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1.
In South Sulawesi, paddy rice (Oryza sativa L.) is generally double cropped with soya-bean (Glycine max L.) in the dry season. Decline in soya-bean yield and response to fertilisers after some years indicates that these cropping systems may not be sustainable in terms of soil strucural properties. We investigated the deterioration of soil structure by measuring penetration resistance, air-filled porosity, bulk density and plant available water content in rice paddy-soya-bean rotations of 10, 16 and 21 years duration. These results were compared with those from a 21 year rotation in which rice was followed by grass fallow. The non-limiting available water range was used to assess cropping system differences.

Rice-soya-bean cropping systems were detrimental to soil physical conditions in the long term. Bulk density and soil strength increased and air-filled porosity decreased significantly over a period of 21 years. At this time, aeration porosity at the upper drained limit was below the critical value for adequate aeration, soil penetration resistance exceeded the limits for root growth within the plant available water content range, and the non-limiting range of plant avaiable water was narrowed. These results indicate that double cropping is unsustainable in terms of soil structure quality. Shorter periods (10 years) of double cropping did not cause the same level of deterioration and the grass fallow system had no discerible limitation to available water as a result of poor alteration or high soil strength. We conclude that grass fallow cropping systems appear to be more sustainable and in long-term double cropped systems, a period of grass fallow is probably required to restore soil structure to a favourable state.  相似文献   


2.
In Indian Punjab, rice–wheat is a dominant cropping system in four agro‐ecosystems, namely undulating subregion (zone 1), Piedmont alluvial plains (zone 2), central alluvial plains (zone 3), and southwestern alluvial plains (zone 4), varying in rainfall and temperature. Static and temporal variabilities in soil physical and chemical properties prevail because of alluvial parent material, management/tillage operations, and duration of rice–wheat rotation. A detailed survey was undertaken to study the long‐term effect of rice–wheat rotation on soil physical (soil separates, bulk density, modulus of rupture, saturated and unsaturated hydraulic conductivities, soil water content, and suction relations) and chemical (organic carbon, pH, electrical conductivity) properties of different textured soils (sandy clay loam, loam, clay loam, and silty clay loam) in these four zones of Punjab. Soil samples (of 0‐ to 30‐cm depth) from 45 sites were collected during 2006 and were analyzed for physical and chemical properties. The results showed that sand content and pH increased whereas silt and organic carbon decreased significantly from zones 1 to 4. Compared to other textures, significantly greater organic carbon, modulus of rupture, and pH in silty clay loam; greater bulk density in clay loam, and greater saturated hydraulic conductivity in sandy clay loam were observed. Irrespective of zone and soil texture, in the subsurface soil, there was a hard pan at 15–22.5 cm deep, which had high soil bulk density, modulus of rupture, more silt and clay contents (by 3–5%) and less organic carbon and hydraulic conductivity than the surface (0–15 cm) layer. These properties deteriorated with fineness of the soil texture and less organic carbon content. Continuous rice–wheat cropping had a deleterious effect on many soil properties. Many of these soils would benefit from the addition of organic matter, and crop yields may also be affected by the distinct hardpan that exists between 15 and 22.5 cm deep.  相似文献   

3.
Soil conditions at sampling and the dimensions of the sample are critical factors when soil aggregation is indirectly characterized by determining the distribution of soil fragments. Our objective was to determine the effects of gravimetric soil water content and core sampler diameter (16, 54, and 84 mm) at sampling on the dry‐fragment‐size distribution of two soils (Typic Paleudalf and Typic Hapludalf) under undisturbed Festuca arundinacea L. sod and recently rototilled treatments. The 16‐mm core diameter sampler compressed the rototilled soil, and it was not appropriate for soil aggregation studies. The fragmentation of samples taken with core diameters greater than 54 mm decreased with decreasing soil water content. A greater probability of discriminating between undisturbed and fragmented silt loam or clay loam soils was observed when sampling with a 54‐mm‐diameter probe and when the soil had a mean soil water content of 237g kg?1 or at a potential of ?0.61MPa.  相似文献   

4.
深松耕作和秸秆还田对农田土壤物理特性的影响   总被引：16，自引：4，他引：16  
[目的]为了增加中国干旱半干旱地区农田土壤蓄水保墒能力。[方法]采用野外试验和室内分析相结合的方法研究了深松和深松结合秸秆还田耕作技术对晋中北部地区两种主要类型土壤物理特性的影响。[结果]深松可以打破土壤犁底层,显著降低黏土和壤土10—30cm土层范围内的土壤容重;调节土壤孔隙度,增加了黏土10—30cm土层范围内的土壤总孔隙度、毛管孔隙度和非毛管孔隙度,同时增加壤土10—30cm土层土壤总孔隙度、毛管孔隙度和20—30cm土层土壤非毛管孔隙度;改善黏土和壤土20—30cm土层土壤固、液、气3相状况;深松结合连年秸秆还田进一步优化了壤土耕层环境,同时显著降低了玉米拔节期土壤地表结皮的厚度和紧实度。[结论]深松结合连年秸秆还田和深松耕作技术可以缓解土壤板结状况,增加降雨入渗。  相似文献   

5.
An automated soil sampler and a system for measuring the physical properties of soil cores in the field were developed for the study of soil compaction and tillage effects on soil physical properties. The system measures the bulk density, air-filled porosity, intrinsic air permeability, and moisture content on 47.6 mm diameter soil cores as well as measuring cone penetration resistance in the field. Results of a laboratory calibration study illustrated that the system measures the soil properties with acceptable accuracy. A main benefit of the system was the fact that it could measure all of the above properties on ten core samples down to a depth of 0.5 m, typically within 15 min.

A field compaction study showed that the system was capable of detecting the effects of a 15.2 tonne axle load on the soil down to a depth of 0.4 m, 1 year after compaction.  相似文献   


6.
容重对土壤水分入渗能力影响模拟试验   总被引：38，自引：21，他引：38  
通过人工改变土壤颗粒级配,配制典型砂壤、中壤、黏壤,并设置不同容重水平,用土柱积水入渗模拟了土壤容重对其入渗能力的影响,为土壤改良和促进天然降水转化利用提供理论依据。结果表明,容重对土壤入渗能力有较大影响。试验土壤入渗能力随容重增大递减,3种典型土壤稳定入渗速率与容重均呈对数负相关,砂壤120 min累积入渗量与容重呈幂函数负相关,中壤、黏壤则呈线性负相关。考斯加科夫入渗模型中,表征初始入渗速率的参数随容重增大递减,表征入渗能力衰减速度的参数则随容重增大递增,说明土壤初始入渗能力随容重增大递减,入渗能力衰减速度随容重增大递增。  相似文献   

7.
Gas diffusivity and permeability, and air-filled porosity, were measured in undisturbed soil cores at six water potentials between -2 kPa and oven dryness. All increased as water potential fell. In silt loam at 30 to 80 mm depth, relative diffusivity and air permeability at -2 kPa were 0.0013 and 5 × 10?8cm2 after direct drilling, and were 6 and 15 times greater respectively after ploughing, presumably because of the larger volume of air-filled large pores in the ploughed soil. These pores may also have been more continuous or less tortuous than in the direct drilled soil. However, at equal air-filled porosities up to 0.18 v/v, the pores were apparently more continuous and less tortuous in the direct drilled than in the ploughed soil. In the direct drilled silt loam at any given matric potential, air-filled porosity, gas diffusivity and permeability within and below the previously ploughed layer were isotropic. In clay loam at 30 to 80 mm depth gas diffusivity and permeability at -2 kPa were greater than in the silt loam irrespective of tillage but increased less on oven drying.  相似文献   

8.
为探索西北干旱地区不同质地土壤以及土壤温度和容重对微咸水上升毛管水运动特性的影响,通过模拟和室内试验,研究了土壤温度和容重对砂壤土和粉壤土上升毛管水运动特性的影响。分别建立了地下水补给量与土壤温度和容重之间的模型,毛管水上升高度与土壤温度和容重之间的模型,其中地下水补给量模型,砂壤土的绝对系数均达到0.96以上,计算值与模拟值最大相对偏差小于10.9%,粉壤土的绝对系数均达到0.96以上,计算值与模拟值最大相对偏差小于8.4%,毛管水上升高度模型,砂壤土的绝对系数均达到0.996以上,计算值与模拟值最大相对偏差小于8.37%,粉壤土的绝对系数均达到0.997以上,计算值与模拟值最大相对偏差小于11.9%,模型拟合程度较好,所建立方程符合实际情况。砂壤土盐分主要聚集在距地表1.70~2.20 m处,粉壤土盐分主要聚集在距地表0.3~1.3 m处,砂壤土土壤盐分分布受土壤温度和容重的影响较显著,而粉壤土土壤盐分分布受其影响并不显著。该研究结果可为盐碱化地区水盐管理提供科学依据。  相似文献   

9.
The effects of zero, minimum and conventional tillage on soil physical properties and on the growth and yield of mungbean (Vigna radiata L.) grown after lowland rice (Oryza sativa L.) were studied in field experiments conducted during the 1984 and 1985 dry seasons (DS) at two Philippine sites (clay loam, Vertic Tropaquept, with shallow water table and sandy loam, Aeric Tropaquept, with deep water table). Effects on maize (Zea mays L.) were studied only in 1984 on clay loam soil.All parameter measurements were not significantly different with minimum and conventional tillage. Tillage, averaged over minimum and conventional and in both seasons, significantly lowered bulk density (10%) and increased aeration porosity (120%) of the 0–0.10 m clay loam soil layer. In sandy loam soil in 1985, it decreased bulk density by 7% and increased aeration porosity by 61%. Tillage only slightly affected the matric suction, strength and temperature of both soils.Maize seedling emergence was 15% higher with zero tillage than with minimum and conventional tillage. Tillage, however, did not affect mungbean emergence. It significantly increased maize plant height (42%) and root length (61%) as compared with no tillage. In mungbean, tillage increased plant height (18%) and root length (60%), as averaged over both sites and seasons. In clay loam soil, tillage increased grain yield of maize by 242%. On the same field, tillage increased mungbean grain yield by 78% in 1984 and 20% in 1985. In sandy loam, tillage produced 38% more mungbean grains than without tillage.  相似文献   

10.
Spatial variability of hydro‐physical properties has long been observed, whereas temporal variation is much less documented and considered in studies and applications, particularly of paddy clay soils under different cropping systems. The objective of this study was therefore to assess the seasonal‐ and inter‐seasonal variation of selected hydro‐physical properties of a paddy clay soil under different rice‐based cropping systems with contrasting tillage. In a long‐term experiment, plots were arranged in a randomized complete block design with four treatments and four replications: (i) rice–rice–rice; (ii) rice–maize–rice; (iii) rice–mung bean–rice; and (iv) rice–mung bean–maize. Soil samples were collected at three depths (0–10, 10–20 and 20–30 cm) at three times during two cropping seasons, i.e., 15 days after soil preparation (DASP), 45 DASP and 90 DASP during the winter–spring and spring–summer seasons. Results show that temporal variability of soil bulk density, macro‐porosity (MacP) and matrix‐porosity within both seasons and between seasons was limited for cropping systems with upland crop rotations, whereas within season variation was significant for rice monoculture system. Observed variation in bulk density, matrix‐porosity and MacP was mainly associated with cropping system and soil depth. Field saturated hydraulic conductivity of topsoil showed great temporal variability, both seasonal and inter‐seasonal, in correspondence with MacP (r  = 0·58). These results highlight the need of depth differentiated soil sampling and time consideration when evaluating management practices on soil physical properties and modeling the hydrological behavior of paddy soil. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

11.
Measurement of soil bulk density is important for understanding the physical, chemical, and biological properties of soil. Accurate and rapid soil bulk density measurement techniques play a significant role in agricultural experimental research. This review is a comprehensive summary of existing measurement methods and evaluates their advantages, disadvantages, potential sources of error, and directions for future development. These techniques can be broadly categorised as direct and indirect methods. Direct methods include core, clod, and excavation sampling, whereas indirect methods include the radiation and regression approaches. The core method is most widely used, but it is time consuming and difficult to use for sampling multiple soil depths. The size of the coring cylinder used, operator experience, sampling depth, and in-situ soil moisture content significantly affect its accuracy. The clod method is suitable for use with heavy clay soils, and its accuracy is dependent on equipment calibration, drying time, and operator experience, but the process is complicated and time consuming. Excavation techniques are most commonly used to evaluate the bulk density of forest soils, but have major limitations as they cannot be used in soils with large pores and their measurement accuracy is strongly influenced by soil texture and the type of analysis selected. The indirect methods appear to have greater accuracy than direct approaches, but have higher costs, are more complex, and require greater operator experience. One such approach uses gamma radiation, and its accuracy is strongly influenced by soil depth. Regression methods are economical as they can make indirect measurements, but these depend on good, quality data of soil texture and organic matter content and geographical and climatic properties. Also, like most of the other approaches, its accuracy decreases with sampling depth.  相似文献   

12.
The relative effects of using light (2–3 Mg) versus heavier (5–7 Mg) tractors, shallow (15 cm) versus deeper (25 cm) ploughing and on-land versus in-furrow wheel placement during ploughing were investigated from 2003 to 2006 in organic rotations (wheat or barley, green manure, oats with peas) and conventionally fertilized barley. Trials were located on loam soil in south-eastern Norway and silty clay loam in central Norway. Ploughing was performed in spring, when the topsoil moisture content was at or below field capacity, using single furrow ploughs that allowed alternative wheel placement and resulted in complete coverage of the surface by wheels each year (ca. 3 times the normal coverage during ploughing). Low tyre inflation pressures (≤80 kPa) were used throughout. The use of a heavy tractor increased topsoil bulk density slightly in the loam soil, and, in combination with in-furrow wheeling, it reduced air-filled pore space and air permeability at 18–22 cm. On the silty clay loam, the use of a heavy tractor did not increase bulk density, but it reduced air-filled pore space throughout the topsoil. In-furrow wheeling reduced air-filled pore space in this soil also, compared to on-land wheeling. Penetration resistance was in this soil always greater at 15–25 cm depth after shallow than after deep ploughing, especially with in-furrow rather than on-land wheeling. Shallow ploughing led on both soils to marked increases in perennial weed biomass compared to deep ploughing. Earthworms were hardly affected by the treatments, but in the loam in 2006 a higher number of individuals were found where the light rather than the heavy tractor had been used. Few significant treatment effects were found on grain yield and quality. Deep ploughing with a light tractor gave the highest wheat yield and protein content in 2 years on the loam soil, and on the silty clay loam the yield of conventionally fertilized barley was higher after deep than after shallow ploughing. In summary, limited evidence was found to support the use of on-land rather than in-furrow wheeling when ploughing is performed at favourable soil moisture and with tractor weights < 5 Mg. There is, however, reason to be wary of using heavy tractors (>5 Mg), even under such conditions. With regard to ploughing depth in organic rotations dominated by cereals, the need to combat perennial weeds by deep ploughing weighs probably more heavily than any possible beneficial effect of shallow ploughing on stimulating nutrient turnover.  相似文献   

13.
Wheat planting in rice-harvested fields without land preparation is more economical, but the physical characteristics of the plant root sphere are not well documented. Comparative changes in the soil compaction in parallel fields used for no-till and conventional tillage were measured in replicated field trials for two soil types and in three randomly selected farmers’ fields. Weakly to moderately developed soils on recent to old Pleistocene calcareous alluvium were studied. They differed in their clay content. No-till wheat sowing resulted in a greater soil bulk density and a lower total porosity in the heavy-textured soils compared to the light-textured soil. In the light-textured Jhakkar soil, the no-till regime resulted in a greater infiltration at the saturated state and under most suction levels and a greater macroporosity compared to the conventional tillage. The silty clay Kotly soil had greater macroporosity in the conventional tillage than in the no-till regime. The wheat root growth and penetration seemed to be favored by the relatively low bulk density resulting from the conventional tillage, particularly in the silty clay loam soil. The dense layer restricted root penetration in the silty clay loam soil, while there was less resistance in the sandy loam soil. The study demonstrated the suitability of the no-till regime for specific soil types. Published in Russian in Pochvovedenie, 2008, No. 11, pp. 1362–1370. The text was submitted by the authors in English.  相似文献   

14.
In a field study, conducted on 10 conventionally managed field sites in Germany, the effects of high axle loads (15–25 Mg) on soil physical properties were investigated. Soil texture classes ranged from loamy sand to silty clay loam. All sites were annually ploughed, and one site was additionally subsoiled to 40 cm depth. In the context of common field operations wheeling was performed either by a sugar beet harvester (45 Mg total mass, 113 kPa average ground contact pressure) or a slurry spreader (30 Mg total mass, 77 kPa average ground contact pressure). Soil moisture conditions varied from 3.2 to 32 kPa water tension during this pass. Penetration resistance was measured before the pass. Soil cores were collected in a grid scheme at each site before and after the machine passed. Bulk density, aggregate density, air-filled porosity and air permeability at seven distinct soil water tensions ranging from 0.1 to 32 kPa were determined in these cores taken from three layers (topsoil, plough pan and subsoil).At most sites, a pass by the sugar beet harvester or slurry spreader strongly affected topsoil properties. Bulk density and aggregate density increased while air-filled porosity and air permeability decreased. The plough pan was already severely compacted before wheeling: therefore changes were small. The subsoil showed no changes or only minor signs of compaction. Only at one site, which was subsoiled the year before, significant signs of compaction (i.e. changes in bulk density, air-filled porosity and air permeability) were detected in subsoil layers.The results show that using present-day heavy agricultural equipment does not necessarily lead to severe subsoil compaction in soils where a compacted plough pan already exists. However, fields which were subsoiled leading to an unstable soil structure are in serious danger of becoming severely compacted.  相似文献   

15.
Most soil sampling techniques are calibrated with standards and against each other, but the error introduced by the individuals performing each technique (sampler error) is often not addressed. We determined that sampler error explains a minimum of 5.5% of the variation in soil bulk density when using a composite coring technique. This source of error is of concern because it could easily obscure the small, but significant differences anticipated with long-term (decadal) research. We suggest three methods for increasing sampling accuracy across spatial and temporal treatments: (1) use > 5 individuals to sample each treatment; (2) consider both the concentration and pool size of soil properties (e.g. nitrate, root mass, etc.); and (3) include measurements of sampler error.  相似文献   

16.
梅江盆地叶塘组紫色岩上发育土壤的物理性质研究   总被引：1，自引：0，他引：1  
采用野外调查、取样和室内实验分析相结合的方法,研究了梅江盆地白垩系上统叶塘组（Kyt^2）紫色岩上土壤物理性质特征扣差异,结果表明：叶塘组紫色岩母质发育的土壤粘粒含量低而砂粒含量高,具有容重较大,比重相对偏小,孔隙度不高,自然含水量偏低的特点。从丘顶、丘腰到丘脚,土层逐渐增厚,土壤粘粒含量逐渐增加,砂粒含量逐渐减少,容重递增而比重减小。孔隙度表现出丘顶〉丘腰〉丘脚的趋势,含水量则表现出丘顶〈丘腰〈丘脚的趋势。针对情况,提出相应建议以维护紫色土利用的可持续发展。  相似文献   

17.
体积置换法直接测量土壤质量含水率及土壤容重   总被引：2，自引：6，他引：2  
土壤含水率直接测量是相关研究和应用的基础,在土壤力学、作物栽培、农田灌溉、生态环境等研究和实践中十分重要。该文提出了一种与传统烘干称质量法相当的体积置换法直接测量土壤质量含水率及土壤容重。该方法在假设一定土壤颗粒密度的前提下,用一定体积的标准取样环刀取得土样后,通过向待测量土体补充水分使土壤达到饱和,用一定体积的水置换土壤中的充气空隙,直到土样达到饱和状态;再通过测量得到的初始/原始土样质量、饱和后土壤的质量以及已知土壤颗粒密度和水密度,计算得到被置换的充气空隙的体积,进而由此计算得到土壤质量含水率和土壤容重。采用3种不同土壤,即陕西杨凌黏黄土、北京粉壤土和江西黏红土,分别预配制成7种不同初始土壤体积含水率,含水率约为:风干土(含水率2%～3%)、5%、10%、15%、25%、30%和饱和含水率,以及3种不同土壤容重:1.25、1.35和1.45g/cm3进行室内试验。用类似的土样,采用传统方法烘干土样8、12、24、48h后,测量确定土壤的质量含水率,通过延长烘干时间测得数据表明,传统方法烘干8h所测得的质量含水率仍有1%～3.2%的含水率误差。最终试验结果表明体积置换方法测得的土壤含水率比传统烘干土样8h所测得的结果大2%～3%,比烘干土样48h所测得的结果大1%左右。体积置换方法测量操作过程简单,耗时较少,节约能源,测量结果具有较高精度。  相似文献   

18.
Relative gas diffusivity, air permeability and hydraulic conductivity were measured in undisturbed soil cores from tillage and traffic experiments. Continuity indices were taken as the quotient of relative diffusivity and air-filled porosity, and of air permeability and air-filled porosity (and the square of air-filled porosity). These were applied to individual measurements or to treatment means. More general continuity indices were derived from the changes in flow or diffusion with porosity, where the variations in porosity were due to both field variability and applied changes of water potential. These indices were the exponent in the relationship between relative diffusivity and air-filled porosity and the slope of log–log plots of air permeability and air-filled porosity or hydraulic conductivity and degree of saturation. Some physical significance was attached to the exponents by comparison with models of soil porosity. Positive intercepts of the relative diffusivity or air permeability plots on the air-filled porosity axes were taken as porosities blocked to gas movement.
Continuity indices and flow measurements showed differences between tillage and traffic treatments which did not necessarily reflect differences in bulk density. Intrinsic permeability was better estimated from air permeability than from unsaturated hydraulic conductivity.  相似文献   

19.
为解决内蒙古河套平原黏性碱化盐土土壤黏重,作物难以正常生长、产量低下等问题,对河套平原黏性碱化盐土进行了土壤耕层(0~20 cm)掺砂的土壤改良试验,研究掺砂对土壤理化性状和玉米产量的影响。结果表明:试验区土壤掺砂可以降低土壤容重,改变土壤机械组成和土壤质地,提高了黏性碱化盐土的通气孔隙度,改善土壤的通气透水性,降低土壤全盐量和碱化度,有效改善玉米生长环境,提高了玉米的产量。掺砂20%处理的土壤容重从1.64 g/cm3(CK)降低到1.49 g/cm3,土壤通气孔隙度从8.57%提高到18.17%,达到正常范围,使土壤砂粒、粉粒、粘粒含量比例趋向适中,土壤质地由壤质黏土转变为黏壤土,土壤全盐量下降了13%,碱化度降低了21%,玉米产量提高了301%。综合分析,掺砂20%处理对当地碱化盐土改良效果较为适宜。  相似文献   

20.
Wood extraction by heavy machinery has always been associated with soil disturbance in mountain forests,and the degree of soil degradation is influenced by several factors,including site and soil characteristics,soil moisture,type of equipment used,and number of machine passes.The effects of ground-based skidding operations on the physical properties of soils with different texture were evaluated at different levels of traffic frequency and trail gradient at two sites in an Iranian temperate forest.The treatments included combinations of three different traffic frequencies(3,8,and 14 passes of a rubber-tired cable skidder),three levels of trail gradient(10%,10%–20%,and20%) and two soil texture classes,clay loam(Site 1) and sandy loam(Site 2).The average gravimetric soil moisture at the time of skidding was 23%(Site 1) and 20%(Site 2).The average dry bulk density and total porosity of the undisturbed soil(control) were0.71 g cm~(-3) and 73.3% at Site 1(clay loam) and 0.86 g cm~(-3)and 59.1% at Site 2(sandy loam),respectively.At site 1(fine-textured soil),rutting began after three passes of the skidder,whereas at site 2(coarse-textured soil),rutting occurred only after eight passes.Independent of the traffic frequency and trail gradient,machine impact on the fine-textured soil caused greater increases in bulk density and rut depth compared to that on the coarse-textured soil.After three skidder passes and independent from trail gradients,dry bulk density at Site 1 increased by 54.8% compared to that of the undisturbed control,and the increase was 45.5% at Site 2.Therefore,medium to fine-textured soils are more susceptible to compaction than coarse-textured soils.Such soils,especially when moist,should be protected using brush mats created from harvesting residues during the forest processing phase.  相似文献   

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