不同水分含量对潮土和火山灰土硝化动态的影响

在试验室条件下研究了不同水分含量对取自中国的潮土和日本的火山灰土硝化动态的影响。潮土在土壤硝化过程中的土壤水分含量以田间持水量的60％～90％较为适宜，低于田间持水量的60％引起土壤硝化力降低。火山灰土在土壤硝化中的土壤水分含量以田间持水量的75％～90％较为适宜，低于田间持水量的75％引起土壤硝化力降低。潮土在硝化培养中有亚硝酸盐出现，火山灰土没有亚硝酸盐被检出。土壤亚硝酸盐含量在低水分含量下峰值低，持续时间较长，在高水分含量下峰值高，持续时间较短。     

高寒草甸土壤温室气体释放对水分变化的响应

青藏高原未来气候变化引起的降水量再分配,将影响土壤水分含量状况,这会对土壤温室气体的释放产生直接影响。为了探明土壤含水量对土壤温室气体释放的影响,以青藏高原高寒草甸土为研究对象,采用室内培养的方法,研究了田间持水量30%、45%、60%、75%和90%不同水分梯度对土壤CO2、CH_4和N_2O三种温室气体释放的影响。结果表明:(1)高寒草甸土壤CO_2和N_2O累积释放量在土壤水分含量为田间持水量的60%时最大,分别为2.74 g kg~(-1)和1.54 mg kg~(-1);(2)土壤水分含量在田间持水量的30%~60%范围内,高寒草甸土壤是CH_4的"汇",土壤水分含量在田间持水量的75%~90%范围内,高寒草甸土壤转变为CH_4的"源";(3)CH_4累积释放量与土壤NO_3~--N含量呈极显著负相关关系,N_2O累积释放量与土壤NO_3~--N含量呈显著负相关关系;(4)不同水分梯度高寒草甸土壤释放温室气体的全球增温潜能(GWP)由大至小顺序为:60%75%90%45%30%。研究结果可为未来气候变化背景下青藏高原高寒生态系统土壤温室气体释放的估算和管理提供一定的科学依据。     

土壤水分对包膜尿素养分释放特性的影响

试验采用土壤培养的方法,以释放期分别为60 d(肥料A)和90 d(肥料B)的两种肥料作为供试肥料,研究了土壤绝对含水量、干湿交替、相对含水量和水势因素对3种土壤中包膜尿素养分释放特性的影响。结果表明:在3种土壤中,土壤绝对含水量从50 g/kg增到200 g/kg时,包膜尿素养分释放率均随土壤水分含量的增加而显著增加,此时水分因素是控制包膜尿素养分释放的主要因素。在干湿交替条件下,两种供试肥料间释放率的差异变大,其中肥料B在潮土中释放速率较其他两种土壤中下降更多。当相对含水量在0%~50%田间持水量范围内,或水势在60~100k Pa范围内时,供试肥料在红壤中的释放显著低于潮土和水稻土,这与红壤中黏粒含量高有关;当相对含水量大于100%田间持水量时,或水势低于60 k Pa时,土壤水分和土壤类型对包膜尿素养分释放的影响基本不再显著。常用的Sugihara方程可以较好地拟合包膜尿素在试验设定水分条件下的养分释放特性,相关系数r0.95。3种不同土壤水分参数均可以用来预测包膜尿素的释放率和释放期,其中水势(x)与包膜尿素释放期(y)的拟合效果最好,关系式为y=64.79e~(0.0066x),r=0.91。     

高寒草原土壤有机碳矿化对水氮添加的响应

[目的]研究不同水氮添加下的高寒草原土壤有机碳矿化过程,探讨土壤性质与土壤碳矿化的关系,为揭示全球变化背景下高寒草原土壤碳转化规律提供科学依据。[方法]设置45%,60%,75%,90%的田间持水量(WHC)4个水分梯度和4个氮添加梯度(0,0.2,0.4,0.8 mg/g)进行室内培养,分析CO_2浓度,测定土壤溶解性有机碳(DOC)、土壤微生物生物量碳(MBC)含量以及土壤酶活性。[结果]①在水或氮添加范围内,土壤有机碳矿化量呈抛物线变化趋势,土壤碳矿化受水分调控更加敏感,氮添加对土壤碳矿化的影响依赖于水分添加量。②土壤水分从45%增加到60%WHC,加速了土壤中可溶性物质溶出,增加了有机碳矿化;施氮量从0 mg/g增加到0.4 mg/g,土壤有机碳含量、土壤微生物量碳含量呈上升趋势,刺激了土壤有机碳的矿化。③90%田间持水量WHC的高水分添加与45%田间持水量土壤水分下的高氮添加(0.8 mg/g)抑制高寒草原土壤碳矿化,高水分添加通过降低土壤通透性抑制有机碳矿化过程,高氮添加通过降低土壤DOC生物有效性、土壤MBC含量、土壤酶活来抑制土壤有机碳矿化过程,高氮添加对碳矿化的抑制作用在90%WHC条件下得到缓解。[结论]随着未来氮沉降量与降雨量的持续增加,青藏高原高寒草原土壤有机碳的矿化作用可能会受到抑制,有利于高寒草原土壤有机碳积累。     

几种常用绿地改良材料对土壤水分特征的影响

分析了几种常用绿地土壤改良材料及其不同配比对土壤水分特征曲线和水分常数的影响,结果表明:利用RETC软件对各配比土壤水分特征曲线van Genuchten方程的参数拟合效果较好,R2均大于0.99;随着砂粒含量的增加,土壤田间持水量降低,土壤中水分有效性比例增加,但砂粒粒径对土壤水分常数影响不显著;绿化植物废弃物能提高土壤田间持水量和有效水含量,降低土壤凋萎含水量;绿化植物废弃物还能提高有效水占田间持水量的比例,以20%绿化植物废弃物的用量为最大,为49.59%;聚丙烯酰胺(PAM)虽然能提高土壤田间持水量,但阻碍土壤水分的释放,降低土壤水分的有效性;脱硫石膏可以增加土壤田间持水量和水分的有效性。综合而言,以70%土、10%砂、20%绿化植物废弃物和0.5 kg/m~3脱硫石膏的配比相对最佳。     

硅钾肥配施对小麦抗条锈病及产量的影响

本文研究了不同土壤水分条件下 ,施用硅肥、钾肥及硅钾肥对冬小麦产量和小麦抗条锈病的影响 ,结果表明 :施用硅肥可减轻小麦病害 ,增强其抗病性 ,硅钾肥配施次之。低水分条件下 (土壤含水量为田间持水量的 35 %～ 4 0 % )施硅钾、硅肥对冬小麦抗条锈的影响优于充足水分条件下 (土壤含水量为田间持水量的 70 %～ 75 % )。施用硅、钾肥能明显增加冬小麦产量。     

不同土壤水分下限对大棚滴灌甜瓜产量和品质的影响

以厚皮甜瓜品种伊莉莎白为材料,研究大棚滴灌条件下营养生长期不同土壤水分下限(75%田间持水量,I75;65%田间持水量,I65;55%田间持水量,I55;45%田间持水量,I45)对甜瓜生长、产量、品质以及灌溉水分利用效率的影响,并以沟灌(G75)作为对照。结果表明,株高、茎粗、叶面积和地上部干重均随着营养生长期土壤水分下限的降低而减小。I75果实横径、皮厚和肉厚均最大,果形指数最小;I65果实纵径最大。果实品质方面,总可溶性固形物(TSS)含量为:I65>I55>I75>I45;可溶性糖含量为:I55>I65>I45>I75;维生素C(Vc)含量为:I55>I65>I75>I45;可溶性蛋白质含量为:I55>I65>I45>I75;游离氨基酸总量为:I45>I65>I55>I75。I75的产量和平均单果重最高;I65的灌溉水分利用效率最高,达到29.16kg/m3,相比沟灌对照提高76.4%,可节水58.1%,而平均单果重仅比对照下降3.2%。综合考虑产量和品质,可以选择65%田间持水量作为武汉地区厚皮甜瓜营养生长期适宜的土壤水分下限指标。     

不同水分条件下3种灌木幼苗的耗水及生长特征

[目的]研究岳武高速公路填方边坡3种绿化灌木幼苗在不同土壤水分条件下的耗水特征及生长表现,为该地区边坡早期植被恢复和护坡植物维护提供参考。[方法]选取马棘、二色胡枝子、紫穗槐幼苗为试验材料,采用盆栽称重法测定其在不同土壤水分处理下〔田间持水量(FC)的30%~45%,45%~60%,60%~75%和75%~90%〕的阶段耗水特征及生长变化。[结果]3种灌木幼苗的日耗水变化曲线均呈单峰型特征,峰值出现在中午时分;月耗水量、总耗水量均随土壤含水量的升高而增大,且差异显著;不同水分条件下灌木幼苗的株高、地径、生物量增量差异显著,马棘长期处于30%~45%FC、二色胡枝子和紫穗槐长期处于30%~45%FC,45%~60%FC水分条件下其幼苗生长受到抑制;土壤水分含量对灌木幼苗的水分利用效率影响较大,75%~90%FC和30%~45%FC均会降低幼苗的水分利用效率。[结论]综合考虑灌木幼苗的耗水量及生长特征,认为马棘幼苗土壤含水量维持在45%~60%FC、胡枝子和紫穗槐维持在60%~75%FC时能够实现幼苗正常生长,同时又能实现水分的高效利用。     

土壤持水量对生菜生长和镉浓度的影响

通过不同水分含量处理的盆栽试验和培养试验,探索土壤持水量对生菜生物量与Cd浓度,土壤pH和土壤Cd有效态的影响。结果表明,土壤持水量显著影响生菜的生物量,75%田间持水量（water holding capacity,WHC）处理生菜地上部鲜重最高,生菜鲜重与土壤持水量呈倒V型关系。土壤持水量也显著影响生菜地上部及根中Cd浓度,2者均与土壤持水量呈显著负相关关系,土壤持水量从45%WHC增加到65%WHC,地上部Cd浓度降低41%,生菜Cd含量从超过无公害标准到低于标准。盆栽试验中,乙酸铵-Cd浓度与水分处理水平没有显著相关性,生菜地上部Cd浓度与土壤的乙酸铵-Cd态也没有显著相关性。水分对土壤pH没有显著影响,但培养试验中土壤乙酸铵-Cd与水分处理水平显著负相关。初步推测土壤水分影响生菜地上部Cd浓度,不是通过影响土壤pH和Cd有效态来实现的。因此,可以通过调节土壤水分来控制中轻度重金属污染的设施菜地上叶菜可食部分的Cd浓度,这是一种具有较好应用前景的绿色调控措施。     

应用15N示踪技术研究土壤水分对氮素有效性的影响

在有防雨设施的试验田里,设置不同的土壤水分处理,应用15N示踪技术研究土壤水分对氮素有效性的影响.试验结果表明:冬小麦对肥料氮素的利用率随土壤水分提高而提高;土壤供应的有效性氮素(A值)在土壤水分由田间持水量的50%提高到60%时出现"跃迁",土壤水分超过田间持水量的60%以后,A值差异不显著,表明土壤氮素有效性对土壤水分存在一个阈值反映.节水、节肥高效的土壤水分下限应控制在土壤田间持水量的60%以上.     

Change of soil hydrological properties of fens as a result of soil development

This study deals with the change and evaluation of hydrological properties of peat soils (Histosols) in the course of soil development. Ash content, volumetric water content, and dry bulk density, unsaturated hydraulic conductivity, water retention function, and wetting properties were measured for 84 fen sites in 19 fen regions of North‐Eastern Germany. Soil development resulted in porosity decrease. On the contrary, the macropore space and the capillary rise increased. With the start of consolidation processes and the development of segregation structure, a'noticeable reduction of the macropores and unsaturated hydraulic conductivity were observed. In course of soil development and decreasing of aggregate size, these processes reversed. Both parameters increased from segregation structure horizon to earthyfied fen and weak moorshyfied fen horizon, until they partly exceeded the starting values of pedogenetic almost unchanged fen in strongly moorshyfied stadium. Differences in wetting properties of peat could not be explained by the changes of peat properties in the course of soil development.     

土壤调节剂对土壤物理性质的改善

Effects of non-ionic polyacrylamide(PAM),anionic polyacrylamide(PHP),cationic polyacrylamide(PCAM),non-ionic polyvinylalcohol(PVA),anionic hydrolyzed polyacrylonitrile(HPAN)and polyethleneoxide(PEO)on the physical properties of three different soil stpes were studied.content of water-stable aggregates larger than 0.25mm increased to varying extents for different soils and soil conditioners,Among the six kinds of condiftioners,non-ionic polyacrylamide(PAM) was the most effective for red soil while polyethyleneoxide(PEO)the least effective for Chao soil,red soil and yellow-brown soil.Water-stable aggregates with the molecular weight of PEO within a certain range.Only evaporation rate of Chao soil decreased after aplication of PAM and HPAN to Chao soil and red soil.     

Early-stage bacterial colonization between a sterilized remoulded soil clod and natural soil aggregates of the same soil

The early stages of bacterial colonization of a sterilized soil put in contact with the same non-sterile soil were investigated. Soil mesocosms of 269 cm³ composed of sterilized spherical remoulded soil clods of 27 mm diameter surrounded by non-sterilized 2-4 mm soil aggregates of the same soil (considered as a source of bacterial colonizers) were designed. Bacterial colonization was monitored from 0 to 14 days in three concentric portions of the sterilized clods (outer, intermediate and inner) and in the surrounding non-sterile soil, by measuring cell numbers and substrate-induced respiration (SIR). In addition, modifications of genetic diversity of the soil bacterial community associated to colonization were monitored with the ribosomal intergenic spacer analysis (RISA) technique in the intermediate portion of the sterilized soil clod and in the surrounding non-sterile soil aggregates. Assessments of bacterial cell numbers and SIR rates showed that the sterilized soil clod was colonized rapidly during incubation time from its outer to its inner portion. In addition, the bacterial genetic structure of the clod varied during incubation time, suggesting succession of bacteria during recolonization. Comparison of cell numbers, SIR rates and bacterial genetic structure between the soil clod and the surrounding soil aggregates showed that the colonization process in the clod led to the establishment of a bacterial community different from the surrounding soil aggregates.     

土壤含水率与土壤碱度对土壤抗剪强度的影响

土壤含水率和土壤碱度是表征土壤物理化学性质的两个重要参数。通过室内三轴不固结不排水试验，研究了土壤含水率和土壤碱度对土壤抗剪强度的影响。试验处理采用5种土壤碱度(土壤可交换钠百分比ESP=0、5、10、20、40)和4种土壤质量含水率(0.05、0.10、0.20以及饱和含水率0.34)水平。试验结果显示，土壤黏聚力随着土壤含水率的增加基本上呈先增大后减小之趋势；当土壤含水率在0.10附近时黏聚力达到其最大值。土壤内摩擦角随着土壤含水率的增加而线性减小。土壤碱度对土壤黏聚力的影响机理较为复杂，其影响效果随土壤含水率的增加而减小；但土壤碱度对土壤内摩擦角的影响较小。土壤碱度对土壤抗剪强度的影响程度明显地小于土壤含水率对其的影响程度。     

A review of visual soil evaluation techniques for soil structure

Soil structure forms a key component of soil quality, and its assessment by semi‐quantitative visual soil evaluation (VSE) techniques can help scientists, advisors and farmers make decisions regarding sampling and soil management. VSE techniques require inexpensive equipment and generate immediate results that correlate well with quantitative measurements of physical and biochemical properties, highlighting their potential utility. We reviewed published VSE techniques and found that soils of certain textures present problems and a lack of research into the influence of soil moisture content on VSE criteria. Generally, profile methods evaluate process interactions at specific locations within a field, exploring both intrinsic aspects and anthropogenic impacts. Spade methods focus on anthropogenic characteristics, providing rapid synopses of soil structure over wider areas. Despite a focus on structural form, some methods include criteria related to stability and resiliency. Further work is needed to improve existing methods regarding texture influences, on‐farm sampling procedures and more holistic assessments of soil structure.     

聚丙烯酸盐类土壤改良剂对燕麦土壤微生物量氮及酶活性的影响

以燕麦田土壤为研究对象,探讨了聚丙烯酸盐类土壤改良剂及其复配(聚丙烯酸钾、聚丙烯酰胺、腐植酸钾、聚丙烯酸钾+腐植酸钾、聚丙烯酰胺+腐植酸钾)对燕麦田土壤微生物量氮及土壤酶活性的影响。结果表明,不同土壤改良剂均能提高土壤有机质、碱解氮、速效磷和速效钾的含量,各指标分别比对照增加了8.24%～30.22%、7.60%～19.29%、5.15%～29.45%和27.86%～68.86%;土壤改良剂能促使燕麦全生育期内0～10、10～20和20～40 cm各土层的土壤微生物量氮含量显著提高,聚丙烯酸钾+腐植酸钾和聚丙烯酰胺+腐植酸钾复配处理较其各单施效果显著,随土壤深度的增加土壤微生物量氮逐层递减;与对照相比,土壤改良剂能显著提高燕麦全生育期各土层过氧化氢酶活性,在抽穗期活性最高,且以聚丙烯酸钾+腐植酸钾较高;但对于脲酶,聚丙烯酸钾+腐植酸钾、聚丙烯酰胺+腐植酸钾和腐植酸钾3个处理在苗期显著低于对照,在抽穗期和成熟期高于对照,两种酶活性均随土壤深度的增加逐渐降低。     

Interrelation between soil physical properties and Enchytraeidae abundances following a single soil compaction in arable land

In spring 1995 a silty clay soil was compacted dynamically by wheeling with graded wheel loads up to 6 times. The reaction towards wheeling was recorded immediately. In the following 3 years some soil physical parameters as well as the Enchytraeidae abundances were recorded regularly. To the first wheeling, the soil reacted plastically in vertical direction. The reaction became elastically after the 4th wheeling. After the 6th passage with a 5‒tonnes wheel load soil structure collapsed totally, which can be concluded from the stress ratios. After the wheeling event, abundances of Enchytraeidae decreased obviously compared to uncompacted plots. The increase in air permeability, air capacity, and the decrease of soil bulk density depend on primary tillage events. The recovery of Enchytraeidae abundances developed in parallel. Abundances seem to be regenerated in the 3rd year after the wheeling event. Primary tillage can help to induce biological and macroscopic structural regeneration of the top soil after a compaction event.     

Soil compaction and soil management – a review

Soil compaction is an important component of the land degradation syndrome which is an issue for soil management throughout the world. It is a long standing phenomenon not only associated with agriculture but also with forest harvesting, amenity land use, pipeline installation, land restoration and wildlife trampling. This review concentrates on the impact of soil compaction on practical soil management issues, an area not previously reviewed. It discusses in the context of the current situation, the causes, identification, effects and alleviation of compaction. The principal causes are when compressive forces derived from wheels, tillage machinery and from the trampling of animals, act on compressible soil. Compact soils can also be found under natural conditions without human or animal involvement. Compaction alters many soil properties and adverse effects are mostly linked to a reduction in permeability to air, water and roots. Many methods can be used to measure the changes. In practical situations, the use of visual and tactile methods directly in the field is recommended. The worst problems tend to occur when root crops and vegetables are harvested from soils at or wetter than field capacity. As discussed by a farmer, the effects on crop uniformity and quality (as well as a reduction in yield) can be marked. By contrast, rendzinas and other calcareous soils growing mainly cereals are comparatively free of compaction problems. The effect of a given level of compaction is related to both weather and climate; where soil moisture deficits are large, a restriction in root depth may have severe effects but the same level of compaction may have a negligible effect where moisture deficits are small. Topsoil compaction in sloping landscapes enhances runoff and may induce erosion particularly along wheeltracks, with consequent off‐farm environmental impacts. Indirect effects of compaction include denitrification which is likely to lead to nitrogen deficiency in crops. The effects of heavy tractors and harvesters can to some extent be compensated for by a reduction in tyre pressures although there is concern that deep‐seated compaction may occur. Techniques for loosening compaction up to depths of 45 cm are well established but to correct deeper problems presents difficulties. Several authors recommend that monitoring of soil physical conditions, including compaction, should be part of routine soil management.     

植烟沙泥田土掺混紫色土对土壤酶活性及理化性质的影响

为了探讨南雄烟区植烟沙泥田土壤改良新途径,采用盆栽方法研究了沙泥田土掺不同比例紫色土后土壤的理化性质和相关酶活性的变化规律。结果表明:当沙泥田土掺混10%~50%的紫色土后,土壤的砂粒含量逐渐下降到11.57%,粉粒含量逐渐上升到62.19%,土壤质地由壤土逐渐变为粉砂壤土,pH值从微酸性逐渐变成弱碱性;氧化还原酶类酶的活性逐渐增强,水解酶类酶活性则逐渐减弱,微量元素含量(钼除外)逐渐降低,中量元素交换性钙和交换性镁含量分别比对照(A1)增加了313%和37.1%;当沙泥田土掺混30%紫色土时,全钾和缓效钾含量分别比对照(A1)高出50%和69.2%,但其它养分含量有不同程度下降;相关分析结果表明,土壤酶活性受到土壤养分和中微量元素含量的影响,过氧化氢酶、多酚氧化酶、酸性磷酸酶和中性磷酸酶活性与pH值、有机质、全氮、碱解氮、有效磷、全钾和速效钾等养分含量均达到显著或极显著相关水平;有效铜、有效锌、有效硼、交换性钙和交换性镁含量与过氧化氢酶、过氧化物酶、多酚氧化酶和中性磷酸酶活性均达到显著或极显著相关水平;通过主成分分析得出沙泥田土掺混10%紫色土后的土壤因子综合主成分分值最高,掺混效果最好。