Pedogenic and Anthropogenic Influence on Calcium and Magnesium Behaviors in Stagnic Anthrosols

The formation of Stagnic Anthrosols is closely related to rice planting and parent materials. Six representative pedons, two from each of three Stagnic Anthrosol subgroups, Vertic Haplic-, Vertic Gleyic-, and Sulfic Gleyic-Stagnic Anthrosols, from different parent materials and soil formation processes, from Liaoning Province, China, were selected and used along with additional supporting data to assess the potential impact in each soil subgroup combination of both pedogenic and anthropogenic factors on the migration and geochemical characteristics of calcium (Ca) and magnesium (Mg) and their relations to soil particle-size composition. Results revealed that exchangeable Mg was correlated positively with clay and silt content, but negatively with sand content, suggesting that clay and silt could retain more exchangeable Mg than sand. Also, in the six pedons exchangeable Ca/Mg ratios generally decreased with depth, which was most likely due to the preferential retention of Mg below the Apl horizon and the effects of bio-cycling in rice-soil systems. The pedons with high pH had smaller exchangeable Ca/Mg ratios than those with low pH. Thus, it was concluded that exchangeable Ca/Mg ratios could be helpful in classification of Stagnic Anthrosols.

Effect of Tillage System on Distribution of Aggregates and Organic Carbon in a Hydragric Anthrosol

The effect of different tillage systems on the size distribution of aggregates and organic carbon distribution and storage in different size aggregates in a Hydragric Anthrosol were studied in a long-term experiment in Chongqing,China. The experiment included three tillage treatments:conventional tillage with rotation of rice and winter fallow(CT-r) system,no-till and ridge culture with rotation of rice and rape(RT-rr) system,and conventional tillage with rotation of rice and rape(CT-rr) system. The results showed that the aggregates 0.02-0.25 mm in diameter accounted for the largest portion in each soil layer under all treatments. Compared with the CT-r system,in the 0-10 cm layer,the amount of aggregates > 0.02 mm was larger under the RT-rr system,but smaller under the CT-rr system. In the 0-20 cm layer,the organic carbon content of all fractions of aggregates was the highest under the RT-rr system and lowest under the CT-rr system. The total organic carbon content showed a positive linear relationship with the amount of aggregates with diameter ranging from 0.25 to 2 mm. The storage of organic carbon in all fractions of aggregates under the RT-rr system was higher than that under the CT-r system in the 0-20 cm layer,but in the 0-60 cm soil layer,there was no distinct difference. Under the CT-rr system,the storage of organic carbon in all fractions of aggregates was lower than that under the CT-r system;most of the newly lost organic carbon was from the aggregates 0.002-0.02 and 0.02-0.25 mm in diameter.

Diversity of Anthrosols in China

Human activities make strong effects on soil formation. Anthropogenic soils are much more intensive and extensive in China for their history of agricultural production can be dated back to more than 7 000 years ago.Owing to different physical conditions and land uses, the aothropogenic soil-forming processes are various.Anthrosols are proposed, and the corresponding soil order is set up in Chinese Soil Taxonomy (CST). Mainly based on 6 Anthropogenic diagnostic horizons, which are anthraquic epipedon, hydragric horizon, irragric epipedon, cumulic epipedon, fimic epipedon and agric horizon, the Anthrosols Order is subdivided into 2 soil suborders and 4 soil groups. Meanwhile the classification of Anthrosols in CST has been basically accepted as the classification of Anthrosols in World Reference Base for Soil Resources (WRB).

Fractal Characteristics of Stagnic Anthrosols and the Relationship with Soil Micro-Structure

The Stagnic Anthrosols developed from quaternary yellow sedimentary parent material occupied an important position in Southwest China. Fractal dimensions of particle size and micro-aggregate size distributions of Stagnie Anthrosols and their relationship to soil micro-structure had been probed. Results showed that the soil particle size distributions were dominated by clay, the fractal dimensions of particle size distributions （Ds） were high and between 2.676-2.925, as the fractal dimensions of micro-aggregate size distributions （Da） were between 2.354-2.853. The fractal dimensions of particlesize distributions were preferably related with the ratio of coarse particles and fine particles （c/f20 ,m） and the micromorphological feature of skeleton grains. The evolution degree of micro-structure among horizons were reflected by the coefficient of variation of Ds within the profile. The fractal dimensions of micro-aggregate size distributions were related with the quantities, distributions of micro-aggregates and micro-pores. Results revealed that the soil micro-structures could be quantified by fractal dimensions preliminarily.

Changes in N,P and K Contents in Eum-orthic Anthrosols at Different Moisture Contents

[Objectives]This study aimed to provide a basis for the management of nitrogen,phosphorus and potassium nutrients in eum-orthic anthrosols and the fertilization of crops.[Methods]Using the indoor culture method,the contents of total nitrogen,available phosphorus and available potassium in eum-orthic anthrosols under three different moisture conditions:long-term drying,long-term logging and alternate drying and logging were analyzed and compared.[Results]The total nitrogen content was higher under the moisture condition of long-term drying.The minimum(0.60 g/kg)appeared on day 30,and the maximum(0.74 g/kg)appeared on day 120,increased by 8.8%compared with the minimum.The available phosphorus content was also higher under the moisture condition of long-term drying.The minimum(16.9 mg/kg)appeared on day 60,and the maximum(22.5 mg/kg)appeared on day 120,increased by 33.1%compared to the minimum.The available potassium content showed a downward trend under long-term logging,and was higher than those under the other two moisture conditions.The maximum(150 mg/kg)appeared on day 30,and the minimum(136 mg/kg)appeared on days 75 and 90,reduced by 9.3%compared with the maximum.[Conclusions]Water plays a positive role in activating nutrients.Different nutrients have different responses to different moisture conditions.

Human-altered soils–Signatures of Anthrosols and their potential for arable lands

The fertility of human-altered soils,Anthrosols,developed from past settlement activities for crop production is scarcely studied.The study evaluated the fertility of Anthrosols developed from the 15th to mid-20th century AD settlement in Old Buipe,Savanna region,Ghana,to determine whether abandoned localities are suitable for arable fields.Human activities enhanced the physical attributes of the Anthrosols:brown to dark brown intergrain fine soil,15%−35%organic matter,15%−30%potsherd,and 5%−15%charred materials.The Anthrosols were slightly acidic to neutral reactions(pH_([H_(2)O])5.67−6.83,pH_([cacl_(2)])5.83−6.95),high cation exchange capacity(CEC;18.77−45.31me/100 g),electric conductivity(EC=0.28−0.36 dS m^(−1)),accumulation,and distribution of organic C,total N,P,Mn,Cu,Zn,K,and Fe,and available P,K,Ca,Mg,S,Mn,Fe,Cu,and Zn.Plant-available nutrients were comparatively higher than concentrations in non-anthropogenic soils.The level of releasability(bioavailable fractions of total concentrations)of P,K,Ca,Mn,Fe,Cu,and Zn partly compensates for low plant-available portions.Enrichment of chemical and physical properties of Anthrosols make them fertile for arable fields.The signatures of settlement activities are strong and can remain in soils for a long time,even under harsh environmental conditions.

水耕人为土时间序列铁氧化物与磁化率演变特征

以我国亚热带地区不同母质起源的水耕人为土时间序列为研究对象,分析不同形态铁氧化物和磁化率随成土时间的动态演变特征及其影响因素。结果表明,石灰性母质起源的水耕人为土0~120 cm土体中全铁(Fet)、游离铁(Fed)和游离度(Fed/Fet)随时间序列演变均逐渐增加,0~50 a内Fet、Fed和Fed/Fet增加速率分别为3.2 t hm^(-2) a^(-1)、1.2 t hm^(-2) a^(-1)和0.04%a^(-1),50~1 000 a内Fet、Fed和Fed/Fet增加速率分别为0.1 t hm^(-2) a^(-1)、0.15 t hm^(-2) a^(-1)和0.01%a^(-1);而酸性母质起源的水耕人为土0~120 cm土体中Fet、Fed和Fed/Fet随时间序列演变均逐渐下降,0~60 a内Fet、Fed和Fed/Fet下降速率分别为0.2 t hm^(-2) a^(-1)、0.5 t hm^(-2) a^(-1)和0.03%a^(-1),60~300 a内Fet、Fed和Fed/Fet下降速率分别为0.9 t hm^(-2) a^(-1)、1.2 t hm^(-2) a^(-1)和0.06%a^(-1)。土壤pH、Eh、以及外源铁输入与土体内铁淋失的相对强度是控制不同母质水耕人为土中铁氧化物转化速率与途径的主要因素。石灰性母质起源的水耕人为土中不同磁学指标随时间演变分为三个阶段:0~50 a内表现为质量磁化率(MS)、饱和等温剩磁(SIRM)和软剩磁(IRMs)的急剧降低;50~300 a内表现为MS、SIRM和IRMs的持续、缓慢降低以及硬剩磁(IRMh)的相对稳定发展;300~1 000 a内表现为MS、SIRM和IRMs的持续、缓慢降低以及IRMh的快速下降。酸性母质起源的水耕人为土0~20 cm和20~120 cm土壤中磁学指标演变呈现截然不同的两个阶段:0~60 a 0~20 cm内MS,SIRM和IRMs的急剧降低,IRMh具有明显增加;而20~120 cm内MS、SIRM和IRMs缓慢下降,IRMh明显降低。60~300 a 0~20 cm内不同磁学指标变化幅度均很小,而20~120 cm内IRMh相对比较稳定,MS、SIRM和IRMs在种稻150 a后快速下降。淹水还原条件下亚铁磁性矿物的破坏是不同母质水耕人为土演变过程中磁性衰减的主要机制。

施氮量和蚕豆/玉米间作对土壤无机氮时空分布的影响

在田间条件下于2006～2007年研究了不同氮水平下（N 0、75、150、2253、00 kg/hm2）蚕豆/玉米间作体系与其相应单作体系土壤无机氮的时空分布规律,旨在为河西走廊灌区蚕豆/玉米间作体系的氮素管理提供理论依据。用土钻法采集土壤剖面样品,CaCl2浸提,流动分析仪测定土壤无机氮的方法研究了施氮量和蚕豆/玉米种间相互作用对土壤无机氮时间和空间变化特点。结果表明：灌漠土无机氮以NO3--N为主。蚕豆和玉米无机氮含量在蚕豆收获前种植方式间均无显著性差异,蚕豆收获后至玉米收获,间作显著降低了两种作物各层无机氮含量;无机氮含量随着施氮量增加而显著增加。蚕豆收获后间作体系0—100 cm土层无机氮累积量略高于单作体系,且0—100cm土层无机氮累积量高于100—160 cm土层;玉米收获后,间作蚕豆和玉米土壤无机氮累积量在0—100 cm土层分别平均降低了51.7%和16.6%,在100—160 cm土层平均降低了42.1%和6.1%;与不施氮相比,施氮蚕豆和玉米无机氮累积量在0—100 cm土层分别平均增加了40.1%和81.5%,在100—160 cm土层分别增加了69.6%和40.6%;与单作体系相比,间作体系0—100 cm和100—160 cm土层土壤无机氮分别降低43.4%和34.1%。因此,施氮肥显著增加土壤无机氮的累积,而豆科/禾本科间作减少了土壤无机氮的残留。

陕西三种类型土壤剖面硝酸盐累积、分布与土壤质地的关系

研究了陕北黄绵土,关中(土娄)土与陕南水稻土土壤剖面中硝酸盐的分布与累积,分析了硝酸盐淋移与土壤剖面粘粒含量的关系.结果表明,黄绵土由于粘粒含量少,土壤疏松,氮肥施入土壤后硝化作用速度快,氮素多以硝态氮存在于土壤中,遇到过量的灌溉或降水,容易引起硝酸盐淋失.在米脂的川道地,施肥2个月后,硝酸盐峰值在50 cm 左右,4个多月后,峰值下移至100 cm 左右,6个月后,该峰值下降到130 cm 左右,一年内,硝酸盐的峰值已经消失,分布在130至 350 cm 之间.因此,在黄绵土地区可以灌溉的川道地,氮素损失的主要途径是硝酸盐淋失.关中(土娄)土,粘粒含量相对较高,硝化作用速度快,但由于在80-120 cm有一粘化层,阻碍了水分与硝酸盐的向下淋移,使得大部分硝酸盐累积在0-100 cm 土层,其累积量占到0-400 cm总累积量的64% ～ 74%,而200-400 cm仅占到7% ～ 13%.而且淋移到100 cm 以下的硝酸盐,也通过反硝化损失了.陕南水稻土,由于深层土壤水饱和,硝酸盐难以向下淋移,氮素主要累积在土壤表层.由于下层土壤长期处于厌气条件,即使淋移到下层的硝酸盐也通过反硝化作用而损失掉了.

过量施肥下氮素形态对旱地土壤细菌多样性的影响

采用细菌16SrDNA的PCR-RFLP技术,以西北地区土垫旱耕人为土为材料,模拟田间过量施肥水平,经室内恒温短期培养,研究了过量施肥下酰胺态氮、硝态氮和铵态氮对土壤细菌多样性的影响。结果显示:PCR-RFLP分析酰胺态氮(T1)、硝态氮(T2)和铵态氮(T3)过量施肥处理的细菌16SrDNA克隆文库,分别得到17、25和130个酶切分型,不施肥对照(CK1)和正常施肥对照(CK2)分别得到119和187个酶切分型,表明正常施肥处理的酶切分型最多,过量使用酰胺态氮和硝态氮减少了酶切类型,而过量施用铵态氮可以维持与不施肥对照相近的酶切类型数量。采用α多样性测度对试验结果进行分析统计表明,不同处理间土壤细菌的多样性指数(H'、Ds)和物种丰富度指数(dM)a均为CK2>T3>CK1>T2>T1处理,表明合理施肥可显著增加土壤中细菌的多样性,而过量施用酰胺态氮则减少细菌的多样性,使用铵态氮处理可维持细菌多样性;除正常施肥对照(CK2)外,其余各处理都出现了优势菌种。通过对优势菌的16SrDNA序列比对发现,酰胺态氮处理都为未培养细菌,硝态氮处理和铵态氮处理的优势菌呈现了菌属多样性,前者包括变形菌门的假单胞菌属和寡养单胞菌属、芽单胞菌门的未培养芽单胞菌属和未培养土壤细菌,后者为未培养酸杆菌属、变形菌门寡养单胞菌属和厚壁菌门芽孢杆菌属,表明不同施肥方式改变了土壤细菌的群落结构。

不同施肥处理对黄泥土微生物生物量碳氮和酶活性的影响

通过室内培育实验,研究了不同施肥处理对黄泥土微生物生物量C、N和脲酶、酸性磷酸酶、蔗糖酶活性的影响。培养过程中,单施化肥处理土壤微生物生物量C、N均呈下降趋势,施用有机肥处理的土壤微生物量C前期升高至一定水平后或保持稳定、或呈下降趋势,而微生物生物量N总体均呈下降趋势;不同施肥处理的脲酶活性呈前期上升后期下降趋势,而酸性磷酸酶和蔗糖酶则单施化肥处理呈上升趋势、配施有机肥处理呈下降趋势。与对照处理相比,单施化肥处理显著降低土壤微生物生物量C、N,高量施用化肥处理还显著降低土壤脲酶活性,但对酸性磷酸酶和蔗糖酶活性的影响并不明显。秸秆施用可显著提高土壤微生物生物量C、N和酶活性,特别是高量施用秸秆的效果更明显。施用猪粪由于同时带入了大量的活性养分,对土壤微生物生物量C、 N和酶活性的影响尚难评价。在高度集约农业利用下,继续保持较高的化肥施用量并不利于土壤生物质量的维护和提高,而秸秆直接还田才是保持土壤健康状态的有效措施。

陕西关中土垫旱耕人为土样区的基层分类研究

选择陕西关中土垫旱耕人为土地区为样区,以该地区代表性土壤土垫旱耕人为土((土娄)土)为研究对象,在野外调查、室内分析及查阅大量有关剖面资料的基础上,根据中国土壤系统分类体系,对土垫旱耕人为土((土娄)土)的基层分类进行了研究.研究表明,应用土壤颗粒大小级别、矿物学型和土壤温度状况等3项指标对土族进行划分,在0～160 cm的控制层段中小于2 mm的土壤平均质地,多数剖面为粘壤土,少数为壤土或砂质壤土,矿物学型属伊利石型、伊利石混合型或蛭石型,土壤温度属温性或温热土壤温度状况.土垫旱耕人为土((土娄)土)土系的控制层段拟定为从表土层上界向下160 cm,对于诊断层的底部在160 cm以下的,则从表土层至诊断层的下部边界,特征土层有肥熟表层、土垫表层、暗沃表层、耕作淀积层、粘化层、粘质层、CaCO3高度淀积层、CaCO3中度淀积层、CaCO3低度淀积层、氧化还原层和稚育层.根据样区9个典型剖面,结合关中地区土垫旱耕人为土((土娄)土)的有关研究资料,划分了土族和土系,并描述了各土系的典型特征及土系间的变异情况.

成都平原水耕人为土诊断层的微形态特征与土壤基层分类

对成都平原地区广泛分布的水耕人为土中 ,就同一亚类的几种典型土系 ,对其诊断层的土壤微形态特征进行研究 ,提出了划分不同土系及其所属土族的土壤属性如 :土壤颗粒、土壤矿物、土壤结构、土壤形成物等的特征的微形态证据。研究表明 :土壤诊断层的微形态特征能够综合地、直观地、准确地反映土壤这些分类属性 ,同时还能提供土壤生产性方面的信息。所以本研究结果在土壤系统分类的基层分类以及应用于生产上 。

长江上游典型区水耕人为土的电导率与肥力评价探讨

土壤电导率 (EC)是土壤电化学性。在非盐渍化地区 ,该特性与土壤营养成分含量密切有关 ,因此可以用于评价土壤肥力水平。本研究探索长江上游典型区的非盐渍化的水耕人为土的电导率特征 ,并以层次分析法 (AHP)和Fuzzy模糊数学方法计算了研究区的土壤肥力综合指标值 (IFI) ,分析其与土壤的电导率间的相关性及定量关系。结果表明 ,该区的肥力综合指数与土壤电导率有显著的相关性 ,并且它们之间存在定量的函数关系。

水耕人为土磁性矿物的生成转化机制研究回顾与展望

随着环境问题的日益突出,人为活动对土壤的影响越来越深刻,需加强对"人为作用"的研究以便解释现代土壤磁性的过程和变化。水耕人为土在发育过程中人为作用的方式多种多样,明确其磁性矿物的生成和转化机制及其影响因素有利于理解人为活动对现代土壤磁性的作用。但目前水耕人为土磁学研究还比较零散,缺乏系统性,已有研究结果有待深入梳理。本文对已有的相关研究报道,包括水耕人为土磁性参数的演变特征、磁性矿物的生成转化机制以及对成土因素的响应等进行综合评述。最后,对当前研究的不足和存在问题进行总结,并对研究方向进行了展望,以期有助于环境磁学的发展。

长江三角洲水稻土主要土种在中国土壤系统分类中的归属

本文概述了长江三角洲水稻土的形成背景,说明了我国水稻土与水耕人为土分类上的区别。在此基础上,将长江三角洲水稻土主要土种按中国土壤系统分类的严格定量指标,分别阐明其在系统分类中的归属。

陕西关中地区塿土在系统分类中的归属

本文对采自关中地区的6个塿土剖面进行了理化性质分析,根据《中国土壤系统分类(修订方案)》确定了它们的诊断层、诊断特性及在中国土壤系统分类中的归属。最后就塿土在中国系统分类中存在的堆垫表层诊断指标问题和土垫旱耕人为土亚类的划分问题进行了讨论。

湘东花岗岩发育水稻土在中国土壤系统分类中的归属

选取湘东7个起源花岗岩风化物的水稻土样点,按中国土壤系统分类指标体系,野外系统调查成土环境、描述土壤剖面形态,室内分析理化性质,研究其在中国土壤系统分类中的归属,评述土系的生产性能。结果表明,在水耕人为土亚纲下,划分出铁聚和潜育水耕人为土2个土类,普通铁聚水耕人为土和普通潜育水耕人为土2个亚类,进一步划分出6个土族和7个土系(车溪系、刘家场系、双家冲系、红阳系、柏树系、湾头系和福安系)。对于同一地区类似母土/母质发育的水耕人为土而言,基于系统分类的定量化指标(颗粒大小和质地层次)比基于发生分类的定性判定具有更强的划分能力。

模拟不同pH降雨和施氮对水耕铁渗人为土酸化的影响

室内模拟研究3个pH梯度降雨和3水平的施氮量对水耕铁渗人为土土壤酸化的影响。结果表明,不同pH降雨及施氮处理土壤的酸度累积量为4.73～15.57 mmol H+每柱,分别以pH 6.5降雨和不施氮处理、pH 2.5添加高氮量(N2)处理酸化速率为最低和最高,相同pH降雨处理下,致酸量随施氮量增加而上升;相同施氮下,不施氮处理土壤酸度累积随降雨pH降低而增加,但中施氮量(150 mg kg-1土)和高施氮量(300 mg kg-1土)下,pH 4.5处理土壤酸度累积量则小于pH 6.5处理;不同降雨及施氮处理NO3-淋溶致酸量为4.32～12.88 mmol每柱,NH+4淋溶消耗H+量为0.01～0.29 mmol每柱;正常酸沉降(pH 6.5)下,中施氮量和高施氮量处理致酸量都大于各梯度pH降雨的致酸量。以上结果表明,单施氮处理的致酸量大于单纯的酸沉降处理,而无论是降雨还是施氮,NO-3淋溶在加速土壤酸化进程中占主导作用。

水耕人为土某些氧化还原形态特征的微结构和形成机理

结合微形态观察和特征微区化学成分的电子能谱测定，对水耕人为土几种典型的氧化还原形态特征的结构进行了解析，并在此基础上提出了它们的形成机理。结果表明，根孔／裂隙淀积铁质胶膜形成于还原亚铁离子在根孔或裂隙面的氧化富集，该过程是Fe2＋吸附于铝硅酸盐粘粒表面被氧化；根际铁质同心圆的形成涉及反应—转移—反馈的自组织过程，导致条带状富铁与贫铁区域的形成；淋失胶膜可分为铁锰淋失胶膜和粘粒淋失膜（淋余膜），二者在微结构和化学成分上有明显不同，后者不仅铁锰的淋失更甚，而且伴随铝硅酸盐粘粒的分解。