops, as most of the previous tillage research had been carried out on relatively light soils. Soil crusting or hardening which may involve an understanding of the physical, chemical and biological properties of the soil, should also receive more attention.  相似文献   

14.
Many tillage studies focus primarily on grain crops, whereas other important agricultural crops receive little attention. This paper presents yield results for various crops grown in the tenth to sixteenth year of a long-term tillage trial on loam soil in southeast Norway. Traditional plough tillage was compared with deep and shallow tine cultivation and with minimum tillage, and the residual effects of tillage were measured in the seventeenth and eighteenth years. Soil bulk density, air permeability and other soil conditions were found to be favourable for crop growth on all treatments in the tenth year. The yield levels of cereals (Hordeum vulgare L., Triticum aestivum L. and Avena sativa L.) and potatoes (Solanum tuberosum L.) showed consistent increases of 2–8% with declining tillage intensity, whereas yields of fodder beet (Beta vulgaris L.) were highest after plough tillage. The latter result was thought to be due to lower soil temperatures under reduced tillage. Yields of brassica crops were greatly affected by tillage intensity, owing to a marked reduction of clubroot (Plasmodiophora brassicae Wor.) infection with reduced tillage. Average yields for these crops were 23%, 52% and 59% higher with deep tine cultivation, shallow tine cultivation and minimum tillage, respectively, than with plough tillage. The effects were particularly dramatic in the case of fodder rape (Brassica napus L. ssp. oleifera Sinsk. f. biennis Reichb.) and cabbage (Brassica oleracea L. var. capita L.). Liming raised the yields of some brassica crops but did not influence the effect of tillage.

Soil acidity was measured twice during the trial period and again in the second residual year, and showed values which were 0.1–0.3 pH units lower with reduced tillage than with plough tillage. This rules out the conclusion that the effect of tillage on clubroot was associated directly with acidity. Positive residual effects of reduced tillage systems were found on the yields of both brassicaceous and gramineous crops. Reduced tillage intensity may thus be recommended for all crops studied, with the exception of fodder beet, on morainic loam soils of southeast Norway.  相似文献   


15.
West African soil resources have high potentials for enhancing agricultural productivity, if well-managed and restored. In this context, the importance of tillage systems have not been fully appreciated as an integral part of good farming systems in order to tally with the peculiarities of the soil, crops and the environment. Most improved tillage systems are not widely used, although the relatively small-scale uncontrolled application of mechanical tillage has had untold adverse effects on properties and productivity of soils in the humid and subhumid regions.

In contrast, mechanical soil tillage involving deep plow-till and soil inversion has proven beneficial on compact soils of arid and semi-arid regions. The plow-based systems not only reduce soil bulk density and soil strength but also improve the efficiency of water and nutrient use.

The exposure of structurally unstable Alfisols and Ultisols predominant in the humid and sub-humid regions by mechanical tillage can cause more adverse effects than beneficial effects on soil properties and crop yields, especially on a long-term basis. On the other hand, the no-till system with crop residue mulch can maintain favorable soil properties. The conservation tillage system, however, requires more research to make it applicable to diverse soil types, crops and ecoregions.

Apart from the long-term effects of tillage on the level of soil organic matter and the attendant release of nutrients, the effects of tillage systems on the chemical properties of soil are often contradictory and are confounded by many other factors so that clear-cut cause and effect relationships are not obvious. The interactions between fertilizer application, liming, soil organic matter content and tillage systems, especially on acid soils, are such examples. More detailed studies on nutrient dynamics under different tillage systems are necessary. The interactions between the relatively new technologies of alley cropping and agroforestry which allow a more continuous use of the land should be investigated vis-à-vis tillage systems.

Long-term, well-designed, adequately equipped experiments (which are scanty in West Africa) should be encouraged to elucidate and confirm results of many short-term experiments.  相似文献   


16.
17.
The effects of cropping systems and management practices on soil properties provide essential information for assessing sustainability and environmental impact. Tillage and fertilizer rates were evaluated for their effects on soil bulk density (BD), penetration resistance, soil organic carbon (SOC) concentration and availability of macronutrients on a sandy clay loam (fine-loamy, mixed, hyperthermic Typic Haplargids, USDA; Luvic Yermosol, FAO) in a semi-arid region of Pakistan. Wheat (Triticum aestivum L.) and cotton (Gossypium hirsutum L.) were double-cropped from 1996 to 1998. Tillage treatments were minimum till (MT), conventional till (CT), and deep till (DT). Low, medium and high fertilizer rates were applied to wheat and cotton. BD was affected neither by tillage nor fertilizer rates. Soil penetration resistance was lower for DT than CT and MT. Tillage methods affected soil P concentration but did not affect N and K concentrations. However, fertilizer application significantly increased soil P and K concentrations. Concentrations of N, P, K and SOC were greater in the plough layer than sub-soil. Grain yield of wheat was significantly negatively correlated with penetration resistance and was positively correlated with soil P and K concentrations. Yield of cotton was significantly negatively correlated with soil BD. These data provide an experimental basis to re-evaluate recommendations for fertilizer rates and tillage methods for production of wheat and cotton in Punjab. Further, there is a strong need to establish long-term experiments to study agronomic and environmental effects of tillage methods, fertilizer rates, and cropping systems on productivity and environment quality.  相似文献   

18.
耕作方式对紫色水稻土全硫及有效硫的影响   总被引:1,自引:0,他引:1  
黄小娟  江长胜  郝庆菊  袁雪 《土壤》2012,44(2):267-273
以位于西南大学农业部重庆紫色土生态环境重点野外科学观测试验站 1990 年设立的长期免耕试验田为研究对象,通过采集 0 ~ 60 cm 土壤,应用等质量计算方法,探讨了冬水田平作(DP)、水旱轮作(SH)、垄作免耕(LM)和垄作翻耕(LF)等不同耕作方式对土壤全硫和有效硫的影响。结果表明,在 0 ~ 60 cm 深度内,土壤全硫和有效硫含量呈现出明显的垂直递减规律,即随着土壤深度的增加,含量逐渐降低;不同耕作方式下,土壤全硫含量及储量为 LM>SH>DP>LF,有效硫含量及储量为 LM>DP>LF>SH。长期垄作免耕提高了土壤全硫及有效硫的含量和储量,与对照 DP 处理相比,LM 处理全硫与有效硫含量分别增加了 20.80% 和 1.31%,储量分别增加了 19.54% 和 5.36%。耕作层(0 ~ 20 cm),DP、SH、LM、LF 处理土壤有效硫平均含量分别为 27.15、13.45、31.43 和 24.01 mg/kg,DP、LF 以及 LM 处理为硫不缺或硫丰足,而 SH 处理为缺硫土壤(土壤有效硫含量<16 mg/kg)。对缺硫土壤,应重视硫肥的施用,以促进农作物产量和品质的提高。  相似文献   

19.
20.
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   

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