Carbon stocks and sequestration potentials of agricultural soils in the federal state of Baden‐Württemberg,SW Germany

Soil organic carbon (SOC) inventories are important tools for studying the effects of land‐use and climate change and evaluating climate‐change policies. A detailed inventory of SOC in the agricultural soils of the federal state of Baden‐Württemberg was therefore prepared based on the highest‐resolution geo‐referenced soil, land‐use, and climate data (BÜK200 inventory). In order to estimate the quality of different approaches, C inventories of the region were also prepared based on data from the National Inventory Report (UBA, 2003) and by applying the IPCC (1997) method to the two data sets. Finally, the BÜK200 inventory was used to estimate potentials of no‐tillage agriculture (NT) and peatland restoration to contribute to C sequestration and greenhouse‐gas (GHG)‐emission mitigation since both measures are discussed in this context. Scenario assumptions were change to NT on 40% of the cropland and restoration of 50% of cultivated peatlands within 20 years. On average, grasslands contained 9.5 kg C m^–2 to 0.3 m depth as compared to only 6.0 kg C m^–2 under cropland, indicating strong land‐use effects. The SOC content depended strongly on waterlogging and elevation, thus reflecting reduced C mineralization under aquic moisture regimes and low temperatures. Comparison of the BÜK200 inventory with the approach used for UBA (2003) showed high inconsistencies due to map resolution and SOC contents, whereas the IPCC method led to fairly good agreements. Results on the simulated effects of NT and peatland restoration suggested that 5%–14% of total agricultural GHG emissions could be abated with NT whereas peat restoration appeared to have a minor mitigation potential (0.2%–2.7%) because the total area of cultivated organic soils was too small to have larger impact.     

松华坝水源地不同植被土壤特性及水源涵养功能

根据松华坝水源地的实际情况,按不同植被类型选择了次生林地、人工林地、园地、耕地四种类型,共挖取36个典型剖面进行采样调查,分别对其进行土壤物理性质、有机质和贮水特性的测定。结果表明,次生林地的水源涵养功能最好,人工林地的最差;次生林转变为人工林、园地的植被变化过程是流域内水源涵养功能恶化的主因。     

石灰用量对污染红壤和黄泥土中有效态铜锌含量的影响

采用外源加入重金属铜锌硝酸盐的方法,制成铜、锌单一及复合污染的三级污染红壤和黄泥土（Cu 200mg/kg、Zn 400 mg/kg）,稳定一个月,施入低（0.50 g/kg）、中（1.50 g/kg）和高（2.50 g/kg）3种不同用量的石灰,稳定两个月后测定土壤有效态铜、锌含量和pH值,以阐明石灰用量对不同污染土壤中重金属有效态含量的影响。结果表明,随石灰用量的增加,复合污染红壤中有效态铜含量较对照依次降低31%、76%和87%;而石灰用量对黄泥土中有效态铜影响的差异不显著;两种土壤中有效态锌含量均随石灰用量的增加而显著减少;复合污染较单一污染相比,有效态铜及有效态锌的含量差异不显著。在复合污染下,低、中量石灰使黄泥土中有效态铜含量较红壤减少89%和63%,有效态锌减少27%和65%。但加入高量石灰,两种土壤差异不显著。石灰能够降低单一与复合污染铜、锌有效态的含量,但其效果因土壤类型而异,在红壤上选择施用高量石灰而在黄泥土上则适宜施用低中量石灰,以取得最佳的修复效果和效益。     

脱硫石膏对次生碱化盐土的改良效果

由于土壤碱化引起物理性质恶化限制了土壤盐分淋洗,降低土壤交换性钠含量,提高土壤入渗率是决定碱化盐土能否改良成功的关键。通过油葵田间试验,探讨了脱硫石膏不同施用量(0、11.25、22.5、33.75、45 t/hm2)对次生碱化盐土的改良效果。结果表明:施用脱硫石膏可有效降低次生碱化盐土pH值、碱化度和总碱度,提高土壤入渗率,促进盐分离子淋洗。当脱硫石膏的施用量为11.25 t/hm2时,土壤pH值、碱化度和总碱度降低至8.20、7.66%和0.12 cmol/kg,并低于土壤发生碱化的临界指标,油葵成熟期株高、根长、单株干质量和产量分别达到74 cm、18.6 cm、57.6 g和1 077.0 kg/hm2。脱硫石膏改良效果和其用量不呈正相关,脱硫石膏过量可增加土壤可溶性全盐含量,抑制油葵生长发育。脱硫石膏中的Hg、Pb、Cr、Cd等重金属元素含量低于我国相关标准要求及试验田土壤背景值,施用脱硫石膏不会引起土壤重金属元素总量变化。     

不同施肥方式下土中有机氯农药的残留特征

Soil samples with three fertilization treatments (no fertilizer, corn straw and farm manure) collected from a Lou soil (Eum-orthic Anthrosol classfied using Chinese Soil Taxonomy) in northwestern China were analysed for residual levels and their characteristics of organochlorine pesticides (α-HCH, β-HCH, γ-HCH, δ-HCH, HCB, o,p'-DDT, p,p'-DDT, o,p'-DDE, p,p'-DDE, p,p'-DDD, a-endosulfan, dieldrin and endrin). Organochlorine pesticides (OCPs) were detected in all soil samples except δ-HCH and their total concentrations ranged from 159.31 ± 9.00 to 179.77 ± 2.58 ng g^-1 with an order of HCHs > DDTs > (dieldrin + endrin) > HCB > α-endosulfan. Among all the compounds, γ-HCH had the highest concentration followed by p,p'-DDE. The residual levels of HCH isomers and DDT as well as their metabolites in soil with different fertilization treatments were in the order of γ-HCH > β-HCH ≈ α-HCH > δ-HCH and p,p'-DDE > p,p'-DDT > o,p'-DDT > p,p'-DDD ≈ o,p'-DDE, respectively. DDE/DDT ratios ranged from 1.59 ±0.13 to 3.35 ± 0.16 and endrin/dieldrin ratios from 1.40 ± 0.06 to 9.20 ± 4.05, both indicating no new occurrence of these pesticides in these soils, while α-HCH/γ-HCH ratios of 0.04 indicated a new input of lindane (almost pure γ-HCH) in the past several years. The farm manure treatments showed lower DDT residues than samples without fertilizer. Also addition of corn straw and farm manure increased soil organic matter content and decreased the soil pH which could retard the degradation of DDT in the soil.     

新疆玛纳斯河流域灌溉技术对土壤盐渍化的影响

评价新疆玛纳斯河流域灌区灌溉技术对土壤盐渍化的影响程度。以石河子垦区为例,着重分析不同阶段灌溉技术对土壤盐渍化的影响;根据土壤盐渍化与灌溉技术水平的关系,用类比法对灌区盐渍化耕地的发展趋势进行初步预测。结果表明:在无排水条件下漫灌、畦灌等传统灌溉技术造成地下水位迅速上升,土层出现严重积盐。井灌井排技术有效地降低了地下水位,土壤明显脱盐,作物产量不断提高。目前大力推广的膜下滴灌由于其良好的节水和压盐效果,土壤中盐分含量逐年下降,随着滴灌年限的增加,土壤平均脱盐率逐渐提高;预计2010年大部分地区水资源达到合理利用后,灌区次生盐渍化耕地比例将下降到35%~40%,2020年区域水资源实现高效利用后,盐渍化耕地将减少到30%以内。随着灌溉技术水平的不断提高,不同类型土壤出现明显脱盐,灌区盐渍化耕地也将逐渐减少,但不会全部消失。     

土壤剖面硝态氮含量的快速测试方法

为缩短分析时间提高时效，建立了田间条件下土壤剖面硝态氮含量测定的方法，主要包括1：1土水质量比快速浸提土壤硝态氮，Merck反射仪进行浸提液硝态氮快速定量及酒精灼烧法快速测定土壤水分，根据土壤容重换算土壤硝态氮含量。将该方法与实验室常规的0．01mol／LCaCl2溶液1：10土水质量比浸提、连续流动分析法比较．结果表明，田间快速法与实验室常规法测定的土壤硝态氮含量具有极显著的相关性，2种方法测定表土层(0～30cm)和底土层(30～90cm)土壤硝态氮质量分数(mg／kgN)的相关系数分别为0．96和0．92，按不同层次土壤容重换算表土层和底土层土壤硝态氮含量(kg／hm^2N)的相关系数为0．93和0．92。     

施肥对金沙江干热河谷退化草地土壤微生物的影响

在金沙江干热河谷区的退化草地上进行了2年的氮磷施肥试验,试验结束后分析了土壤特性及土壤微生物数量和生物量的变化。结果表明,在施氮量为5 ,15g/ (m2 ·a)时,土壤微生物的数量和生物量均没有明显变化,而当施氮量增加到2 5g/ (m2 ·a)时,土壤微生物的数量和生物量比对照明显增加。施磷没有引起土壤微生物数量和生物量的明显增加。施氮和施磷均没有引起土壤细菌、真菌和放线菌组成的变化。这表明氮虽然影响土壤微生物的数量,但对土壤微生物的组成没有影响。施氮导致土壤硝态氮增加,但对氨态氮影响不大,硝态氮可能是影响土壤微生物数量的重要因素。施氮和施磷后植物群落地上生物量均出现增加的趋势,但土壤有机质没有明显增加。施氮和施磷也没有引起土壤pH和含水率的明显改变。我们的试验结果表明,在干热河谷退化草地生态系统,仅靠短期施用无机肥料恢复土壤微生物群落是困难的     

土壤生态系统耗散结构变异规律研究的理论与方法探讨

根据贝塔朗菲系统自生长的微分方程 ,可建立表征土壤生态系统动态变化的动力学方程 :dx/dt =(f-s)x-bx2 ,t为时间 ,x为土壤微生物数量 ,f为其繁殖系数 ,s为死亡系数 ,b为饱和系数 .其解 (1)x=x0 e(f-s)t,(2 )x =(f -s) /b.方程 (1)表明 ,如s>f,则当t→∞时 ,x→ 0 ,表明土壤生态系统处于热力学分支 ,将向退化的方向发展 ;方程 (2 )表明 ,如f>s ,其临界点x =(f -s) /b ,如x>x ,则表明土壤生态系统处于耗散结构分支 ,将向进化的方向演替