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1.
为揭示排土场土体裂缝区植物根系和抗剪强度分布特征,采用根钻法、WinRHIZO根系分析系统和直剪仪研究了0—60 cm土层植物根系、黏聚力和内摩擦角随土层深度的变化规律。结果表明:3个样地根系特征参数不同,随土层深度增加而减小,主要分布在0—20 cm土层,根密度和根重密度为88.81~303.03个/103cm3,0.15~2.69 mg/cm3。根系以径级d≤0.1 mm和0.1 mm相似文献   

2.
土壤质地对玉米不同生理指标水分有效性的影响   总被引:2,自引:1,他引:1  
为确定土壤质地对玉米不同生理指标水分有效性的影响,该文利用3种土壤(重壤土、中壤土和砂壤土)的盆栽控水试验和1种土壤(重壤土)的田间小区控水试验,研究了玉米不同生理指标随相对土壤含水率(土壤含水率占田间持水率的比)的动态变化。结果表明:3种土壤中各生理指标相对值在相对土壤含水率降低到土壤水分阈值之前保持不变,低于此阈值时随相对含水率的进一步降低而线性降低,且均可用分段函数来拟合(R2=0.824~0.999)。土壤水分有效性大小排序为:砂壤土>中壤土>重壤土,而且瞬时生理指标的土壤水分阈值低于日变化和整个试验阶段的累积指标。因此土壤质地和不同生理指标的时间尺度都会影响玉米生理指标对土壤水分有效性的响应。  相似文献   

3.
开沟播种是一种可显著提高地下滴灌春玉米出苗率的新型播种方式,为了优化该技术模式,该文通过两年田间试验分析了地下滴灌玉米出苗率与灌水后种子处土壤有效饱和度(effective saturation)的关系,并基于HYDRUS-2D构建了地下滴灌开沟播种土壤水分运动模型,以90%玉米出苗率为前提,研究了不同土质和土壤初始含水率条件下3个技术参数——开沟深度、滴灌带埋深和灌水量对种子处土壤有效饱和度的影响.结果表明:1)出苗率随土壤有效饱和度线性递增,土壤有效饱和度不小于0.77时,出苗率超过90%;2)地下滴灌开沟播种HYDRUS-2D模型模拟精度较高,模拟得到的土壤有效饱和度随开沟深度增大而增大,随滴灌带埋深增大而减小;3)满足土壤有效饱和度为0.77所需的出苗水灌水量随土壤黏粒含量、土壤初始含水率和开沟深度增大而减小,随滴灌带埋深增大而增大.当表层土壤初始含水率为40%田持~60%田持时,开沟深度每增加5cm,砂壤土的出苗水灌水量减小15~20mm,粉壤和粉黏土的出苗水灌水量减小6~18mm;滴灌带埋深由30cm增大到35cm时,砂壤土的出苗水灌水量增大16~21mm,粉壤和粉黏土的出苗水灌水量增大4~14mm.不同埋深和开沟深度下,当表层土壤初始含水率由40%田持增大到60%田持时,砂壤土的出苗水灌水量减小9~14mm,粉壤和粉黏土的出苗水灌水量减小9~19mm;4)综合考虑土壤质地、玉米根系分布、机械作业、耗能、耕作深度和土壤水深层渗漏以及土壤初始含水率,玉米地下滴灌适宜的滴灌带埋深为30~35cm,开沟深度为10~15cm,灌水量范围为25~67mm.农业生产者可以根据当地实际情况对以上3个技术参数进行合理配置.  相似文献   

4.
反求根系吸水速率方法的探讨   总被引:7,自引:2,他引:5  
植物生长条件下土壤水分运动方程的逆问题具有强烈的非线性性与不适定性,该文探讨分析了两种现有的模拟根系吸水速率的反求方法,并提出了一种新的数值迭代反求方法。数值实验结果表明:含水率(或基质势)剖面实测值与模拟值的对比不足以论证根系吸水模型的正确与否;当初始剖面土壤水分变化较为剧烈时,提出的新的数值迭代反求方法可以较好地模拟根系吸水速率在土壤剖面上的分布,在任意两次“实测”时间间隔内,当根系吸水速率变化不大时,选用时间间隔分别为1、2、5、10和15 d的“实测”土壤水分剖面均可以获得与理论吸水分布较为一致的结果,模拟所得的“实际”蒸腾强度与理论值的相对误差均在3%以内。  相似文献   

5.
长江中上游地区坡耕地土壤抗剪强度特征   总被引:1,自引:0,他引:1  
在长江中上游地区,坡耕地是造成严重水土流失的主要地貌单元。土壤抗剪强度是水土流失定量评价和预测的重要指标。通过在长江中上游9个省(市)坡耕地选取37个测试点,现场原位测试土壤抗剪强度并取样分析土壤理化性质,研究土壤抗剪强度与土壤质地、含水率间的关系,结果表明:①表层(0 cm)与底层(20 cm深度)的土壤抗剪强度均呈现出黏土>黏壤土>壤土,其中黏土在表层和底层的平均土壤抗剪强度分别为0.56、0.99 kg/cm~2。此外,土壤含水率、粉粒及黏粒含量之和也呈现出与土壤抗剪强度相同的分布规律。②3种土壤质地表层平均抗剪强度均随含水率增大呈先增大后减小的变化趋势,而底层土壤抗剪强度均随含水率增大而减小。研究结果进一步完善了长江中上游地区坡耕地土壤理化性质特征数据库,也为长江流域坡耕地水土流失定量评价及预测提供了科学依据。  相似文献   

6.
植物根系吸收土壤水分的研究综述   总被引:9,自引:0,他引:9  
植物根系吸收土壤水分是土壤-植物-大气连续体中水分运动的一个重要环节。本文从土壤-植物-大气连续体入手,对植物根系吸收土壤水分的影响因素,植物根系吸收土壤水分的微观模型及植物根系吸收土壤水分的宏观模型等,进行了介绍和评述。  相似文献   

7.
黑河中游地区土壤剖面砂、黏层次相间排列的特点及部分区域剖面中出现的不透水层对土壤中的水分运动和溶质迁移具有重要影响。该研究调查了黑河中游100km2区域内土壤剖面的质地分层情况,运用一维嵌入马尔可夫链模型模拟该地区的土壤质地剖面。研究表明,研究区土壤剖面共出现砂土、壤质砂土、砂质壤土、壤土、黏质壤土、粉黏壤土和粉黏土7种质地类型,层次厚度呈对数正态分布。粉黏土未在表层土壤出现,而砂土在表层出现的概率明显高于其余质地类型,剖面某一质地层之下多出现细粒含量比其高的下一质地类型。剖面上相邻两质地层之间的转移具有明显的马尔可夫链特征(简称马氏性),且马氏链是平稳的。一维嵌入马尔可夫链模型能够较好地描述研究区土壤质地层次的垂向变化,剖面主要的质地层次组合为:砂—壤、壤—砂、壤—黏、黏—壤。对土壤质地剖面的定量模拟,可以为开展该区域土壤水循环、转化和溶质迁移等相关研究提供参考。  相似文献   

8.
为准确模拟土壤计划湿润层内墒情动态变化,基于土壤-植物-大气连续体物质能量运动及土壤水动力学的基本理论,考虑作物根系伸展和吸水特性,把土壤水分变化土层划分为随作物根系伸展而改变深度的包含主要根系的动态根区和无根系的储水区,构建了变根区墒情动态二区模型。模型根区深度随着作物根系伸展改变,以此准确表达土壤计划湿润层内墒情的动态变化;将储水区的土壤水分作为模型变量,计算根区下界面水分通量,由此间接地考虑了深层土壤水分对作物蒸发蒸腾量的影响。将模型拟合误差作为目标函数,采用自由搜索算法率定模型参数。应用建立的模型进行墒情模拟,模拟相对误差小于±5%和±10%所占的比例分别为49.09%和94.55%;经t检验和回归分析表明预测值和实测值相差不大,具有较好的一致性,决定系数为0.779,模型具有较高的模拟精度,能准确反映计划湿润层内墒情的变化。  相似文献   

9.
[目的]探究三峡库区紫色土坡耕地3种草本地埂植物根系分布及抗拉特征,为揭示地埂植物根系固结地埂提供理论依据和数据支持。[方法]以三峡库区自然恢复的蓑草、人工种植的韭菜和蚕豆这3种草本地埂植物根系为研究对象,对比分析其根系在不同地埂土壤深度的分布规律及根系抗拉特性。[结果](1)在0—40cm深度土壤中3种草本地埂植物根系直径变化表现出:蚕豆根系韭菜根系蓑草根系。3种草本地埂植物根系直径与地埂土壤的土层深度间服从指数函数关系。(2)在0—40cm地埂土层深度范围内,韭菜根系生物量与蓑草根系和蚕豆根系生物量之间存在显著性差异(p0.05),韭菜和蚕豆地埂植物根系生物量随土层深度的增加而逐渐减小,蓑草地埂植物根系生物量随土层深度的增加先增加后减小。(3)3种草本地埂植物根系的单根平均抗拉力次序为蚕豆根系(10.53N)蓑草根系(6.03N)韭菜根系(4.51N),3种地埂植物根系单根抗拉力与根径呈幂函数关系(p0.05)。3种地埂植物根系的抗拉强度表现为蓑草根系(45.91 MPa)蚕豆根系(18.02MPa)韭菜根系(12.20 MPa)。(4)3种草本地埂植物根系黏聚力变化顺序为:蓑草根系(0.013 1kPa)蚕豆根系(0.009 4kPa)韭菜根系(0.005 5kPa)且3种地埂植物根系黏聚力与土层深度呈指数函数关系(p0.01)。[结论]自然恢复的蓑草地埂在三峡库区较其他两种人工种植的地埂植物有更好的固结地埂效果,从而有效控制坡面土壤侵蚀和水土流失。草本植物固结地埂可为三峡库区坡耕地治理提供新思路。  相似文献   

10.
为确定土壤质地对旱生植物长柄扁桃(Amygdalus pedunculata Pall)和沙柳(Salix psammophila)幼苗不同生理指标水分有效性的影响,采用盆栽控水试验,研究了黄土高原2种典型质地土壤(砂土和壤土)下长柄扁桃和沙柳幼苗不同生理指标随相对土壤含水率(土壤含水率占田间持水率的比值)的动态变化。结果表明:2种质地土壤下长柄扁桃和沙柳幼苗各生理指标相对值在相对含水率降低至土壤水分阈值之前保持相对稳定,低于此阈值时随相对含水率的降低而迅速下降,且均可用非线性连续函数来拟合(R~2=0.8905~0.9864)。2种植物土壤水分有效性因选取指标的不同而略有差异,当以瞬时气体交换指标(相对净光合速率R_(Pn)和相对气孔导度R_(Gs))为评价指标时,砂土水分有效性高于壤土;当以相对水分利用效率R_(WUE)为评价指标时,壤土水分有效性高于砂土。瞬时气体交换指标(R_(Pn)和R_(Gs))的水分阈值高于日变化指标(相对日蒸腾速率R_(Td)),表明土壤质地和时间尺度均会影响植物生理指标对土壤水分有效性的响应。因此,在黄土高原进行植被恢复与生态建设时应考虑土壤质地对植物水分有效性的影响。  相似文献   

11.
不同质地土壤玉米秸秆还田配施腐熟剂效应的研究   总被引:5,自引:0,他引:5       下载免费PDF全文
为研究鉴选不同质地土壤秸秆还田适宜的秸秆腐熟剂,于2017—2018年在西辽河平原灌区中壤土和砂壤土秸秆还田配施人元腐熟剂和中农绿康腐熟剂,以秸秆还田不施腐熟剂为对照,共设置6个处理,测定玉米秸秆腐解率、玉米产量、玉米根系特性和土壤化学性状,研究不同秸秆腐熟剂对玉米产量及土壤特性的影响。结果表明:不同质地土壤2种腐熟剂秸秆腐解率间无显著差异;中壤土2年各处理玉米产量及根系特性、土壤化学性状均表现为人元腐熟剂中农绿康腐熟剂秸秆还田不施腐熟剂,且中农绿康腐熟剂和人元腐熟剂显著高于秸秆还田不施腐熟剂,而2种腐熟剂处理之间无显著差异;砂壤土2年各处理玉米产量及根系特性、土壤化学性状均表现为中农绿康腐熟剂人元腐熟剂秸秆还田不施腐熟剂,且中农绿康腐熟剂显著高于人元腐熟剂和秸秆还田不施腐熟剂。2年不同质地土壤中配施腐熟剂在根系特性、土壤化学性状方面表现为砂壤土配施中农绿康腐熟剂效果优于人元腐熟剂,而中壤土配施2种腐熟剂效果无显著性差异。  相似文献   

12.
Considering the model that the hydrothermal coupling moving rule of the seasonal frozen soil under freezing and thawing effect, a research was made that how deep we bury and the soil texture are to effect the rule of the diffusion and evaporation of water vapor. By monitoring the moisture content and temperature of the profile of the continuous freezing and thawing soil in region named Xiaotangshan mountain in Beijing and using the hydrothermal coupling moving model, the water transferring rule of clay and sandy loam in different depth that we buried was summarized. Many long-term field experiments showed that when frozen layer buried in a deep way was in a frozen state, the interactive movement of the water in the soil was not active and evaporated slowly. The average value of the water evaporation of clay was about 0.51 mm/day approximately and the situation of the sandy loam soil was 1.24 mm/day. By qualitative analyzing and observation, the less we buried (less than 0.8 m), the ice in the frozen soil layer got more. Besides, the density of the frozen soil layer went higher but the water barely diffused. On the contrary, with the increase of the depth, the diffusion went stronger and stronger due to the contact between the soil and the groundwater. In addition, according to the different soil texture detections, the diameter of soil particle has great influence on the diffusion of the water vapor in the soil. The diffusion rate of the water vapor in the sandy loam soil was twice than that of in clay. Other field water coupling experiments showed that, the soil moisture content was greater, soil freezing period density was larger, and soil water infiltration rate was zero. Soil evaporation was gradually decreased with the increasing of groundwater depth, and the size of soil particle would have a more obvious effect on soil water vapor diffusion and evaporation. Our research results can provide scientific basis for the buried area where contains groundwater to keep moisture in the winter and the resource content of the groundwater in Beijing and the locations in the same latitude of Beijing. This paper’s purpose was to research the law of water vapor diffusion and evaporation, with different soil texture and burial depth, so it can verify the coupled model of seasonal frozen soil water and heat migration.  相似文献   

13.
Soil tilth has been defined in terms of a ‘Physical Index’ based on the product of the ratings of eight physical properties — soil depth, bulk density, available water storage capacity, cumulative infiltration or apparent hydraulic conductivity, aggregation or organic matter, non-capillary pore space, water table depth and slope. The Physical Index and a tillage guide were used to identify the tillage requirements of different soils varying in texture from loamy sand to clay in the semi-arid tropics. The physical index was 0.389 for a loamy sand, 0.518 for a black clay loam and 0.540 for a red sandy loam soil and the cumulative rating indices in summer and winter seasons were 45 and 44 for loamy sand, 52 and 51 for red sandy loam and 54 and 52 for black clay loam soils, respectively. The compaction of the loamy sand by eight passes of a 490 kg tractor-driven roller (0.75 m diameter and 1.00 m length) increased the physical index to 0.658 and chiselling of the red sandy loam and black clay loam increased the physical indices to 0.686 and 0.729, respectively. The grain yields of rainfed pearl millet and guar and irrigated pearl millet, wheat and barley increased significantly over the control (no compaction) yields by compaction.

The chiselling of the soils varying in texture from loamy sand to clay at 50 to 120-cm intervals up to 30–40 cm depth, depending upon the row spacing of seedlines and depth of the high mechanical impedance layer, increased the grain yields of rainfed and irrigated maize on alluvial loamy sand, rainfed maize on alluvial sandy loam and red sandy loam, rainfed sorghum on red sandy loam and black clay loam, irrigated sorghum on black clay loam and rainfed black gram on red sandy loam, pod yield of rainfed groundnut, tuber yield of irrigated tapioca and fresh fruit yield of rainfed tomato on red sandy loam and sugarcane yield on black clay soil, significantly over the yields of no-chiselling systems of tillage such as disc harrow and country plough.  相似文献   


14.
The continuous use of heavy machinery and vehicular traffic on agricultural land led to an increase in soil compaction, which reduces crop yield and deteriorates the physical conditions of the soil. A pot experiment was conducted under greenhouse conditions to study the effects of induced soil compaction on growth and yield of two wheat (Triticum aestivum) varieties grown under two different soil textures, sandy loam and sandy clay loam. Three compaction levels [C0, C1, and C2 (0, 10 and 20 beatings)], two textural classes (sandy loam and sandy clay loam), and two genotypes of wheat were selected for the experiment. Results indicated that induced soil compaction adversely affected the bulk density (BD) and total porosity of soil in both sandy loam and sandy clay loam soils. Compaction progressively increased soil BD from 1.19 Mg m?3 in the control to 1.27 Mg m?3 in C1 and 1.40 Mg m?3 in C2 in sandy loam soil while the corresponding increase in BD in sandy clay loam was 1.56 Mg m?3 in C1 and 1.73 Mg m?3 in C2 compared to 1.24 Mg m?3 in the control. On the other hand, compaction tended to decrease total porosity of soil. In case of sandy loam, porosity declined by 5% and 17% in C1 and C2, respectively, and declined in sandy clay loam by 29% and 54%, respectively. Averaged over genotypes and textures, shoot length decreased by 15% and 26% at C1 and C2, respectively, and straw yield decreased by 21% and 61%, respectively. The compaction levels C1 and C2 significantly decreased grain yield by 12% and 41%, respectively, over the control. The deleterious effect of compaction was more pronounced on root elongation and root mass, and compaction levels C1 and C2 decreased root length by 47% and 95% and root mass by 41% and 114%, respectively, over the control. Response of soil texture to compaction was significant for almost all the parameters, and the detrimental effects of soil compaction were greater in sandy clay loam compared to sandy loam soil. The results from the experiment revealed that soil compaction adversely affected soil physical conditions, thereby restricting the root growth, which in turn may affect the whole plant growth and grain yield. Therefore, appropriate measures to avoid damaging effects of compaction on soil physical conditions should be practiced. These measures may include soil management by periodic chiseling, controlled traffic, conservation tillage, addition of organic manures, and incorporating crops with deep tap root systems in a rotation cycle.  相似文献   

15.
The Atterberg limits and the Proctor compaction test are used by engineers for classifying soils and for predicting stability of building foundations. Field capacity and wilting point (agronomic limits) are used to indicate available water for plant uptake. Few studies have related the engineering criteria to the agronomic ones with regard to compaction hazard for soils. This study investigated the relationships between Atterberg limits, agronomic limits and the critical moisture content (moisture content at Proctor maximum density) for three disturbed soils (sandy loam and clay loam soils from a reclaimed Highvale mine site, and a silt loam soil from a grazing site at Lacombe) of different textures. Relationships between bulk density, moisture content and penetration resistance for these soils were also investigated. For the sandy loam and loam soils, the field capacity was close to the critical moisture content but lower than the plastic limit. Therefore, cultivation of these two soils at moisture contents close to field capacity should be avoided since maximum densification occurs at these moisture contents. Overall, the critical moisture content or field capacity would be a better guide for trafficking of sandy loam and loam textured soils than the Atterberg limits. For the clay loam, field capacity was within the plastic range. Thus trafficking this soil at field capacity would cause severe compaction. In conclusion, either field capacity or plastic limit, whichever is less, can be used as a guide to avoid trafficking at this moisture content and beyond. For the sandy loam and loam soils penetration resistance significantly increased only with increased bulk density (P≤0.05). For the clay loam soil, penetration resistance was positively related to bulk density and negatively related to moisture content.  相似文献   

16.
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   

17.
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   

18.
通过系统观察不同土壤类型棉花土壤水分动态变化规律,研究膜下滴灌棉花土壤水分的变化,以有效地提高棉花产量和水分利用效率。结果表明:膜下滴灌棉花土壤含水量呈现规律性的变化:在黏土地上,土壤含水量的变化趋势近似于抛物线,0~20cm土壤含水量最低,随土层深度增加,土壤含水量逐渐增加,至60-80cm达最大,随后又降低。而在沙土地,土壤含水量的变化趋势与黏土地相反。这种变化与土壤的理化、生物学特性以及棉花根系的生长发育有关。不同土壤类型膜下滴灌棉花产量、总耗水量及水分利用效率存在明显差异。  相似文献   

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